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0704.1401 | Flat Pencils of Symplectic Connections and Hamiltonian Operators of
Degree 2 | Bi-Hamiltonian structures involving Hamiltonian operators of degree 2 are
studied. Firstly, pairs of degree 2 operators are considered in terms of an
algebra structure on the space of 1-forms, related to so-called Fermionic
Novikov algebras. Then, degree 2 operators are considered as deformations of
hydrodynamic type Poisson brackets.
| nlin.SI math.SG |
0704.1402 | IR-active optical phonons in Pnma-1, Pnma-2 and R3c phases of
LaMnO_{3+\delta} | Infrared-active phonons in LaMnO_{3+\delta} were studied by means of the
reflection and transmission spectroscopy from 50 to 800 cm^{-1} at room
temperature. Powder and ceramic samples of the phases of Pnma-2 (\delta=0.02),
Pnma-1 (\delta=0.08), and R3c (\delta=0.15) were investigated. Besides,
energies of the dipole-active phonons in Pnma-2, Pnma-1 phases were obtained by
lattice-dynamics calculations. The transformations of IR-active phonons with
the increase of \delta in the sequence of Pnma-2, Pnma-1, R3c are discussed.
| cond-mat.str-el |
0704.1403 | Equivalences of Higher Derived Brackets | This note elaborates on Th. Voronov's construction
[math/0304038,math/0412202] of $L_\infty$-structures via higher derived
brackets with a Maurer-Cartan element. It is shown that gauge equivalent
Maurer-Cartan elements induce $L_\infty$-isomorphic structures. Applications in
symplectic, Poisson and Dirac geometry are discussed.
| math.QA math.DG math.SG |
0704.1404 | Neutron matter from low-momentum interactions | We present a perturbative calculation of the neutron matter equation of state
based on low-momentum two- and three-nucleon interactions. Our results are
compared to the model-independent virial equation of state and to variational
calculations, and we provide theoretical error estimates by varying the cutoff
used to regulate nuclear interactions. In addition, we study the dependence of
the BCS $^1$S$_0$ superfluid pairing gap on nuclear interactions and on the
cutoff. The resulting gaps are well constrained by the nucleon-nucleon
scattering phase shifts, and the cutoff dependence is very weak for sharp or
sufficiently narrow smooth regulators with cutoffs $\lm > 1.6 \fmi$.
| nucl-th |
0704.1405 | Euclidean analysis of the entropy functional formalism | The attractor mechanism implies that the supersymmetric black hole near
horizon solution is defined only in terms of the conserved charges and is
therefore independent of asymptotic moduli. Starting only with the near horizon
geometry, Sen's entropy functional formalism computes the entropy of an extreme
black hole by means of a Legendre transformation where the electric fields are
defined as conjugated variables to the electric charges. However, traditional
Euclidean methods require the knowledge of the full geometry to compute the
black hole thermodynamic quantities. We establish the connection between the
entropy functional formalism and the standard Euclidean formalism taken at zero
temperature. We find that Sen's entropy function 'f' (on-shell) matches the
zero temperature limit of the Euclidean action. Moreover, Sen's near horizon
angular and electric fields agree with the chemical potentials that are defined
from the zero-temperature limit of the Euclidean formalism.
| hep-th gr-qc |
0704.1406 | On the existence of chaotic circumferential waves in spinning disks | We use a third-order perturbation theory and Melnikov's method to prove the
existence of chaos in spinning circular disks subject to a lateral point load.
We show that the emergence of transverse homoclinic and heteroclinic points
respectively lead to a random reversal in the traveling direction of
circumferential waves and a random phase shift of magnitude $\pi$ for both
forward and backward wave components. These long-term phenomena occur in
imperfect low-speed disks sufficiently far from fundamental resonances.
| nlin.CD |
0704.1407 | First principles theory of chiral dichroism in electron microscopy
applied to 3d ferromagnets | Recently it was demonstrated (Schattschneider et al., Nature 441 (2006),
486), that an analogue of the X-ray magnetic circular dichroism (XMCD)
experiment can be performed with the transmission electron microscope (TEM).
The new phenomenon has been named energy-loss magnetic chiral dichroism (EMCD).
In this work we present a detailed ab initio study of the chiral dichroism in
the Fe, Co and Ni transition elements. We discuss the methods used for the
simulations together with the validity and accuracy of the treatment, which
can, in principle, apply to any given crystalline specimen. The dependence of
the dichroic signal on the sample thickness, accuracy of the detector position
and the size of convergence and collection angles is calculated.
| cond-mat.mtrl-sci cond-mat.str-el |
0704.1408 | Probing MACHOs by observation of M31 pixel lensing with the 1.5m Loiano
telescope | We analyse a series of pilot observations in order to study microlensing of
(unresolved) stars in M31 with the 1.5m Loiano telescope, including
observations on both identified variable source stars and reported microlensing
events. We also look for previously unknown variability and discover a nova. We
discuss an observing strategy for an extended campaign with the goal of
determining whether MACHOs exist or whether all microlensing events are
compatible with lens stars in M31.
| astro-ph |
0704.1409 | Preconditioned Temporal Difference Learning | This paper has been withdrawn by the author. This draft is withdrawn for its
poor quality in english, unfortunately produced by the author when he was just
starting his science route. Look at the ICML version instead:
http://icml2008.cs.helsinki.fi/papers/111.pdf
| cs.LG cs.AI |
0704.1410 | QCD thermodynamics and confinement from a dynamical quasiparticle point
of view | In this study it is demonstrated that a simple picture of the
QCD gluon liquid emerges in the dynamical quasiparticle model that specifies
the active degrees of freedom in the time-like sector and yields a potential
energy density in the space-like sector. By using the time-like gluon density
(or scalar gluon density) as an independent degree of freedom - instead of the
temperature $T$ as a Lagrange parameter - variations of the potential energy
density lead to effective mean-fields for time-like gluons and an effective
gluon-gluon interaction strength at low density. The latter yields a simple
dynamical picture for the gluon fusion to color neutral glueballs when
approaching the phase boundary from a temperature higher than $T_c$ and paves
the way for an off-shell transport theoretical description of the parton
dynamics.
| nucl-th |
0704.1411 | Trellis-Coded Quantization Based on Maximum-Hamming-Distance Binary
Codes | Most design approaches for trellis-coded quantization take advantage of the
duality of trellis-coded quantization with trellis-coded modulation, and use
the same empirically-found convolutional codes to label the trellis branches.
This letter presents an alternative approach that instead takes advantage of
maximum-Hamming-distance convolutional codes. The proposed source codes are
shown to be competitive with the best in the literature for the same
computational complexity.
| cs.IT math.IT |
0704.1412 | Dynamic fracture of icosahedral model quasicrystals: A molecular
dynamics study | Ebert et al. [Phys. Rev. Lett. 77, 3827 (1996)] have fractured icosahedral
Al-Mn-Pd single crystals in ultrahigh vacuum and have investigated the cleavage
planes in-situ by scanning tunneling microscopy (STM). Globular patterns in the
STM-images were interpreted as clusters of atoms. These are significant
structural units of quasicrystals. The experiments of Ebert et al. imply that
they are also stable physical entities, a property controversially discussed
currently. For a clarification we performed the first large scale fracture
simulations on three-dimensional complex binary systems. We studied the
propagation of mode I cracks in an icosahedral model quasicrystal by molecular
dynamics techniques at low temperature. In particular we examined how the shape
of the cleavage plane is influenced by the clusters inherent in the model and
how it depends on the plane structure. Brittle fracture with no indication of
dislocation activity is observed. The crack surfaces are rough on the scale of
the clusters, but exhibit constant average heights for orientations
perpendicular to high symmetry axes. From detailed analyses of the fractured
samples we conclude that both, the plane structure and the clusters, strongly
influence dynamic fracture in quasicrystals and that the clusters therefore
have to be regarded as physical entities.
| cond-mat.mtrl-sci |
0704.1413 | Preparation and detection of magnetic quantum phases in optical
superlattices | We describe a novel approach to prepare, detect and characterize magnetic
quantum phases in ultra-cold spinor atoms loaded in optical superlattices. Our
technique makes use of singlet-triplet spin manipulations in an array of
isolated double well potentials in analogy to recently demonstrated quantum
control in semiconductor quantum dots. We also discuss the many-body
singlet-triplet spin dynamics arising from coherent coupling between nearest
neighbor double wells and derive an effective description for such system. We
use it to study the generation of complex magnetic states by adiabatic and
non-equilibrium dynamics.
| cond-mat.other |
0704.1414 | Sobolev solution for semilinear PDE with obstacle under monotonicity
condition | We prove the existence and uniqueness of the solution of a semilinear PDE's
and also PDE's with obstacle under monotonicity condition. Moreover we give the
probabilistic interpretation of the Sobolev's solutions in term of Backward SDE
and reflected Backward SDE respectively.
| math.PR |
0704.1415 | Exact distribution of the sample variance from a gamma parent
distribution | Several representations of the exact cdf of the sum of squares of n
independent gamma-distributed random variables Xi are given, in particular by a
series of gamma distribution functions. Using a characterization of the gamma
distribution by Laha, an expansion of the exact distribution of the sample
variance is derived by a Taylor series approach with the former distribution as
its leading term. In particular for integer orders alpha some further series
are provided, including a convex combination of gamma distributions for alpha =
1 and nearly of this type for alpha > 1. Furthermore, some representations of
the distribution of the angle Phi between (X1,...,Xn) and (1,...,1) are given
by orthogonal series. All these series are based on the same sequence of easily
computed moments of cos(Phi).
