March 1998 arXiv papers — page 11

Guang-jiong Ni

The relation between the special relativity and quantum mechanics is discussed. Based on the postulate that space-time inversion is equavalent to particle-antiparticle transformation, the essence of special relativity is explored and the relativistic modification on Stationary Schrödinger Equation is derived.

Anatol N. Kirillov, Mark Shimozono

Combinatorial objects called rigged configurations give rise to q-analogues of certain Littlewood-Richardson coefficients. The Kostka-Foulkes polynomials and two-column Macdonald-Kostka polynomials occur as special cases. Conjecturally these polynomials coincide with the Poincare polynomials of isotypic components of certain graded GL(n)-modules supported in

Hans Schneider

The title says it all

J. F. Gomes, G. M. Sotkov, A. H. Zimerman

The classical and quantum algebras of a class of conformal NA-Toda models are studied. It is shown that the $SL(2,R)_q$ Poisson brackets algebra generated by certain chiral and antichiral charges of the nonlocal currents and the global U(1) charge appears as an algebra of the symmetries of these models.

C. Hamzaoui, M. Pospelov

Large corrections to the quark mass matrices at the supersymmetric threshold allow the theory to have identical Yukawa matrices in the superpotential. We demonstrate that Up-Down unification can take place in a moderate quark-squark alignment scenario with an average squark mass of the order 1 TeV and with $\tanβ>15$

G. J. Gounaris

If all new particles are too heavy to be directly produced in the future Colliders, then the long sought New Physics (NP) could only appear in the form of new interactions, beyond those of the Standard Model (SM). Many of the processes that could be used to study these interactions, have already been discussed in the literature. Here, I first briefly discuss

W. Unruh

Hawking and Turok have recently published a solution to the WKB "wave-function for the universe" which they claim leads in a natural way to an open universe as the end point of the evolution for a universe dominated by a scalar field. They furthermore argue that their solution a preferred solution under the rules of the game. This paper will, I hope,

Wojciech Florek

Extensions of a direct product T of two cyclic groups Z_n1 and Z_n2 by an Abelian (gauge) group G with the trivial action of T on G are considered. All possible (nonequivalent) factor systems are determined using the Mac Lane method. Some of resulting groups describe magnetic translation groups. As examples extensions with G=U(1) and G=Z_n are considered and

Wojciech Florek

Magnetic translation groups are considered as central extensions of the translation group T=Z^n by the group of factors (a~gauge group) U(1). The obtained general formulae allow to consider a magnetic field as an~antisymmetric tensor (of rank 2) and factor systems are determined by a transvection of this tensor with a tensor product t \otimes t'.

Wojciech Florek

Central extensions of the three-dimensional translation group T=Z^3 by the unitary group U(1) (a group of factors) are considered within the frame of the Mac~Lane method. All nonzero vectors t in T are considered to be generators of T. This choice leads to very illustrative relations between the Mac~Lane method and Zak's approach to magnetic translation

G. Seibold, C. Castellani, C. Di Castro, M. Grilli

We investigate the formation of partially filled domain walls in the two-dimensional Hubbard model in the presence of long-range interaction. Using an unrestricted Gutzwiller variational approach we show that: i) the strong local interaction favors charge segregation in stripe domain walls; ii) The long-range interaction favors the formation of half-filled v

Tomaso Aste

The shell map is a very simple representation of the structure of foams, combining the geometrical (random tiling) and dynamical (loss of information from an arbitrary cell out) aspects of disorder. The structure is built from the central cell outward like an ever expanding jigsaw puzzle without boundary. The radial map, from one spherical layer of cells to

O. P. Sushkov, V. N. Kotov

We study the excitation spectrum of the two-leg antiferromagnetic S=1/2 Heisenberg ladder. Our approach is based on the description of the excitations as triplets above a strong-coupling singlet ground state. The quasiparticle spectrum is calculated by treating the excitations as a dilute Bose gas with infinite on-site repulsion. We find singlet (S=0) and tr

Eduardo Bica, Doug Geisler, Horacio Dottori, Juan J. Clariá

We present Washington system C,T_1 CMDs of 13 star clusters and their surrounding fields which lie in the outer parts of the LMC disk. Ages are determined by means of the magnitude difference between the giant branch clump and the turnoff, while metallicities are derived from the location of the giant and subgiant branches as compared to fiducial star cluste

