April 2002 arXiv papers — page 8

Ciprian Acatrinei

A simple method to canonically quantize noncommutative field theories is proposed. As a result, the elementary excitations of a (2n+1)-dimensional scalar field theory are shown to be bilocal objects living in an (n+1)-dimensional space-time. Feynman rules for their scattering are derived canonically. They agree, upon suitable redefinitions, with the rules ob

H. Reinhardt

In this talk I study the topology of mathematically idealised center vortices, defined in a gauge invariant way as closed (infinitely thin) flux surfaces (in D=4 dimensions) which contribute the $n^{th}$ power of a non-trivial center element to Wilson loops when they are n-foldly linked to the latter. In ordinary 3-space generic center vortices represent clo

A. Brandhuber, K. Sfetsos

Using the AdS/CFT correspondence we study vacua of N=4 SYM for which part of the gauge symmetry is broken by expectation values of scalar fields. A specific subclass of such vacua can be analyzed with gauged supergravity and the corresponding domain wall solutions lift to continuous distributions of D3-branes in type IIB string theory. Due to the non-trivial

F. T. Brandt, Ashok Das, J. Frenkel, D. G. C. McKeon

We show that the high temperature limit of the noncommutative thermal Yang-Mills theory can be directly obtained from the Boltzmann transport equation of classical particles. As an illustration of the simplicity of the Boltzmann method, we evaluate the two and the three-point gluon functions in the noncommutative U(N) theory at high temperatures T. These amp

Soon-Tae Hong, Yong-Wan Kim, Young-Jai Park, Klaus D. Rothe

We consider the master Lagrangian of Deser and Jackiw, interpolating between the self-dual and the Maxwell-Chern-Simons Lagrangian, and quantize it following the symplectic approach, as well as the traditional Dirac scheme. We demonstrate the equivalence of these procedures in the subspace of the second-class constraints. We then proceed to embed this mixed

Andrei Frolov, Lev Kofman, Alexei Starobinsky

We consider the evolution of FRW cosmological models and linear perturbations of tachyon matter rolling towards a minimum of its potential. The tachyon coupled to gravity is described by an effective 4d field theory of string theory tachyon. In the model where a tachyon potential $V(T)$ has a quadratic minimum at finite value of the tachyon field $T_0$ and $

D. Kharzeev, E. Levin, K. Tuchin

QCD at the classical level possesses scale invariance which is broken by quantum effects. This ``dimensional transmutation'' phenomenon can be mathematically described by formulating classical gluodynamics in a curved, conformally flat, space-time with non-vanishing cosmological constant. We study QCD high-energy scattering in this theory. We find th

Paul H. Frampton, Myoung C. Oh, Tadashi Yoshikawa

It is shown how to obtain recently-proposed two-zero Majorana mass textures in models with three Higgs triplets with small VEVs and a sufficiently massive triplet Majoron by using abelian discrete symmetries. It is briefly discussed how in SU(5) grand unification where the triplets occur in {\bf 15}'s the neutrino textures can be related to up- and down-

H. Hogaasen, K. Kubodera, F. Myhrer

The simple independent quark models have difficulties explaining simultaneously the totality of the known hyperon magnetic moments and hyperon semi-leptonic decay rates. We show that both the Goldstone boson loop contributions and the two-quark effective exchange currents are essential in explaining these observables.

Kari Enqvist, Shinta Kasuya, Anupam Mazumdar

We describe a new mechanism for reheating the Universe through evaporation of a surface charge of a fragmented inflaton condensate. We show that for a range of Yukawa coupling of the inflaton to the matter sector evaporation gives rise to a much smaller reheat temperature compared to the standard perturbative decay. As a consequence, reheating through a surf

J. Bartels, H. Jung, A. Kyrieleis

We calculate the cross section for $c\bar{c}g$-production in diffractive DIS with finite quark masses at zero momentum transfer $t$. The calculation is done in the leading log(1/$x_{P}$) approximation and is valid in the region of high diffractive masses $M$ (small $β$). We apply our cross section formula including both $c{\bar c}$- and $c\bar{c}g$ in a Mont

A. V. Berezhnoy, A. K. Likhoded

In the framework of perturbative QCD and a model for the production of charmed hadrons the structure function $F^c_2$ is calculated and compared with the experimental data of H1 and ZEUS Collaborations. We show that the spectator mechanism of the $D^*$-meson production independent of a hadronic remnant is valid at $p_T>10$ GeV, only. We find that the evoluti

V. N. Baier, V. M. Katkov

The radiation at collision of high-energy particles is formed over a rather long distances and therefore is sensitive to an environment. In particular the smallness of the transverse dimensions of the colliding beams leads to suppression of bremsstrahlung cross section for soft photons. This beam-size effect was discovered and investigated at INP, Novosibirs

J. A. Gracey

We determine the complete set of independent dimension six and eight Lorentz scalar operators in Yang-Mills theory for an arbitrary colour group. The anomalous dimension mixing matrix is determined at one loop.