| math.ST stat.TH |
0704.1416 | Framework for non-perturbative analysis of a Z(3)-symmetric effective
theory of finite temperature QCD | We study a three dimensional Z(3)-symmetric effective theory of high
temperature QCD. The exact lattice-continuum relations, needed in order to
perform lattice simulations with physical parameters, are computed to order
O(a^0) in lattice perturbation theory. Lattice simulations are performed to
determine the phase structure of a subset of the parameter space.
| hep-lat hep-ph |
0704.1417 | Constraints on Regge models from perturbation theory | We study the constraints that the operator product expansion imposes on large
$N_c$ inspired QCD models for current-current correlators. We focus on the
constraints obtained by going beyond the leading-order parton computation. We
explicitly show that, assumed a given mass spectrum: linear Regge behavior in
$n$ (the principal quantum number) plus corrections in $1/n$, we can obtain the
logarithmic (and constant) behavior in $n$ of the decay constants within a
systematic expansion in $1/n$. Our example shows that it is possible to have
different large $n$ behavior for the vector and pseudo-vector mass spectrum and
yet comply with all the constraints from the operator product expansion.
| hep-ph hep-th nucl-th |
0704.1418 | Asymptotic stability at infinity for bidimensional Hurwitz vector fields | Let $X:U-->R^2$ be a differentiable vector field. Set $Spc(X)={eigenvalues of
DX(z) : z\in U}$. This $X$ is called Hurwitz if $Spc(X)\subset{z\in
C:\Re(z)<0}$. Suppose that $X$ is Hurwitz and $U\subset R^2$ is the complement
of a compact set. Then by adding to $X$ a constant $v$ one obtains that the
infinity is either an attractor or a repellor for $X+v.$
| math.DS math.CA |
0704.1419 | Quantitative LEED I-V and ab initio study of the Si(111)-3x2-Sm surface
structure and the missing half order spots in the 3x1 diffraction pattern | We have used Low Energy Electron Diffraction (LEED) I-V analysis and ab
initio calculations to quantitatively determine the honeycomb chain model
structure for the Si(111)-3x2-Sm surface. This structure and a similar 3x1
recontruction have been observed for many Alkali-Earth and Rare-Earth metals on
the Si(111) surface. Our ab initio calculations show that there are two almost
degenerate sites for the Sm atom in the unit cell and the LEED I-V analysis
reveals that an admixture of the two in a ratio that slightly favours the site
with the lower energy is the best match to experiment. We show that the I-V
curves are insensitive to the presence of the Sm atom and that this results in
a very low intensity for the half order spots which might explain the
appearance of a 3x1 LEED pattern produced by all of the structures with a 3x2
unit cell.
| cond-mat.mtrl-sci |
0704.1420 | Renormalization of Hamiltonian QCD | We study to one-loop order the renormalization of QCD in the Coulomb gauge
using the Hamitonian formalism. Divergences occur which might require
counter-terms outside the Hamiltonian formalism, but they can be cancelled by a
redefinition of the Yang-Mills electric field.
| hep-th |
0704.1421 | What made GRBs 060505 and 060614? | Recent observations of two nearby SN-less long-duration gamma-ray bursts
(GRBs), which share no obvious characteristics in their prompt emission,
suggest a new phenomenological type of massive stellar death. Here we briefly
review the observational properties of these bursts and their proposed hosts,
and discuss whether a new GRB classification scheme is needed.
| astro-ph |
0704.1422 | A new, very massive modular Liquid Argon Imaging Chamber to detect low
energy off-axis neutrinos from the CNGS beam. (Project MODULAr) | The paper is considering an opportunity for the CERN/GranSasso (CNGS)
neutrino complex, concurrent time-wise with T2K and NOvA, to search for
theta_13 oscillations and CP violation. Compared with large water Cherenkov
(T2K) and fine grained scintillators (NOvA), the LAr-TPC offers a higher
detection efficiency and a lower backgrounds, since virtually all channels may
be unambiguously recognized. The present proposal, called MODULAr, describes a
20 kt fiducial volume LAr-TPC, following very closely the technology developed
for the ICARUS-T60o, and is focused on the following activities, for which we
seek an extended international collaboration:
(1) the neutrino beam from the CERN 400 GeV proton beam and an optimised horn
focussing, eventually with an increased intensity in the framework of the LHC
accelerator improvement program;
(2) A new experimental area LNGS-B, of at least 50000 m3 at 10 km off-axis
from the main Laboratory, eventually upgradable to larger sizes. A location is
under consideration at about 1.2 km equivalent water depth;
(3) A new LAr Imaging detector of at least 20 kt fiducial mass. Such an
increase in the volume over the current ICARUS T600 needs to be carefully
considered. It is concluded that a very large mass is best realised with a set
of many identical, independent units, each of 5 kt, "cloning" the technology of
the T600. Further phases may foresee extensions of MODULAr to meet future
physics goals.
The experiment might reasonably be operational in about 4/5 years, provided a
new hall is excavated in the vicinity of the Gran Sasso Laboratory and adequate
funding and participation are made available.
| hep-ph |
0704.1423 | Momentum distributions in time-dependent density functional theory:
Product phase approximation for non-sequential double ionization in strong
laser fields | We investigate the possibility to deduce momentum space properties from
time-dependent density functional calculations. Electron and ion momentum
distributions after double ionization of a model Helium atom in a strong
few-cycle laser pulse are studied. We show that, in this case, the choice of
suitable functionals for the observables is considerably more important than
the choice of the correlation potential in the time-dependent Kohn-Sham
equations. By comparison with the solution of the time-dependent Schroedinger
equation, the insufficiency of functionals neglecting electron correlation is
demonstrated. We construct a functional of the Kohn-Sham orbitals, which in
principle yields the exact momentum distributions of the electrons and the ion.
The product-phase approximation is introduced, which reduces the problem of
approximating this functional significantly.
| physics.atom-ph |
0704.1424 | The Amadeus project at Dafne | The change of the hadron masses and hadron interactions in the nuclear medium
and the structure of cold dense hadronic matter are hot topics of hadron
physics today. These important, yet unsolved, problems will be the research
field of AMADEUS (Antikaonic Matter At DAFNE: Experiments with Unraveling
Spectroscopy) - new experiment proposal at DAFNE accelerator at LNF-INFN.
AMADEUS will search for antikaon-mediated deeply bound nuclear states produced
in helium by stopping K- from DAFNE, both in the formation and in the decay
processes.
| nucl-ex |
0704.1425 | Measurements and analysis of the upper critical field $H_{c2}$ on an
underdoped and overdoped $La_{2-x}Sr_xCuO_4$ compounds | The upper critical field $H_{c2}$ is one of the many non conventional
properties of high-$T_c$ cuprates. It is possible that the $H_{c2}(T)$
anomalies are due to the presence of inhomogeneities in the local charge
carrier density $\rho$ of the $CuO_2$ planes. In order to study this point, we
have prepared good quality samples of polycrystalline $La_{2-x}Sr_xCuO_{4}$
using the wet-chemical method, which has demonstrated to produce samples with a
better cation distribution. In particular, we have studied the temperature
dependence of the second critical field, $H_{c2}(T)$, through the magnetization
measurements on two samples with opposite average carrier concentration
($\rho_m=x$) and nearly the same critical temperature, namely $\rho_m = 0.08$
(underdoped) and $\rho_m = 0.25$ (overdoped). The results close to $T_c$ do not
follow the usual Ginzburg-Landau theory and are interpreted by a theory which
takes into account the influence of the inhomogeneities.
| cond-mat.supr-con cond-mat.str-el |
0704.1426 | Thermal Hadronization and Hawking-Unruh Radiation in QCD | We conjecture that because of color confinement, the physical vacuum forms an
event horizon for quarks and gluons which can be crossed only by quantum
tunneling, i.e., through the QCD counterpart of Hawking radiation by black
holes. Since such radiation cannot transmit information to the outside, it must
be thermal, of a temperature determined by the chromodynamic force at the
confinement surface, and it must maintain color neutrality. We explore the
possibility that the resulting process provides a common mechanism for thermal
hadron production in high energy interactions, from $e^+e^-$ annihilation to
heavy ion collisions.
| hep-ph |
0704.1427 | Photo-assisted shot noise in Coulomb interacting systems | We consider the fluctuations of the electrical current (shot noise) in the
presence of a voltage time-modulation. For a non-interacting metal, it is known
that the derivative of the photo-assisted noise has a staircase behavior. In
the presence of Coulomb interactions, we show that the photo-assisted noise
presents a more complex profile, in particular for the two following systems:
1) a two-dimensional electron gas in the fractional quantum Hall regime for
which we have obtained evenly spaced singularities in the noise derivative,
with a spacing related to the filling factor and, 2) a carbon nanotube for
which a smoothed staircase in the noise derivative is obtained.
| cond-mat.mes-hall |
0704.1428 | A unified projection formalism for the Al-Pd-Mn quasicrystal
Xi-approximants and their metadislocations | The approximants xi, xi' and xi'_n of the quasicrystal Al-Mn-Pd display most
interesting plastic properties as for example phason-induced deformation
processes (Klein, H., Audier, M., Boudard, M., de Boissieu, M., Beraha, L., and
Duneau, M., 1996, Phil. Mag. A, 73, 309.) or metadislocations (Klein, H.,
Feuerbacher, M., Schall, P., and Urban, K., 1999, Phys. Rev. Lett., 82, 3468.).
Here we demonstrate that the phases and their deformed or defected states can
be described by a simple projection formalism in three-dimensional space - not
as usual in four to six dimensions. With the method we can interpret
microstructures observed with electron microscopy as phasonic phase boundaries.
