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0704.0401

Ariane Lan\c{c}on

A. Lan\c{c}on, J.S. Gallagher, R. de Grijs, P. Hauschildt, D. Ladjal, M. Mouhcine, L.J. Smith, P.R. Wood, N. F\"orster Schreiber

Modelling the Near-IR Spectra of Red Supergiant-dominated Populations

Proceedings of IAU Symp. 241 on Stellar Populations as Building Blocks of Galaxies, ed. A. Vazdekis et al. (2007). 4 pages, 6 postscript figures, uses iaus.cls.

10.1017/S1743921307007673

astro-ph

We report on recent progress in the modelling of the near-IR spectra of young stellar populations, i.e. populations in which red supergiants (RSGs) are dominant. First, we discuss the determination of fundamental parameters of RSGs using fits to their near-IR spectra with new PHOENIX model spectra; RSG-specific surface abundances are accounted for and effects of the microturbulence parameter are explored. New population synthesis predictions are then described and, as an example, it is shown that the spectra of young star clusters in M82 can be reproduced very well from 0.5 to 2.4 micrometers. We warn of remaining uncertainties in cluster ages.

0704.0402

Yi Li

Yi Li and Chunshan Zhao

Locating the peaks of least-energy solutions to a quasilinear elliptic Neumann problem

Keywords: Quasilinear Neumann problem, m-Laplacian operator, least-energy solution, exponential decay, mean curvature.

10.1093/imamat/hxl032

math.AP

In this paper we study the shape of least-energy solutions to a singularly perturbed quasilinear problem with homogeneous Neumann boundary condition. We use an intrinsic variation method to show that at limit, the global maximum point of least-energy solutions goes to a point on the boundary faster than the linear rate and this point on the boundary approaches to a point where the mean curvature of the boundary achieves its maximum. We also give a complete proof of exponential decay of least-energy solutions.

0704.0403

Andrew Shields

Andrew J Shields

Review: Semiconductor Quantum Light Sources

preprint version

Nature Photonics 1, 215 (2007)

10.1038/nphoton.2007.46

quant-ph

Lasers and LEDs display a statistical distribution in the number of photons emitted in a given time interval. New applications exploiting the quantum properties of light require sources for which either individual photons, or pairs, are generated in a regulated stream. Here we review recent research on single-photon sources based on the emission of a single semiconductor quantum dot. In just a few years remarkable progress has been made in generating indistinguishable single-photons and entangled photon pairs using such structures. It suggests it may be possible to realise compact, robust, LED-like semiconductor devices for quantum light generation.

0704.0404

Mikhail Vysotsky

A.B.Kaidalov, M.I.Vysotsky

To the origin of the difference of FSI phases in $B\to\pi\pi$ and $B\to\rho\rho$ decays

19 pages, 1 figure

Phys.Lett.B652:203-212,2007

10.1016/j.physletb.2007.07.017

hep-ph hep-ex

The final state interactions (FSI) model in which soft rescattering of low mass intermediate states dominates is suggested. It explains why the strong interaction phases are large in the $B_d\to\pi\pi$ channel and are considerably smaller in the $B_d\to\rho\rho$ one. Direct CP asymmetries of $B_d\to\pi\pi$ decays which are determined by FSI phases are considered as well.

0704.0405

R. J. Williams

W. Kang, R. J. Williams

An invariance principle for semimartingale reflecting Brownian motions in domains with piecewise smooth boundaries

Published at http://dx.doi.org/10.1214/105051606000000899 in the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org)

Annals of Applied Probability 2007, Vol. 17, No. 2, 741-779

10.1214/105051606000000899

IMS-AAP-AAP414

math.PR

Semimartingale reflecting Brownian motions (SRBMs) living in the closures of domains with piecewise smooth boundaries are of interest in applied probability because of their role as heavy traffic approximations for some stochastic networks. In this paper, assuming certain conditions on the domains and directions of reflection, a perturbation result, or invariance principle, for SRBMs is proved. This provides sufficient conditions for a process that satisfies the definition of an SRBM, except for small random perturbations in the defining conditions, to be close in distribution to an SRBM. A crucial ingredient in the proof of this result is an oscillation inequality for solutions of a perturbed Skorokhod problem. We use the invariance principle to show weak existence of SRBMs under mild conditions. We also use the invariance principle, in conjunction with known uniqueness results for SRBMs, to give some sufficient conditions for validating approximations involving (i) SRBMs in convex polyhedrons with a constant reflection vector field on each face of the polyhedron, and (ii) SRBMs in bounded domains with piecewise smooth boundaries and possibly nonconstant reflection vector fields on the boundary surfaces.

0704.0406

Dariush Heidarian

Dariush Heidarian and Sandro Sorella

Finite Drude weight for 1D low temperature conductors

4 pages, 4 figures

10.1103/PhysRevB.75.241104

cond-mat.str-el cond-mat.supr-con

We apply well established finite temperature Quantum Monte Carlo techniques to one dimensional Bose systems with soft and hardcore constraint, as well as to spinless fermion systems. We give clear and robust numerical evidence that, as expected, no superfluid density for Bosons or Meissner fraction for fermions. is possible at {\em any} non zero temperature in one dimensional interacting Bose or fermi lattice models, whereas a finite Drude weight is generally observed in gapless systems, in partial disagreement to previous expectations.

0704.0407

Jose Ricardo Marinelli

S.S. Avancini, J.R. Marinelli, D.P. Menezes, M.M.W. de Moraes and C. Provid\^encia

Density dependent hadronic models and the relation between neutron stars and neutron skin thickness

13 pages, 10 figures, accepted for publication in Phys. Rev. C

Phys.Rev.C75:055805,2007

10.1103/PhysRevC.75.055805

nucl-th

In the present work we investigate the main differences in the lead neutron skin thickness, binding energy, surface energy and density profiles obtained with two different density dependent relativistic hadronic models, within the Thomas-Fermi approximation. We show that the asymmetry parameter for low momentum transfer polarized electron scattering is not sensitive to the model parametrization differences.

0704.0408

Janne K. Viljas

J. K. Viljas, F. Pauly and J. C. Cuevas

Photoconductance of organic single-molecule contacts

4 pages, 2 figures

Phys. Rev. B 76, 033403 (2007)

10.1103/PhysRevB.76.033403

cond-mat.mes-hall

We study the dc conductance of organic single-molecule contacts in the presence of external electromagnetic radiation (photoconductance). In agreement with previous predictions, we find that the radiation can lead to large enhancements of the conductance of such contacts by bringing off-resonant levels into resonance through photoassisted processes. In our analysis we make use of the simplifying fact that, under certain assumptions, the photoconductance can be expressed in terms of the transmission function in the absence of the radiation. The conductance enhancement is demonstrated for oligophenylene molecules between gold electrodes, whose electronic structure is calculated based on density-functional theory. It is shown that the exponential decay of the conductance with the length of the molecule can be replaced by a length-independent value in the presence of radiation.

0704.0409

D. Levkov

D.G. Levkov, A.G. Panin, S.M. Sibiryakov

On the over-barrier reflection in quantum mechanics with multiple degrees of freedom

Journal version. Introduction expanded, references added

Phys. Rev. A 76, 032114 (2007)

10.1103/PhysRevA.76.032114

CERN-PH-TH/2007-065

quant-ph hep-th nlin.CD physics.atom-ph physics.chem-ph

We present an analytic example of two dimensional quantum mechanical system, where the exponential suppression of the probability of over-barrier reflection changes non-monotonically with energy. The suppression is minimal at certain "optimal" energies where reflection occurs with exponentially larger probability than at other energies.

0704.0410

R. J. Nicholas

R.S. Deacon, K-C. Chuang, R. J.Nicholas, K.S. Novoselov, A.K. Geim

Cyclotron Resonance study of the electron and hole velocity in graphene monolayers

Phys. Rev. B 76, 081406(R) (2007)

10.1103/PhysRevB.76.081406

cond-mat.mes-hall

We report studies of cyclotron resonance in monolayer graphene. Cyclotron resonance is detected using the photoconductive response of the sample for several different Landau level occupancies. The experiments measure an electron velocity at the K- (Dirac) point of $c_{K}^{*}$ = 1.093 x 10$^{6}$ ms$^{-1}$ and in addition detect a significant asymmetry between the electron and hole bands, leading to a difference in the electron and hole velocities of 5% by energies of 125 meV away from the Dirac point.

0704.0411

Xu Zhiping

Zhiping Xu

Molecular circuits based on graphene nano-ribbon junctions

10 pages, including 4 figures

Applied Physics Letters 90, 223115 (2007)

10.1063/1.2745268

cond-mat.mes-hall cond-mat.mtrl-sci

Graphene nano-ribbons junctions based electronic devices are proposed in this Letter. Non-equilibrium Green function calculations show that nano-ribbon junctions tailored from single layer graphene with different edge shape and width can act as metal-semiconductor junctions and quantum dots can be implemented. In virtue of the possibilities of patterning monolayer graphene down to atomic precision, these structures, quite different from the previously reported two-dimensional bulk graphene or carbon nanotube devices, are expected to be used as the building blocks of the future nano-electronics.

0704.0412

Martin Hertweck

Martin Hertweck

Unit groups of integral finite group rings with no noncyclic abelian finite subgroups

5 pages

math.RT math.RA

It is shown that in the units of augmentation one of an integral group ring $\mathbb{Z} G$ of a finite group $G$, a noncyclic subgroup of order $p^{2}$, for some odd prime $p$, exists only if such a subgroup exists in $G$. The corresponding statement for $p=2$ holds by the Brauer--Suzuki theorem, as recently observed by W. Kimmerle.

0704.0413

Toru Kojo

Toru Kojo, Daisuke Jido and Arata Hayashigaki

Exotic Hadron in Pole-dominated QCD Sum Rules

4pages, 2figures, Talk at the Yukawa International Seminar (YKIS) 2006, "New frontiers in QCD", Kyoto, Japan

Prog.Theor.Phys.Suppl.168:58-61,2007

10.1143/PTPS.168.58

hep-ph

We study pentaquark $\Theta^{+} (I=0,J=1/2)$ in the QCD sum rules emphasizing that we can not extract any properties of the pentaquark outside of the Borel window. To find the appropriate Borel window, we prepare a favorable set up of the correlators and carry out the operator product expansion up to dimension 15 within factorization hypothesis. Our procedures reduce the unwanted high energy contaminations and enhance the low energy correlation. In the Borel window, independent analyses for the chiral-even and odd sum rules give the consistent values of the $\Theta^+$ mass, $1.68\pm0.22$ GeV, and the residue. The parity is found to be {\it positive}.

0704.0414

Antoine Moreau

Antoine Moreau (LASMEA), Didier Felbacq (GES)

Leaky modes of a left-handed slab

journal of the european optical society : rapid publications 3 (2008) 08032

10.2971/jeos.2008.08032

physics.optics

http://arxiv.org/licenses/nonexclusive-distrib/1.0/

Using complex plane analysis we show that left-handed slab may support either leaky slab waves, which are backward because of negative refraction, or leaky surface waves, which are backward or forward depending on the propagation direction of the surface wave itself. Moreover, there is a general connection between the reflection coefficient of the left-handed slab and the one of the corresponding right-handed slab (with opposite permittivity and permeability) so that leaky slab modes are excited for the same angle of incidence of the impinging beam for both structures. Many negative giant lateral shifts can be explained by the excitation of these leaky modes.

0704.0415

Oleg Raichev E

O. E. Raichev

Coulomb blockade of field emission from nanoscale conductors

Phys. Rev. B 73, 195328 (2006)

10.1103/PhysRevB.73.195328

cond-mat.mes-hall

Theoretical description of the field emission of electrons from nanoscale objects weakly coupled to the cathode is presented. It is shown that the field- emission current increases in a step-like fashion due to single-electron charging which leads to abrupt changes of the effective electric field responsible for the field emission. A detailed consideration of the current-voltage characteristics is carried out for a nanocluster modelled by a metallic spherical particle in the close vicinity of the cathode and for a cylindrical silicon nanowire grown on the cathode surface.