Tsung-Wen Yeh

The next-to-leading-order $O(1/Q^4)$ power correction for $ηγ$ and $η^\primeγ$ form factors are evaluated and employed to explore the $η-η^\prime$ mixing. The parameters of the two mixing angle scheme are extracted from the data for form factors, two photon decay widths and radiative $J/ψ$ decays. The $χ^2$ analysis gives the result: $f_{η_1}=(1.16\pm0.06)f_

Michael Engelhardt

A model for the infrared sector of SU(2) Yang-Mills theory, based on magnetic vortex degrees of freedom represented by (closed) random world-surfaces, is presented. The model quantitatively describes both the confinement properties (including the finite-temperature transition to a deconfined phase) and the topological susceptibility of the Yang-Mills ensembl

Fermilab E706 Collaboration, L. Apanasevich

We present results on the production of high transverse momentum pizero and eta mesons in pp and pBe interactions at 530 and 800 GeV/c. The data span the kinematic ranges: 1 < p_T < 10 GeV/c in transverse momentum and 1.5 units in rapidity. The inclusive pizero cross sections are compared with next-to-leading order QCD calculations and to expectations based

Ghazal Geshnizjani, Robert Brandenberger

We calculate the back reaction of cosmological perturbations on a general relativistic variable which measures the local expansion rate of the Universe. Specifically, we consider a cosmological model in which matter is described by a single field. We analyze back reaction both in a matter dominated Universe and in a phase of scalar field-driven chaotic infla

L. Rezzolla, O. Zanotti

In Newtonian and relativistic hydrodynamics the Riemann problem consists of calculating the evolution of a fluid which is initially characterized by two states having different values of uniform rest-mass density, pressure and velocity. When the fluid is allowed to relax, one of three possible wave-patterns is produced, corresponding to the propagation in op

M. Bouhmadi-Lopez, L. J. Garay, P. F. Gonzalez-Diaz

We study the quantum vacuum fluctuations around closed Friedmann-Robertson-Walker (FRW) radiation-filled universes with nonvanishing cosmological constant. These vacuum fluctuations are represented by a conformally coupled massive scalar field and are treated in the lowest order of perturbation theory. In the semiclassical approximation, the perturbations ar

J. B. Neaton, C. -L. Hsueh, K. M. Rabe

The structure, polarization, and zone-center phonons of bulk tetragonal BaTiO$_3$ under compressive epitaxial stress are calculated using density functional theory within the local density approximation. The polarization, computed using the Berry-phase formalism, increases with increasing tetragonality and is found to be enhanced by nearly 70% for the larges

R. A. Ribeiro, S. L. Bud`ko, C. Petrovic, P. C. Canfield

We present a study of the effects of non-stoichiometry, boron purity, wire diameter and post-synthesis treatment (etching and Mg distilling) on the temperature dependent resistance and resistivity of sintered MgB2 pellets and wire segments. Whereas the residual resistivity ratio (RRR) varies between RRR \~ 4 to RRR > 20 for different boron purity, it is only

K. Malarz, S. Kaczanowska, K. Kulakowski

Dynamic mean field theory is applied to the problem of forest fires. The starting point is the Monte Carlo simulation in a lattice of million cells. The statistics of the clusters is obtained by means of the Hoshen--Kopelman algorithm. We get the map $p_n\to p_{n+1}$, where $p_n$ is the probability of finding a tree in a cell, and $n$ is the discrete time. W

Joel E. Moore

The universal anomalous diffusion scaling is obtained for the semiclassical quantum Hall transition, which has been argued to describe samples with dissipation or correlated impurities. The results explain a discrepancy between existing numerics and the expected scaling $η= 2 x_1 = {1/2}$, which is violated because of a cancellation in the scaling function.