Emi Miyata, H. Tsunemi, T. Kohmura, S. Suzuki

We observed the center portion of the Cygnus Loop supernova remnant with the ASCA observatory. The X-ray spectrum of the center portion was significantly different from that obtained at the North-East (NE) limb. The emission lines from Si and S were quite strong while those of O and the continuum emission were similar to those obtained at the NE limb. Based

S. Chaudhuri, D. Minic

Banks, Fischler, Klebanov and Susskind have proposed a model for black hole thermodynamics based on the principle that the entropy is of order the number of particles at the phase transition point in a Boltzmann gas of D0-branes. We show that the deviations from Boltzmann scaling found in $d<6$ noncompact spatial dimensions have a simple explanation in the a

Jaume Gomis

We propose supergravity duals to non-trivial fixed points of the renormalization group in three dimensions with ADE global symmetries. All the fixed point symmetries are identified with space-time symmetries.

B. Kamal, Z. Merebashvili

The cross section for massive fermion production in two-photon collisions was examined at next-to-leading order in QCD/QED for general photon helicity. The delta function (virtual+soft) part of the differential cross section was analytically integrated over the final state phase space. Series expansions for the complete differential and total cross sections

Claudio Coriano, Cetin Savkli

A complete numerical implementation, in both singlet and non-singlet sectors, of a very elegant method to solve the QCD Evolution equations, due to Furmanski and Petronzio, is presented. The algorithm is directly implemented in x-space by a Laguerre expansion of the parton distributions. All the leading-twist distributions are evolved: longitudinally polariz

D. Babusci, G. Giordano, A. I. L&#39;vov, G. Matone

The general structure of the cross section of $γN$ scattering with polarized photon and/or nucleon in initial and/or final state is systematically described and exposed through invariant amplitudes. A low-energy expansion of the cross section up to and including terms of order $ω^4$ is given which involves ten structure parameters of the nucleon (dipole, qua

Werner Krauth, Hermann Nicolai, Matthias Staudacher

We discuss supersymmetric Yang-Mills theory dimensionally reduced to zero dimensions and evaluate the SU(2) and SU(3) partition functions by Monte Carlo methods. The exactly known SU(2) results are reproduced to very high precision. Our calculations for SU(3) agree closely with an extension of a conjecture due to Green and Gutperle concerning the exact value

T. P. Devereaux, A. Virosztek, A. Zawadowski

The momentum dependent lineshape of the out-of-phase oxygen vibration as measured in recent neutron scattering measurements is investigated. Starting from a microscopic coupling of the phonon vibration to a local crystal field, the phonon lineshift and broadening is calculated as a function of transfered momentum in the superconducting state of YBa$_{2}$Cu$_

Herbert Neuberger

The Wilson-Dirac matrix for SU(2) with I=1/2 fermions is written in an explicitly real form. The basis change relating it to the conventional form in which the matrix has complex entries is also given. Some applications are presented.

K. S. Stelle

This review considers the properties of classical solutions to supergravity theories with partially unbroken supersymmetry. These solutions saturate Bogomol&#39;ny-Prasad-Sommerfield bounds on their energy densities and are the carriers of the $p$-form charges that appear in the supersymmetry algebra. The simplest such solutions have the character of $(p+1)$

Juan M. Lopez, Henrik Jeldtoft Jensen

We introduce a simple model of yeast-like growth of fungi colonies, which exhibits a continuous roughening transition far from equilibrium from a smooth ($α= 0$) to rough phase ($α= 1/2$) in 1+1 dimensions. At the transition some scaling exponents are calculated by mapping the problem onto a directed percolation process. The model reproduces the roughening t

Claus Kiefer

This review gives an introduction to various attempts to understand the quantum nature of black holes. The first part focuses on thermodynamics of black holes, Hawking radiation, and the interpretation of entropy. The second part is devoted to the detailed treatment of black holes within canonical quantum gravity. The last part adds a brief discussion of bla

D. J. Lee

The effect of retardation on dynamical mass generation in is studied, in the imaginary time formalism. The photon porarization tensor is evaluated to leading order in 1/N (N is the number of flavours), and simple closed form expressions are found for the fully retarded longitudinal and transverse propagators, which have the correct limit when T goes to zero.

E. Stein, M. Maul, L. Mankiewicz, A. Schäfer

We analyze power corrections to flavour singlet deep inelastic scattering structure functions in the framework of the infrared renormalon model. Our calculations, together with previous results for the non-singlet contribution, allow to model the x-dependence of higher twist corrections to F_2, F_L and g_1 in the whole x domain.

