January 2002 arXiv papers — page 5

T. W. Giblin, V. Connaughton, J. van Paradijs, R. D. Preece

The connection between Gamma-Ray Bursts (GRBs) and their afterglows is currently not well understood. Afterglow models of synchrotron emission generated by external shocks in the GRB fireball model predict emission detectable in the gamma-ray regime ($\gax 25$ keV). In this paper, we present a temporal and spectral analysis of a subset of BATSE GRBs with smo

S. Laycock, R. H. D. Corbet, D. Perrodin, M. J. Coe

Rossi X-Ray Timing Explorer observations of the Small Magellanic Cloud have revealed a previously unknown transient X-ray pulsar with a pulse period of 95s. Provisionally designated XTE SMC95, the pulsar was detected in three Proportional Counter Array observations during an outburst spanning 4 weeks in March/April 1999. The pulse profile is double peaked re

Filippo Mannucci

We present a method based on two broad-band colors to investigate the nature of the Extremely Red Objects (EROs), i.e., the galaxies selected to have very red optical-to-infrared colors. Dusty starburst and old ellipticals at redshifts between 1 and 2 appear to occupy two different regions of the J-K vs. I-K color diagram, allowing for an easy classification

Mark Hindmarsh, M. Christensson, A. Brandenburg

We have carried out numerical simulations of freely decaying magnetohydrodynamic (MHD) turbulence in three dimensions, which can be applied to the evolution of stochastic magnetic fields in the early Universe. For helical magnetic fields an inverse cascade effect is observed in which magnetic helicity and energy is transfered from smaller scales to larger sc

Grazina Tautvaisiene, Bengt Edvardsson

The sensitivity of stellar spectra to alpha/Fe abundance changes is investigated with the aim to be detected photometricly and employed for scientific goals of the GAIA mission. A grid of plane parallel, line blanketed, flux constant, LTE model atmospheres with different [alpha/Fe] ratios was calculated. As a first step, the modelled stellar energy fluxes fo

Hyerim Noh

Considering the inflation model based on a $f(R)$ gravity theory, we obtain several important constraints from the large angular scale CMBR observations. First, the ordinary slow-roll assumption during the inflation together with Harrison-Zel'dovich spectral conditions chooses $R^2$ gravity as a unique candidate. Second, the $R^2$ gravity leads to specif

G. Ricker, K. Hurley, D. Lamb, S. Woosley

On September 21 at 18950.56 SOD (05:15:50.56) UT the FREGATE gamma-ray instrument on the High Energy Transient Explorer (HETE) detected a bright gamma-ray burst (GRB). The burst was also seen by the X-detector on the WXM X-ray instrument and was therefore well-localized in the X direction; however, the burst was outside the fully-coded field-of-view of the W

M. J. I. Brown

The AGN-galaxy cross-correlation function of radio-quiet AGN and radio galaxies has been measured with the Panoramic Deep Fields. Colour selection criteria and photometric redshifts have been used to significantly increase the signal-to-noise of the angular cross-correlation function. Radio-quiet AGN environments are comparable to the environments of early-t

J. A. Clayhold, M. Ulutagay-Kartin, S. -J. Hwu, H. -J. Koo

The magnetic properties of a new compound, Na5RbCu4(AsO4)4Cl2 are reported. The material has a layered structure comprised of square Cu4O4 tetramers. The Cu ions are divalent and the system behaves as a low-dimensional S=1/2 antiferromagnet. Spin exchange in Na5RbCu4(AsO4)4Cl2 appears to be quasi-two-dimensional and non-frustrated. Measurements of the bulk m

V. Barger, S. L. Glashow, D. Marfatia, K. Whisnant

We examine how constraints can be placed on the neutrino component of dark matter by an accurate measurement of neutrinoless double beta ($0νββ$) decay and the solar oscillation amplitude. We comment on the alleged evidence for $0νββ$ decay.