Piotr Habdas, Eric R. Weeks

Colloidal suspensions are simple model systems for the study of phase transitions. Video microscopy is capable of directly imaging the structure and dynamics of colloidal suspensions in different phases. Recent results related to crystallization, glasses, and 2D systems complement and extend previous theoretical and experimental studies. Moreover, new techni

Akihisa Koga, Akira Kawaguchi, Kouichi Okunishi, Norio Kawakami

We give a short review of our recent works on the first-order quantum phase transitions in frustrated spin chains with orthogonal-dimer structure. When the ratio of the competing antiferromagnetic exchange couplings is varied, a first-order transition occurs between the dimer phase and the plaquette phase, which is accompanied by the discontinuity in the spi

S. J. J. M. F. Kokkelmans, M. J. Holland

In a recent experiment, a Feshbach scattering resonance was exploited to observe Ramsey fringes in a $^{85}$Rb Bose-Einstein condensate. The oscillation frequency corresponded to the binding energy of the molecular state. We show that the observations are remarkably consistent with predictions of a resonance field theory in which the fringes arise from oscil

R. Lemanski, J. K. Freericks, G. Banach

The observation of charge stripe order in the doped nickelate and cuprate materials has motivated much theoretical effort to understand the underlying mechanism of the stripe phase. Numerical studies of the Hubbard model show two possibilities: (i) stripe order arises from a tendency toward phase separation and its competition with the long-range Coulomb int

Eduardo Menendez-Proupin

In a recent paper [E. P. Pokatilov et al, PRB 65, 075316 (2002) the Raman selection rules in spherical nanocrystals with a degenerate valence band are analyzed. Some precisions are given here.

Bumsoo Kyung, A. M. -S. Tremblay

In this paper the phase diagram of high $T_{c}$ cuprates is {\it qualitatively} studied in the context of competing orders: antiferromagnetism, d-wave superconductivity and $d$-density wave. {\it Local} correlation functions are estimated from a mean-field solution of the $t-J$ Hamiltonian. With decreasing doping the superconducting mean-field $T^{MF}_{c}$ a

D. S. Novikov, L. S. Levitov

Electron properties of Carbon nanotubes can change qualitatively in a transverse electric field. In metallic tubes the sign of Fermi velocity can be reversed in a sufficiently strong field, while in semiconducting tubes the effective mass can change sign. These changes in the spectrum manifest themselves in a breakup of the Fermi surface and in the energy ga

A. E. Pogorelov, K. P. Ryaboshapka, A. F. Zhuravlyov

The dynamic processes in the surface layers of metals subjected activity of a pulsing laser irradiation, which destroyed not the crystalline structure in details surveyed. The procedure of calculation of a dislocation density generated in bulk of metal during the relaxation processes and at repeated pulse laser action is presented. The results of evaluations

Jorge Iniguez, D. Vanderbilt

We investigate the temperature-pressure phase diagram of BaTiO_3 using a first-principles effective-Hamiltonian approach. We find that the zero-point motion of the ions affects the form of the phase diagram dramatically. Specifically, when the zero-point fluctuations are included in the calculations, all the polar (tetragonal, orthorhombic, and rhombohedral)

Anjan Kundu

A scheme based on a unifying q-deformed algebra and associated with a generalized Lax operator is proposed for generating integrable quantum and statistical models. As important applications we derive known as well as novel quantum models and obtain new series of vertex models related to q-spin, q-boson and their hybrid combinations. Generic q, q roots of un

Stefano Lise, Maya Paczuski

We numerically investigate the Olami-Feder-Christensen model on a quenched random graph. Contrary to the case of annealed random neighbors, we find that the quenched model exhibits self-organized criticality deep within the nonconservative regime. The probability distribution for avalanche size obeys finite size scaling, with universal critical exponents. In

Stefano Lise

We numerically investigate the approach to the stationary state in the nonconservative Olami-Feder-Christensen (OFC) model for earthquakes. Starting from initially random configurations, we monitor the average earthquake size in different portions of the system as a function of time (the time is defined as the input energy per site in the system). We find th

Jizhong Lou, Shaojin Qin, Changfeng Chen, Zhaobin Su

We study the spin-1/2 antiferromagnetic Heisenberg chain in both uniform and (perpendicular) staggered magnetic fields using the density-matrix renormalization-group method. This model has been shown earlier to describe the physics of the copper benzoate materials in magnetic field. In the present work, we extend the study to more general case for a systemat