K. Schoutens

We determine the exclusion statistics properties of the fundamental edge quasi-particles over a specific $ν=\half$ non-abelian quantum Hall state known as the pfaffian. The fundamental excitations are the edge electrons of charge $-e$ and the edge quasi-holes of charge $+{e \over 4}$. We explicitly determine thermodynamic distribution functions and establish

John D. Barrow, Mariusz P. Dabrowski

We show that homogeneous Gödel spacetimes need not contain closed timelike curves in low-energy-effective string theories. We find exact solutions for the Gödel metric in string theory for the full $O(α^{\prime})$ action including both dilaton and axion fields. The results are valid for bosonic, heterotic and super-strings. To first order in the inverse stri

L. K. Hunt, F. Mannucci, L. Testi, S. Migliorini

We report J, H and K photometry of 86 stars in 40 fields in the northern hemisphere. The fields are smaller than or comparable to a 4x4 arcmin field-of-view, and are roughly uniformly distributed over the sky, making them suitable for a homogeneous broadband calibration network for near-infrared panoramic detectors. K magnitudes range from 8.5 to 14, and J-K

Atsuo Kuniba, Kazumitsu Sakai, Junji Suzuki

Thermodynamics of the spin 1/2 XXZ model is studied in the critical regime using the quantum transfer matrix (QTM) approach. We find functional relations indexed by the Takahashi-Suzuki numbers among the fusion hierarchy of the QTM&#39;s (T-system) and their certain combinations (Y-system). By investigating analyticity of the latter, we derive a closed set o

Luca Angelani, Giorgio Parisi, Giancarlo Ruocco, Gabriele Viliani

A simple model to investigate the long time dynamics of glass-formers is presented and applied to study a Lennard-Jones system in supercooled and glassy phases. According to our model, the point representing the system in the configurational phase space performs harmonic vibrations around (and activated jumps between) minima pertaining to a connected network

Vito Latora, Andrea Rapisarda, Stefano Ruffo

We study the dynamical and statistical behavior of the Hamiltonian Mean Field (HMF) model in order to investigate the relation between microscopic chaos and phase transitions. HMF is a simple toy model of $N$ fully-coupled rotators which shows a second order phase transition. The canonical thermodynamical solution is briefly recalled and its predictions are

Sergey A. Cherkis, Anton Kapustin

We construct D_k asymptotically locally flat gravitational instantons as moduli spaces of solutions of Nahm equations. This allows us to find their twistor spaces and Kahler potentials.

P. Beran

The density matrix of the 2D system of spinless electrons confined to the lowest Landau level is expressed using both basis of states parametrized by electron locations and basis of states parametrized by hole locations. In this representation, the electron-electron repulsion can be viewed as an electron-hole attraction. Electron-hole pairs stabilized by thi

J. L. Chkareuli, I. G. Gogoladze

The significant heavy threshold effect is found in the supersymmetric SU(5) model with two adjoint scalars, one of which is interpreted as a massive string mode decoupled from the lower-energy particle spectra. This threshold related with the generic mass splitting of the basic adjoint moduli is shown to alter properly the running of gauge couplings, thus gi

Tao Huang, Jin Min Yang, Bing-Lin Young, Xinmin Zhang

The dimension-six CP-violating SU_L(2)\times U_Y(1) invariant operators involving the tau lepton are studied. The constraints from the available experimental data on tau dipole moments are derived. Under the current constraints, the induced CP-violating effects could possibly be observed in tau -> 3πν_τ at the future tau-charm factory.

T. R. Klassen

Anisotropic lattices, with a temporal lattice spacing smaller than the spatial one, allow precision Monte Carlo calculations of problems that are difficult to study otherwise: heavy quarks, glueballs, hybrids, and high temperature thermodynamics, for example. We here perform the first step required for such studies with the (quenched) Wilson gauge action, na

T. Hikihara, A. Furusaki

The density-matrix renormalization-group technique is used to calculate the spin correlation functions <S^x_jS^x_k> and <S^z_jS^z_k> of the one-dimensional S=1/2 XXZ model in the gapless regime. The numerical results for open chains of 200 spins are analyzed by comparing them with correlation functions calculated from a low-energy field theory. This gives pr