Furthermore we determine the metadislocations of lowest energy and relate them
uniquely to experimentally observed ones. Since moving metadislocations in the
xi'-phase can create new phason-planes, we suggest a dislocation induced phase
transition from xi' to xi'_n. The methods developed in this paper can as well
be used for various other complex metallic alloys.
| cond-mat.mtrl-sci |
0704.1429 | Light stops in the MSSM parameter space | We consider the regions of the MSSM parameter space where the top squarks
become light and even may be the LSP. This happens when the triple scalar
coupling A becomes very big compared to m_0. We show that in this case the
requirement that the LSP is neutral imposes noticeable constraint on the
parameter space excluding low m_0 and m_{1/2} similar to constraint from the
Higgs mass limit. In some cases these constraints overlap. This picture takes
place in a wide region of \tan\beta. In a narrow band close to the border line
the stops are long-lived particles and decay into quarks and neutralino
(chargino). The cross-section of their production at LHC via gluon fusion
mechanism in this region may reach a few pb.
| hep-ph |
0704.1430 | The blue plume population in dwarf spheroidal galaxies: genuine blue
stragglers or young stellar population? | Abridged... Blue stragglers (BSS) are thought to be the product of either
primordial or collisional binary systems. In the context of dwarf spheroidal
galaxies it is hard to firmly disentangle a genuine BSS population from young
main sequence (MS) stars tracing a ~1-2 Gyr old star forming episode. Assuming
that their blue plume populations are made of BSS, we estimate the BSS
frequency for 8 Local Group non star-forming dwarf galaxies, using a
compilation of ground and space based photometry.
Our results can be summarized as follows: (i) The BSS frequency in dwarf
galaxies, at any given Mv, is always higher than that in globular clusters of
similar luminosities; (ii) the BSS frequency for the lowest luminosity dwarf
galaxies is in excellent agreement with that observed in the Milky Way halo;
and most interestingly (iii) derive a statistically significant
anti-correlation between the BSS frequency and the galaxy Mv.
The low density, almost collision-less, environments of our dwarf galaxy
sample allow us to infer (i) their very low dynamical evolution; (ii) a
negligible production of collisional BSS; and consequently (iii) that their
blue plumes are mainly made of primordial binaries. The dwarf galaxies
anti-correlation can be used as a discriminator: galaxies obeying the
anti-correlation are more likely to possess genuine primordial BSS rather than
young main sequence stars.
| astro-ph |
0704.1431 | Generalized characteristic polynomials of graph bundles | In this paper, we find computational formulae for generalized characteristic
polynomials of graph bundles. We show that the number of spanning trees in a
graph is the partial derivative (at (0,1)) of the generalized characteristic
polynomial of the graph. Since the reciprocal of the Bartholdi zeta function of
a graph can be derived from the generalized characteristic polynomial of a
graph, consequently, the Bartholdi zeta function of a graph bundle can be
computed by using our computational formulae.
| math.CO |
0704.1432 | Some invariants of pretzel links | We show that nontrivial classical pretzel knots L(p,q,r) are hyperbolic with
eight exceptions which are torus knots. We find Conway polynomials of n-pretzel
links using a new computation tree. As applications, we compute the genera of
n-pretzel links using these polynomials and find the basket number of pretzel
links by showing that the genus and the canonical genus of a pretzel link are
the same.
| math.GT |
0704.1433 | Exact retrospective Monte Carlo computation of arithmetic average Asian
options | Taking advantage of the recent litterature on exact simulation algorithms
(Beskos, Papaspiliopoulos and Roberts) and unbiased estimation of the
expectation of certain fonctional integrals (Wagner, Beskos et al. and
Fearnhead et al.), we apply an exact simulation based technique for pricing
continuous arithmetic average Asian options in the Black and Scholes framework.
Unlike existing Monte Carlo methods, we are no longer prone to the
discretization bias resulting from the approximation of continuous time
processes through discrete sampling. Numerical results of simulation studies
are presented and variance reduction problems are considered.
| q-fin.CP math.PR |
0704.1434 | Rotationally-invariant slave-boson formalism and momentum dependence of
the quasiparticle weight | We generalize the rotationally-invariant formulation of the slave-boson
formalism to multiorbital models, with arbitrary interactions, crystal fields,
and multiplet structure. This allows for the study of multiplet effects on the
nature of low-energy quasiparticles. Non-diagonal components of the matrix of
quasiparticle weights can be calculated within this framework. When combined
with cluster extensions of dynamical mean-field theory, this method allows us
to address the effects of spatial correlations, such as the generation of the
superexchange and the momentum dependence of the quasiparticle weight. We
illustrate the method on a two-band Hubbard model, a Hubbard model made of two
coupled layers, and a two-dimensional single-band Hubbard model (within a
two-site cellular dynamical mean-field approximation).
| cond-mat.str-el |
0704.1435 | On the failure of subadditivity of the Wigner-Yanase entropy | It was recently shown by Hansen that the Wigner-Yanase entropy is, for
general states of quantum systems, not subadditive with respect to
decomposition into two subsystems, although this property is known to hold for
pure states. We investigate the question whether the weaker property of
subadditivity for pure states with respect to decomposition into more than two
subsystems holds. This property would have interesting applications in quantum
chemistry. We show, however, that it does not hold in general, and provide a
counterexample.
| math-ph math.MP quant-ph |
0704.1436 | Symmetries and the cosmological constant puzzle | We outline the evaluation of the cosmological constant in the framework of
the standard field-theoretical treatment of vacuum energy and discuss the
relation between the vacuum energy problem and the gauge-group spontaneous
symmetry breaking. We suggest possible extensions of the 't Hooft-Nobbenhuis
symmetry, in particular, its complexification till duality symmetry and discuss
the compatible implementation on gravity. We propose to use the discrete
time-reflection transform to formulate a framework in which one can eliminate
the huge contributions of vacuum energy into the effective cosmological
constant and suggest that the breaking of time--reflection symmetry could be
responsible for a small observable value of this constant.
| gr-qc astro-ph hep-th |
0704.1437 | The property of kappa-deformed statistics for a relativistic gas in an
electromagnetic field: kappa parameter and kappa-distribution | We investigate the physical property of the kappa parameter and the
kappa-distribution in the kappa-deformed statistics, based on Kaniadakis
entropy, for a relativistic gas in an electromagnetic field. We derive two
relations for the relativistic gas in the framework of kappa-deformed
statistics, which describe the physical situation represented by the
relativistic kappa-distribution function, provide a reasonable connection
between the parameter kappa, the temperature four-gradient and the four-vector
potential gradient, and thus present for the case kappa different from zero a
clearly physical meaning. It is shown that such a physical situation is a
meta-equilibrium state of the system, but has a new physical characteristic.
| cond-mat.stat-mech astro-ph |
0704.1438 | A KK-monopole giant graviton in AdS_5 x Y_5 | We construct a new giant graviton solution in AdS_5 x Y_5, with Y_5 a
quasi-regular Sasaki-Einstein manifold, consisting on a Kaluza-Klein monopole
wrapped around the Y_5 and with its Taub-NUT direction in AdS_5. We find that
this configuration has minimal energy when put in the centre of AdS_5, where it
behaves as a massless particle. When we take Y_5 to be S^5, we provide a
microscopical description in terms of multiple gravitational waves expanding
into the fuzzy S^5 defined as an S^1 bundle over the fuzzy CP^2. Finally we
provide a possible field theory dual interpretation of the construction.
| hep-th |
0704.1439 | Critical Behavior of a Trapped Interacting Bose Gas | The phase transition of Bose-Einstein condensation is studied in the critical
regime, when fluctuations extend far beyond the length scale of thermal de
Broglie waves. Using matter-wave interference we measure the correlation length
of these critical fluctuations as a function of temperature. The diverging
behavior of the correlation length above the critical temperature is observed,
from which we determine the critical exponent of the correlation length for a
trapped, weakly interacting Bose gas to be $\nu=0.67\pm 0.13$. This measurement
has direct implications for the understanding of second order phase
transitions.
| cond-mat.stat-mech |
0704.1440 | Tiling models for metadislocations in AlPdMn approximants | The AlPdMn quasicrystal approximants xi, xi', and xi'_n of the 1.6 nm
decagonal phase and R, T, and T_n of the 1.2 nm decagonal phase can be viewed
as arrangements of cluster columns on two-dimensional tilings. We substitute
the tiles by Penrose rhombs and show, that alternative tilings can be
constructed by a simple cut and projection formalism in three dimensional
hyperspace. It follows that in the approximants there is a phasonic degree of
freedom, whose excitation results in the reshuffling of the clusters. We apply
the tiling model for metadislocations, which are special textures of partial
dislocations.
| cond-mat.mtrl-sci |
0704.1441 | Heisenberg antiferromagnet with anisotropic exchange on the Kagome
lattice: Description of the magnetic properties of volborthite | We study the properties of the Heisenberg antiferromagnet with spatially
anisotropic nearest-neighbour exchange couplings on the kagome net, i.e. with
coupling J in one lattice direction and couplings J' along the other two
directions. For J/J' > 1, this model is believed to describe the magnetic
properties of the mineral volborthite. In the classical limit, it exhibits two
kinds of ground states: a ferrimagnetic state for J/J' < 1/2 and a large
manifold of canted spin states for J/J' > 1/2. To include quantum effects
self-consistently, we investigate the Sp(N) symmetric generalisation of the
original SU(2) symmetric model in the large-N limit. In addition to the
dependence on the anisotropy, the Sp(N) symmetric model depends on a parameter
kappa that measures the importance of quantum effects. Our numerical
calculations reveal that in the kappa-J/J' plane, the system shows a rich phase
diagram containing a ferrimagnetic phase, an incommensurate phase, and a
decoupled chain phase, the latter two with short- and long-range order. We
corroborate these results by showing that the boundaries between the various
phases and several other features of the Sp(N) phase diagram can be determined
by analytical calculations. Finally, the application of a block-spin
perturbation expansion to the trimerised version of the original spin-1/2 model
leads us to suggest that in the limit of strong anisotropy, J/J' >> 1, the
ground state of the original model is a collinearly ordered antiferromagnet,
which is separated from the incommensurate state by a quantum phase transition.