Debdeep Jena, Sten Heikman, Daniel Green, Ilan B. Yaacov

We present the concept and experimental realization of polarization-induced bulk electron doping in III-V nitride semiconductors. By exploiting the large polarization charges in the III-V nitrides, we are able to create wide slabs of high density mobile electrons without introducing shallow donors. Transport measurements reveal the superior properties of the

Eugeny Kochetov, Marcin Mierzejewski

We show that the resonating valence bond (RVB) state of the t-J Hamiltonian can be described within an effective boson-fermion model. We derive a boson-fermion Hamiltonian which describes the lowest order coupling between holons and spinon waves. The RVB order parameter determines a hybridization between the both types of excitations. The effective Hamiltoni

Marina Bastea, Sorin Bastea

We report measurements of the electrical conductivity of a liquid alkali metal - lithium - at pressures up to 1.8 Mbar and fourfold compression, achieved through shock compression experiments. We find that the results are consistent with a departure of the electronic properties of lithium from the nearly free electron approximation at high pressures.

R. Q. Mao, J. Yang, C. Henkel, Z. B. Jiang

We present molecular line and submillimeter dust continuum observations of the Lynds 870 cloud in the vicinity of IRAS 20231+3440. Two submillimeter cores, SMM1 and SMM2, are identified mapping the 870 micron dust continuum and ammonia emission. The total molecular mass is ~70-110 solar mass. The northern core is warmer and denser than the southern one. Mole

Klaus W. Hodapp, Christopher J. Davis

We present the results of a deep search for the molecular hydrogen shock fronts associated with young stellar outflows in the giant molecular cloud and massive star forming region W51. A total of 14 outflows were identified, and a few of these were studied in detail with high-resolution imaging and spectroscopy.

Aigen Li, J. Mayo Greenberg, Gang Zhao

The {\it assumption of additive absorptivity} by different components in compound particles is a widely used method applied in the literature to the analysis of the chemical and structural properties of astronomical (circumstellar, interstellar, protostellar, and cometary) silicates as well as other materials. The errors intrinsic in this additivity assumpti

Aigen Li, J. Mayo Greenberg

In the framework of the silicate core-carbonaceous organic mantle interstellar dust model, the bulk of the visual/near-IR extinction and the entire polarization are from nonspherical and aligned core-mantle grains. The 3.4 micron C-H and 9.7 micron Si-O absorption features, respectively arising from the hydrocarbon mantle and the amorphous silicate core, are

Aigen Li, J. Mayo Greenberg

The past century of interstellar dust has brought us from first ignoring it to finding that it is an important component of the interstellar medium and plays an important role in the evolution of galaxies, the formation of stars and planetary systems, and possibly, the origins of life. Current observational results in our galaxy provide a complex physical an

Stanimir A. Metchev, Jonathan E. Grindlay

We present a two-dimensional version of the classical one-dimensional Kolmogorov-Smirnov (K-S) test, extending an earlier idea due to Peacock (1983) and an implementation proposed by Fasano & Franceschini (1987). The two-dimensional K-S test is used to optimise the goodness of fit in an iterative source-detection scheme for astronomical images. The method is

Y. Inoue, T. Namba, S. Moriyama, M. Minowa

A search for solar axions has been performed using an axion helioscope which is equipped with a 2.3m-long 4T superconducting magnet, PIN-photodiode X-ray detectors, and a telescope mount mechanism to track the sun. In addition, a gas container to hold dispersion-matching gas has been developed and a mass region up to m_a=0.27eV was newly explored. From the a

B. Fuchs

An attempt is made to set constraints on the otherwise ambiguous decomposition of the rotation curves of low surface brightness galaxies into contributions due to the various components of the galaxies. For this purpose galaxies are selected which show clear spiral structure. Arguments of density wave theory of galactic spiral arms are then used to estimate

A. Vidal-Madjar, R. Ferlet

The deuterium abundance evaluation in the direction of Capella has for a long time been used as a reference for the local interstellar medium (ISM) within our Galaxy. We show here that broad and weak HI components could be present on the Capella line of sight, leading to a large new additional systematic uncertainty on the N(HI) evaluation. The D/H ratio tow