0704.0416

Gabriela Schmithuesen

Gabriela Schmithuesen

Origamis with non congruence Veech groups

25 pages

Proceedings of 34th Symposium on Transformation Groups, Edited by T. Kawakami, Wing Co., Ltd., 2007 (p.31 - 55).

math.GT math.AG

As main result we show that for each g > 1 there is some translation surface of genus g whose Veech group is a non congruence subgroup of SL(2,Z). We use origamis/square-tiled surfaces to produce our examples. The article is divided into two parts: In the first part we introduce translation surfaces, origamis, Veech groups and Teichmueller curves and show for two origamis in genus 2 that their Veech groups are non congruence groups; in the second part we provide a technique that produces sequences of origamis whose Veech groups are decreasing. This is used to prove the main result.

0704.0417

Bernhard Baumgartner

Bernhard Baumgartner

Thermodynamic Stability - A note on a footnote in Ruelle's book

8 pages

UWThPh-2007-09

math-ph math.MP

Thermodynamic stable interaction pair potentials which are not of the form ``positive function + real continuous function of positive type'' are presented in dimension one. Construction of such a potential in dimension two is sketched. These constructions use only elementary calculations. The mathematical background is discussed separately.

0704.0418

Yu-Cheng Lin

Yu-Cheng Lin, Ferenc Igloi and Heiko Rieger

Entanglement entropy at infinite randomness fixed points in higher dimensions

References updated; Accepted for publication in Phys. Rev. Lett

Phys. Rev. Lett. 99, 147202 (2007)

10.1103/PhysRevLett.99.147202

cond-mat.dis-nn quant-ph

The entanglement entropy of the two-dimensional random transverse Ising model is studied with a numerical implementation of the strong disorder renormalization group. The asymptotic behavior of the entropy per surface area diverges at, and only at, the quantum phase transition that is governed by an infinite randomness fixed point. Here we identify a double-logarithmic multiplicative correction to the area law for the entanglement entropy. This contrasts with the pure area law valid at the infinite randomness fixed point in the diluted transverse Ising model in higher dimensions.

0704.0419

Yoonseok Lee

H.C. Choi, N. Masuhara, B.H. Moon, P. Bhupathi, M.W. Meisel, Y. Lee, N. Mulders, S. Higashitani, M. Miura, and K. Nagai

Ultrasound attenuation of superfluid $^{3}$He in aerogel

4 pages, 3 figures. Submitted to PRL

10.1103/PhysRevLett.98.225301

cond-mat.supr-con

We have performed longitudinal ultrasound (9.5 MHz) attenuation measurements in the B-phase of superfluid $^3$He in 98% porosity aerogel down to the zero temperature limit for a wide range of pressures at zero magnetic field. The absolute attenuation was determined by direct transmission of sound pulses. Compared to the bulk fluid, our results revealed a drastically different behavior in attenuation, which is consistent with theoretical accounts with gapless excitations and a collision drag effect.

0704.0420

Donald McCartor

Donald McCartor

The Hourglass - Consequences of Pure Hamiltonian Evolution of a Radiating System

12 pages, no figures

quant-ph

Hourglass is the name given here to a formal isolated quantum system that can radiate. Starting from a time when it defines the system it represents clearly and no radiation is present, it is given straightforward Hamiltonian evolution. The question of what significance hourglasses have is raised, and this question is proposed to be more consequential than the measurement problem.

0704.0421

Dragana Ili\'c

D. Urosevic, B. Vukotic, B. Arbutina, D. Ilic

The Sigma-D Relation for Planetary Nebulae: Preliminary Analysis

4 pages, 2 figures

Serb. Astron. J., vol. 174, p. 73-76 (2007)

10.2298/SAJ0774073U

astro-ph

An analysis of the relation between radio surface brightness and diameter, so-called Sigma-D relation, for planetary nebulae (PNe) is presented: i) the theoretical Sigma-D relation for the evolution of bremsstrahlung surface brightness is derived; ii) contrary to the results obtained earlier for the Galactic supernova remnant (SNR) samples, our results show that the updated sample of Galactic PNe does not severely suffer from volume selection effect - Malmquist bias (same as for the extragalactic SNR samples) and; iii) we conclude that the empirical Sigma-D relation for PNe derived in this paper is not useful for valid determination of distances for all observed PNe with unknown distances.

0704.0422

Pablo Bianucci

Pablo Bianucci, Chris Fietz, John W. Robertson, Gennady Shvets and Chih-Kang Shih

Polarization conversion in a silica microsphere

RevTeX4, 7 pages, 4 figures. Revised version, added 1 figure

Optics Express, Vol. 15, Issue 11, pp. 7000-7005 (2007)

10.1364/OE.15.007000

physics.optics

We experimentally demonstrate controlled polarization-selective phenomena in a whispering gallery mode resonator. We observed efficient ($\approx 75 %$) polarization conversion of light in a silica microsphere coupled to a tapered optical fiber with proper optimization of the polarization of the propagating light. A simple model treating the microsphere as a ring resonator provides a good fit to the observed behavior.

0704.0423

Sun Kee Kim

H. S. Lee, H. C. Bhang, J. H. Choi, H. Dao, I. S. Hahn, M. J. Hwang, S. W. Jung, W. G. Kang, D. W. Kim, H. J. Kim, S. C. Kim, S. K. Kim, Y. D. Kim, J. W. Kwak, Y. J. Kwon, J. Lee, J. H. Lee, J. I. Lee, M. J. Lee, S. J. Lee, J. Li, X. Li, Y. J. Li, S. S. Myung, S. Ryu, J. H. So, Q. Yue, J. J. Zhu

Limits on WIMP-nucleon interactions with CsI(Tl) crystal detectors

11 pages, 6 figures

Phys.Rev.Lett.99:091301,2007

10.1103/PhysRevLett.99.091301

DMRC-0701

astro-ph

The Korea Invisible Mass Search(KIMS) experiment presents new limits on WIMP-nucleon cross section using the data from an exposure of 3409 kgd taken with low background CsI(Tl) crystals at Yangyang underground laboratory. The most stringent limit on the spin dependent interaction for pure proton case is obtained. The DAMA signal region for both spin independent and spin dependent interactions for the WIMP mass higher than 20 GeV/c^2are excluded by the single experiment with crystal scintillators.

0704.0424

Luo Xiao-Feng

Xiao-Feng Luo, Xin Dong, Ming Shao, Ke-Jun Wu, Cheng Li, Hong-Fang Chen, Hu-Shan Xu

Stopping effects in U+U collisions with a beam energy of 520 MeV/nucleon

7 pages, 9 figures. Phys. Rev. C 76, 044902 (2007)

Phys.Rev.C76:044902,2007

10.1103/PhysRevC.76.044902

nucl-ex

A Relativistic Transport Model (ART1.0) is applied to simulate the stopping effects in tip-tip and body-body U+U collisions, at a beam kinetic energy of 520 MeV/nucleon. Our simulation results have demonstrated that both central collisions of the two extreme orientations can achieve full stopping, and also form a bulk of hot, dense nuclear matter with a sufficiently large volume and long duration, due to the largely deformed uranium nuclei. The nucleon sideward flow in the tip-tip collisions is nearly 3 times larger than that in body-body ones at normalized impact parameter $b/b_{max}<0.5$, and that the body-body central collisions have a largest negative nucleon elliptic flow $v_{2}=-12%$ in contrast to zero in tip-tip ones. Thus the extreme circumstance and the novel experimental observables in tip-tip and body-body collisions can provide a good condition and sensitive probe to study the nuclear EoS, respectively. The Cooling Storage Ring (CSR) External Target Facility (ETF) to be built at Lanzhou, China, delivering the uranium beam up to 520 MeV/nucleon is expected to make significant contribution to explore the nuclear equation of state (EoS).

0704.0425

Tobias Gleim

Tobias Gleim

QED for fields obeying a square root operator equation

hep-th

Instead of using local field equations - like the Dirac equation for spin-1/2 and the Klein-Gordon equation for spin-0 particles - one could try to use non-local field equations in order to describe scattering processes. The latter equations can be obtained by means of the relativistic energy together with the correspondence principle, resulting in equations with a square root operator. By coupling them to an electromagnetic field and expanding the square root (and taking into account terms of quadratic order in the electromagnetic coupling constant e), it is possible to calculate scattering matrix elements within the framework of quantum electrodynamics, e.g. like those for Compton scattering or for the scattering of two identical particles. This will be done here for the scalar case. These results are then compared with the corresponding ones based on the Klein-Gordon equation. A proposal of how to transfer these reflections to the spin-1/2 case is also presented.

0704.0426

Leonid Chuzhoy

Leonid Chuzhoy, Michael Kuhlen, Paul R. Shapiro

Feedback from first radiation sources: H- photodissociation

4 pages, 2 figures

Astrophys.J.665:L85-L88, 2007

10.1086/521438

astro-ph

During the epoch of reionization, the formation of radiation sources is accompanied by the growth of a H- photodissociating flux. We estimate the impact of this flux on the formation of molecular hydrogen and cooling in the first galaxies, assuming different types of radiation sources (e.g. Pop II and Pop III stars, miniquasars). We find that H- photodissociation reduces the formation of H2 molecules by a factor of ~1+1000k_s*x/(f_esc*delta), where x is the mean ionized fraction in the IGM, f_esc is the fraction of ionizing photons that escape from their progenitor halos, delta is the local gas overdensity and k_s is an order unity constant which depends on the type of radiation source. By the time a significant fraction of the universe becomes ionized, H- photodissociation may significantly reduce the H2 abundance and, with it, the primordial star formation rate, delaying the progress of reionization.

0704.0427

Ettore Vicari

Martin Hasenbusch, Francesco Parisen Toldin, Andrea Pelissetto, Ettore Vicari

The 3D +-J Ising model at the ferromagnetic transition line

23 pages, 12 figs

Phys. Rev. B 76 (2007) 094402

10.1103/PhysRevB.76.094402

cond-mat.dis-nn cond-mat.stat-mech

We study the critical behavior of the three-dimensional $\pm J$ Ising model [with a random-exchange probability $P(J_{xy}) = p \delta(J_{xy} - J) + (1-p) \delta(J_{xy} + J)$] at the transition line between the paramagnetic and ferromagnetic phase, which extends from $p=1$ to a multicritical (Nishimori) point at $p=p_N\approx 0.767$. By a finite-size scaling analysis of Monte Carlo simulations at various values of $p$ in the region $p_N<p<1$, we provide strong numerical evidence that the critical behavior along the ferromagnetic transition line belongs to the same universality class as the three-dimensional randomly-dilute Ising model. We obtain the results $\nu=0.682(3)$ and $\eta=0.036(2)$ for the critical exponents, which are consistent with the estimates $\nu=0.683(2)$ and $\eta=0.036(1)$ at the transition of randomly-dilute Ising models.

0704.0428

David Ciardi

David R. Ciardi and Cynthia Gomez Martin

Star Formation in the Bok Globule CB54

Accepted for Publication in The Astrophysical Journal

Astrophys.J.664:377-383,2007

10.1086/518651

astro-ph

We present mid-infrared (10.4 \micron, 11.7 \micron, and 18.3 \micron) imaging intended to locate and characterize the suspected protostellar components within the Bok globule CB54. We detect and confirm the protostellar status for the near-infrared source CB54YC1-II. The mid-infrared luminosity for CB54YC1-II was found to be $L_{midir} \approx 8 L_\sun$, and we estimate a central source mass of $M_* \approx 0.8 M_\sun$ (for a mass accretion rate of ${\dot M}=10^{-6} M_\sun yr^{-1}$). CB54 harbors another near-infrared source (CB54YC1-I), which was not detected by our observations. The non-detection is consistent with CB54YC1-I being a highly extinguished embedded young A or B star or a background G or F giant. An alternative explanation for CB54YC1-I is that the source is an embedded protostar viewed at an extremely high inclination angle, and the near-infrared detections are not of the central protostar, but of light scattered by the accretion disk into our line of sight. In addition, we have discovered three new mid-infrared sources, which are spatially coincident with the previously known dense core in CB54. The source temperatures ($\sim100$K) and association of the mid-infrared sources with the dense core suggests that these mid-infrared objects may be embedded class 0 protostars.