R. Myrzakulov, S. Vijayalakshmi, R. N. Syzdykova, M. Lakshmanan

Using a moving space curve formalism, geometrical as well as gauge equivalence between a (2+1) dimensional spin equation (M-I equation) and the (2+1) dimensional nonlinear Schrödinger equation (NLSE) originally discovered by Calogero, discussed then by Zakharov and recently rederived by Strachan, have been estabilished. A compatible set of three linear equat

Yasuhiro Fujii, Miki Wadati

The finite XXZ model with boundaries is considered. We use the Matrix Product Ansatz (MPA), which was originally developed in the studies on the asymmetric simple exclusion process and the quantum antiferromagnetic spin chain. The MPA tells that the eigenstate of the Hamiltonian is constructed by the Zamolodchikov-Faddeev algebra (ZF-algebra) and the boundar

J. C. Flores

A mesoscopic evolution equation for an ensemble of mesoparticles follows after the elimination of internal degrees of freedom. If the system is composed of a hierarchy of scales, the reduction procedure could be worked repeatedly and the characterization of this iterating method is carried out. Namely, a prescription describing a discrete hierarchy of master

S. Scheel, L. Knoell, D. -G. Welsch

Recently a quantization scheme for the phenomenological Maxwell theory of the full electromagnetic field in an inhomogeneous three-dimensional, dispersive, and absorbing dielectric medium has been developed and applied to a system consisting of two infinite half-spaces with a common planar interface (H.T. Dung, L. Knoell, and D.-G. Welsch, Phys. Rev. A 57, i

S. J. van Enk

The argument given by M.D. Westmoreland and B. Schumacher in quant-ph/9801014 leading to the purported conclusion that superluminal signaling violates the no-cloning theorem is shown to be incorrect.

Carlo Rovelli

Without addressing the measurement problem (i.e. what causes the wave function to ``collapse&#39;&#39;, or to ``branch&#39;&#39;, or a history to become realized, or a property to actualize), I discuss the problem of the timing of the quantum measurement: assuming that in an appropriate sense a measurement happens, when precisely does it happen? This questio

P. A. Dando, T. S. Monteiro

A brief review of the manifestations of classical chaos observed in atomic systems is presented. Particular attention is paid to the analysis of atomic spectra by periodic orbit-type theories. For diamagnetic non-hydrogenic Rydberg atoms, the dynamical explanation for observed spectral features has been disputed. By building on our previous work on the photo

J. T. Balewski, A. Budzanowski, C. Goodman, D. Grzonka

Constraints on the spin-averaged $Λp$ scattering length and effective range have been obtained from measurements of the $pp\to pK^+Λ$ reaction close to the production threshold by comparing model phase-space Dalitz plot occupations with experimental ones. The data fix well the position of the virtual bound state in the $Λp$ system. Combining this with inform

Wolfgang M. Ruppert

Let A be an abelian variety defined over a number field K and let Kab be the maximal abelian extension of K. We show that there only finitely many torsion points of A which are defined over Kab iff A has no abelian subvariety with complex multiplication over K. We use this to give another proof of Ribet&#39;s result that A has only finitely many torsion poin

Hans Schneider, Hans F. Weinberger

Let $\|A\|_{p,q}$ be the norm induced on the matrix $A$ with $n$ rows and $m$ columns by the Hölder $\ell_p$ and $\ell_q$ norms on $R^n$ and $R^m$ (or $C^n$ and $C^m$), respectively. It is easy to find an upper bound for the ratio $\|A\|_{r,s}/\|A\|_{p,q}$. In this paper we study the classes of matrices for which the upper bound is attained. We shall show th

Giuseppe Dito

We study sun-products on $\R^n$, i.e. generalized Abelian deformations associated with star-products for general Poisson structures on $\R^n$. We show that their cochains are given by differential operators. As a consequence, the weak triviality of sun-products is established and we show that strong equivalence classes are quite small. When the Poisson struc

N. Andruskiewitsch, H. -J. Schneider

We propose the following principle to study pointed Hopf algebras, or more generally, Hopf algebras whose coradical is a Hopf subalgebra. Given such a Hopf algebra A, consider its coradical filtration and the associated graded coalgebra grad(A). Then grad(A) is a graded Hopf algebra, since the coradical A_0 of A is a Hopf subalgebra. In addition, there is a

David Blanc

The question of whether a given H-space X is, up to homotopy, a loop space has been studied from a variety of viewpoints. Here we address this question from the aspect of homotopy operations, in the classical sense of operations on homotopy groups. First, we show how an H-space structure on X can be used to define the action of the primary homotopy operation

Alexander B. Givental

A conjecture expressing genus 1 Gromov-Witten invariants in mirror-theoretic terms of semi-simple Frobenius structures and complex oscillating integrals is formulated. The proof of the conjecture is given for torus-equivariant Gromov - Witten invariants of compact Kähler manifolds with isolated fixed points and for concave bundle spaces over such manifolds.