A. J. J. Raassen, R. Mewe, M. Audard, M. Guedel

We report the analysis of the high-resolution soft X-ray spectrum of the nearby F-type star Procyon in the wavelength range from 5 to 175 Angstrom obtained with the Low Energy Transmission Grating Spectrometer (LETGS) on board Chandra and with the Reflection Grating Spectrometers (RGS) and the EPIC-MOS CCD spectrometers on board XMM-Newton. Line fluxes have

J. Halenka, J. Madej

We present extensive tables of the Atomic Partition Function for iron ions, Fe I -- Fe X, and discuss details of the computational method. Partition functions are given in wide range of temperatures, 10^3 K < T < 10^6 K, and lowering of ionization energy (0.001 eV < LIE < 5.0 eV). Our APF take into account all energy levels predicted by quantum mechanics, in

Timothy A. McKay, Erin Scott Sheldon, David Johnston, Eva K. Grebel

Galaxy masses can be estimated by a variety of methods; each applicable in different circumstances, and each suffering from different systematic uncertainties. Confirmation of results obtained by one technique with analysis by another is particularly important. Recent SDSS weak lensing measurements of the projected-mass correlation function reveal a linear r

L. Mantegazza, E. Antonello, D. Fugazza, S. Covino

The variable star V39 in the field of IC 1613 is discussed in the light of the available photometric and new spectroscopic data. It has strong emission Balmer lines, and the observed characteristics could be explained by a W Vir pulsating star with a period of 14.341 d, located at more than 115 kpc, that is in the very outer halo of our Galaxy. It should hav

S. B. Charnley, S. D. Rodgers, H. M. Butner, P. Ehrenfreund

Recent developments in the chemical modelling of cometary comae are described. We discuss the cyanide chemistry and present new HCN observations of the recent comet C/2002 C1 (Ikeya-Zhang). The connection between interstellar and cometary organic molecules is discussed from the perspective of recent theories of interstellar gas-grain chemistry.

L. Hansen, L. F. Olsen, H. E. Jorgensen

We report the results of the first multi-object spectroscopic observations at the Danish 1.54m telescope at La Silla, Chile. Observations of five cluster candidates from the ESO Imaging Survey Cluster Candidate Catalog are described. From these observations we confirm the reality of the five clusters with measured redshifts of 0.11<=z<=0.35. We estimate velo

C. M. Boily, E. Athanassoula, P. Kroupa

The purpose of this article is to show that when dynamically cold, dissipationless self-gravitating systems collapse, their evolution is a strong function of the symmetry in the initial distribution. We explore with a set of pressure-less homogeneous fluids the time-evolution of ellipsoidal distributions and map the depth of potential achieved during relaxat

K. M. V. Apparao

It is suggested that Dark Matter in the Universe is made of stars and black holes of WIMP matter.

R. S. Sutherland, D. K. Bisset, G. V. Bicknell

We address a numerical instability that arises in the directionally split computation of hydrodynamic flows when shock fronts are parallel to a grid plane. Transverse oscillations in pressure, density and temperature are produced that are exacerbated by thermal instability when cooling is present, forming post--shock `stripes&#39;. These are orthogonal to th

Jack R. Gabel, Frederick C. Bruhweiler

We present a comprehensive study to determine if the LINER/H II region transition spectrum in NGC 4569 can be generated solely by photoionization by the nuclear starburst. A review of the multiwavelength data from the literature reveals no additional sources that contribute to the ionization. We find that the young starburst dominating the UV emission is dis

Iddo Ussishkin, S. L. Sondhi, David A. Huse

We calculate the contribution of superconducting fluctuations to thermal transport in the normal state, for low magnetic fields. We do so in the Gaussian approximation to their critical dynamics which is also the Aslamazov-Larkin approximation in the microscopics. Our results for the thermal conductivity tensor and the transverse thermoelectric response are

Valeri V. Dvoeglazov

Ambiguities have recently been found in the definition of the partial derivative (in the case of presence of both explicit and implicit dependencies of the function subjected to differentiation). We investigate the possible influence of this subject on quantum mechanics and the classical/quantum field theory. Surprisingly, some commutators of operators of sp

Kyungwha Park, M. A. Novotny, N. S. Dalal, S. Hill

We examine quantitatively the temperature dependence of the linewidths and line shifts in electron paramagnetic resonance experiments on single crystals of the single-molecule magnets Fe$_8$ and Mn$_{12}$, at fixed frequency, with an applied magnetic field along the easy axis. We include inter-molecular spin-spin interactions (dipolar and exchange) and distr