0704.0429

Ping Ao

P. Ao

Quantitative Resolution to some "Absolute Discrepancies" in Cancer Theories: a View from Phage lambda Genetic Switch

latex, 7 pages

CellularOncology29:67-69,2007

q-bio.SC q-bio.CB

Is it possible to understand cancer? Or more specifically, is it possible to understand cancer from genetic side? There already many answers in literature. The most optimistic one has claimed that it is mission-possible. Duesberg and his colleagues reviewed the impressive amount of research results on cancer accumulated over 100 years. It confirms the a general opinion that considering all available experimental results and clinical observations there is no cancer theory without major difficulties, including the prevailing gene-based cancer theories. They have then listed 9 "absolute discrepancies" for such cancer theory. In this letter the quantitative evidence against one of their major reasons for dismissing mutation cancer theory, by both in vivo experiment and a first principle computation, is explicitly pointed out.

0704.0430

Alvaro Pelayo

J.J. Duistermaat and A. Pelayo

Reduced phase space and toric variety coordinatizations of Delzant spaces

18 pages

math.SG math.AG

In this note we describe the natural coordinatizations of a Delzant space defined as a reduced phase space (symplectic geometry view-point) and give explicit formulas for the coordinate transformations. For each fixed point of the torus action on the Delzant polytope, we have a maximal coordinatization of an open cell in the Delzant space which contains the fixed point. This cell is equal to the domain of definition of one of the natural coordinatizations of the Delzant space as a toric variety (complex algebraic geometry view-point), and we give an explicit formula for the toric variety coordinates in terms of the reduced phase space coordinates. We use considerations in the maximal coordinate neighborhoods to give simple proofs of some of the basic facts about the Delzant space, as a reduced phase space, and as a toric variety. These can be viewed as a first application of the coordinatizations, and serve to make the presentation more self-contained.

0704.0431

Burkhard Zink

Burkhard Zink, Nikolaos Stergioulas, Ian Hawke, Christian D. Ott, Erik Schnetter, Ewald Mueller

Fragmentation of general relativistic quasi-toroidal polytropes

2 pages, 1 figure. Submitted to the Proceedings of the 11th Marcel Grossmann Meeting (MG11) in Berlin, Germany, July 23-29, 2006

10.1142/9789812834300_0199

gr-qc astro-ph.HE

We investigate the role of rotational instabilities in the context of black hole formation in relativistic stars. In addition to the standard scenario - an axially symmetric dynamical instability forming a horizon at the star's center - the recently found low-$T/|W|$ instabilities are shown to lead to fragmentation and off-center horizon formation in differentially rotating stars. This process might be an alternative pathway to produce SMBHs from supermassive stars with inefficient angular momentum transport.

0704.0432

Fusun Akman

Fusun Akman and Lucian M. Ionescu

A Survey of Huebschmann and Stasheff's Paper: Formal Solution of the Master Equation via HPT and Deformation Theory

24 pages

math.QA

These notes, based on the paper "Formal Solution of the Master Equation via HPT and Deformation Theory" by Huebschmann and Stasheff, were prepared for a series of talks at Illinois State University with the intention of applying Homological Perturbation Theory to the derived bracket constructions of Kosmann-Schwarzbach and T. Voronov, and eventually writing Part II of the paper "Higher Derived Brackets and Deformation Theory I" by the present authors.

0704.0433

Antonio De Nicola

Antonio De Nicola, Wlodzimierz M. Tulczyjew

A variational formulation of electrodynamics with external sources

23 pages, to appear in Int. J. Geom. Methods Mod. Phys. (IJGMMP)

Int. J. Geom. Methods Mod. Phys. 6 (2009), 173-200

10.1142/S0219887809003461

math-ph math.DG math.MP

http://arxiv.org/licenses/nonexclusive-distrib/1.0/

We present a variational formulation of electrodynamics using de Rham even and odd differential forms. Our formulation relies on a variational principle more complete than the Hamilton principle and thus leads to field equations with external sources and permits the derivation of the constitutive relations. We interpret a domain in space-time as an odd de Rham 4-current. This permits a treatment of different types of boundary problems in an unified way. In particular we obtain a smooth transition to the infinitesimal version by using a current with a one point support.

0704.0434

Viatcheslav Berejnov V

Viatcheslav V. Berejnov

Protein and ionic surfactants - promoters and inhibitors of contact line pinning

3 pages, 4 figures

physics.chem-ph physics.flu-dyn

We report a new effect of surfactants in pinning a drop contact line, specifically that lysozyme promotes while lauryl sulfate inhibits pinning. We explain the pinning disparity assuming difference in wetting: the protein-laden drop wets a "clean" surface and the surfactant-laden drop wets an auto-precursored surface.

0704.0435

Marcello Ortaggio

Vojtech Pravda, Alena Pravdova, Marcello Ortaggio

Type D Einstein spacetimes in higher dimensions

24 pages. v2: new appendix on geometric optics of higher dimensional Kerr-NUT-AdS black holes, minor changes in the text. To appear in Class.Quant.Grav

Class.Quant.Grav.24:4407-4428,2007

10.1088/0264-9381/24/17/009

gr-qc hep-th

We show that all static spacetimes in higher dimensions are of Weyl types G, I_i, D or O. This applies also to stationary spacetimes if additional conditions are fulfilled, as for most known black hole/ring solutions. (The conclusions change when the Killing generator becomes null, such as at Killing horizons.) Next we demonstrate that the same Weyl types characterize warped product spacetimes with a one-dimensional Lorentzian (timelike) factor, whereas warped spacetimes with a two-dimensional Lorentzian factor are restricted to the types D or O. By exploring the Bianchi identities, we then analyze the simplest non-trivial case from the above classes - type D vacuum spacetimes, possibly with a cosmological constant, dropping, however, the assumptions that the spacetime is static, stationary or warped. It is shown that for ``generic'' type D vacuum spacetimes the corresponding principal null directions are geodetic in any dimension (this applies also to type II spacetimes). For n>=5, however, there may exist particular cases of type D spacetimes which admit non-geodetic multiple principal null directions and we present such examples in any n>=7. Further studies are restricted to five dimensions, where the type D Weyl tensor is described by a 3x3 matrix \Phi_{ij}. In the case with ``twistfree'' (A_{ij}=0) principal null geodesics we show that in a ``generic'' case \Phi_{ij} is symmetric and eigenvectors of \Phi_{ij} coincide with those of the expansion matrix S_{ij}, providing us with three preferred spacelike directions of the spacetime. Similar results are also obtained when relaxing the twistfree condition and assuming instead that \Phi_{ij} is symmetric. The n=5 Myers-Perry black hole and Kerr-NUT-AdS metrics in arbitrary dimension are briefly studied as specific examples of type D vacuum spacetime.

0704.0436

Ying-Qiu Gu

Ying-Qiu Gu, Ta-tsien Li

Eigen Equation of the Nonlinear Spinor

8 pages, no figures

physics.gen-ph

How to effectively solve the eigen solutions of the nonlinear spinor field equation coupling with some other interaction fields is important to understand the behavior of the elementary particles. In this paper, we derive a simplified form of the eigen equation of the nonlinear spinor, and then propose a scheme to solve their numerical solutions. This simplified equation has elegant and neat structure, which is more convenient for both theoretical analysis and numerical computation.

0704.0437

Pamela Morehouse

CLEO Collaboration: T. K. Pedlar, et al

Measurement of B(D_S^+ --> ell^+ nu) and the Decay Constant f_D_{S^+}

24 pages postscript,also available through http://www.lns.cornell.edu/public/CLNS/2007/, Submitted to PRD

Phys.Rev.D76:072002,2007

10.1103/PhysRevD.76.072002

CLNS 07/1990, CLEO 07-02

hep-ex hep-lat hep-ph

We examine e+e- --> Ds- Ds*+ and Ds*- Ds+ interactions at 4170 MeV using the CLEO-c detector in order to measure the decay constant fDs+. We use the Ds+ --> l+ nu channel, where the l+ designates either a mu+ or a tau+, when the tau+ --> pi+ nu. Analyzing both modes independently, we determine B(Ds+ --> mu+ nu) = (0.594 +- 0.066 +- 0.031)%, and B(Ds+ --> tau+ nu) = (8.0 +- 1.3 +- 0.4)%. We also analyze them simultaneously to find an effective value of B{eff}(Ds+ --> mu+ nu) = (0.638 +- 0.059 +- 0.033)% and extract fDs = (274 +- 13 +- 7) MeV. Combining with our previous determination of B(D+ -> mu+ nu), we also find the ratio fDs/fD+ = 1.23 +- 0.11 +- 0.04. We compare to current theoretical estimates. Finally, we find B(Ds+ --> e+ nu) < 1.3 x10^{-4} at 90% confidence level.

0704.0438

Michael Graesser

Michael L. Graesser

Broadening the Higgs Boson with Right-Handed Neutrinos and a Higher Dimension Operator at the Electroweak Scale

17+1 pages. Corrected a small error and updated references

Phys.Rev.D76:075006,2007

10.1103/PhysRevD.76.075006

RUNHETC-04-2007

hep-ph

The existence of certain TeV suppressed higher-dimension operators may open up new decay channels for the Higgs boson to decay into lighter right-handed neutrinos. These channels may dominate over all other channels if the Higgs boson is light. For a Higgs boson mass larger than $2 m_W$ the new decays are subdominant yet still of interest. The right-handed neutrinos have macroscopic decay lengths and decay mostly into final states containing leptons and quarks. A distinguishing collider signature of this scenario is a pair of displaced vertices violating lepton number. A general operator analysis is performed using the minimal flavor violation hypothesis to illustrate that these novel decay processes can occur while remaining consistent with experimental constraints on lepton number violating processes. In this context the question of whether these new decay modes dominate is found to depend crucially on the approximate flavor symmetries of the right-handed neutrinos.

0704.0439

James Nesteroff

Dmitri V. Averin and James A. Nesteroff

Coulomb blockade of anyons

Published version, 4 pages including 3 figures

Phys. Rev. Lett. 99, 096801 (2007)

10.1103/PhysRevLett.99.096801

cond-mat.mes-hall

Coulomb interaction turns anyonic quasiparticles of a primary quantum Hall liquid with filling factor $\nu =1/(2m+1)$ into hard-core anyons. We have developed a model of coherent transport of such quasiparticles in systems of multiple antidots by extending the Wigner-Jordan description of 1D abelian anyons to tunneling problems. We show that the anyonic exchange statistics manifests itself in tunneling conductance even in the {\em absence} of quasiparticle exchanges. In particular, it can be seen as a non-vanishing resonant peak associated with quasiparticle tunneling through a line of three antidots.

0704.0440

Damski Bogdan

Bogdan Damski and Wojciech H. Zurek

Dynamics of a quantum phase transition in a ferromagnetic Bose-Einstein condensate

4 pages & figures, significantly improved presentation with respect to the first submission

Phys.Rev.Lett.99:130402,2007

10.1103/PhysRevLett.99.130402

LAUR-07-1400

cond-mat.other hep-th quant-ph

We discuss dynamics of a slow quantum phase transition in a spin-1 Bose-Einstein condensate. We determine analytically the scaling properties of the system magnetization and verify them with numerical simulations in a one dimensional model.