| cond-mat.str-el cond-mat.stat-mech |
0704.1442 | On the Nature of Ultra-Luminous X-ray Sources from Optical/IR
Measurements | We present a model for the prediction of the optical/infra-red emission from
ULXs. In the model, ULXs are binary systems with accretion taking place through
Roche lobe overflow. We show that irradiation effects and presence of an
accretion disk significantly modify the optical/infrared flux compared to
single stars, and also that the system orientation is important. We include
additional constraints from the mass transfer rate to constrain the parameters
of the donor star, and to a lesser extent the mass of the BH. We apply the
model to fit photometric data for several ULX counterparts. We find that most
donor stars are of spectral type B and are older and less massive than reported
elsewhere, but that no late-type donors are admissable. The degeneracy of the
acceptable parameter space will be significantly reduced with observations over
a wider spectral range, and if time-resolved data become available.
| astro-ph |
0704.1443 | Dephasing due to a fluctuating fractional quantum Hall edge current | The dephasing rate of an electron level in a quantum dot, placed next to a
fluctuating edge current in the fractional quantum Hall effect, is considered.
Using perturbation theory, we first show that this rate has an anomalous
dependence on the bias voltage applied to the neighboring quantum point
contact, because of the Luttinger liquid physics which describes the fractional
Hall fluid. Next, we describe exactly the weak to strong backscattering
crossover using the Bethe-Ansatz solution.
| cond-mat.mes-hall |
0704.1444 | Fracture of complex metallic alloys: An atomistic study of model systems | Molecular dynamics simulations of crack propagation are performed for two
extreme cases of complex metallic alloys (CMAs): In a model quasicrystal the
structure is determined by clusters of atoms, whereas the model C15 Laves phase
is a simple periodic stacking of a unit cell. The simulations reveal that the
basic building units of the structures also govern their fracture behaviour.
Atoms in the Laves phase play a comparable role to the clusters in the
quasicrystal. Although the latter are not rigid units, they have to be regarded
as significant physical entities.
| cond-mat.mtrl-sci |
0704.1445 | Deformed Wigner crystal in a one-dimensional quantum dot | The spatial Fourier spectrum of the electron density distribution in a finite
1D system and the distribution function of electrons over single-particle
states are studied in detail to show that there are two universal features in
their behavior, which characterize the electron ordering and the deformation of
Wigner crystal by boundaries. The distribution function has a $\delta$-like
singularity at the Fermi momentum $k_F$. The Fourier spectrum of the density
has a step-like form at the wavevector $2k_F$, with the harmonics being absent
or vanishing above this threshold. These features are found by calculations
using exact diagonalization method. They are shown to be caused by Wigner
ordering of electrons, affected by the boundaries. However the common Luttinger
liquid model with open boundaries fails to capture these features, because it
overestimates the deformation of the Wigner crystal. An improvement of the
Luttinger liquid model is proposed which allows one to describe the above
features correctly. It is based on the corrected form of the density operator
conserving the particle number.
| cond-mat.str-el cond-mat.mes-hall |
0704.1446 | Curvature in Synthetic Differential Geometry of Groupoids | We study the fundamental properties of curvature in groupoids within the
framework of synthetic differential geometry. As is usual in synthetic
differential geometry, its combinatorial nature is emphasized. In particular,
the classical Bianchi identity is deduced from its combinatorial one.
| math.DG |
0704.1447 | Can Gravity Probe B usefully constrain torsion gravity theories? | In most theories of gravity involving torsion, the source for torsion is the
intrinsic spin of matter. Since the spins of fermions are normally randomly
oriented in macroscopic bodies, the torsion generated is normally negligible.
However, in a recent paper, Mao et al. point out that there is a class of
theories in which the angular momentum of macroscopic spinning bodies generates
a significant amount of torsion. They argue that by the principle of action
equals reaction, one would expect the angular momentum of test bodies to couple
to a background torsion field, and therefore the precession of the GPB
gyroscopes should be affected in these theories by the torsion generated by the
Earth. We show that in fact the principle of action equals reaction does not
apply to these theories. We examine in detail a generalization of the
Hayashi-Shirafuji theory suggested by Mao et al. called
Einstein-Hayashi-Shirafuji theory. There are a variety of different versions of
this theory, depending on the precise form of the coupling to matter chosen for
the torsion. We show that for any coupling to matter that is compatible with
the spin transport equation postulated by Mao et al., the theory has either
ghosts or an ill-posed initial value formulation. These theoretical problems
can be avoided by specializing the parameters of the theory and in addition
choosing the standard minimal coupling to matter of the torsion tensor. This
yields a consistent theory, but one in which the action equals reaction
principle is violated, and in which the angular momentum of the gyroscopes does
not couple to the Earth's torsion field. Thus, the Einstein-Hayashi-Shirafuji
theory does not predict a detectable torsion signal for Gravity Probe B. There
may be other torsion theories which do.
| gr-qc astro-ph hep-th |
0704.1448 | Structures in the Universe and Origin of Galaxies | The analysis of images (of obtained in various ranges of the lengths of
waves) of luminous objects in the Universe by means of a method of multilevel
dynamic contrasting led author to the conclusions: a) the structures of all
observable galaxies represents a complicated constructions which have the
tendency to self-similarity and made of separate (basic) blocks, which are a
coaxially tubular structures and a cartwheel-like structures; b) the majority
of observable objects in the Universe are luminous butt-ends of almost
invisible (of almost completely transparent) of filamentary formations which
structures are seen only near to their luminous butt-ends; c) the result of
analysis of images of cosmic objects show the structure of many pairs of
cooperating galaxies point to opportunity of their formation at butt-ends
generated in a place of break of the similar filament; d) the interacting
galaxies (M 81 and M 82) show they are butt-ends of sawed off of two branches
of a treelike filament and their interaction is coming out through this
filament; e) as our Universe is in dynamics the processes of formation of
stars, galaxies and their congestions can go presently by means of a fracturing
of filaments with a corresponding diameters and of the time for their such
formation is necessary much less, than along existing standard model.
| astro-ph |
0704.1449 | The classification ofseparable simple C*-algebras which are inductive
limits of continuous-trace C*-algebraswith spectrum homeomorphic to the
closed interval [0,1] | A classification is given of certain separable nuclear C*-algebras not
necessarily of real rank zero, namely, the class of separable simple
C*-algebras which are inductive limits of continuous-trace C*-algebras whose
building blocks have spectrum homeomorphic to the closed interval [0,1], or to
a disjoint union of copies of this space. Also, the range of the invariant is
calculated.
| math.OA |
0704.1450 | U B V R I Photometry of Stellar Structures throughout the Disk of the
Barred Galaxy NGC 3367 | We report new detailed surface U, B, V, R, and I photometry of 81 stellar
structures in the disk of the barred galaxy NGC 3367. The images show many
different structures indicating that star formation is going on in the most
part of the disk. NGC 3367 is known to have a very high concentration of
molecular gas distribution in the central regions of the galaxy and bipolar
synchrotron emission from the nucleus with two lobes (at 6 kpc) forming a
triple structure similar to a radio galaxy. We have determined the U, B, V, R,
and I magnitudes and U - B, B - V, U - V, and V - I colors for the central
region (nucleus), a region which includes supernovae 2003 AA, and 79 star
associations throughout NGC 3367. Estimation of ages of star associations is
very difficult due to several factors, among them: filling factor, metallicity,
spatial distribution of each structure and the fact that we estimated the
magnitudes with a circular aperture of 16 pixels in diameter, equivalent to
$6''.8\sim1.4$ kpc. However, if the colors derived for NGC 3367 were similar to
the colors expected of star clusters with theoretical evolutionary star tracks
developed for the LMC and had a similar metallicity, NGC 3367 show 51 percent
of the observed structures with age type SWB I (few tens of Myrs), with seven
sources outside the bright surface brightness visible disk of NGC 3367.
| astro-ph |
0704.1451 | Proton Decay Constraints on Low Scale AdS/CFT Unification | Dark matter candidates and proton decay in a class of models based on the
AdS/CFT correspondence are discussed. We show that the present bound on the
proton decay lifetime is inconsistent with ${\cal N} = 1$ SUSY, and strongly
constrains ${\cal N} = 0$ non-SUSY, low scale trinification type unification of
orbifolded AdS$\otimes S^5$ models.
| hep-ph |
0704.1452 | BPS Black Holes | The entropy of BPS black holes in four space-time dimensions is discussed
from both macroscopic and microscopic points of view.
| hep-th |
0704.1453 | Structure factors of harmonic and anharmonic Fibonacci chains by
molecular dynamics simulations | The dynamics of quasicrystals is characterized by the existence of phason
excitations in addition to the usual phonon modes. In order to investigate
their interplay on an elementary level we resort to various one-dimensional
model systems. The main observables are the static, the incoherent, and the
coherent structure factor, which are extracted from molecular dynamics
simulations. For the validation of the algorithms, results for the harmonic
periodic chain are presented. We then study the Fibonacci chain with harmonic
and anharmonic interaction potentials. In the dynamic Fibonacci chain
neighboring atoms interact by double-well potentials allowing for phason flips.