Robert F. Carswell, Joop Schaye, Tae-Sun Kim

A search for O VI at redshifts corresponding to Ly-alpha lines in the z_em ~ 2.4 QSOs HE1122-1648 and HE2217-2818 reveals that a substantial fraction of those with H I column densities log N(HI) > 14 (cm^{-2}) are highly ionized and show some heavy element enrichment. If these two sight lines are typical, then the O VI systems contain a cosmologically signif

C. R. Gwinn, C. Hirano, S. Boldyrev

We sought to determine the scale of scintillation in the interstellar plasma of PSR J0437-4715. We used the Very Long Baseline Array to obtain scintillation amplitude and phase data, from dynamic spectra at 327 MHz. We observe two scales of scintillation of pulsar PSR J0437-4715, differing by more than an order of magnitude in scintillation bandwidth. The wi

Victor Barzykin, Lev P. Gor&#39;kov

We consider 2D surface superconductivity in high magnetic fields parallel to the surface. We demonstrate that the spin-orbit interaction at the surface changes the properties of the inhomogeneous superconducting Larkin-Ovchinnikov-Fulde-Ferrell state that develops above fields given by the paramagnetic criterion. Strong spin-orbit interaction significantly b

M. Bertola, B. Eynard, J. Harnad

For one-matrix models with polynomial potentials, the explicit relationship between the partition function and the isomonodromic tau function for the 2x2 polynomial differential systems satisfied by the associated orthogonal polynomials is derived.

Martin Wolf

In this paper we study the noncommutative extension of a modified U(n) sigma model in 2+1 dimensions. Using the method of dressing transformations, an iterative approach for the construction of solutions from a given seed solution, we demonstrate the construction of multi-soliton and soliton-antisoliton configurations for general n. As illustrative examples

D. M. Ghilencea, H. P. Nilles

We analyze the ultraviolet stability of the Higgs mass in recently proposed Kaluza-Klein models compactified on S_1/Z_2 or S_1/(Z_2\times Z_2&#39;), both at the field theory and string theory level. Fayet-Iliopoulos terms of U(1) hypercharge are shown to be of vital importance for this discussion. Models with a single Higgs doublet seem to be generically aff

Massimo Blasone, Antonio Capolupo, Giuseppe Vitiello

We study in detail the Quantum Field Theory of mixing among three generations of Dirac fermions (neutrinos). We construct the Hilbert space for the flavor fields and determine the generators of the mixing transformations. By use of these generators, we recover all the known parameterizations of the three-flavor mixing matrix and we find a number of new ones.

Miroslav Kotrla, Frantisek Slanina, Jakub Steiner

We found that models of evolving random networks exhibit dynamic scaling similar to scaling of growing surfaces. It is demonstrated by numerical simulations of two variants of the model in which nodes are added as well as removed [Phys. Rev. Lett. 83, 5587 (1999)]. The averaged size and connectivity of the network increase as power-laws in early times but la

V. Barger, D. Marfatia, K. Whisnant, B. P. Wood

We perform a global analysis in the framework of two active neutrino oscillations of all solar neutrino data, including the recent SNO day and night spectra (comprised of the charged current (CC), elastic scattering (ES) and neutral current (NC) events), the Super-Kamiokande (SK) day and night spectra (from 1496 days) and the updated SAGE results. We find th

Viqar Husain

We give observations about dualities where one of the dual theories is geometric. These are illustrated with a duality between the simple harmonic oscillator and a topological field theory. We then discuss the Wilson loop in the context of the AdS/CFT duality. We show that the Wilson loop calculation for certain asymptotically AdS scalar field spacetimes wit

T. Opatrny, N. Korolkova, G. Leuchs

The question of efficient multimode description of optical pulses is studied. We show that a relatively very small number of nonmonochromatic modes can be sufficient for a complete quantum description of pulses with Gaussian quadrature statistics. For example, a three-mode description was enough to reproduce the experimental data of photon number correlation

Sebastian Silva

Given a boundary of spacetime preserved by a Diff(S^{1}) sub-algebra, we propose a systematic method to compute the zero mode and the central extension of the associated Virasoro algebra of charges. Using these values in the Cardy formula, we may derive an associated statistical entropy to be compared with the Bekenstein-Hawking result. To illustrate our met