0704.0441

Jens Rodmann

J. Setiawan (1), P. Weise (1), Th. Henning (1), R. Launhardt (1), A. M\"uller (1), J. Rodmann (2) ((1) Max Planck Institute for Astronomy, Heidelberg, Germany, (2) European Space Agency / ESTEC, Noordwijk, The Netherlands)

Evidence for a planetary companion around a nearby young star

11 pages, 4 figures, to be published in ApJL

10.1086/518213

astro-ph

We report evidence for a planetary companion around the nearby young star HD 70573. The star is a G type dwarf located at a distance of 46 pc with age estimation between 20 and 300 Myrs. We carried out spectroscopic observations of this star with FEROS at the 2.2 m MPG/ESO telescope at La Silla. Our spectroscopic analysis yields a spectral type of G1-1.5V and an age of about 100 Myrs. Variations in stellar radial velocity of HD 70573 have been monitored since December 2003 until January 2007. The velocity accuracy of FEROS within this period is about 10 m/s. HD 70573 shows a radial velocity variation with a period of 852 +/- 12 days and a semi-amplitude of 149 +/- 6 m/s. The period of this variation is significantly longer than its rotational period, which is 3.3 days. Based on the analysis of the Ca II K emission line, Halpha and Teff variation as stellar activity indicators as well as the lack of a correlation between the bisector velocity span and the radial velocity, we can exclude the rotational modulation and non-radial pulsations as the source of the long-period radial velocity variation. Thus, the presence of a low-mass companion around the star provides the best explanation for the observed radial velocity variation. Assuming a primary mass m1=1.0 +/- 0.1 Msun for the host star, we calculated a minimum mass of the companion m2sini of 6.1 Mjup, which lies in the planetary mass regime, and an orbital semi-major axis of 1.76 AU. The orbit of the planet has an eccentricity of e=0.4. The planet discovery around the young star HD 70573 gives an important input for the study of debris disks around young stars and their relation to the presence of planets.

0704.0442

Claudio Conti

Alessandro Ciattoni, Claudio Conti

Quantum electromagnetic X-waves

4 pages

JOSA B, Vol. 24, Issue 9, pp. 2195-2198 (2007)

10.1364/JOSAB.24.002195

physics.optics physics.gen-ph quant-ph

We show that two distinct quantum states of the electromagnetic field can be associated to a classical vector X wave or a propagation-invariant solution of Maxwell equations. The difference between the two states is of pure quantum mechanical origin since they are internally entangled and disentangled, respectively and can be generated by different linear or nonlinear processes. Detection and generation of Schr\"odinger-cat states comprising two entangled X-waves and their possible applications are discussed.

0704.0443

Vadim Lensky

V. Lensky, V. Baru, E. Epelbaum, C. Hanhart, J. Haidenbauer, A. Kudryavtsev, Ulf-G. Mei{\ss}ner

Neutron-neutron scattering length from the reaction gamma d --> pi^+ nn employing chiral perturbation theory

14 pages, 8 figures

Eur.Phys.J.A33:339-348,2007

10.1140/epja/i2007-10461-y

FZJ-IKP-TH-2007-13, HISKP-TH-07/12

nucl-th nucl-ex

We discuss the possibility to extract the neutron-neutron scattering length a_{nn} from experimental spectra on the reaction gamma d --> pi^+ nn. The transition operator is calculated to high accuracy from chiral perturbation theory. We argue that for properly chosen kinematics, the theoretical uncertainty of the method can be as low as 0.1 fm.

0704.0444

Jacob Bourjaily

Jacob L. Bourjaily

Multiple Unfoldings of Orbifold Singularities: Engineering Geometric Analogies to Unification

4 pages, 2 figures.

10.1103/PhysRevD.79.046005

hep-th

Katz and Vafa showed how charged matter can arise geometrically by the deformation of ADE-type orbifold singularities in type IIa, M-theory, and F-theory compactifications. In this paper we use those same basic ingredients, used there to geometrically engineer specific matter representations, here to deform the compactification manifold itself in a way which naturally compliments many features of unified model building. We realize this idea explicitly by deforming a manifold engineered to give rise to an $SU_5$ grand unified model into a one giving rise to the Standard Model. In this framework, the relative local positions of the singularities giving rise to Standard Model fields are specified in terms of the values of a small number of complex structure moduli which deform the original manifold, greatly reducing the arbitrariness of their relative positions.

0704.0445

Jacob Bourjaily

Jacob L. Bourjaily

Geometrically Engineering the Standard Model: Locally Unfolding Three Families out of E8

10 pages, 3 figures. Corrected typos and general editing blemishes

Phys.Rev.D76:046004,2007

10.1103/PhysRevD.76.046004

hep-th

This paper extends and builds upon the results of an earlier paper, in which we described how to use the tools of geometrical engineering to deform geometrically-engineered grand unified models into ones with lower symmetry. This top-down unfolding has the advantage that the relative positions of singularities giving rise to the many `low energy' matter fields are related by only a few parameters which deform the geometry of the unified model. And because the relative positions of singularities are necessary to compute the superpotential, for example, this is a framework in which the arbitrariness of geometrically engineered models can be greatly reduced. In our earlier paper, this picture was made concrete for the case of deforming the representations of an SU(5) model into their Standard Model content. In this paper we continue that discussion to show how a geometrically engineered 16 of SO(10) can be unfolded into the Standard Model, and how the three families of the Standard Model uniquely emerge from the unfolding of a single, isolated E8 singularity.

0704.0446

Francesco Polizzi

Giovanna Carnovale, Francesco Polizzi

The classification of surfaces with p_g=q=1 isogenous to a product of curves

19 pages. Final version, to appear in Adv. Geom

Adv. Geom. 9 (2009), 233-256

10.1515/ADVGEOM.2009.015

math.AG math.GR

http://arxiv.org/licenses/nonexclusive-distrib/1.0/

A projective surface S is said to be isogenous to a product if there exist two smooth curves C, F and a finite group G acting freely on C \times F so that S=(C \times F)/G. In this paper we classify all surfaces with p_g=q=1 which are isogenous to a product.

0704.0447

Georgios Kavoulakis

J. Christensson (1), S. Bargi (1), K. Karkkainen (1), Y. Yu (1), G. M. Kavoulakis (1), M. Manninen (2), and S. M. Reimann (1) ((1) LTH, Lund, (2) Jyvaskyla)

Manipulating the rotational properties of a two-component Bose gas

4 pages, RevTex, 4 figures

New J. Phys., 10 (2008) 033029

10.1088/1367-2630/10/3/033029

cond-mat.mes-hall

A rotating, two-component Bose-Einstein condensate is shown to exhibit vortices of multiple quantization, which are possible due to the interatomic interactions between the two species. Also, persistent currents are absent in this system. Finally, the order parameter has a very simple structure for a range of angular momenta.

0704.0448

Richard Edgar

R. G. Edgar

Giant Planet Migration in Viscous Power-Law Discs

Accepted by ApJ Figures adjusted for astro-ph

Astrophys.J.663:1325-1334,2007

10.1086/518591

astro-ph

Many extra-solar planets discovered over the past decade are gas giants in tight orbits around their host stars. Due to the difficulties of forming these `hot Jupiters' in situ, they are generally assumed to have migrated to their present orbits through interactions with their nascent discs. In this paper, we present a systematic study of giant planet migration in power law discs. We find that the planetary migration rate is proportional to the disc surface density. This is inconsistent with the assumption that the migration rate is simply the viscous drift speed of the disc. However, this result can be obtained by balancing the angular momentum of the planet with the viscous torque in the disc. We have verified that this result is not affected by adjusting the resolution of the grid, the smoothing length used, or the time at which the planet is released to migrate.

0704.0449

Volker Braun

Volker Braun, Maximilian Kreuzer, Burt A. Ovrut, Emanuel Scheidegger

Worldsheet Instantons and Torsion Curves, Part B: Mirror Symmetry

59 pages, LaTeX

JHEP0710:023,2007

10.1088/1126-6708/2007/10/023

UPR 1178-T, DISTA-2007, TUW-07-08

hep-th

We apply mirror symmetry to the problem of counting holomorphic rational curves in a Calabi-Yau threefold X with Z_3 x Z_3 Wilson lines. As we found in Part A [hep-th/0703182], the integral homology group H_2(X,Z)=Z^3 + Z_3 + Z_3 contains torsion curves. Using the B-model on the mirror of X as well as its covering spaces, we compute the instanton numbers. We observe that X is self-mirror even at the quantum level. Using the self-mirror property, we derive the complete prepotential on X, going beyond the results of Part A. In particular, this yields the first example where the instanton number depends on the torsion part of its homology class. Another consequence is that the threefold X provides a non-toric example for the conjectured exchange of torsion subgroups in mirror manifolds.

0704.0450

Maria Carolina O. Aguiar

M. C. O. Aguiar, V. Dobrosavljevic, E. Abrahams, G. Kotliar

Disorder screening near the Mott-Anderson transition

2 pages, 3 figures, submitted to SCES proceedings

Physica B 403, 1417 (2008)

10.1016/j.physb.2007.10.213

cond-mat.str-el

Correlation-driven screening of disorder is studied within the typical-medium dynamical mean-field theory (TMT-DMFT) of the Mott-Anderson transition. In the strongly correlated regime, the site energies epsilon_R^i characterizing the effective disorder potential are strongly renormalized due to the phenomenon of Kondo pinning. This effect produces very strong screening when the interaction U is stronger then disorder W, but applies only to a fraction of the sites in the opposite limit (U<W).

0704.0451

Douglas Natelson

D.R. Ward, N.K. Grady, C.S. Levin, N.J. Halas, Y. Wu, P. Nordlander, D. Natelson

Electromigrated nanoscale gaps for surface-enhanced Raman spectroscopy

29 pages, 11 figures (includes supp. material)

Nano Lett. 7, 1396-1400 (2007)

10.1021/nl070625w

cond-mat.mes-hall

Single-molecule detection with chemical specificity is a powerful and much desired tool for biology, chemistry, physics, and sensing technologies. Surface-enhanced spectroscopies enable single molecule studies, yet reliable substrates of adequate sensitivity are in short supply. We present a simple, scaleable substrate for surface-enhanced Raman spectroscopy (SERS) incorporating nanometer-scale electromigrated gaps between extended electrodes. Molecules in the nanogap active regions exhibit hallmarks of very high Raman sensitivity, including blinking and spectral diffusion. Electrodynamic simulations show plasmonic focusing, giving electromagnetic enhancements approaching those needed for single-molecule SERS.

0704.0452

Chulhoon Chang

Chulhoon Chang and Wei Cui

Dramatic Variability of X-ray Absorption Lines in the Black Hole Candidate Cygnus X-1

19 pages, 7 figures, 1 table, accepted by ApJ

Astrophys.J.663:1207-1214,2007

10.1086/518639

astro-ph

We report results from a 30 ks observation of Cygnus X-1 with the High Energy Transmission Grating Spectrometer (HETGS) on board the {\em Chandra X-ray Observatory}. Numerous absorption lines were detected in the HETGS spectrum. The lines are associated with highly ionized Ne, Na, Mg, Al, Si, S, and Fe, some of which have been seen in earlier HETGS observations. Surprisingly, however, we discovered dramatic variability of the lines over the duration of the present observation. For instance, the flux of the Ne X line at 12.14 \AA\ was about $5 \times 10^{-3}$ photons cm$^{-2}$ s$^{-1}$ in the early part of the observation but became subsequently undetectable, with a 99% upper limit of $0.06 \times 10^{-3}$ photons cm$^{-2}$ s$^{-1}$ on the flux of the line. This implies that the line weakened by nearly two orders of magnitude on a timescale of hours. The overall X-ray flux of the source did also vary during the observation but only by 20--30%. For Cyg X-1, the absorption lines are generally attributed to the absorption of X-rays by ionized stellar wind in the binary system. Therefore, they may provide valuable diagnostics on the physical condition of the wind. We discuss the implications of the results.

0704.0453

Pierre Richard

P. Richard, M. Neupane, Y.-M. Xu, P. Fournier, S. Li, Pengcheng Dai, Z. Wang and H. Ding

Antiferromagnetism-superconductivity competition in electron-doped cuprates triggered by oxygen reduction

4 pages, 4 figures

Physical Review Letters 99, 157002 (2007)

10.1103/PhysRevLett.99.157002

cond-mat.supr-con cond-mat.str-el

We have performed a systematic angle-resolved photoemission study of as-grown and oxygen-reduced Pr$_{2-x}$Ce$_x$CuO$_4$ and Pr$_{1-x}$LaCe$_{x}$CuO$_4$ electron-doped cuprates. In contrast to the common belief, neither the band filling nor the band parameters are significantly affected by the oxygen reduction process. Instead, we show that the main electronic role of the reduction process is to remove an anisotropic leading edge gap around the Fermi surface. While the nodal leading edge gap is induced by long-range antiferomagnetic order, the origin of the antinodal one remains unclear.