Anastasia Doikou, Rafael I. Nepomechie

We consider both closed and open integrable antiferromagnetic chains constructed with the SU(N)-invariant R matrix. For the closed chain, we extend the analyses of Sutherland and Kulish-Reshetikhin by considering also complex ``string&#39;&#39; solutions of the Bethe Ansatz equations. Such solutions are essential to describe general multiparticle excited sta

Jorgen Rasmussen

In this letter the explicit form of general two-point functions in affine SL(N) current algebra is provided for all representations, integrable or non-integrable. The weight of the conjugate field to a primary field of arbitrary weight is immediately read off.

Anatoly Morosov

We have studied a problem of the tachyon mediated D-brane - D-brane annihilation from the underlying world-volume gauge field theory point of view. The initial state was chosen in the form of two D-branes crossing at a non-zero angle, which is non-supersymmetric configuration generically. This state was not a groundstate of the theory and the problem at hand

I. Ya. Aref&#39;eva, I. V. Volovich

It was proposed by Maldacena that the large $N$ limit of certain conformal field theories can be described in terms of supergravity on anti-De Sitter spaces (AdS). Recently, Gubser, Klebanov and Polyakov and Witten have conjectured that the generating functional for certain correlation functions in conformal field theory is given by the classical supergravit

Lionel E. Gordon, Mehrdad Goshtasbpour, Gordon P. Ramsey

Using QCD motivated and phenomenological considerations, we construct x- dependent polarized parton distributions, which evolve under GLAP evolution, satisfy DIS data and are within positivity constraints. Each flavor is done separately and the overall set can be used to predict polarization asymmetries for various processes. We perform our NLO analysis stri

Elizabeth Jenkins

A spin-flavor symmetry emerges for baryons in the large-N_c limit. Large-N_c baryons form irreducible representations of the spin-flavor algebra, and their static properties can be computed in a systematic expansion in 1/N_c. Symmetry relations for static baryon matrix elements are obtained at various orders in the 1/N_c expansion by neglecting subleading 1/

M. Bleicher, C. Spieles, C. Ernst, L. Gerland

We study the transverse expansion in central Pb+Pb collisions at the CERN SPS. Strong collective motion of hadrons can be created. This flow is mainly due to meson baryon rescattering. It allows to study the angular distribution of intermediate mass meson baryon interactions.

M. Bleicher, M. Belkacem, C. Ernst, H. Weber

We perform an event-by-event analysis of the transverse momentum distribution of final state particles in central Pb(160AGeV)+Pb collisions within a microscopic non-equilibrium transport model (UrQMD). Strong influence of rescattering is found. The extracted momentum distributions show less fluctuations in A+A collisions than in p+p reactions. This is in con

Joaquin Diaz-Alonso, Armando Perez, Horacio D. Sivak

We investigate screening effects of the medium on the potential interaction between two static &#39;charges&#39; for different models of dense plasmas in the one-boson exchange approximation. The potential can exhibit an oscillatory behavior, which is related to the analytic structure of the corresponding boson propagators in the complex $q$-plane. We have f

D. Melikhov, N. Nikitin, S. Simula

We argue that the longitudinal lepton polarization and the forward-backward asymmetries in exclusive $B\to (K,K^*)\ell^+\ell^-$ decays are largely unaffected by the theoretical uncertainties in the long-distance contributions both induced by the long-range charming penguins in the $\ell^+\ell^-$ channel and those in the meson channels encoded in the meson tr

Krishna Rajagopal

We use a variational procedure to study finite density QCD in an approximation in which the interaction between quarks is modelled by that induced by instantons. We find that uniform states with conventional chiral symmetry breaking have negative pressure with respect to empty space at all but the lowest densities, and are therefore unstable. This is a preci

Kalman Varga, Marco Genovese, Jean-Marc Richard, Bernard Silvestre-Brac

We discuss the isospin-breaking mass differences among baryons, with particular attention in the charm sector to the $Σ_c^{+}-Σ_c^0$, $Σ_c^{++}-Σ_c^0$, and $Ξ_c^+-Ξ_c^0$ splittings. Simple potential models cannot accommodate the trend of the available data on charmed baryons. More precise measurements would offer the possibility of testing how well potential