Fuqiang Wang

It is observed that K-/pi in A+A and possibly p+p and pbar+p collisions follows an interesting systematic in omega, the pion transverse energy per unit of rapidity and transverse overlap area. The systematics show a linear increase of K-/pi with omega in the AGS and SPS energy regime and a saturation at RHIC energy. The systematics indicate that omega might

H. Murayama, A. Pierce

We revisit the electroweak baryogenesis within the context of the minimal supersymmetric standard model (MSSM), studying its potential collider signatures. We find that this mechanism of baryogenesis does not give a new CP violating signal at the $B$-factories. The first circumstantial evidence may come from enhanced $B_s$ or $B_d$ mixing. If a light right-h

U. Seljak

Observations of galaxy-galaxy lensing from Sloan Digital Sky Survey (SDSS) are combined with the Tully-Fisher and fundamental plane relations to derive constraints on galactic halo profiles.We show that both for early and late type galaxies around L* the rotation velocity drops significantly from its peak value at the optical radius to the virial radius, v_o

Peter A. Horvathy, Mikhail S. Plyushchay

We show that the Lukierski et al. model, invariant with respect to the two-fold centrally extended Galilei group, can be decomposed into an infinite number of independent copies (differing in their spin) of the ``exotic'' particle of Duval et al. The difference between the two models is found to be sensitive to electromagnetic coupling. The nature of

L. -M. Duan

We propose an experimentally feasible scheme to generate Greenberger-Horne-Zeilinger (GHZ) type of maximal entanglement between many atomic ensembles based on laser manipulation and single-photon detection. The scheme, with inherent fault tolerance to the dominant noise and efficient scaling of the efficiency with the number of ensembles, allows to maximally

A. V. Sologubenko, J. Jun, S. M. Kazakov, J. Karpinski

The ab-plane thermal conductivity $κ$ of single-crystalline hexagonal MgB_2 has been measured as a function of magnetic field H with orientations both parallel and perpendicular to the c-axis and at temperatures between 0.5 and 300 K. In the mixed state, $κ(H)$ measured at constant temperatures reveals features that are not typical for common type-II superco

R. R. Metsaev

Free arbitrary spin massless and self-dual massive fields propagating in $AdS_5$ are investigated. We study totally symmetric and mixed symmetry fields on an equal footing. Light-cone gauge action for such fields is constructed. As an example of application of light-cone formalism we discuss $AdS/CFT$ correspondence for massless arbitrary spin $AdS$ fields a

Timothy F. Havel

Given an quantum dynamical semigroup expressed as an exponential superoperator acting on a space of N-dimensional density operators, eigenvalue methods are presented by which canonical Kraus and Lindblad operator sum representations can be computed. These methods provide a mathematical basis on which to develop novel algorithms for quantum process tomography

W. R. Johnson, I. M. Savukov, U. I. Safronova, A. Dalgarno

Wavelengths and transition rates are given for E1 transitions between singlet S, P, D, and F states, between triplet S, P, and D states, and between triplet P and singlet S states in ions of astrophysical interest: helium-like carbon, nitrogen, oxygen, neon, silicon, and argon. All possible E1 transitions between states with J < 4 and n < 7 are considered. E

Fei Zhou

Spin ordering and its effect on low energy quasiparticles in a p-wave superconducting liquid are investigated. We show that there is a new 2D p-wave superconducting liquid where the ground state is rotation invariant. In quantum spin disordered liquids, the low energy quasiparticles are bound states of the bare Bogolubov- De Gennes (${\em BdeG}$) quasipartic

Ilya P. Vadeiko, Georgii P. Miroshnichenko, Andrei V. Rybin, Jussi Timonen

An algebraic method is introduced for an analytical solution of the eigenvalue problem of the Tavis-Cummings (TC) Hamiltonian, based on polynomially deformed su(2), i.e. su_n(2), algebras. In this method the eigenvalue problem is solved in terms of a specific perturbation theory, developed here up to third order. Generalization to the N-atom case of the Rabi

Carlos Castro

It is shown that an action inspired from a BF and Chern-Simons model, based on the $AdS_4$ isometry group SO(3, 2), with the inclusion of a Higgs potential term, furnishes the MacDowell-Mansouri-Chamseddine-West action for gravity, with a Gauss-Bonnet and cosmological constant term. The $AdS_4$ space is a natural vacuum of the theory. Using Vasiliev&#39;s pr

Ofer Aharony, Ehud Schreiber, Jacob Sonnenschein

We study a deformation of the type IIB Maldacena-Nunez background which arises as the near-horizon limit of NS5 branes wrapped on a two-cycle. This background is dual to a &#34;little string theory&#34; compactified on a two-sphere, a theory which at low energies includes four-dimensional N = 1 super Yang-Mills theory. The deformation we study corresponds to

O. W. Greenberg

An interacting theory that violates CPT invariance necessarily violates Lorentz invariance. On the other hand, CPT invariance is not sufficient for out-of-cone Lorentz invariance. Theories that violate CPT by having different particle and antiparticle masses must be nonlocal.