0704.0454

David Bennett

D.P. Bennett, J. Anderson, J.-P. Beaulieu, I. Bond, E. Cheng, K. Cook, S. Friedman, B.S. Gaudi, A. Gould, J. Jenkins, R. Kimble, D. Lin, M. Rich, K. Sahu, D. Tenerelli, A. Udalski, and P. Yock

An Extrasolar Planet Census with a Space-based Microlensing Survey

White Paper Submitted to the NASA/NSF ExoPlanet Task Force

astro-ph

A space-based gravitational microlensing exoplanet survey will provide a statistical census of exoplanets with masses down to 0.1 Earth-masses and orbital separations ranging from 0.5AU to infinity. This includes analogs to all the Solar System's planets except for Mercury, as well as most types of planets predicted by planet formation theories. Such a survey will provide results on the frequency of planets around all types of stars except those with short lifetimes. Close-in planets with separations < 0.5 AU are invisible to a space-based microlensing survey, but these can be found by Kepler. Other methods, including ground-based microlensing, cannot approach the comprehensive statistics on the mass and semi-major axis distribution of extrasolar planets that a space-based microlensing survey will provide. The terrestrial planet sensitivity of a ground-based microlensing survey is limited to the vicinity of the Einstein radius at 2-3 AU, and space-based imaging is needed to identify and determine the mass of the planetary host stars for the vast majority of planets discovered by microlensing. Thus, a space-based microlensing survey is likely to be the only way to gain a comprehensive understanding of the nature of planetary systems, which is needed to understand planet formation and habitability. The proposed Microlensing Planet Finder (MPF) mission is an example of a space-based microlensing survey that can accomplish these objectives with proven technology and a cost that fits comfortably under the NASA Discovery Program cost cap.

0704.0455

Adam Kraus

Adam L. Kraus, Lynne A. Hillenbrand (Caltech)

USco1606-1935: An Unusually Wide Low-Mass Triple System?

Accepted to ApJ; 11 pages, 6 figures in emulateapj format

Astrophys.J.664:1167-1175,2007

10.1086/518826

astro-ph

We present photometric, astrometric, and spectroscopic observations of USco160611.9-193532 AB, a candidate ultrawide (~1600 AU), low-mass (M_tot~0.4 M_sun) multiple system in the nearby OB association Upper Scorpius. We conclude that both components are young, comoving members of the association; we also present high-resolution observations which show that the primary is itself a close binary system. If the Aab and B components are gravitationally bound, the system would fall into the small class of young multiple systems which have unusually wide separations as compared to field systems of similar mass. However, we demonstrate that physical association can not be assumed purely on probabilistic grounds for any individual candidate system in this separation range. Analysis of the association's two-point correlation function shows that there is a significant probability (25%) that at least one pair of low-mass association members will be separated in projection by <15", so analysis of the wide binary population in Upper Sco will require a systematic search for all wide systems; the detection of another such pair would represent an excess at the 98% confidence level.

0704.0456

Daniel Arteaga

Daniel Arteaga

Particle propagation in cosmological backgrounds

7 pages. To appear in the proceedings of the IRGAC 2006 conference

J.Phys.A40:6901-6906,2007

10.1088/1751-8113/40/25/S37

gr-qc

We study the quantum propagation of particles in cosmological backgrounds, by considering a doublet of massive scalar fields propagating in an expanding universe, possibly filled with radiation. We focus on the dissipative effects related to the expansion rate. At first order, we recover the expected result that the decay rate is determined by the local temperature. Beyond linear order, the decay rate has an additional contribution governed by the expansion parameter. This latter contribution is present even for stable particles in the vacuum. Finally, we analyze the long time behaviour of the propagator and briefly discuss applications to the trans-Planckian question.

0704.0457

Miles P. Blencowe

M. P. Blencowe, E. Buks

Quantum analysis of a linear DC SQUID mechanical displacement detector

33 pages, 4 figures, published version

Physical Review B 76, 014511 (2007)

10.1103/PhysRevB.76.014511

cond-mat.supr-con cond-mat.mes-hall quant-ph

We provide a quantum analysis of a DC SQUID mechanical displacement detector within the sub-critical Josephson current regime. A segment of the SQUID loop forms the mechanical resonator and motion of the latter is transduced inductively through changes in the flux threading the loop. Expressions are derived for the detector signal response and noise, which are used to evaluate the position and force detection sensitivity. We also investigate cooling of the mechanical resonator due to back reaction noise from the detector.

0704.0458

Jo-Anne Brown

J.C. Brown, M. Haverkorn, B.M. Gaensler, A.R. Taylor, N.S. Bizunok, N.M. McClure-Griffiths, J.M. Dickey, A.J. Green

Rotation Measures of Extragalactic Sources Behind the Southern Galactic Plane: New Insights into the Large-Scale Magnetic Field of the Inner Milky Way

16 pages, 4 colour figures, 1 B/W figure, 1 table; Accepted for publication in ApJ on March 26, 2007

Astrophys.J.663:258-266,2007

10.1086/518499

astro-ph

We present new Faraday rotation measures (RMs) for 148 extragalactic radio sources behind the southern Galactic plane (253o < l < 356o, |b| < 1.5o), and use these data in combination with published data to probe the large-scale structure of the Milky Way's magnetic field. We show that the magnitudes of these RMs oscillate with longitude in a manner that correlates with the locations of the Galactic spiral arms. The observed pattern in RMs requries the presence of at least one large-scale magnetic reversal in the fourth Galactic quadrant, located between the Sagittarius- Carina and Scutum-Crux spiral arms. To quantitatively compare our measurements to other recent studies, we consider all available extragalactic and pulsar RMs in the region we have surveyed, and jointly fit these data to simple models in which the large-scale field follows the spiral arms. In the best-fitting model, the magnetic field in the fourth Galactic quadrant is directed clockwise in the Sagittarius-Carina spiral arm (as viewed from the North Galactic pole), but is oriented counter- clockwise in the Scutum-Crux arm. This contrasts with recent analyses of pulsar RMs alone, in which the fourth-quadrant field was presumed to be directed counter-clockwise in the Sagittarius- Carina arm. Also in contrast to recent pulsar RM studies, our joint modeling of pulsar and extragalactic RMs demonstrates that large numbers of large-scale magnetic field reversals are not required to account for observations.

0704.0459

Yahya Ould Hamidoune

Yahya Ould Hamidoune

On iterated image size for point-symmetric relations

math.CO

Let $\Gamma =(V,E)$ be a point-symmetric reflexive relation and let $v\in V$ such that $|\Gamma (v)|$ is finite (and hence $|\Gamma (x)|$ is finite for all $x$, by the transitive action of the group of automorphisms). Let $j\in \N$ be an integer such that $\Gamma ^j(v)\cap \Gamma ^{-}(v)=\{v\}$. Our main result states that $$ |\Gamma ^{j} (v)|\ge | \Gamma ^{j-1} (v)| + |\Gamma (v)|-1.$$ As an application we have $ |\Gamma ^{j} (v)| \ge 1+(|\Gamma (v)|-1)j.$ The last result confirms a recent conjecture of Seymour in the case of vertex-symmetric graphs. Also it gives a short proof for the validity of the Caccetta-H\"aggkvist conjecture for vertex-symmetric graphs and generalizes an additive result of Shepherdson.

0704.0460

Joshua Pepper

Joshua Pepper (1), Richard W. Pogge (1), D. L. DePoy (1), J. L. Marshall (1), K. Z. Stanek (1), Amelia M. Stutz (2), Shawn Poindexter (1), Robert Siverd (1), Thomas P. O'Brien (1), Mark Trueblood (3), Patricia Trueblood (3) ((1) The Ohio State University Department of Astronomy, (2) University of Arizona Department of Astronomy, (3) Winer Observatory)

The Kilodegree Extremely Little Telescope (KELT): A Small Robotic Telescope for Large-Area Synoptic Surveys

21 pages, 13 figures; accepted to PASP

Publ.Astron.Soc.Pac.119:923,2007

10.1086/521836

astro-ph

The Kilodegree Extremely Little Telescope (KELT) project is a survey for planetary transits of bright stars. It consists of a small-aperture, wide-field automated telescope located at Winer Observatory near Sonoita, Arizona. The telescope surveys a set of 26 x 26 degree fields, together covering about 25% of the Northern sky, targeting stars in the range of 8<V<10 mag, searching for transits by close-in Jupiters. This paper describes the system hardware and software and discusses the quality of the observations. We show that KELT is able to achieve the necessary photometric precision to detect planetary transits around solar-type main sequence stars.

0704.0461

Anil Shaji

Thomas F. Jordan, Anil Shaji and E. C. G. Sudarshan

Entanglement increase from local interactions with not-completely-positive maps

6 Pages, new title, substantially revised

10.1103/PhysRevA.76.022102

quant-ph

Simple examples are constructed that show the entanglement of two qubits being both increased and decreased by interactions on just one of them. One of the two qubits interacts with a third qubit, a control, that is never entangled or correlated with either of the two entangled qubits and is never entangled, but becomes correlated, with the system of those two qubits. The two entangled qubits do not interact, but their state can change from maximally entangled to separable or from separable to maximally entangled. Similar changes for the two qubits are made with a swap operation between one of the qubits and a control; then there are compensating changes of entanglement that involve the control. When the entanglement increases, the map that describes the change of the state of the two entangled qubits is not completely positive. Combination of two independent interactions that individually give exponential decay of the entanglement can cause the entanglement to not decay exponentially but, instead, go to zero at a finite time.

0704.0462

Elena Orlando

Elena Orlando, Dirk Petry and Andrew Strong

Extended solar emission - an analysis of the EGRET data

2 pages, 2 figures, Proceedings of the First GLAST Symposium, February 5-8, 2007, Stanford University

AIP Conf.Proc.921:502-503,2007

10.1063/1.2757422

astro-ph

The Sun was recently predicted to be an extended source of gamma-ray emission, produced by inverse-Compton scattering of cosmic-ray electrons with the solar radiation. The emission was predicted to contribute to the diffuse extragalactic background even at large angular distances from the Sun. While this emission is expected to be readily detectable in future by GLAST, the situation for available EGRET data is more challenging. We present a detailed study of the EGRET database, using a time dependent analysis, accounting for the effect of the emission from 3C 279, the moon, and other sources, which interfere with the solar signal. The technique has been tested on the moon signal, with results consistent with previous work. We find clear evidence for emission from the Sun and its vicinity. The observations are compared with our model for the extended emission.

0704.0463

Brenda Matthews

B. C. Matthews (Herzberg Institute of Astrophysics, Canada), P. G. Kalas (UC Berkeley, U.S.A.), M. C. Wyatt (University of Cambridge, U.K.)

Mass and Temperature of the TWA 7 Debris Disk

8 pages, 3 figures, accepted for publication in The Astrophysical Journal

Astrophys.J.663:1103-1109,2007

10.1086/518643

astro-ph

We present photometric detections of dust emission at 850 and 450 micron around the pre-main sequence M1 dwarf TWA 7 using the SCUBA camera on the James Clerk Maxwell Telescope. These data confirm the presence of a cold dust disk around TWA 7, a member of the TW Hydrae Association. Based on the 850 micron flux, we estimate the mass of the disk to be 18 lunar masses (0.2 Earth masses) assuming a mass opacity of 1.7 cm^2/g with a temperature of 45 K. This makes the TWA 7 disk (d=55 pc) an order of magnitude more massive than the disk reported around AU Microscopii (GL 803), the closest (9.9 pc) debris disk detected around an M dwarf. This is consistent with TWA 7 being slightly younger than AU Mic. We find that the mid-IR and submillimeter data require the disk to be comprised of dust at a range of temperatures. A model in which the dust is at a single radius from the star, with a range of temperatures according to grain size, is as effective at fitting the emission spectrum as a model in which the dust is of uniform size, but has a range of temperatures according to distance. We discuss this disk in the context of known disks in the TW Hydrae Association and around low-mass stars; a comparison of masses of disks in the TWA reveals no trend in mass or evolutionary state (gas-rich vs. debris) as a function of spectral type.

0704.0464

Edward Lyman Ph.D.