Athanasios Dedes

The radiative electroweak symmetry breaking, the b-τYukawa and gauge couplings unification in the MSSM and its SU(5) extensions are studied in detail. In the framework of the two-loop renormalization group equations both low- and high-energy threshold effects are included. In the case of the minimal SU(5), the values of α_s obtained are somewhat larger than

Yuri L. Dokshitzer

Status of hard/perturbative QCD phenomena is briefly reviewed. Landau-Pomeranchuk-Migdal effect is discussed as a means for establishing links between particle and nuclear high-energy physics.

M. Jezabek, M. Peter, Y. Sumino

We derive a formula which relates the QCD potentials in momentum space and in position space in terms of the beta-function of the renormalization-group equation for the potential. This formula is used to study the theoretical uncertainties in the potential and in particular in its application to the determination of the pole mass m_b when we use perturbative

Daniel Enstrom

This M.Sc. thesis in Engineering Physics is an overview of the present theory of quark-gluon plasma (QGP) as well as an analysis of the stability criterion for possible stable cosmic QGP objects left over from the quark-hadron transition in the early Universe. It covers fundamental ideas of the formation and decay of the plasma, including the standard model,

Lee Lindblom, Benjamin J. Owen, Sharon M. Morsink

We show that gravitational radiation drives an instability in hot young rapidly rotating neutron stars. This instability occurs primarily in the l=2 r-mode and will carry away most of the angular momentum of a rapidly rotating star by gravitational radiation. On the timescale needed to cool a young neutron star to about T=10^9 K (about one year) this instabi

Janna Levin

Singular spacetimes are a natural prediction of Einstein&#39;s theory. Most memorable are the singular centers of black holes and the big bang. However, dilatonic extensions of Einstein&#39;s theory can support nonsingular spacetimes. The cosmological singularities can be avoided by dilaton driven inflation. Furthermore, a nonsingular black hole can be const

R. B. Mann

This is a summary of the workshop A.6 on Alternative Theories of Gravity, prepared for the proceedings for the GR15 conference.

Raphael Bousso, Andrew Chamblin

In quantum cosmology, one often considers tunneling phenomena which may have occurred in the early universe. Processes requiring quantum penetration of a potential barrier include black hole pair creation and the decay of vacuum domain walls. Ideally, one calculates the rates for such processes by finding an instanton, or Euclidean solution of the field equa

A. G. Abanov, J. C. Talstra, P. B. Wiegmann

We present asymptotically exact solutions of an incommensurate Harper equation---one-dimensional Schroedinger equation of one particle on a lattice in a cosine potential. The wave functions can be written as an infinite product of string polynomials. The roots of these polynomials are solutions of Bethe equations. They are classified according to the string

T. Asselmeyer, R. Keiper

The formation of composite particles in the electron liquid under QHE conditions discussed by Jain in generalizing Laughlins many-particle state is considered by using a model for two-dimensional guiding center configurations. Describing the self-consistent field of electron repulsion by a negative parabolic potential on effective centers and an inter-center

O. J. O&#39;Loan, M. R. Evans, M. E. Cates

We study a simple lattice model of shear-induced clustering in two dimensions in which clusters of particles aggregate under an imposed shear flow and fragment stochastically. Two non-equilibrium steady states are identified: an unjammed state and a jammed state characterised by a system-spanning cluster. A discontinuous jamming transition with strong hyster

A. K. Kolezhuk, H. -J. Mikeska

We study two-leg S=1/2 ladders with general isotropic exchange interactions between spins on neighboring rungs, whose ground state can be found exactly in a form of finitely correlated (matrix product) wave function. Two families of models admitting an exact solution are found: one yields translationally invariant ground states and the other describes sponta

Yeong E. Kim, Alexander L. Zubarev

We investigate the stability of the Bose-Einstein condensate (BEC) the case of atoms with negative scattering lengths at zero temperature using the Ginzburg-Pitaevskii-Gross (GPG) stationary theory. We have found a new exact equation for determining the upper bound of the critical numbers $N_{cr}$ of atoms for a metastable state to exist. Our calculated valu