J. Guzik, U. Seljak

We present a theoretical analysis of galaxy-galaxy lensing in the context of halo models with CDM motivated dark matter profiles. The model enables us to separate between the central galactic and noncentral group/cluster contributions. We apply the model to the recent SDSS measurements with known redshifts and luminosities of the lenses. This allows one to a

Alexander V. Milovanov, Jens J. Rasmussen

Self-assembling organic polymers and copper-oxide compounds are two classes of &#34;strange&#34; superconductors, whose challenging behavior does not comply with the traditional picture of Bardeen, Cooper, and Schrieffer (BCS) superconductivity in regular crystals. In this paper, we propose a theoretical model that accounts for the strange superconducting pr

Emmanuel Trizac, Lyderic Bocquet, Miguel Aubouy

We revisit the popular notion of effective or renormalized charge, which is a concept of central importance in the field of highly charged colloidal or polyelectrolyte solutions. Working at the level of a linear Debye-Hückel like theory only, we propose a simple, efficient and versatile method to predict the saturated amount of charge renormalization, which

W. Liu, C. M. Ko

Using an effective hadronic Lagrangian with physical hadron masses and coupling constants determined either empirically or from SU(4) flavor symmetry, we study the production cross sections of charm mesons from pion and rho meson interactions with nucleons. With a cutoff parameter of 1 GeV at interaction vertices as usually used in studying the cross section

P. Aschieri, L. Castellani, A. P. Isaev

Discretized nonabelian gauge theories living on finite group spaces G are defined by means of a geometric action \int Tr F \wedge *F. This technique is extended to obtain discrete versions of the Born-Infeld action. The discretizations are in 1-1 correspondence with differential calculi on finite groups. A consistency condition for duality invariance of the

D. Bahns, S. Doplicher, K. Fredenhagen, G. Piacitelli

It is shown that the violation of unitarity observed in space/time noncommutative field theories is due to an improper definition of quantum field theory on noncommutative spacetime.

Jianyang He, Z. G. Xiao, H. Q. Zheng

A new dispersion relation for the partial wave $ππ$ scattering $S$ matrix is set up. Using the dispersion relation we generalize the single channel unitarity condition, $SS^+=1$, to the entire complex $s$ plane, which is equivalent to the generalized unitarity condition in quantum mechanics. The pole positions of the $σ$ resonance and the $f_0(980)$ resonanc

Angel M. Uranga

We describe a topological effect on configurations of D-branes in the presence of NS-NS and RR field strength fluxes. The fluxes induce the appearance of chiral anomalies on lower dimensional submanifolds of the D-brane worldvolume. This anomaly is not associated to a dynamical chiral fermion degree of freedom, but rather should be regarded as an explicit fl

Wellington da Cruz

We consider the {\it fractal von Neumann entropy} associated with the {\it fractal distribution function} and we obtain for some {\it universal classes h of fractons} their entropies. We obtain also for each of these classes a {\it fractal-deformed Heisenberg algebra}. This one takes into account the braid group structure of these objects which live in two-d

Ji-feng Yang, Jian-Hong Ruan

The two loop effective potential of massless $λϕ^4$ theory was presented in several regularization and renormalization prescriptions and the dynamical symmetry breaking solution was obtained in strong coupling situation in several prescriptions except the Coleman-Weinberg prescription. The beta function in the broken phase becomes negative and the UV fixed p

Y. Kitazawa

The vertex operators for the supergravity multiplet can be constructed through the Wilson lines in IIB matrix model. We investigate the structure of the vertex operators and the symmetry of their correlation functions. For this purpose, we perturb the theory by the Wilson lines dual to the supergravity multiplet. The structure of the Wilson lines can be dete

F. Mohamed, I. Luk'yanchuk, M. Troyer, G. Blatter

Using a perturbative approach to the infinitely degenerate Bogomolnyi vortex state for a superconductor with kappa = 2^(-1/2), T -> T_c, we calculate the interaction of vortices in a superconductor with kappa close to 2^(-1/2). We find, numerically and analytically, that depending on the material the interaction potential between the vortices varies with dec