Edward Lyman and Daniel M. Zuckerman

Annealed importance sampling of dileucine peptide

10.1063/1.2754267

q-bio.BM

Annealed importance sampling is a means to assign equilibrium weights to a nonequilibrium sample that was generated by a simulated annealing protocol. The weights may then be used to calculate equilibrium averages, and also serve as an ``adiabatic signature'' of the chosen cooling schedule. In this paper we demonstrate the method on the 50-atom dileucine peptide, showing that equilibrium distributions are attained for manageable cooling schedules. For this system, as naively implemented here, the method is modestly more efficient than constant temperature simulation. However, the method is worth considering whenever any simulated heating or cooling is performed (as is often done at the beginning of a simulation project, or during an NMR structure calculation), as it is simple to implement and requires minimal additional CPU expense. Furthermore, the naive implementation presented here can be improved.

0704.0465

Veit Schw\"ammle

Veit Schwammle, Evaldo M. F. Curado, Fernando D. Nobre

A General Nonlinear Fokker-Planck Equation and its Associated Entropy

17 pages, submitted to Eur. Phys. J. B

10.1140/epjb/e2007-00217-1

cond-mat.stat-mech cond-mat.other

A recently introduced nonlinear Fokker-Planck equation, derived directly from a master equation, comes out as a very general tool to describe phenomenologically systems presenting complex behavior, like anomalous diffusion, in the presence of external forces. Such an equation is characterized by a nonlinear diffusion term that may present, in general, two distinct powers of the probability distribution. Herein, we calculate the stationary-state distributions of this equation in some special cases, and introduce associated classes of generalized entropies in order to satisfy the H-theorem. Within this approach, the parameters associated with the transition rates of the original master-equation are related to such generalized entropies, and are shown to obey some restrictions. Some particular cases are discussed.

0704.0466

Ferenc Simon

F. Simon, F. Mur\'anyi, T. Feh\'er, A. J\'anossy, L. Forr\'o, C. Petrovic, S.L. Bud'ko, P.C. Canfield

Conduction electron spin-lattice relaxation time in the MgB2 superconductor

6 pages, 5 figures

Phys. Rev. B 75, 024519 (2007)

10.1103/PhysRevB.76.024519

cond-mat.supr-con cond-mat.str-el

The spin-lattice relaxation time, $T_{1}$, of conduction electrons is measured as a function of temperature and magnetic field in MgB$_2$. The method is based on the detection of the $z$ component of the conduction electron magnetization under electron spin resonance conditions with amplitude modulated microwave excitation. Measurement of $T_{1}$ below $T_c$ at 0.32 T allows to disentangle contributions from the two Fermi surfaces of MgB$_{2}$ as this field restores normal state on the Fermi surface part with $\pi$ symmetry only.

0704.0467

Gabor Pszota

Gabor Pszota and Wei Cui

Modeling Accretion Disk X-ray Continuum of Black Hole Candidates

- final journal version: typos, wordings refined, commas, added missing reference - 15 pages, 4 figures, accepted to ApJ Changes: fig4b was not the right graph, wrong chi squared/dof numbers at one place. (doesn't make significant difference)

Astrophys.J.663:1201-1206,2007

10.1086/518823

astro-ph

We critically examine issues associated with determining the fundamental properties of the black hole and the surrounding accretion disk in an X-ray binary based on modeling the disk X-ray continuum of the source. We base our work mainly on two XMM-Newton observations of GX 339-4, because they provided high-quality data at low energies (below 1 keV) which are critical for reliably modeling the spectrum of the accretion disk. A key issue examined is the determination of the so-called "color correction factor", which is often empirically introduced to account for the deviation of the local disk spectrum from a blackbody (due to electron scattering). This factor cannot be pre-determined theoretically because it may vary with, e.g., mass accretion rate, among a number of important factors. We follow up on an earlier suggestion to estimate the color correction observationally by modeling the disk spectrum with saturated Compton scattering. We show that the spectra can be fitted well and the approach yields reasonable values for the color correction factor. For comparison, we have also attempted to fit the spectra with other models. We show that even the high-soft-state continuum (which is dominated by the disk emission) cannot be satisfactorily fitted by state-of-the-art disk models. We discuss the implication of the results.

0704.0468

Jinsong Tan

Jinsong Tan

Inapproximability of Maximum Weighted Edge Biclique and Its Applications

LNCS 4978, TAMC 2008, pp 282-293

cs.CC cs.DS

http://arxiv.org/licenses/nonexclusive-distrib/1.0/

Given a bipartite graph $G = (V_1,V_2,E)$ where edges take on {\it both} positive and negative weights from set $\mathcal{S}$, the {\it maximum weighted edge biclique} problem, or $\mathcal{S}$-MWEB for short, asks to find a bipartite subgraph whose sum of edge weights is maximized. This problem has various applications in bioinformatics, machine learning and databases and its (in)approximability remains open. In this paper, we show that for a wide range of choices of $\mathcal{S}$, specifically when $| \frac{\min\mathcal{S}} {\max \mathcal{S}} | \in \Omega(\eta^{\delta-1/2}) \cap O(\eta^{1/2-\delta})$ (where $\eta = \max\{|V_1|, |V_2|\}$, and $\delta \in (0,1/2]$), no polynomial time algorithm can approximate $\mathcal{S}$-MWEB within a factor of $n^{\epsilon}$ for some $\epsilon > 0$ unless $\mathsf{RP = NP}$. This hardness result gives justification of the heuristic approaches adopted for various applied problems in the aforementioned areas, and indicates that good approximation algorithms are unlikely to exist. Specifically, we give two applications by showing that: 1) finding statistically significant biclusters in the SAMBA model, proposed in \cite{Tan02} for the analysis of microarray data, is $n^{\epsilon}$-inapproximable; and 2) no polynomial time algorithm exists for the Minimum Description Length with Holes problem \cite{Bu05} unless $\mathsf{RP=NP}$.

0704.0469

Giancarlo Urzua A

Giancarlo Urzua

On line arrangements with applications to 3-nets

19 pages, to appear in Advances in Geometry. Sections 5, 6 and 7 of old version are worked out in more detail at the beginning of "Arrangements of rational sections over curves and the varieties they define"

math.AG math.CO

http://arxiv.org/licenses/nonexclusive-distrib/1.0/

We show a one-to-one correspondence between arrangements of d lines in the projective plane, and lines in P^{d-2}. We apply this correspondence to classify (3,q)-nets over the complex numbers for all q<=6. When q=6, we have twelve possible combinatorial cases, but we prove that only nine of them are realizable. This new case shows several new properties for 3-nets: different dimensions for moduli, strict realization over certain fields, etc. We also construct a three dimensional family of (3,8)-nets corresponding to the Quaternion group.

0704.0470

Andrei Tokovinin

A. Tokovinin, M. Sarazin, A. Smette

Testing turbulence model at metric scales with mid-infrared VISIR images at the VLT

Accepted for publication in MNRAS. 8 pages, 11 figures

Mon.Not.Roy.Astron.Soc.378:701-708,2007

10.1111/j.1365-2966.2007.11803.x

astro-ph

We probe turbulence structure from centimetric to metric scales by simultaneous imagery at mid-infrared and visible wavelengths at the VLT telescope and show that it departs significantly from the commonly used Kolmogorov model. The data can be fitted by the von Karman model with an outer scale of the order of 30 m and we see clear signs of the phase structure function saturation across the 8-m VLT aperture. The image quality improves in the infrared faster than the standard lambda^{-1/5} scaling and may be diffraction-limited at 30-m apertures even without adaptive optics at wavelengths longer than 8 micron.

0704.0471

Dinesh Shetty

D.V. Shetty, S.J. Yennello, and G.A. Souliotis

Density dependence of the symmetry energy and the nuclear equation of state: A Dynamical and Statistical model perspective

16 pages, 14 figures

Phys.Rev.C76:024606,2007; Erratum-ibid.C76:039902,2007

10.1103/PhysRevC.76.024606 10.1103/PhysRevC.76.039902

nucl-ex nucl-th

The density dependence of the symmetry energy in the equation of state of isospin asymmetric nuclear matter is of significant importance for studying the structure of systems as diverse as the neutron-rich nuclei and the neutron stars. A number of reactions using the dynamical and the statistical models of multifragmentation, and the experimental isoscaling observable, is studied to extract information on the density dependence of the symmetry energy. It is observed that the dynamical and the statistical model calculations give consistent results assuming the sequential decay effect in dynamical model to be small. A comparison with several other independent studies is also made to obtain important constraint on the form of the density dependence of the symmetry energy. The comparison rules out an extremely " stiff " and " soft " form of the density dependence of the symmetry energy with important implications for astrophysical and nuclear physics studies.

0704.0472

David P. Sanders

David P. Sanders, Hern\'an Larralde, Fran\c{c}ois Leyvraz (Instituto de Ciencias F\'isicas, Universidad Nacional Aut\'onoma de M\'exico)

Competitive nucleation and the Ostwald rule in a generalized Potts model with multiple metastable phases

4 pages, 5 figures. Version with one higher-quality figure available at http://www.fis.unam.mx/~dsanders/publications.html v2: Corrected labels on inset of figure 3. v3: Corrected link

Phys. Rev. B 75, 132101 (2007) (Brief Report)

10.1103/PhysRevB.75.132101

cond-mat.stat-mech cond-mat.mtrl-sci cond-mat.soft

We introduce a simple nearest-neighbor spin model with multiple metastable phases, the number and decay pathways of which are explicitly controlled by the parameters of the system. With this model we can construct, for example, a system which evolves through an arbitrarily long succession of metastable phases. We also construct systems in which different phases may nucleate competitively from a single initial phase. For such a system, we present a general method to extract from numerical simulations the individual nucleation rates of the nucleating phases. The results show that the Ostwald rule, which predicts which phase will nucleate, must be modified probabilistically when the new phases are almost equally stable. Finally, we show that the nucleation rate of a phase depends, among other things, on the number of other phases accessible from it.

0704.0473

Delfim F. M. Torres

Delfim F. M. Torres, George Leitmann

Contrasting Two Transformation-Based Methods for Obtaining Absolute Extrema

9 pages

J. Optim. Theory Appl. 137 (2008), no. 1, 53--59

10.1007/s10957-007-9292-z

math.OC

In this note we contrast two transformation-based methods to deduce absolute extrema and the corresponding extremizers. Unlike variation-based methods, the transformation-based ones of Carlson and Leitmann and the recent one of Silva and Torres are direct in that they permit obtaining solutions by inspection.

0704.0474

Ahmed E. Ismail

Pieter J. in 't Veld, Ahmed E. Ismail, and Gary S. Grest

Application of Ewald summations to long-range dispersion forces

9 pages, 3 figures, accepted by J. Chem. Phys. v. 2: Expanded discussion of results, definitions added, performance comparison for water added

J. Chem. Phys. 127, 144711 (2007)

10.1063/1.2770730

cond-mat.mtrl-sci cond-mat.stat-mech

We present results illustrating the effects of using explicit summation terms for the $r^{-6}$ dispersion term on the interfacial properties of a Lennard-Jones fluid and SPC/E water. For the Lennard-Jones fluid, we find that the use of long-range summations, even with a short ``crossover radius,'' yields results that are consistent with simulations using large cutoff radii. Simulations of SPC/E water demonstrate that the long-range dispersion forces are of secondary importance to the Coulombic forces. In both cases, we find that the ratio of box size $L_{\parallel}$ to crossover radius $r_{\rm c}^{\mathbf k}$ plays an important role in determining the magnitude of the long-range dispersion correction, although its effect is secondary when Coulombic interactions are also present.