The difference between the structure factors of the dynamic and the harmonic
Fibonacci chain lies in the temperature dependence of the phonon line width. If
a bias is introduced in the well depth, dispersionless optic phonon bands split
off.
| cond-mat.other |
0704.1454 | Ground-Based Direct Detection of Exoplanets with the Gemini Planet
Imager (GPI) | The Gemini Planet (GPI) imager is an "extreme" adaptive optics system being
designed and built for the Gemini Observatory. GPI combines precise and
accurate wavefront control, diffraction suppression, and a speckle-suppressing
science camera with integral field and polarimetry capabilities. GPI's primary
science goal is the direct detection and characterization of young, Jovian-mass
exoplanets. For systems younger than 2 Gyr exoplanets more massive than 6 MJ
and semimajor axes beyond 10 AU are detected with completeness greater than
50%. GPI will also discover faint debris disks, explore icy moons and minor
planets in the solar system, reveal high dynamic range main-sequence binaries,
and study mass loss from evolved stars. This white paper explains the role of
GPI in exoplanet discovery and characterization and summarizes our
recommendations to the NSF-NASA-DOE Astronomy and Astrophysics Advisory
Committee ExoPlanet Task Force.
| astro-ph |
0704.1455 | A Better Good-Turing Estimator for Sequence Probabilities | We consider the problem of estimating the probability of an observed string
drawn i.i.d. from an unknown distribution. The key feature of our study is that
the length of the observed string is assumed to be of the same order as the
size of the underlying alphabet. In this setting, many letters are unseen and
the empirical distribution tends to overestimate the probability of the
observed letters. To overcome this problem, the traditional approach to
probability estimation is to use the classical Good-Turing estimator. We
introduce a natural scaling model and use it to show that the Good-Turing
sequence probability estimator is not consistent. We then introduce a novel
sequence probability estimator that is indeed consistent under the natural
scaling model.
| cs.IT math.IT |
0704.1456 | Effective temperature vs line-depth ratio for ELODIE spectra. Gravity
and rotational velocity effects | The dependence on the temperature of photospheric line-depth ratios (LDRs) in
the spectral range 6190-6280 A is investigated by using a sample of 174 ELODIE
Archive stellar spectra of luminosity class from V to III. The rotational
broadening effect on LDRs is also studied. We provide useful calibrations of
effective temperature versus LDRs for giant and main sequence stars with
3800<Teff<6000 K and vsini in the range 0-30 km/s. We found that, with the
exception of very few line pairs, LDRs, measured at a spectral resolution as
high as 42000, depend on vsini and that, by neglecting the rotational
broadening effect, one can mistake the Teff determination of 100 K in the worst
cases.
| astro-ph |
0704.1457 | Chaos and Symmetry in String Cosmology | We review the recently discovered interplay between chaos and symmetry in the
general inhomogeneous solution of many string-related Einstein-matter systems
in the vicinity of a cosmological singularity. The
Belinsky-Khalatnikov-Lifshitz-type chaotic behaviour is found, for many
Einstein-matter models (notably those related to the low-energy limit of
superstring theory and M-theory), to be connected with certain
(infinite-dimensional) hyperbolic Kac-Moody algebras. In particular, the
billiard chambers describing the asymptotic cosmological behaviour of pure
Einstein gravity in spacetime dimension d+1, or the metric-three-form system of
11-dimensional supergravity, are found to be identical to the Weyl chambers of
the Lorentzian Kac-Moody algebras AE_d, or E_{10}, respectively. This suggests
that these Kac-Moody algebras are hidden symmetries of the corresponding
models. There even exists some evidence of a hidden equivalence between the
general solution of the Einstein-three-form system and a null geodesic in the
infinite dimensional coset space E_{10} / K(E_{10}), where K(E_{10}) is the
maximal compact subgroup of E_{10}.
| gr-qc |
0704.1458 | Radio Emission from the Intermediate-mass Black Hole in the Globular
Cluster G1 | We have used the Very Large Array (VLA) to search for radio emission from the
globular cluster G1 (Mayall-II) in M31. G1 has been reported by Gebhardt et al.
to contain an intermediate-mass black hole (IMBH) with a mass of ~2 x 10^4
solar masses. Radio emission was detected within an arcsecond of the cluster
center with an 8.4 GHz power of 2 x 10^{15} W/Hz. The radio/X-ray ratio of G1
is a few hundred times higher than that expected for a high-mass X-ray binary
in the cluster center, but is consistent with the expected value for accretion
onto an IMBH with the reported mass. A pulsar wind nebula is also a possible
candidate for the radio and X-ray emission from G1; future high-sensitivity
VLBI observations might distinguish between this possibility and an IMBH. If
the radio source is an IMBH, and similar accretion and outflow processes occur
for hypothesized ~ 1000-solar-mass black holes in Milky Way globular clusters,
they are within reach of the current VLA and should be detectable easily by the
Expanded VLA when it comes on line in 2010.
| astro-ph |
0704.1459 | Even infinite dimensional real Banach spaces | This article is a continuation of a paper of the first author \cite{F} about
complex structures on real Banach spaces. We define a notion of even infinite
dimensional real Banach space, and prove that there exist even spaces,
including HI or unconditional examples from \cite{F} and $C(K)$ examples due to
Plebanek \cite{P}. We extend results of \cite{F} relating the set of complex
structures up to isomorphism on a real space to a group associated to
inessential operators on that space, and give characterizations of even spaces
in terms of this group. We also generalize results of \cite{F} about totally
incomparable complex structures to essentially incomparable complex structures,
while showing that the complex version of a space defined by S. Argyros and A.
Manoussakis \cite{AM} provide examples of essentially incomparable complex
structures which are not totally incomparable.
| math.FA |
0704.1460 | Landau-Lifshitz sigma-models, fermions and the AdS/CFT correspondence | We define Landau-Lifshitz sigma models on general coset space $G/H$, with $H$
a maximal stability sub-group of $G$. These are non-relativistic models that
have $G$-valued N\"other charges, local $H$ invariance and are classically
integrable. Using this definition, we construct the $PSU(2,2|4)/PS(U(2|2)^2)$
Landau-Lifshitz sigma-model. This sigma model describes the thermodynamic limit
of the spin-chain Hamiltonian obtained from the complete one-loop dilatation
operator of the N=4 super Yang-Mills (SYM) theory. In the second part of the
paper, we identify a number of consistent truncations of the Type IIB
Green-Schwarz action on $AdS_5\times S^5$ whose field content consists of two
real bosons and 4,8 or 16 real fermions. We show that $\kappa$-symmetry acts
trivially in these sub-sectors. In the context of the large spin limit of the
AdS/CFT correspondence, we map the Lagrangians of these sub-sectors to
corresponding truncations of the $PSU(2,2|4)/PS(U(2|2)^2)$ Landau-Lifshitz
sigma-model.
| hep-th |
0704.1461 | Trajectory of neutron$-$neutron$-^{18}C$ excited three-body state | The trajectory of the first excited Efimov state is investigated by using a
renormalized zero-range three-body model for a system with two bound and one
virtual two-body subsystems. The approach is applied to $n-n-^{18}$C, where the
$n-n$ virtual energy and the three-body ground state are kept fixed. It is
shown that such three-body excited state goes from a bound to a virtual state
when the $n-^{18}$C binding energy is increased. Results obtained for the
$n-^{19}$C elastic cross-section at low energies also show dominance of an
$S-$matrix pole corresponding to a bound or virtual Efimov state. It is also
presented a brief discussion of these findings in the context of ultracold atom
physics with tunable scattering lengths.
| nucl-th cond-mat.soft nucl-ex |
0704.1462 | Physical parameters of evolved stars in clusters and in the field from
line-depth ratios | We present a high-resolution spectroscopic analysis of two samples of evolved
stars selected in the field and in the intermediate-age open cluster IC 4651,
for which detailed measurements of chemical composition were made in the last
few years. Applying the Gray's method based on ratios of line depths, we
determine the effective temperature and compare our results with previous ones
obtained by means of the curves of growth of iron lines. The knowledge of the
temperature enables us to estimate other fundamental stellar parameters, such
as color excess, age, and mass.
| astro-ph |
0704.1463 | Large deviations of Poisson cluster processes | In this paper we prove scalar and sample path large deviation principles for
a large class of Poisson cluster processes. As a consequence, we provide a
large deviation principle for ergodic Hawkes point processes.
| math.PR |
0704.1464 | Distributed quantum information processing with minimal local resources | We present a protocol for growing graph states, the resource for one-way
quantum computing, when the available entanglement mechanism is highly
imperfect. The distillation protocol is frugal in its use of ancilla qubits,
requiring only a single ancilla qubit when the noise is dominated by one Pauli
error, and two for a general noise model. The protocol works with such scarce
local resources by never post-selecting on the measurement outcomes of
purification rounds. We find that such a strategy causes fidelity to follow a
biased random walk, and that a target fidelity is likely to be reached more
rapidly than for a comparable post-selecting protocol. An analysis is presented
of how imperfect local operations limit the attainable fidelity. For example, a
single Pauli error rate of 20% can be distilled down to $\sim 10$ times the
imperfection in local operations.