Andre Gsponer, Jean-Pierre Hurni

150 years after the discovery of quaternions, Hamilton's conjecture that quaternions are a fundamental language for physics is reevaluated and shown to be essentially correct, provided one admits complex numbers in both classical and quantum physics, and accepts carrying along the intricacies of the relativistic formalism. Examples are shown in classical dyn

Han-xin He

We study the possible quantum anomaly for the transverse Ward-Takahashi relations in four dimensional gauge theories based on the method of computing the axial-vector and the vector current operator equations. In addition to the well-known anomalous axial-vector divergence equation (the Adler-Bell-Jackiw anomaly), we find the anomalous axial-vector curl equa

Dongsheng Du, Haijun Gong, Junfeng Sun, Deshan Yang

We study the hadronic charmless two-body B decays to final states involving pseudoscalar and vector mesons with QCD factorization approach, including the contributions from the chirally enhanced power corrections and weak annihilations. The CP-averaged branching ratios and CP-violating asymmetries are given. Most of our results are in agreement with the pres

R. M. Cavalcanti

We present the correct solution of the Dirac equation in 1+1 dimensions with the Lorentz scalar potential V(x)=g|x|.

Silvio De Siena, Antonio Di Lisi, Fabrizio Illuminati

We introduce nonlinear canonical transformations that yield effective Hamiltonians of multiphoton down conversion processes, and we define the associated non-Gaussian multiphoton squeezed states as the coherent states of the multiphoton Hamiltonians. We study in detail the four-photon processes and the associated non-Gaussian four-photon squeezed states. The

Gianluca Panati, Herbert Spohn, Stefan Teufel

A systematic perturbation scheme is developed for approximate solutions to the time-dependent Schroedinger equation with a space-adiabatic Hamiltonian. For a particular isolated energy band, the basic approach is to separate kinematics from dynamics. The kinematics is defined through a subspace of the full Hilbert space for which transitions to other band su

A. M. Ilyanok, I. A. Timoshchenko

The hypothesis of quantization of masses of the solar system planets is considered. It is supposed that the solar system was bearing during the Protosun squeezing from the red giant to a yellow dwarf. According to mass and orbit redistribution of interior planets the condition of the origin of satellites of internal and external planets located in the eclipt

R. W. Kuhne

The aim of this note is to give a short and popular review of the ideas which led to my model of magnetic monopoles (hep-ph/9708394) and my prediction of the second kind of electromagnetic radiation. I will also point out the many and far-reaching consequences if these magnetic photon rays would be confirmed.

Rajesh R. Parwani

This article summarises a Web-book on &#34;Complexity&#34; that was developed to introduce undergraduate students to interesting complex systems in the biological, physical and social sciences, and the common tools, principles and concepts used for their study.

R. Id Betan, R. J. Liotta, N. Sandulescu, T. Vertse

A formalism to evaluate the resonant states produced by two particles moving outside a closed shell core is presented. The two particle states are calculated by using a single particle representation consisting of bound states, Gamow resonances and scattering states in the complex energy plane (Berggren representation). Two representative cases are analysed

R. Schiavilla, R. B. Wiringa

The $^6$He beta decay and $^7$Be electron capture processes are studied using variational Monte Carlo wave functions, derived from a realistic Hamiltonian consisting of the Argonne $v_{18}$ two-nucleon and Urbana-IX three-nucleon interactions. The model for the nuclear weak axial current includes one- and two-body operators with the strength of the leading t

Refik Turhan

Non-autonomous degenerate KdV systems in (1+1) dimensions are considered for integrability classification. Integrability of the systems is associated with the existence of a recursion operator. Some new non-autonomous degenerate two-component KdV systems are found.

Jean Avan, Genevieve Rollet

We define the notion of C^{(2)}_{N+1} Ruijsenaars-Schneider models and construct their Lax formulation. They are obtained by a particular folding of the A_{2N+1} systems. Their commuting Hamiltonians are linear combinations of Koornwinder-van Diejen ``external fields&#39;&#39; Ruijsenaars-Schneider models, for specific values of the exponential one-body coup

Anton S. Desyatnikov, Yuri S. Kivshar, Kristian Motzek, Friedemann Kaiser

We study (2+1)-dimensional multicomponent spatial vector solitons with a nontrivial topological structure of their constituents, and demonstrate that these solitary waves exhibit a symmetry-breaking instability provided their total topological charge is nonzero. We describe a novel type of stable multicomponent dipole-mode solitons with intriguing swinging d

Herve Kunz

We compute the survival probability of an initial state, with an energy in a certain window, by means of random matrix theory. We determine its probability distribution and show that is is universal, i.e. caracterised only by the symmetry class of the hamiltonian and independent of the initial state.