0704.0475

Norbert Werner

N. Werner, J.S. Kaastra, Y. Takei, R. Lieu, J. Vink, T. Tamura

Possible non-thermal nature of the soft-excess emission in the cluster of galaxies Sersic 159-03

to appear in A&A

10.1051/0004-6361:20077211

astro-ph

We present an analysis of new Suzaku data and archival data from XMM-Newton of the cluster of galaxies Sersic 159-03, which has a strong soft X-ray excess emission component. The Suzaku observation confirms the presence of the soft excess emission, but it does not confirm the presence of redshifted OVII lines in the cluster. Radial profiles and 2D maps derived from XMM-Newton observations show that the soft excess emission has a strong peak at the position of the central cD galaxy and the maps do not show any significant azimuthal variations. Although the soft excess emission can be fitted equally well with both thermal and non-thermal models, its spatial distribution is neither consistent with the models of intercluster warm-hot filaments, nor with models of clumpy warm intracluster gas associated with infalling groups. Using the data obtained by the XMM-Newton Reflection Grating Spectrometers we do not confirm the presence of the warm gas in the cluster centre with the expected properties assuming the soft excess is of thermal origin. The observed properties of the soft excess emission are consistent with the non-thermal interpretation. While the high density of relativistic electrons associated with the peak of the soft emission in the cluster centre might have been provided by an active galactic nucleus in the central cD galaxy, the underlying population might have been accelerated in diffuse shocks.

0704.0476

Zhang Peng

P. Zhang and L. You

Geometric phase of an atom inside an adiabatic radio frequency potential

12 pages, 7 figures, submitted to Phys. Rev. A

10.1103/PhysRevA.76.033615

quant-ph

We investigate the geometric phase of an atom inside an adiabatic radio frequency (rf) potential created from a static magnetic field (B-field) and a time dependent rf field. The spatial motion of the atomic center of mass is shown to give rise to a geometric phase, or Berry's phase, to the adiabatically evolving atomic hyperfine spin along the local B-field. This phase is found to depend on both the static B-field along the semi-classical trajectory of the atomic center of mass and an ``effective magnetic field'' of the total B-field, including the oscillating rf field. Specific calculations are provided for several recent atom interferometry experiments and proposals utilizing adiabatic rf potentials.

0704.0477

Britton Smith

Britton D. Smith, Steinn Sigurdsson

The Transition from the First Stars to the Second Stars in the Early Universe

13 pages, 3 color figures, 1 table, submitted to ApJL

10.1086/518692

astro-ph

We observe a sharp transition from a singular, high-mass mode of star formation, to a low-mass dominated mode, in numerical simulations, at a metallicity of 10^-3 Zsolar. We incorporate a new method for including the radiative cooling from metals into adaptive mesh-refinement hydrodynamic simulations. Our results illustrate how metals, produced by the first stars, led to a transition from the high-mass star formation mode of Pop III stars, to the low-mass mode that dominates today. We ran hydrodynamic simulations with cosmological initial conditions in the standard LambdaCDM model, with metallicities, from zero to 10^-2 Zsolar, beginnning at redshift, z = 99. The simulations were run until a dense core forms at the center of a 5 x 10^5 Msolar dark matter halo, at z ~ 18. Analysis of the central 1 Msolar core reveals that the two simulations with the lowest metallicities, Z = 0 and 10^-4 Zsolar, contain one clump with 99% of the mass, while the two with metallicities, Z = 10^-3 and 10^-2 Zsolar, each contain two clumps that share most of the mass. The Z = 10^-3 Zsolar simulation also produced two low-mass proto-stellar objects with masses between 10^-2 and 10^-1 Msolar. Gas with Z >= 10^-3 Zsolar is able to cool to the temperature of the CMB, which sets a lower limit to the minimum fragmentation mass. This suggests that the second generation stars produced a spectrum of lower mass stars, but were still more massive on average than stars formed in the local universe.

0704.0478

Nate McCrady

Nate McCrady and James R. Graham

Super Star Cluster Velocity Dispersions and Virial Masses in the M82 Nuclear Starburst

19 pages, 8 figures, ApJ accepted

Astrophys.J.663:844-856,2007

10.1086/518357

astro-ph

We use high-resolution near-infrared spectroscopy from Keck Observatory to measure the stellar velocity dispersions of 19 super star clusters (SSCs) in the nuclear starburst of M82. The clusters have ages on the order of 10 Myr, which is many times longer than the crossing times implied by their velocity dispersions and radii. We therefore apply the Virial Theorem to derive the kinematic mass for 15 of the SSCs. The SSCs have masses of 2 x 10^5 to 4 x 10^6 solar masses, with a total population mass of 1.4 x 10^7 solar masses. Comparison of the loci of the young M82 SSCs and old Milky Way globular clusters in a plot of radius versus velocity dispersion suggests that the SSCs are a population of potential globular clusters. We present the mass function for the SSCs, and find a power law fit with an index of gamma = -1.91 +/- 0.06. This result is nearly identical to the mass function of young SSCs in the Antennae galaxies.

0704.0479

Thomas Geisser H

T.Geisser

The affine part of the Picard scheme

This is a correct version of the original paper published in Compositio Mathematica after O.Gabber pointed out a mistake

math.AG math.KT

http://arxiv.org/licenses/nonexclusive-distrib/1.0/

We describe the maximal torus and maximal unipotent subgroup of the Picard variety of a proper scheme over a perfect field.

0704.0480

Sungyun Kim Dr

Sungyun Kim, Artem Dudarev and Joachim Brand

Enhanced quantum Zeno effect and bunching in the decay of interacting bosons from an unstable state

paper withdrawn by author

cond-mat.mes-hall

paper withdrawn due to the possible error in numerical eigenfunction calculation

0704.0481

Varese Tim\'oteo

A. Delfino, T. Frederico, V.S. Timoteo, Lauro Tomio

The few scales of nuclei and nuclear matter

Physics Letters B 634 (2006) 185

10.1016/j.physletb.2006.01.046

nucl-th

The well-known correlations of low-energy three and four-nucleon observables with a typical three-nucleon scale (e.g., the Tjon line) is extended to light nuclei and nuclear matter. Evidence for the scaling between light nuclei binding energies and the triton one are pointed out. We argue that the saturation energy and density of nuclear matter are correlated to the triton binding energy. The available systematic nuclear matter calculations indicate a possible band structure representing these correlations.

0704.0482

Zhang-qi Yin

Zhang-qi Yin, Fu-li Li, Peng Peng

Implementation of holonomic quantum computation through engineering and manipulating environment

4 pages, 2 figures; v2, We have maken considerable changes. New model to engineer effective reservoir without broadband squeezing light is proposed, which makes the scheme more practical. Main results are not changed; v3, accepted for PRA. Change style to PRA

Phys. Rev. A 76, 062311 (2007)

10.1103/PhysRevA.76.062311

quant-ph

We consider an atom-field coupled system, in which two pairs of four-level atoms are respectively driven by laser fields and trapped in two distant cavities that are connected by an optical fiber. First, we show that an effective squeezing reservoir can be engineered under appropriate conditions. Then, we show that a two-qubit geometric CPHASE gate between the atoms in the two cavities can be implemented through adiabatically manipulating the engineered reservoir along a closed loop. This scheme that combines engineering environment with decoherence-free space and geometric phase quantum computation together has the remarkable feature: a CPHASE gate with arbitrary phase shift is implemented by simply changing the strength and relative phase of the driving fields.

0704.0483

Masanori Ichioka

Masanori Ichioka, Hiroto Adachi, Takeshi Mizushima, Kazushige Machida

Vortex state in a Fulde-Ferrell-Larkin-Ovchinnikov superconductor based on the quasiclassical theory

11 pages, 10 figures

Phys. Rev. B 76, 014503 (2007)

10.1103/PhysRevB.76.014503

cond-mat.supr-con

We investigate the vortex state with Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) modulations suggested for a high field phase of CeCoIn_5. On the basis of the quasiclassical Eilenberger theory, we calculate the three dimensional structure of pair potentials, internal magnetic fields, paramagnetic moments, and electronic states, for the s-wave and the d-wave pairings comparatively. The \pi-phase shift of the pair potential at the FFLO nodal plane or at the vortex core induces sharp peak states in the local density of states, and enhances the local paramagnetic moment. We also discuss the NMR spectrum and the neutron scattering as methods to detect the FFLO structure.

0704.0484

Phillip Broussard

J. O. McCaslin and P. R. Broussard

Search for Chaotic Behavior in a Flapping Flag

11 pages, 9 figures. To be published in American Journal of Physics

physics.ed-ph physics.gen-ph

We measured the correlation of the times between successive flaps of a flag for a variety of wind speeds and found no evidence of low dimensional chaotic behavior in the return maps of these times. We instead observed what is best modeled as random times determined by an exponential distribution. This study was done as an undergraduate experiment and illustrates the differences between low dimensional chaotic and possibly higher dimensional chaotic systems.

0704.0485

Gao ZhiMing

Z.M. Gao, Y.C. Ma, H.W. Zhuang

Optimal Shape Design for Stokes Flow Via Minimax Differentiability

math.OC

This paper is concerned with a shape sensitivity analysis of a viscous incompressible fluid driven by Stokes equations with nonhomogeneous boundary condition. The structure of shape gradient with respect to the shape of the variable domain for a given cost function is established by using the differentiability of a minimax formulation involving a Lagrangian functional combining with function space parametrization technique or function space embedding technique. We apply an gradient type algorithm to our problem. Numerical examples show that our theory is useful for practical purpose and the proposed algorithm is feasible.

0704.0486

Young-Wook Lee

Young-Wook Lee, Hansung B. Gim, Dana I. Casetti-Dinescu

Kinematic Decoupling of Globular Clusters with Extended Horizontal-Branch

Accepted for publication in ApJ Letters

10.1086/518653

astro-ph

About 25% of the Milky Way globular clusters (GCs) exhibit unusually extended color distribution of stars in the horizontal-branch (HB) phase. This phenomenon is now best understood as due to the presence of helium enhanced second generation subpopulations, which has raised a possibility that these peculiar GCs might have a unique origin. Here we show that these GCs with extended HB are clearly distinct from other normal GCs in kinematics and mass. The GCs with extended HB are more massive than normal GCs, and are dominated by random motion with no correlation between kinematics and metallicity. Surprisingly, however, when they are excluded, most normal GCs in the inner halo show clear signs of dissipational collapse that apparently led to the formation of the disk. Normal GCs in the outer halo share their kinematic properties with the extended HB GCs, which is consistent with the accretion origin. Our result further suggests heterogeneous origins of GCs, and we anticipate this to be a starting point for more detailed investigations of Milky Way formation, including early mergers, collapse, and later accretion.

0704.0487

John Hodge

J. C. Hodge

Scalar potential model progress

Presented APS Apr07 meeting session s1.00014

physics.gen-ph

Because observations of galaxies and clusters have been found inconsistent with General Relativity (GR), the focus of effort in developing a Scalar Potential Model (SPM) has been on the examination of galaxies and clusters. The SPM has been found to be consistent with cluster cellular structure, the flow of IGM from spiral galaxies to elliptical galaxies, intergalactic redshift without an expanding universe, discrete redshift, rotation curve (RC) data without dark matter, asymmetric RCs, galaxy central mass, galaxy central velocity dispersion, and the Pioneer Anomaly. In addition, the SPM suggests a model of past expansion, past contraction, and current expansion of the universe. GR corresponds to the SPM in the limit in which the effect of the Sources and Sinks approximate a flat scalar potential field such as between clusters and on the solar system scale, which is small relative to the distance to a Source.

0704.0488

Muhammad Sharif

M. Sharif and M. Jamil Amir

Teleparallel Version of the Stationary Axisymmetric Solutions and their Energy Contents

18 pages, accepted for publication in Gen. Relativ. Grav

Gen.Rel.Grav.39:989-1002,2007

10.1007/s10714-007-0431-5

gr-qc

This work contains the teleparallel version of the stationary axisymmetric solutions. We obtain the tetrad and the torsion fields representing these solutions. The tensor, vector and axial-vector parts of the torsion tensor are evaluated. It is found that the axial-vector has component only along $\rho$ and $z$ directions. The three possibilities of the axial vector depending on the metric function $B$ are discussed. The vector related with spin has also been evaluated and the corresponding extra Hamiltonian is furnished. Further, we use the teleparallel version of M$\ddot{o}$ller prescription to find the energy-momentum distribution of the solutions. It is interesting to note that (for $\lambda=1$) energy and momentum densities in teleparallel theory are equal to the corresponding quantities in GR plus an additional quantity in each, which may become equal under certain conditions. Finally, we discuss the two special cases of the stationary axisymmetric solutions.