Jesper Sommer-Larsen, Martin Gotz, Laura Portinari

TreeSPH simulations of galaxy formation in a LCDM cosmology, with star formation, energetic stellar feedback and a meta-galactic UV field have been performed, resulting in realistic disk, S0 and E galaxies at z=0. The disk galaxies are deficient in angular momentum by only about a factor of two compared to observations for runs where fairly strong star-burst

Xavier Calmet, Harald Fritzsch

Astrophysical indications that the fine structure constant has undergone a small time variation during the cosmological evolution are discussed within the framework of the standard model of the electroweak and strong interactions and of grand unification. A variation of the electromagnetic coupling constant could either be generated by a corresponding time v

H. Potempa, L. Schweitzer

We investigate a disordered two-dimensional lattice model for noninteracting electrons with long-range power-law transfer terms and apply the method of level statistics for the calculation of the critical properties. The eigenvalues used are obtained numerically by direct diagonalization. We find a metal-insulator transition for a system with orthogonal symm

Anjan Kundu

Applying a unifying Lax operator approach to statistical systems a new class of integrable vertex models based on quantum algebra is proposed, which exhibits a rich variety for generic q, q roots of unity and q -> 1. Exact solutions are formulated through algebraic Bethe ansatz and a novel possibility of hybrid vertex models is introduced.

Makoto Makita, Shin Mineshige

We propose a new method, emission-line eclipse mapping, to map the velocity fields of an accretion disk in position space. Quiescent dwarf novae usually exhibit double-peaked emission line profiles because of disk rotation. Since a part of the disk having a different line-of-sight velocity is successively obscured by a companion in eclipsing systems, they sh

S. Frixione, B. R. Webber

We propose a method for matching the next-to-leading order (NLO) calculation of a given QCD process with a parton shower Monte Carlo (MC) simulation. The method has the following features: fully exclusive events are generated, with hadronization according to the MC model; total exclusive rates are accurate to NLO; NLO results for distributions are recovered

L. Tewordt, D. Fay

The specific heat C and the electronic and phononic thermal conductivities kappa_e and kappa_{ph} are calculated in the mixed state for magnetic fields H near H_{c2}. The effects of supercurrent flow and Andreev scattering of the Abrikosov vortex lattice on the quasiparticles are taken into account. The resulting function C(H) is nearly linear while kappa_e(

P. M. O&#39;Neill, E. Kuulkers, R. K. Sood, M. van der Klis

Sco X-2 (GX 349+2) is a low-mass X-ray binary and Z source. We have analysed 156 ks of Rossi X-ray Timing Explorer data, obtained in 1998 January, on this source. We investigated the fast-time variability as a function of position on the Z track. During these observations, Sco X-2 traced out the most extensive Z track ever reported from this object, making t

N. P. Konstantinidis, D. Coffey

We apply degenerate perturbation theory to investigate the effects of magnetic anisotropy in the magnetic molecule V15. Magnetic anisotropy is introduced via Dzyaloshinskii-Moriya (DM) interaction in the full Hilbert space of the system. Our model provides an explanation for the rounding of transitions in the magnetization as a function of applied field at l

R. Foot, S. Mitra

Mirror symmetry is a plausible candidate for a fundamental symmetry of particle interactions which can be exactly conserved if a set of mirror particles exist. The properties of the mirror particles seem to provide an excellent candidate to explain the inferred dark matter of the Universe and might also be responsible for a variety of other puzzles in partic

Zhe Chang, Zhi-zhong Xing

Possible effects of noncommutative geometry on weak CP violation and unitarity triangles are discussed by taking account of a simple version of the momentum-dependent quark mixing matrix in the noncommutative standard model. In particular, we calculate nine rephasing invariants of CP violation and illustrate the noncommutative CP-violating effect in a couple

D. Gorbunov, P. Tinyakov, I. Tkachev, S. Troitsky

A set of potentially gamma-ray--loud BL Lac objects is selected by intersecting the EGRET and BL Lac catalogs. Of the resulting 14 objects, eight are found to correlate with arrival directions of ultra--high-energy cosmic rays (UHECRs), with significance of the order of 5 sigma. This suggests that gamma-ray emission can be used as a distinctive feature of th

H. Wu, S. J. Xue, X. Y. Xia, Z. G. Deng

We report the optical identifications of two X-ray luminous point sources in the spiral galaxy NGC4565 based on archive data of Chandra and the Hubble Space Telescope. The central X-ray point source, RXJ1236.3+2559, is found to be the nucleus of NGC4565 with an X-ray luminosity of Lx= 4.3 10^{39} erg. We show that its multi-waveband properties are consistent