Rolando Alvarado Flores, Maximo A. Aguero Granados

In this paper we prove an algebraic criterion which characterizes singular quasi-bi-hamiltonian structures constructed on the lines of a general, simple, new formal procedure proposed by the authors. This procedure shows that for the definition of a quasi-bi-hamiltonian system the requirement of non-singular Poisson tensors, contained in the original definit

Razvan Gelca, Alejandro Uribe

We prove that, for the moduli space of flat SU(2)-connections on the torus, the Weyl quantization and the quantization using the quantum group of SL(2,C) are unitarily equivalent. This is done by comparing the matrices of the operators associated by the two quantization to cosine functions. We also discuss the *-product of the Weyl quantization and show that

Mark Haiman, Bernd Sturmfels

We introduce the multigraded Hilbert scheme, which parametrizes all homogeneous ideals with fixed Hilbert function in a polynomial ring that is graded by any abelian group. Our construction is widely applicable, it provides explicit equations, and it allows us to prove a range of new results, including Bayer&#39;s conjecture on equations defining Grothendiec

D. N. Yetter

We show that isotopy classes of simple closed curves in any oriented surface admit a quandle structure with operations induced by Dehn twists, the Dehn quandle of the surface. We further show that the monodromy of a Lefschetz fibration can be conveniently encoded as a quandle homomorphism from the knot quandle of the base as a manifold with a codimension 2 s

Daniel Didt

In this article we develop some aspects of the construction of new Hopf algebras found recently by Andruskiewitsch and Schneider. There the authors classified (under some slight restrictions) all pointed finite dimensional Hopf algebras with coradical (Z/p)^s. We contribute to this work by giving a closer description of the possible ``exotic&#39;&#39; linkin

F. Meylan, N. Mir, D. Zaitsev

We establish results on holomorphic extension of CR-mappings of class $C^\infty$ between a real-analytic CR-submanifold of $\C^N$ and a real-algebraic CR-submanifold of $\C^{N&#39;}$.

Pawel Nurowski, Andrzej Trautman

A Lorentzian manifold is defined here as a smooth pseudo-Riemannian manifold with a metric tensor of signature ((2n +1, 1)). A Robinson manifold is a Lorentzian manifold (M) of dimension (\geqslant 4) with a subbundle (N) of the complexification of (TM) such that the fibers of (N\to M) are maximal totally null (isotropic) and ([\Sec N, \Sec N]\subset \Sec N)

W. Sarlet, T. Mestdag, E. Martinez

We introduce the notion of a Lie algebroid structure on an affine bundle whose base manifold is fibred over the real numbers. It is argued that this is the framework which one needs for coming to a time-dependent generalization of the theory of Lagrangian systems on Lie algebroids. An extensive discussion is given of a way one can think of forms acting on se

Thomas Friedrich

We study Spin(9)-structures on 16-dimensional Riemannian manifolds and characterize the geometric types admitting a connection with totally skew-symmetric torsion.

S. M. Gersten, D. F. Holt, T. R. Riley

We prove that every finitely generated nilpotent group of class c admits a polynomial isoperimetric function of degree c+1 and a linear upper bound on its filling length function.

Radoslav Rashkov, K Sankaran Viswanathan

A previous calculation on the tachyon state arising as fluctuations of a $D$ brane in vacuum string field theory is extended to include the vector state. We use the boundary conformal field theory approach of Rastelli, Sen and Zwiebach to construct a vector state. It is shown that the vector field satisfies the linearized equations of motion provided the two

Bobby Acharya, Sergei Gukov, Xenia de la Ossa

In this note we study warped compactifications of M-theory on manifolds of Spin(7) holonomy in the presence of background 4-form flux. The explicit form of the superpotential can be given in terms of the self -dual Cayley calibration on the Spin(7) manifold, in agreement with the general formula propsed in hep-th/9911011.