| quant-ph |
0704.1465 | X-Raying the MOJAVE Sample of Compact Extragalactic Radio Jets | The MOJAVE sample is the first large radio-selected, VLBI-monitored AGN
sample for which complete X-ray spectral information is being gathered. We
report on the status of Swift survey observations which complement the
available archival X-ray data at 0.3-10 keV and in the UV with its XRT and UVOT
instruments. Many of these 133 radio-brightest AGN in the northern sky are now
being observed for the first time at these energies. These and complementary
other multi-wavelength observations provide a large statistical sample of
radio-selected AGN whose spectral energy distributions are measured from radio
to gamma-ray wavelengths, available at the beginning of GLAST operations in
2008. Here, we report the X-ray spectral characteristics of 36 of these
previously unobserved MOJAVE sources. In addition, the number of MOJAVE sources
detected by the BAT instrument in the hard X-ray band is growing: we report the
detection of five new blazars with BAT.
| astro-ph |
0704.1466 | Sparse Estimators and the Oracle Property, or the Return of Hodges'
Estimator | We point out some pitfalls related to the concept of an oracle property as
used in Fan and Li (2001, 2002, 2004) which are reminiscent of the well-known
pitfalls related to Hodges' estimator. The oracle property is often a
consequence of sparsity of an estimator. We show that any estimator satisfying
a sparsity property has maximal risk that converges to the supremum of the loss
function; in particular, the maximal risk diverges to infinity whenever the
loss function is unbounded. For ease of presentation the result is set in the
framework of a linear regression model, but generalizes far beyond that
setting. In a Monte Carlo study we also assess the extent of the problem in
finite samples for the smoothly clipped absolute deviation (SCAD) estimator
introduced in Fan and Li (2001). We find that this estimator can perform rather
poorly in finite samples and that its worst-case performance relative to
maximum likelihood deteriorates with increasing sample size when the estimator
is tuned to sparsity.
| math.ST stat.ME stat.TH |
0704.1467 | Capillary ordering and layering transitions in two-dimensional hard-rod
fluids | In this article we calculate the surface phase diagram of a two-dimensional
hard-rod fluid confined between two hard lines. In a first stage we study the
semi-infinite system consisting of an isotropic fluid in contact with a single
hard line. We have found complete wetting by the columnar phase at the
wall-isotropic fluid interface. When the fluid is confined between two hard
walls, capillary columnar ordering occurs via a first-order phase transition.
For higher chemical potentials the system exhibits layering transitions even
for very narrow slits (near the one-dimensional limit). The theoretical model
used was a density-functional theory based on the Fundamental-Measure
Functional applied to a fluid of hard rectangles in the restricted-orientation
approximation (Zwanzig model). The results presented here can be checked
experimentally in two-dimensional granular media made of rods, where vertical
motions induced by an external source and excluded volume interactions between
the grains allow the system to explore those stationary states which
entropically maximize packing configurations. We claim that some of the surface
phenomena found here can be present in two-dimensional granular-media fluids.
| cond-mat.stat-mech cond-mat.soft |
0704.1468 | Generation of Entanglement Outside of the Light Cone | The Feynman propagator has nonzero values outside of the forward light cone.
That does not allow messages to be transmitted faster than the speed of light,
but it is shown here that it does allow entanglement and mutual information to
be generated at space-like separated points. These effects can be interpreted
as being due to the propagation of virtual photons outside of the light cone or
as a transfer of pre-existing entanglement from the quantum vacuum. The
differences between these two interpretations are discussed.
| quant-ph |
0704.1469 | Monte Carlo Simulations of Quantum Spin Systems in the Valence Bond
Basis | We discuss a projector Monte Carlo method for quantum spin models formulated
in the valence bond basis, using the S=1/2 Heisenberg antiferromagnet as an
example. Its singlet ground state can be projected out of an arbitrary basis
state as the trial state, but a more rapid convergence can be obtained using a
good variational state. As an alternative to first carrying out a time
consuming variational Monte Carlo calculation, we show that a very good trial
state can be generated in an iterative fashion in the course of the simulation
itself. We also show how the properties of the valence bond basis enable
calculations of quantities that are difficult to obtain with the standard basis
of Sz eigenstates. In particular, we discuss quantities involving
finite-momentum states in the triplet sector, such as the dispersion relation
and the spectral weight of the lowest triplet.
| cond-mat.str-el cond-mat.stat-mech |
0704.1470 | N-dimensional sl(2)-coalgebra spaces with non-constant curvature | An infinite family of ND spaces endowed with sl(2)-coalgebra symmetry is
introduced. For all these spaces the geodesic flow is superintegrable, and the
explicit form of their common set of integrals is obtained from the underlying
sl(2)-coalgebra structure. In particular, ND spherically symmetric spaces with
Euclidean signature are shown to be sl(2)-coalgebra spaces. As a byproduct of
this construction we present ND generalizations of the classical Darboux
surfaces, thus obtaining remarkable superintegrable ND spaces with non-constant
curvature.
| hep-th math-ph math.MP |
0704.1471 | The Generalized PT-Symmetric Sinh-Gordon Potential Solvable within
Quantum Hamilton-Jacobi Formalism | The generalized Sinh-Gordon potential is solved within quantum Hamiltonian
Jacobi approach in the framework of PT symmetry. The quasi exact solutions of
energy eigenvalues and eigenfunctions of the generalized Sinh-Gordon potential
are found for n=0,1 states.
| quant-ph |
0704.1472 | Emergence of U(1) symmetry in the 3D XY model with Zq anisotropy | We study the three-dimensional XY model with a Z_q anisotropic term. At
temperatures T < Tc this dangerously irrelevant perturbation is relevant only
above a length scale Lambda, which diverges as a power of the correlation
length; Lambda ~ xi^a_q. Below Lambda the order parameter is U(1) symmetric. We
derive the full scaling function controlling the emergence of U(1) symmetry and
use Monte Carlo results to extract the exponent a_q for q=4,...,8. We find that
a_q = a_4 (q/4)^2, with a_4 only marginally larger than 1. We discuss these
results in the context of U(1) symmetry at "deconfined" quantum critical points
separating antiferromagnetic and valence-bond-solid states in quantum spin
systems.
| cond-mat.str-el cond-mat.stat-mech |
0704.1473 | Existence of Universal Entangler | A gate is called entangler if it transforms some (pure) product states to
entangled states. A universal entangler is a gate which transforms all product
states to entangled states. In practice, a universal entangler is a very
powerful device for generating entanglements, and thus provides important
physical resources for accomplishing many tasks in quantum computing and
quantum information. This Letter demonstrates that a universal entangler always
exists except for a degenerated case. Nevertheless, the problem how to find a
universal entangler remains open.
| quant-ph |
0704.1474 | Fan-shaped and toric textures of mesomorphic oxadiazoles | When a family of non symmetrical heterocycled compounds is investigated, a
variety of mesophases can be observed with rather different features. Here we
report the behaviour of seven different members among a family of such
materials, that consists of mesomorphic oxadiazole compounds. In two of these
compounds, the optical microscope investigation shows very interesting
behaviours. In their smectic phases, fan-shaped and toric textures, sometimes
with periodic instability, are observed. Moreover, the nematic phase displays a
texture transition. Texture transitions have been previously observed only
inside the nematic phase of some compounds belonging to the families of the
oxybenzoic and cyclohexane acids. In these two oxadiazole compounds we can
observe what we define as a "toric nematic phase", heating the samples from the
smectic phase. The toric nematic texture disappears as the sample is further
heated, changing into a smooth texture.
| cond-mat.soft |
0704.1475 | Williams' decomposition of the L\'evy continuous random tree and
simultaneous extinction probability for populations with neutral mutations | We consider an initial Eve-population and a population of neutral mutants,
such that the total population dies out in finite time. We describe the
evolution of the Eve-population and the total population with continuous state
branching processes, and the neutral mutation procedure can be seen as an
immigration process with intensity proportional to the size of the population.
First we establish a Williams' decomposition of the genealogy of the total
population given by a continuous random tree, according to the ancestral
lineage of the last individual alive. This allows us give a closed formula for
the probability of simultaneous extinction of the Eve-population and the total
population.
| math.PR |
0704.1476 | TeV-scale gravity in Horava-Witten theory on a compact complex
hyperbolic threefold | The field equations and boundary conditions of Horava-Witten theory,
compactified on a smooth compact spin quotient of CH^3, where CH^3 denotes the
hyperbolic cousin of CP^3, are studied in the presence of Casimir energy
density terms. If the Casimir energy densities near one boundary result in a
certain constant of integration taking a value greater than around 10^5 in
units of the d = 11 gravitational length, a form of thick pipe geometry is
found that realizes TeV-scale gravity by the ADD mechanism, with that boundary
becoming the inner surface of the thick pipe, where we live. Three alternative
ways in which the outer surface of the thick pipe might be stabilized
consistent with the observed value of the effective d = 4 cosmological constant
are considered. In the first alternative, the outer surface is stabilized in
the classical region and the constant of integration is fixed at around 10^{13}
in units of the d = 11 gravitational length for consistency with the observed
cosmological constant. In the second alternative, the four observed dimensions
have reduced in size down to the d = 11 gravitational length at the outer
surface, and there are Casimir effects near the outer surface. In the third
alternative, the outer surface is stabilized in the classical region by extra
fluxes of the three-form gauge field, whose four-form field strength wraps
three-cycles of the compact six-manifold times the radial dimension of the
thick pipe. Some problems related to fitting the strong/electroweak Standard
Model are considered.