M. Iwanaga, M. Shirai, K. Tanaka, T. Hayashi

We have comprehensively investigated localized states of photoinduced electron-hole pairs with electron-spin-resonance technique and photoluminescence (PL) in a wide temperature range of 5-200 K. At low temperatures below 70 K, holes localize on Pb$^{2+}$ ions and form self-trapping hole centers of Pb$^{3+}$. The holes transfer to other trapping centers abov

Kashif Alvi

First-order hyperbolic systems are promising as a basis for numerical integration of Einstein&#39;s equations. In previous work, the lapse and shift have typically not been considered part of the hyperbolic system and have been prescribed independently. This can be expensive computationally, especially if the prescription involves solving elliptic equations.

Alexander G. Kyriakos

In the previous paper (quant-ph/0204037) we proved that the quantum mechanics not only has statistic interpretation, but also the specific electromagnetic form. Here, from this point of view we show that all the formal particularities of Dirac&#39;s equation have also the known electromagnetic sense.

Bassano Vacchini

A structure of generator of a quantum dynamical semigroup for the dynamics of a test particle interacting through collisions with the environment is considered, which has been obtained from a microphysical model. The related master-equation is shown to go over to a Fokker-Planck equation for the description of Brownian motion at quantum level in the long wav

Mustapha Maamache, Hacene Bekkar

The geometrical phase of a time-dependent singular oscillator is obtained in the framework of Gaussian wave packet. It is shown by a simple geometrical approach that the geometrical phase is connected to the classical nonadiabatic Hannay angle of the generalized harmonic oscillator.

N. Gurappa, Prasanta K. Panigrahi, R. Atre, T. Shreecharan

A unified approach, for solving a wide class of single and many-body quantum problems, commonly encountered in literature is developed based on a recently proposed method for finding solutions of linear differential equations. Apart from dealing with exactly and quasi-exactly solvable problems, the present approach makes transparent various properties of the

Walter T. Strunz, Fritz Haake, Daniel Braun

We consider environment induced decoherence of quantum superpositions to mixtures in the limit in which that process is much faster than any competing one generated by the Hamiltonian $H_{\rm sys}$ of the isolated system. This interaction dominated decoherence limit has previously not found much attention even though it is of importance for the emergence of

J. M. Isidro

We formulate a relation between quantum-mechanical coherent states and complex-differentiable structures on the classical phase space ${\cal C}$ of a finite number of degrees of freedom. Locally-defined coherent states parametrised by the points of ${\cal C}$ exist when there is an almost complex structure on ${\cal C}$. When ${\cal C}$ admits a complex stru

Frédéric Grosshans, Philippe Grangier

We introduce new quantum key distribution protocols using quantum continuous variables, that are secure against individual attacks for any transmission of the optical line between Alice and Bob. In particular, it is not required that this transmission is larger than 50 %. Though squeezing or entanglement may be helpful, they are not required, and there is no

Karo Michaelian

The population dynamics and stability of ecosystems of interacting species is studied from the perspective of non-equilibrium thermodynamics by assuming that species, through their biotic and abiotic interactions, are units of entropy production and exchange in an open thermodynamic system with constant external constraints. Within the context of the linear

B. K. Rao, P. Jena

Using first principles calculations based on density functional theory, we show that the stability and magnetic properties of small Mn clusters can be fundamentally altered by the presence of nitrogen. Not only are their binding energies substantially enhanced, but also the coupling between the magnetic moments at Mn sites remains ferromagnetic irrespective

Ayan Banerjee, Dipankar Das, Vasant Natarajan

We use a diode laser locked to a Rb transition as the frequency reference along with a scanning Michelson interferometer to make precise measurements on the $D_1$ and $D_2$ lines of potassium. The Rb reference frequency is known with sub-MHz accuracy. We obtain the following values for the energy levels: 12 985.169 60(13)(15) cm$^{-1}$ for the $4P_{1/2}$ sta

Jacques Moret-Bailly

In the classical theory, an electromagnetic field obeying Maxwell&#39;s equations cannot be absorbed quickly by matter, so that it remains a zero point field. Splitting the total, genuine electromagnetic field into the sum of a conventional field and a zero point field is physically meaningless until a receiver attenuates the genuine field down to the zero p