J. Zinn-Justin

When a quantum field theory has a symmetry, global or local like in gauge theories, in the tree or classical approximation formal manipulations lead to believe that the symmetry can also be implemented in the full quantum theory, provided one uses the proper quantization rules. While this is often true, it is not a general property and therefore requires a p

D. V. Fursaev

We study asymptotic distribution of eigen-values $ω$ of a quadratic operator polynomial of the following form $(ω^2-L(ω))ϕ_ω=0$, where $L(ω)$ is a second order differential positive elliptic operator with quadratic dependence on the spectral parameter $ω$. We derive asymptotics of the spectral density in this problem and show how to compute coefficients of i

B. Sathiapalan

We give a simplified and more complete description of the loop variable approach for writing down gauge invariant equations of motion for the fields of the open string. A simple proof of gauge invariance to all orders is given. In terms of loop variables, the interacting equations look exactly like the free equations, but with a loop variable depending on an

O. A. Olkhov

A new concept for the geometrisation of electromagnetic interaction is proposed. Instead of the concept &#34;extended field--point sources&#34;, interacting Maxwell&#39;s and Dirac&#39;s fields are considered as a unified closed noneuclidean and nonriemannean space--time 4-manifold. This manifold can be considered as geometrical realisation of the &#34;dress

Prasanta Das, Uma Mahanta

In this brief report we show that tadpole diagrams due to KK modes of the graviton and radion do not contribute to the vectorial isospin breaking $ρ$ parameter. Our result is fairly general and it holds both for ADD and RS type scenarios. It shows that the difference between the results of different publications on this subject is not due to some of them not

A. I. Rez, V. B. Semikoz

We demonstrate that the neutrino kinetic equation derived by the standard Bogolyubov method is formally gauge non-invariant and give a recipe how to recast it to the gauge invariant form recovering the standard Lorentz form weak force term which apparently conserves the lepton current. The analogy with the QED plasma case is traced which in asymptotic region

K. J. Eskola, H. Honkanen, V. J. Kolhinen, C. A. Salgado

The $Q^2$ dependence of the ratios of the cross sections of deep inelastic lepton--nucleus scattering is studied in the framework of leading twist, lowest order perturbative QCD. The $\log Q^2$ slope of the ratio $F_2^{\rm Sn}/F_2^{\rm C}$ is computed by using the DGLAP evolution equations, and shown to be sensitive to the nuclear gluon distribution function

Jong B. Choi, Byeong S. Choi, Su K. Lee

The assumption of angular ordering in gluon radiation is essential to obtain quantitative results concerning gluonic behaviors. In order to prove the validity of this assumption, we have applied our momentum space flux-tube formalism to check out the angular dependences of gluon radiation. We have calculated the probability amplitudes to get new gluon, and h

Y. Kiyo, Y. Sumino

We calculate O(alpha_S^4 m) and O(alpha_S^4 m log(alpha_S)) corrections to the quarkonium 1S energy level analytically, which have been overlooked in recent studies. These are the contributions from one Coulomb-gluon exchange with the 1-loop vacuum polarization insertion. A part of the corrections was computed numerically some time ago; we correct its error.

Mireille Schneider

Recent results on searches for physics beyond the Standard Model obtained by the H1 and ZEUS experiments are reported here. After a brief introduction to the HERA collider, indirect searches for contact interactions and extra-dimensions are presented as well as direct searches for new physics including leptoquarks, lepton-flavour violation, squarks produced

The BABAR Collaboration, B. Aubert

New measurements of Ds+ and Ds*+ meson production rates from B decays and from qqbar continuum events near the Y(4S) resonance are presented. Using 20.8 fb-1 of data on the Y(4S) resonance and 2.6 fb-1 off resonance, we find the inclusive branching fractions BR(B --> Ds+ X) = (10.93+/-0.19+/-0.58+/-2.73)% and BR(B --> Ds*+ X) = (7.9+/-0.8+/-0.7+/-2.0)%, wher

Artem Starodubtsev

The loop quantum gravity technique is applied to the free bosonic string. A Hilbert space similar to loop space in loop quantum gravity as well as representations of diffeomorphism and hamiltonian constraints on it are constructed. The string in this representation can be viewed as a set of interacting relativistic particles each carrying a certain momentum.