0704.0489

Ramazan Sever

Sameer M. Ikhdair, Ramazan Sever

Relativistic treatment in D-dimensions to a spin-zero particle with noncentral equal scalar and vector ring-shaped Kratzer potential

20 pages

Cent. Eur. J. Phys. 6, 141(2008)

10.2478/s11534-008-0018-0

quant-ph

The Klein-Gordon equation in D-dimensions for a recently proposed Kratzer potential plus ring-shaped potential is solved analytically by means of the conventional Nikiforov-Uvarov method. The exact energy bound-states and the corresponding wave functions of the Klein-Gordon are obtained in the presence of the noncentral equal scalar and vector potentials. The results obtained in this work are more general and can be reduced to the standard forms in three-dimensions given by other works.

0704.0490

Daniel Stancil

Daniel D. Stancil

Long Distance Signaling Using Axion-like Particles

18 pages, including 3 figures Version 2 has been modified to show portions of the coupling-mass plane that may lead to long distance communication, rather than concentrating on an example using the PVLAS parameters

Phys.Rev.D76:111701,2007

10.1103/PhysRevD.76.111701

hep-ph astro-ph hep-th

The possible existence of axion-like particles could lead to a new type of long distance communication. In this work, basic antenna concepts are defined and a Friis-like equation is derived to facilitate long-distance link calculations. An example calculation is presented showing that communication over distances of 1000 km or more may be possible for $m_{a}< 3.5$ meV and $g_{a\gamma \gamma} > 5 \times 10^{- 8} {\text{GeV}}^{- 1}$.

0704.0491

Juan G. Restrepo

Juan G. Restrepo, Edward Ott, Brian R. Hunt

Weighted percolation on directed networks

4 pages, 2 figures

10.1103/PhysRevLett.100.058701

cond-mat.soft cond-mat.dis-nn

We present an analysis of the percolation transition for general node removal strategies valid for locally tree-like directed networks. On the basis of heuristic arguments we predict that, if the probability of removing node $i$ is $p_i$, the network disintegrates if $p_i$ is such that the largest eigenvalue of the matrix with entries $A_{ij}(1-p_i)$ is less than 1, where $A$ is the adjacency matrix of the network. The knowledge or applicability of a Markov network model is not required by our theory, thus making it applicable to situations not covered by previous works. We test our predicted percolation criterion against numerical results for different networks and node removal strategies.

0704.0492

Shenghui Su

Shenghui Su, and Shuwang Lu

Refuting the Pseudo Attack on the REESSE1+ Cryptosystem

14 pages, and 2 table

cs.CR

http://arxiv.org/licenses/nonexclusive-distrib/1.0/

We illustrate through example 1 and 2 that the condition at theorem 1 in [8] dissatisfies necessity, and the converse proposition of fact 1.1 in [8] does not hold, namely the condition Z/M - L/Ak < 1/(2 Ak^2) is not sufficient for f(i) + f(j) = f(k). Illuminate through an analysis and ex.3 that there is a logic error during deduction of fact 1.2, which causes each of fact 1.2, 1.3, 4 to be invalid. Demonstrate through ex.4 and 5 that each or the combination of qu+1 > qu * D at fact 4 and table 1 at fact 2.2 is not sufficient for f(i) + f(j) = f(k), property 1, 2, 3, 4, 5 each are invalid, and alg.1 based on fact 4 and alg.2 based on table 1 are disordered and wrong logically. Further, manifest through a repeated experiment and ex.5 that the data at table 2 is falsified, and the example in [8] is woven elaborately. We explain why Cx = Ax * W^f(x) (% M) is changed to Cx = (Ax * W^f(x))^d (% M) in REESSE1+ v2.1. To the signature fraud, we point out that [8] misunderstands the existence of T^-1 and Q^-1 % (M-1), and forging of Q can be easily avoided through moving H. Therefore, the conclusion of [8] that REESSE1+ is not secure at all (which connotes that [8] can extract a related private key from any public key in REESSE1+) is fully incorrect, and as long as the parameter Omega is fitly selected, REESSE1+ with Cx = Ax * W^f(x) (% M) is secure.

0704.0493

Hiroshi Koibuchi

Hiroshi Koibuchi

Phase structure of a surface model on dynamically triangulated spheres with elastic skeletons

9 pages with 10 figures

Phys. Rev. E75, 051115 (2007)

10.1103/PhysRevE.75.051115

ICT-Koi-2007-2

cond-mat.stat-mech cond-mat.soft

We find three distinct phases; a tubular phase, a planar phase, and the spherical phase, in a triangulated fluid surface model. It is also found that these phases are separated by discontinuous transitions. The fluid surface model is investigated within the framework of the conventional curvature model by using the canonical Monte Carlo simulations with dynamical triangulations. The mechanical strength of the surface is given only by skeletons, and no two-dimensional bending energy is assumed in the Hamiltonian. The skeletons are composed of elastic linear-chains and rigid junctions and form a compartmentalized structure on the surface, and for this reason the vertices of triangles can diffuse freely only inside the compartments. As a consequence, an inhomogeneous structure is introduced in the model; the surface strength inside the compartments is different from the surface strength on the compartments. However, the rotational symmetry is not influenced by the elastic skeletons; there is no specific direction on the surface. In addition to the three phases mentioned above, a collapsed phase is expected to exist in the low bending rigidity regime that was not studied here. The inhomogeneous structure and the fluidity of vertices are considered to be the origin of such variety of phases.

0704.0494

Yuriy Kuzmin

Yuriy I. Kuzmin

Vortex Dynamics at the Initial Stage of Resistive Transition in Superconductors with Fractal Cluster Structure

Invited Talk at NATO Advanced Research Workshop "Vortex Dynamics in Superconductors and other Complex Systems", Yalta, Ukraine, Sept 13-17 (2004); 6 pages, 3 figures, 23 refs

J. Low Temp. Phys. 139 (2005) 155-166

10.1007/BF02769574

cond-mat.supr-con cond-mat.mtrl-sci

The effect of fractal normal-phase clusters on vortex dynamics in a percolative superconductor is considered. The superconductor contains percolative superconducting cluster carrying a transport current and clusters of a normal phase, acting as pinning centers. A prototype of such a structure is YBCO film, containing clusters of columnar defects, as well as the BSCCO/Ag sheathed tape, which is of practical interest for wire fabrication. Transition of the superconductor into a resistive state corresponds to the percolation transition from a pinned vortex state to a resistive state when the vortices are free to move. The dependencies of the free vortex density on the fractal dimension of the cluster boundary as well as the resistance on the transport current are obtained. It is revealed that a mixed state of the vortex glass type is realized in the superconducting system involved. The current-voltage characteristics of superconductors containing fractal clusters are obtained and their features are studied.

0704.0495

Metod Saniga

Metod Saniga (ASTRINSTSAV), Michel Planat (FEMTO-ST), Petr Pracna (JH-Inst), Hans Havlicek (TUW)

The Veldkamp Space of Two-Qubits

7 pages, 3 figures, 2 tables; Version 2 - math nomenclature fine-tuned and two references added; Version 3 - published in SIGMA (Symmetry, Integrability and Geometry: Methods and Applications) at http://www.emis.de/journals/SIGMA/

SIGMA 3 (2007) 075, 7 pages

quant-ph math-ph math.MP

Given a remarkable representation of the generalized Pauli operators of two-qubits in terms of the points of the generalized quadrangle of order two, W(2), it is shown that specific subsets of these operators can also be associated with the points and lines of the four-dimensional projective space over the Galois field with two elements - the so-called Veldkamp space of W(2). An intriguing novelty is the recognition of (uni- and tri-centric) triads and specific pentads of the Pauli operators in addition to the "classical" subsets answering to geometric hyperplanes of W(2).

0704.0496

Cedric Simenel

C\'edric Simenel (SPhN, GANIL), Philippe Chomaz (GANIL), Gilles De France (GANIL)

Fusion process studied with preequilibrium giant dipole resonance in time dependent Hartree-Fock theory

15 pages, 19 figures, revised version

Phys.Rev.C76:024609,2007

10.1103/PhysRevC.76.024609

nucl-th

The equilibration of macroscopic degrees of freedom during the fusion of heavy nuclei, like the charge and the shape, are studied in the Time-Dependent Hartree-Fock theory. The pre-equilibrium Giant Dipole Resonance (GDR) is used to probe the fusion path. It is shown that such isovector collective state is excited in N/Z asymmetric fusion and to a less extent in mass asymmetric systems. The characteristics of this GDR are governed by the structure of the fused system in its preequilibrium phase, like its deformation, rotation and vibration. In particular, we show that a lowering of the pre-equilibrium GDR energy is expected as compared to the statistical one. Revisiting experimental data, we extract an evidence of this lowering for the first time. We also quantify the fusion-evaporation enhancement due to gamma-ray emission from the pre-equilibrium GDR. This cooling mechanism along the fusion path may be suitable to synthesize in the future super heavy elements using radioactive beams with strong N/Z asymmetries in the entrance channel.

0704.0497

Bruno Fornet

Bruno Fornet (LATP, LMRS)

Penalization approach for mixed hyperbolic systems with constant coefficients satisfying a Uniform Lopatinski Condition

math.AP

In this paper, we describe a new, systematic and explicit way of approximating solutions of mixed hyperbolic systems with constant coefficients satisfying a Uniform Lopatinski Condition via different Penalization approaches.

0704.0498

Guillaume Mention

Guillaume Mention (DAPNIA), Thierry Lasserre (DAPNIA, APC), Dario Motta (DAPNIA)

A unified analysis of the reactor neutrino program towards the measurement of the theta_13 mixing angle

28 pages, 7 figures, 14 tables, one appendix

Journal of Physics: Conference Series 110, 8 (2008) 082013

10.1088/1742-6596/110/8/082013

hep-ex

We present in this article a detailed quantitative discussion of the measurement of the leptonic mixing angle theta_13 through currently scheduled reactor neutrino oscillation experiments. We thus focus on Double Chooz (Phase I & II), Daya Bay (Phase I & II) and RENO experiments. We perform a unified analysis, including systematics, backgrounds and accurate experimental setup in each case. Each identified systematic error and background impact has been assessed on experimental setups following published data when available and extrapolating from Double Chooz acquired knowledge otherwise. After reviewing the experiments, we present a new analysis of their sensitivities to sin^2(2 theta_13) and study the impact of the different systematics based on the pulls approach. Through this generic statistical analysis we discuss the advantages and drawbacks of each experimental setup.

0704.0499

Lawrence Ong

Lawrence Ong and Mehul Motani

Optimal Routing for Decode-and-Forward based Cooperation in Wireless Networks

Accepted and to be presented at Fourth Annual IEEE Communications Society Conference on Sensor, Mesh, and Ad Hoc Communications and Networks (SECON 2007), San Diego, California, June 18-21 2007

Proceedings of the 4th Annual IEEE Communications Society Conference on Sensor, Mesh, and Ad Hoc Communications and Networks (SECON 2007), San Diego, CA, pp. 334-343, Jun. 18-21 2007.

10.1109/SAHCN.2007.4292845

cs.IT math.IT

We investigate cooperative wireless relay networks in which the nodes can help each other in data transmission. We study different coding strategies in the single-source single-destination network with many relay nodes. Given the myriad of ways in which nodes can cooperate, there is a natural routing problem, i.e., determining an ordered set of nodes to relay the data from the source to the destination. We find that for a given route, the decode-and-forward strategy, which is an information theoretic cooperative coding strategy, achieves rates significantly higher than that achievable by the usual multi-hop coding strategy, which is a point-to-point non-cooperative coding strategy. We construct an algorithm to find an optimal route (in terms of rate maximizing) for the decode-and-forward strategy. Since the algorithm runs in factorial time in the worst case, we propose a heuristic algorithm that runs in polynomial time. The heuristic algorithm outputs an optimal route when the nodes transmit independent codewords. We implement these coding strategies using practical low density parity check codes to compare the performance of the strategies on different routes.

0704.0500

G\'erard Endimioni

G. Endimioni

On the polynomial automorphisms of a group

math.GR

We prove that if a group is nilpotent (resp. metabelian), then so is the subgroup of its automorphism group generated by all polynomial automorphisms.