| hep-th |
0704.1477 | Balance of forces in simulated bilayers | Two kinds of simulated bilayers are described and the results are reported
for lateral tension and for partial contributions of intermolecular forces to
it.Data for a widest possible range of areas per surfactant head, from tunnel
formation through tensionless state, transition to floppy bilayer,to its
disintegration, are reported and discussed. The significance of the tensionless
state, is discussed. Conclusions: (1) the tensionless state is a
coincidence;(2) the transition from extended to floppy bilayer occurs nearby
and has hallmarks of a phase transition (3) there is no theory of that
transition.(4)The lateral tension of the floppy bilayer scales with size; that
of the extended bilayer does not depend on size. (4) The drumhead model not
appropriate for interfaces as these fluctuate via diffusion.(5) The radius of
gyration also! shows a discontinuity.
| cond-mat.soft cond-mat.stat-mech |
0704.1478 | Search for the radiative leptonic decay B+ --> gamma l+ nu | We present the results of a search for $B^{+}\to\gamma \ell^{+}\nu_{\ell}$,
where $\ell = e, \mu$. We use a sample of 232 million $B\bar{B}$ pairs recorded
at the $\Upsilon(4S)$ with the BaBar detector at the PEP-II $B$ Factory. We
measure a partial branching fraction $\Delta\mathcal{B}$ in a restricted region
of phase space that reduces the effect of theoretical uncertainties, requiring
the lepton energy to be between 1.875 and 2.850GeV, the photon energy to be
between 0.45 and 2.35GeV, and the cosine of the angle between the lepton and
photon momenta to be less than -0.36, with all quantities computed in the
$\Upsilon(4S)$ center-of-mass frame. We find $\Delta\mathcal{B}(B^{+}\to\gamma
\ell^{+}\nu_{\ell}) = (-0.3^{+1.3}_{-1.5} ({stat}) \pm 0.6 ({syst}) \pm 0.1
({th})) \times 10^{-6}$, assuming lepton universality. Interpreted as a 90%
C.L. Bayesian upper limit, the result corresponds to $1.7\times10^{-6}$ for a
prior flat in amplitude, and $2.3\times10^{-6}$ for a prior flat in branching
fraction.
| hep-ex |
0704.1479 | Possible experimental manifestations of the many-body localization | Recently, it was predicted that if all one-electron states in a
non-interacting disordered system are localized, the interaction between
electrons in the absence of coupling to phonons leads to a finite-temperature
metal-insulator trnasition. Here we show that even in the presence of a weak
coupling to phonons the transition manifests itself (i) in the nonlinear
conduction, leading to a bistable $I$-$V$ curve, (ii) by a dramatic enhancement
of the nonequilibrium current noise near the transition.
| cond-mat.mes-hall |
0704.1480 | Magnetic structure of Sm2IrIn8 | The magnetic structure of the intermetallic antiferromagnet Sm2IrIn8 was
determined using x-ray resonant magnetic scattering (XRMS). Below TN = 14.2,
Sm2IrIn8 has a commensurate antiferromagnetic structure with a propagation
vector (1/2,0,0). The Sm magnetic moments lie in the ab plane and are rotated
roughly 18 degrees away from the a axis. The magnetic structure of this
compound was obtained by measuring the strong dipolar resonant peak whose
enhancement was of over two orders of magnitude at the L2 edge. At the L3 edge
both quadrupolar and dipolar features were observed in the energy line shape.
The magnetic structure and properties of Sm2IrIn8 are found to be consistent
with the general trend already seen for the Nd-, Tb- and the Ce-based compounds
from the RmMnIn3m+2n family (R = rare earth; M=Rh or Ir, m = 1, 2; n = 0, 1),
where the crystalline electrical field (CEF) effects determine the direction of
magnetic moments and the TN evolution in the series. The measured Neel
temperature for Sm2IrIn8 is slightly suppressed when compared to the TN of the
parent cubic compound SmIn3.
| cond-mat.str-el |
0704.1481 | TEXES Observations of Pure Rotational H2 Emission From AB Aurigae | We present observations of pure rotational molecular hydrogen emission from
the Herbig Ae star, AB Aurigae. Our observations were made using the Texas
Echelon Cross Echelle Spectrograph (TEXES) at the NASA Infrared Telescope
Facility and the Gemini North Observatory. We searched for H2 emission in the
S(1), S(2), and S(4) lines at high spectral resolution and detected all three.
By fitting a simple model for the emission in the three transitions, we derive
T = 670 +/- 40 K and M = 0.52 +/- 0.15 earth masses for the emitting gas. Based
on the 8.5 km/s FWHM of the S(2) line, assuming the emission comes from the
circumstellar disk, and with an inclination estimate of the AB Aur system taken
from the literature, we place the location for the emission near 18 AU.
Comparison of our derived temperature to a disk structure model suggests that
UV and X-ray heating are important in heating the disk atmosphere.
| astro-ph |
0704.1482 | Deciphering top flavor violation at the LHC with B factories | The LHC will have unprecedented sensitivity to flavor-changing neutral
current (FCNC) top quark decays, whose observation would be a clear sign of
physics beyond the standard model. Although many details of top flavor
violation are model dependent, the standard model gauge symmetries relate top
FCNCs to other processes, which are strongly constrained by existing data. We
study these constraints in a model independent way, using a low energy
effective theory from which the new physics is integrated out. We consider the
most important operators which contribute to top FCNCs and analyze the current
constraints on them. We find that the data rule out top FCNCs at a level
observable at the LHC due to most of the operators comprising left-handed first
or second generation quark fields, while there remains a substantial window for
top decays mediated by operators with right-handed charm or up quarks. If FCNC
top decays are observed at the LHC, such an analysis may help decipher the
underlying physics.
| hep-ph |
0704.1483 | Exploring Infrared Properties of Giant Low Surface Brightness Galaxies | Abridged: We present analysis of Spitzer Space Telescope observations of the
three low surface brightness (LSB) optical giant galaxies Malin 1, UGC 6614 and
UGC 9024. Mid- and far-infrared morphology, spectral energy distributions, and
integrated colors are used to derive the dust mass, dust-to-gas mass ratio,
total infrared luminosity, and star formation rate (SFR). The 8 micron images
indicate that polycyclic aromatic hydrocarbon molecules are present in the
central regions of all three metal-poor LSB galaxies. The diffuse optical disks
of Malin 1 and UGC 9024 remain undetected at mid- and far-infrared wavelengths.
The dustiest of the three LSB galaxies, UGC 6614, has infrared morphology that
varies significantly with wavelength. The 8 and 24 micron emission is
co-spatial with H\alpha emission previously observed in the outer ring of UGC
6614. The estimated dust-to-gas ratios, from less than 10^{-3} to 10^{-2},
support previous indications that the LSB galaxies are relatively dust poor
compared to the HSB galaxies. The total infrared luminosities are approximately
1/3 to 1/2 the blue band luminosities, suggesting that old stellar populations
are the primary source of dust heating in these LSB objects. The SFR estimated
from the infrared data ranges ~0.01-0.88 M_sun yr^{-1}, consistent with results
from optical studies.
| astro-ph |
0704.1484 | One-time pad booster for Internet | One-time pad encrypted files can be sent through Internet channels using
current Internet protocols. However, the need for renewing shared secret keys
make this method unpractical. This work shows how users can use a fast physical
random generator based on fluctuations of a light field and the Internet
channel to directly boost key renewals. The transmitted signals are
deterministic but carries imprinted noise that cannot be eliminated by the
attacker. Thus, a one-time pad for Internet can be made practical. Security is
achieved without third parties and not relying on the difficulty of factoring
numbers in primes. An informational fragility to be avoided is discussed.
Information-theoretic analysis is presented and bounds for secure operation are
determined.
| quant-ph |
0704.1485 | A Local Concept of Wave Velocities | The classical characterization of \wp, as a typical concept for far field
phenomena, has been successfully applied to many \w phenomena in past decades.
The recent reports of superluminal tunnelling times and negative group
velocities challenged this concept. A new local approach for the definition of
\wvs avoiding these difficulties while including the classical definitions as
particular cases is proposed here. This generalisation of the conventional
non-local approach can be applied to arbitrary \w forms and propagation media.
Some applications of the formalism are presented and basic properties of the
concept are summarized.
| math-ph math.MP |
0704.1486 | Nodal/Antinodal Dichotomy and the Two Gaps of a Superconducting Doped
Mott Insulator | We study the superconducting state of the hole-doped two-dimensional Hubbard
model using Cellular Dynamical Mean Field Theory, with the Lanczos method as
impurity solver. In the under-doped regime, we find a natural decomposition of
the one-particle (photoemission) energy-gap into two components. The gap in the
nodal regions, stemming from the anomalous self-energy, decreases with
decreasing doping. The antinodal gap has an additional contribution from the
normal component of the self-energy, inherited from the normal-state pseudogap,
and it increases as the Mott insulating phase is approached.
| cond-mat.str-el |
0704.1487 | Wavelet frames, Bergman spaces and Fourier transforms of Laguerre
functions | The Fourier transforms of Laguerre functions play the same canonical role in
wavelet analysis as do the Hermite functions in Gabor analysis. We will use
them as analyzing wavelets in a similar way the Hermite functions were recently
by K. Groechenig and Y. Lyubarskii in "Gabor frames with Hermite functions, C.