Marc Mars

We find all the perfect fluid G2 diagonal cosmologies with the property that the quotient of the norms of the two orthogonal Killing vectors is constant along each fluid world-line. We find four different families depending each one on two or three arbitrary parameters which satisfy that the metric coefficients are not separable functions. Some physical prop

Sergei Alexandrov

We investigate the Hilbert space in the Lorentz covariant approach to loop quantum gravity. We restrict ourselves to the space where all area operators are simultaneously diagonalizable, assuming that it exists. In this sector quantum states are realized by a generalization of spin network states based on Lorentz Wilson lines projected on irreducible represe

Walter Rantner, Xiao-Gang Wen

We propose that underdoped high $T_c$ superconductors are described by an algebraic spin liquid (ASL) at high energies, which undergoes a spin-charge recombination transition at low energies. The spin correlation in the ASL is calculated via its effective theory - a system of massless Dirac fermions coupled to a U(1) gauge field. We find that without fine tu

Viktor V. Struzhkin, Yuri A. Timofeev, Eugene Gregoryanz, Russell J. Hemley

We review recent advances in diamond anvil cell development, focusing on the details of magnetic susceptibility techniques. We have developed and implemented highly sensitive technique that allowed observations of superconductivity using magnetic susceptibility at megabar pressures, including the observation of a Tc in sulfur to above 230 GPa. The advancemen

Jian-Xin Zhu, Ivar Martin, A. R. Bishop

By solving self-consistently an effective Hamiltonian including interactions for both antiferromagnetic spin-density wave (SDW) and d-wave superconducting (DSC) orderings, a comparison study is made for the local magnetic structure around superconducting vortices and unitary impurities. To represent the optimally doped regime of cuprates, the parameter value

Akihisa Koga, Norio Kawakami

We investigate quantum phase transitions in the frustrated orthogonal-dimer chain with an arbitrary spin $S \geq 1/2$. When the ratio of the competing exchange couplings is varied, first-order phase transitions occur 2S times among distinct spin-gap phases. The introduction of single-ion anisotropy further enriches the phase diagram. The phase transitions de

Ines Samengo

Estimating the probability distribution &#39;q&#39; governing the behaviour of a certain variable by sampling its value a finite number of times most typically involves an error. Successive measurements allow the construction of a histogram, or frequency count &#39;f&#39;, of each of the possible outcomes. In this work, the probability that the true distribu

Rene Messina, Christian Holm, Kurt Kremer

We investigate the complexation of a highly charged sphere with a long flexible polyelectrolyte, \textit{both negatively charged} in salt free environment. Electroneutrality is insured by the presence of divalent counterions. Using molecular dynamics (MD) within the framework of the primitive model, we consider different Coulomb coupling regimes. At strong C

Vygintas Gontis

A simple analytically solvable model exhibiting a 1/f spectrum in an arbitrarily wide frequency range was recently proposed by Kaulakys and Meskauskas (KM). Signals consisting of a sequence of pulses show that inherent origin of the 1/f noise is Brownian fluctuations of the average intervent time between subsequent pulses of the pulse sequence. We generalize

J. P. Castellan, B. D. Gaulin, J. van Duijn, M. J. Lewis

Single crystal X-ray diffraction measurements have been carried out on Cd_2Re_2O_7 near and below the phase transition it exhibits at Tc&#39; ~195 K. Cd_2Re_2O_7 was recently discovered as the first, and to date only, superconductor with the cubic pyrochlore structure. Superlattice Bragg peaks show an apparently continuous structural transition at Tc&#39;, h

G. G. N. Angilella, G. Balestrino, P. Cermelli, P. Podio-Guidugli

We propose a Ginzburg-Landau phenomenological model for the dependence of the critical temperature on microscopic strain in tetragonal high-Tc cuprates. Such a model is in agreement with the experimental results for LSCO under epitaxial strain, as well as with the hydrostatic pressure dependence of Tc in most cuprates. In particular, a nonmonotonic dependenc

M. S. O. Massunaga, M. Bahiana

We study the onset of synchronization in lattices of limit cycle oscillators with long-range coupling by means of numerical simulations. In this regime the critical coupling strength depends on the system size and interaction range reflecting the non extensive behavior of the system, but an adequate scaling removes the dependency and collapses the long-range

Tomoya Isoshima, Kazushige Machida

The relative stability of various axisymmetric vortices in a spinor Bose-Einstein condensate with F=1 is examined within extended Bogoliubov theory. This yields the phase diagram in the plane of external rotation frequency vs magnetization. We compare antiferromagnetic, nonmagnetic, and ferromagnetic cases. The excitation spectrum is evaluated under rotation

F. De Pasquale, S. M. Giampaolo

We show that an high temperature expansion at fixed order parameter can be derived for the quantum Ising model. The basic point is to consider a statistical generating functional associated to the local spin state. The probability at thermal equilibrium of this state reflects directly the occurrence of a spontaneous symmetry breaking. It is possible to recov

R. Silva, A. R. Plastino, J. A. S. Lima

Maxwell&#39;s first derivation of the equilibrium distribution function for a dilute gas is generalized in the spirit of the nonextensive q-statistics proposed by Tsallis. As an application, the q-Doppler broadening of spectral lines due to the random thermal motion of the radiating atoms is derived.

M. M. Tardio, R. Ramirez, R. Gonzalez, Y. Chen

The phenomenally large enhancement in conductivity observed when Li-doped MgO crystals are oxidized at elevated temperatures was investigated by dc and ac electrical measurements in the temperature interval 250-673 K. The concentration of ([Li]^{0}) centers (Li^{+} ions each with a trapped hole) resulting from oxidation was monitored by optical absorption me

M. d&#39;Astuto, P. K. Mang, P. Giura, A. Shukla

The phonon dispersions of $\mathrm{Nd_{1.86}Ce_{0.14}CuO_{4+δ}}$ along the $[ξ,0,0]$ direction have been determined by inelastic x-ray scattering. Compared to the undoped parent compound, the two highest longitudinal phonon branches, associated with the Cu-O bond-stretching and out-of-plane oxygen vibration, are shifted to lower energies. Moreover, an anomal

L. L. Bonilla, O. Sanchez, J. Soler

A stochastic discrete drift-diffusion model is proposed to account for the effects of shot noise in weakly coupled, highly doped semiconductor superlattices. Their current-voltage characteristics consist of a number stable multistable branches corresponding to electric field profiles displaying two domains separated by a domain wall. If the initial state cor

A. Oosawa, T. Kato, H. Tanaka, K. Kakurai

TlCuCl$_3$ has a singlet ground state with the excitation gap $Δ=0.65$ meV. The magnetic excitations in TlCuCl$_3$ have been investigated by means of neutron inelastic scattering experiments. The constant-$\it{\pmb Q}$ energy scan profiles were collected in the $a^*-c^*$ plane. A well-defined single magnetic excitation mode was observed. The dispersion relat

Colin Denniston, Geza Toth, Julia M. Yeomans

We extend a lattice Boltzmann algorithm of liquid crystal hydrodynamics to include an applied electric field. The approach solves the equations of motion written in terms of a tensor order parameter. Back-flow effects and the hydrodynamics of topological defects are included. We investigate some of the dynamics relevant to liquid crystal devices; in particul

B. A. Williams, M. S. Yun, L. Verdes-Montenegro

Using the VLA, we have made spectral-line and continuum observations of the neutral hydrogen in the direction of the compact group of galaxies Stephan&#39;s Quintet. The high-velocity clouds between 5600 and 6600 km/s, the disk of the foreground galaxy, NGC 7320, at 800 km/s, the extended continuum ridge near the center of the group, and 3 faint dwarf-like g

R. T. Zavala, G. B. Taylor

Parsec-scale Faraday rotation measure (RM) maps are presented for the radio galaxies M87, 3C 111, and 3C 120. These Very Long Baseline Array observations were made at 8, 12, and 15 GHz. M87 has an extreme RM distribution that varies from -4000 radians m^-2 to more than 9000 radians m^-2 across a projected distance of 0.3 pc in its jet. M87 has no polarized f

M. V. McSwain, D. R. Gies

There is much evidence to suggest that stellar wind capture, rather than Roche lobe overflow, serves as the accretion mechanism onto the compact secondary object in the massive X-ray binary LS 5039. The lack of significant emission combined with only a modest X-ray flux provide observational evidence that no large-scale mass transfer is occurring (consistent

Christopher Sneden, John J. Cowan, James E. Lawler, Scott Burles

Europium isotopic abundance fractions are reported for the very metal-poor, neutron-capture-rich giant stars CS 22892-052, HD 115444, and BD +17 3248. The abundance fractions, derived from analysis of several strong Eu II lines appearing in high-resolution spectra of these stars, are in excellent agreement with each other and with their values in the Solar S

Subhanjoy Mohanty, Gibor Basri

We analyze rotation velocities and chromospheric (H-alpha) activity, derived from multi-year, high-resolution spectra, in 56 mid-M to L dwarfs. Rotational velocities are found to increase from mid-M to L. This is consistent with a lengthening of spin-down timescale with later type, though in the L types the trend may also be a function of stellar age. From M