R. Acad. Sci. Paris, Ser. I 344 157-162 (2007)". Building on the work of K.
Seip, "Beurling type density theorems in the unit disc, Invent. Math., 113,
21-39 (1993)", concerning sampling sequences on weighted Bergman spaces, we
find a sufficient density condition for constructing frames by translations and
dilations of the Fourier transform of the nth Laguerre function. As in
Groechenig-Lyubarskii theorem, the density increases with n, and in the special
case of the hyperbolic lattice in the upper half plane it is given by b\log
a<\frac{4\pi}{2n+\alpha}, where alpha is the parameter of the Laguerre
function.
| math.CA math.CV |
0704.1488 | On Beltrami fields with nonconstant proportionality factor on the plane | We consider the equation rotB+aB=0 (1) in the plane with a being a
real-valued function and show that it can be reduced to a Vekua equation of a
special form. In the case when a depends on one Cartesian variable a complete
system of exact solutions of the Vekua equation and hence of equation (1) is
constructed based on L. Bers' theory of formal powers.
| math-ph math.MP |
0704.1489 | Where the monotone pattern (mostly) rules | We consider pattern containment and avoidance with a very tight definition
that was used first by Riordan more than 60 years ago. Using this definition,
we prove the monotone pattern is easier to avoid than almost any other pattern
of the same length.
We also show that with this definition, almost all patterns of length $k$ are
avoided by the same number of permutations of length $n$. The corresponding
statements are not known to be true for more relaxed definitions of pattern
containment. This is the first time we know of that expectations are used to
compare numbers of permutations avoiding certain patterns.
| math.CO math.PR |
0704.1490 | Staggered Heavy Baryon Chiral Perturbation Theory | Although taste violations significantly affect the results of staggered
calculations of pseudoscalar and heavy-light mesonic quantities, those entering
staggered calculations of baryonic quantities have not been quantified. Here I
develop staggered chiral perturbation theory in the light-quark baryon sector
by mapping the Symanzik action into heavy baryon chiral perturbation theory.
For 2+1 dynamical quark flavors, the masses of flavor-symmetric nucleons are
calculated to third order in partially quenched and fully dynamical staggered
chiral perturbation theory. To this order the expansion includes the leading
chiral logarithms, which come from loops with virtual decuplet-like states, as
well as terms the order of the cubed pion mass, which come from loops with
virtual octet-like states. Taste violations enter through the meson propagators
in loops and tree-level terms the order of the squared lattice spacing. The
pattern of taste symmetry breaking and the resulting degeneracies and mixings
are discussed in detail. The resulting chiral forms are appropriate to lattice
results obtained with operators already in use and could be used to study the
restoration of taste symmetry in the continuum limit. I assume that the fourth
root of the fermion determinant can be incorporated in staggered chiral
perturbation theory using the replica method.
| hep-lat |
0704.1491 | Imaging Magnetic Focusing of Coherent Electron Waves | The magnetic focusing of electrons has proven its utility in fundamental
studies of electron transport. Here we report the direct imaging of magnetic
focusing of electron waves, specifically in a two-dimensional electron gas
(2DEG). We see the semicircular trajectories of electrons as they bounce along
a boundary in the 2DEG, as well as fringes showing the coherent nature of the
electron waves. Imaging flow in open systems is made possible by a cooled
scanning probe microscope. Remarkable agreement between experiment and theory
demonstrates our ability to see these trajectories and to use this system as an
interferometer. We image branched electron flow as well as the interference of
electron waves. This technique can visualize the motion of electron waves
between two points in an open system, providing a straightforward way to study
systems that may be useful for quantum information processing and spintronics.
| cond-mat.mes-hall |
0704.1492 | On the solution of the static Maxwell system in axially symmetric
inhomogeneous media | We consider the static Maxwell system with an axially symmetric dielectric
permittivity and construct complete systems of its solutions which can be used
for analytic and numerical solution of corresponding boundary value problems.
| math-ph math.MP |
0704.1493 | On a {K_4,K_{2,2,2}}-ultrahomogeneous graph | The existence of a connected 12-regular $\{K_4,K_{2,2,2}\}$-ultrahomogeneous
graph $G$ is established, (i.e. each isomorphism between two copies of $K_4$ or
$K_{2,2,2}$ in $G$ extends to an automorphism of $G$), with the 42 ordered
lines of the Fano plane taken as vertices. This graph $G$ can be expressed in a
unique way both as the edge-disjoint union of 42 induced copies of $K_4$ and as
the edge-disjoint union of 21 induced copies of $K_{2,2,2}$, with no more
copies of $K_4$ or $K_{2,2,2}$ existing in $G$. Moreover, each edge of $G$ is
shared by exactly one copy of $K_4$ and one of $K_{2,2,2}$. While the line
graphs of $d$-cubes, ($3\le d\in\ZZ$), are $\{K_d, K_{2,2}\}$-ultrahomogeneous,
$G$ is not even line-graphical. In addition, the chordless 6-cycles of $G$ are
seen to play an interesting role and some self-dual configurations associated
to $G$ with 2-arc-transitive, arc-transitive and semisymmetric Levi graphs are
considered.
| math.CO |
0704.1494 | Unconventional approaches to combine optical transparency with
electrical conductivity | Combination of electrical conductivity and optical transparency in the same
material -- known to be a prerogative of only a few oxides of post-transition
metals, such as In, Sn, Zn and Cd -- manifests itself in a distinctive band
structure of the transparent conductor host. While the oxides of other elements
with $s^2$ electronic configuration, for example, Mg, Ca, Sc and Al, also
exhibit the desired optical and electronic features, they have not been
considered as candidates for achieving good electrical conductivity because of
the challenges of efficient carrier generation in these wide-bandgap materials.
Here we demonstrate that alternative approaches to the problem not only allow
attaining the transport and optical properties which compete with those in
currently utilized transparent conducting oxides (TCO), but also significantly
broaden the range of materials with a potential of being developed into novel
functional transparent conductors.
| cond-mat.mtrl-sci |
0704.1495 | Exponential Decay of Correlations for Randomly Chosen Hyperbolic Toral
Automorphisms | We consider pairs of toral automorphisms (A,B) satisfying an invariant cone
property. At each iteration, A acts with probability p and B with probability
1-p. We prove exponential decay of correlations for a class of Holder
continuous observables.
| math.DS math-ph math.MP |
0704.1496 | Follow-up observations of pulsating subdwarf B stars: Multisite
campaigns on PG 1618+563B and PG 0048+091 | We present follow-up observations of pulsating subdwarf B (sdB) stars as part
of our efforts to resolve the pulsation spectra for use in asteroseismological
analyses. This paper reports on multisite campaigns of the pulsating sdB stars
PG 1618+563B and PG 0048+091. Data were obtained from observatories placed
around the globe for coverage from all longitudes. For PG 1618+563B, our
five-site campaign uncovered a dichotomy of pulsation states: Early during the
campaign the amplitudes and phases (and perhaps frequencies) were quite
variable while data obtained late in the campaign were able to fully resolve
five stable pulsation frequencies. For PG 0048+091, our five-site campaign
uncovered a plethora of frequencies with short pulsation lifetimes. We find
them to have observed properties consistent with stochastically excited
oscillations, an unexpected result for subdwarf B stars. We discuss our
findings and their impact on subdwarf B asteroseismology.
| astro-ph |
0704.1497 | Connecting microscopic simulations with kinetically constrained models
of glasses | Kinetically constrained spin models are known to exhibit dynamical behavior
mimicking that of glass forming systems. They are often understood as
coarse-grained models of glass formers, in terms of some "mobility" field. The
identity of this "mobility" field has remained elusive due to the lack of
coarse-graining procedures to obtain these models from a more microscopic point
of view. Here we exhibit a scheme to map the dynamics of a two-dimensional soft
disc glass former onto a kinetically constrained spin model, providing an
attempt at bridging these two approaches.
| cond-mat.dis-nn cond-mat.soft cond-mat.stat-mech |
0704.1498 | DIRBE Minus 2MASS: Confirming the CIRB in 40 New Regions at 2.2 and 3.5
Microns | With the release of the 2MASS All-Sky Point Source Catalog, stellar fluxes
from 2MASS are used to remove the contribution due to Galactic stars from the
intensity measured by DIRBE in 40 new regions in the North and South Galactic
polar caps. After subtracting the interplanetary and Galactic foregrounds, a
consistent residual intensity of 14.69 +/- 4.49 kJy/sr at 2.2 microns is found.
Allowing for a constant calibration factor between the DIRBE 3.5 microns and
the 2MASS 2.2 microns fluxes, a similar analysis leaves a residual intensity of
15.62 +/- 3.34 kJy/sr at 3.5 microns. The intercepts of the DIRBE minus 2MASS
correlation at 1.25 microns show more scatter and are a smaller fraction of the
foreground, leading to a still weak limit on the CIRB of 8.88 +/- 6.26 kJy/sr
(1 sigma).
| astro-ph |
0704.1499 | Averaging of the electron effective mass in multicomponent transparent
conducting oxides | We find that layered materials composed of various oxides of cations with
$s^2$ electronic configuration, $XY_2$O$_4$, $X$=In or Sc, $Y$=Ga, Zn, Al, Cd
and/or Mg, exhibit isotropic electron effective mass which can be obtained via
averaging over those of the corresponding single-cation oxide constituents.
This effect is due to a hybrid nature of the conduction band formed from the
s-states of {\it all} cations and the oxygen p-states. Moreover, the observed
insensitivity of the electron effective mass to the oxygen coordination and to
the distortions in the cation-oxygen chains suggests that similar behavior can
be expected in technologically important amorphous state. These findings
significantly broaden the range of materials as efficient transparent conductor
hosts.
| cond-mat.mtrl-sci |
0704.1500 | A Search for Electron Neutrino Appearance at the Delta m**2 ~ 1 eV**2
Scale | The MiniBooNE Collaboration reports first results of a search for $\nu_e$
appearance in a $\nu_\mu$ beam. With two largely independent analyses, we
observe no significant excess of events above background for reconstructed
neutrino energies above 475 MeV. The data are consistent with no oscillations
within a two neutrino appearance-only oscillation model.
| hep-ex |