Da-Jiang Liu, John D. Weeks

We use a one-dimensional step model to study quantitatively the growth of step bunches on Si(111) surfaces induced by a direct heating current. Parameters in the model are fixed from experimental measurements near 900 deg C under the assumption that there is local mass transport through surface diffusion and that step motion is limited by the attachment rate

A. Lodder, J. P. Dekker

The voltage induced driving force on a migrating atom in a metallic system is discussed in the perspective of the Hellmann-Feynman force concept, local screening concepts and the linear-response approach. Since the force operator is well defined in quantum mechanics it appears to be only confusing to refer to the Hellmann-Feynman theorem in the context of el

S. A. van Langen, H. P. A. Knops, J. C. J. Paasschens, C. W. J. Beenakker

An electron spin moving adiabatically in a strong, spatially non-uniform magnetic field accumulates a geometric phase or Berry phase, which might be observable as a conductance oscillation in a mesoscopic ring. Two contradicting theories exist for how strong the magnetic field should be to ensure adiabaticity if the motion is diffusive. To resolve this contr

L. F. Lemmens, F. Brosens, J. T. Devreese

Recent investigations show that the statistical mechanics of a finite number of particles in ideal harmonic systems predicts different results for the same physical properties, depending on the ensemble under consideration. Path integral methods for a finite number of bosons with equidistant energy levels give the same answers for the mean energy, the specif

Jonathan Doye, Daan Frenkel

Based upon kinetic Monte Carlo simulations of crystallization in a simple polymer model we present a new picture of the mechanism by which the thickness of lamellar polymer crystals is constrained to a value close to the minimum thermodynamically stable thickness. This description contrasts with those given by the two dominant theoretical approaches.

F. Bentosela, P. Exner, V. A. Zagrebnov

We investigate an electron in the plane interacting with the magnetic field due to an electric current forming a localized rotationally symmetric vortex. We show that independently of the vortex profile an electron with spin antiparallel to the magnetic field can be trapped if the vortex current is strong enough. In addition, the electron scattering on the v

Enrique Abad, Andreas Mielke

This work deals with the overdamped motion of a particle in a fluctuating one-dimensional periodic potential. If the potential has no inversion symmetry and its fluctuations are asymmetric and correlated in time, a net flow can be generated at finite temperatures. We present results for the stationary current for the case of a piecewise linear potential, esp

T. Masuda, A. Fujioka, Y. Uchiyama, I. Tsukada

We discovered a first-order phase transition between dimerized-antiferromagnetic and uniform-antiferromagnetic phases in impurity-doped spin-Peierls (SP) cuprate Cu{1-x}MgxGeO3. As impurity concentration increases, linear reduction of SP transition temperature (T{SP}) and linear increase of Neel temperature (TN) are observed up to x = 0.023. At this critical

Z. F. Ezawa

A field theory of quantum Hall effects is constructed based on the \CB picture. It is tightly related with the microscopic wave-function theory. The characteristic feature is that the field operator describes solely the physical degrees of freedom representing the deviation from the Laughlin state. It presents a powerful tool to analyze excited states within

Tetsuo Ohmi, Kazushige Machida

The Bogoliubov theory is extended to a Bose-Einstein condensation with internal degrees of freedom, realized recently in $^{23}$Na gases where several hyperfine states are simultaneously cooled optically. Starting with a Hamiltonian constructed from general gauge and spin rotation symmetry principles fundamental equations for condensate are derived. The grou

P. A. Dando, T. S. Monteiro, S. M. Owen

Although hydrogen in external fields is a paradigm for the application of periodic orbits and the Gutzwiller trace formula to a real system, the trace formula has never been applied successfully to other Rydberg atoms. We show that spectral fluctuations of general Rydberg atoms are given with remarkable precision by the addition of diffractive terms. Previou

Fan Fang, David L. Shupe, Cong Xu, Perry B. Hacking

We have established a model to systematically estimate the contribution of the mid-infrared emission features between 3 and 11.6 micron to the IRAS in-band fluxes, using the results of ISO PHT-S observation of 16 galaxies by Lu et al. (1997). The model is used to estimate more properly the k-corrections for calculating the restframe 12 and 25 micron fluxes a

Amy E. Nelson, Dennis Zaritsky, Roc M. Cutri

We measure the extent of 100 micron galactic emission in two independent galaxy samples using the IRAS 100 micron Sky Survey images and constrain the distribution of dust at large ($\ltsim$30 kpc) radii. The first sample consists of 90 nearby (v < 6000 km/s) galaxies from the RC3 catalog with similar angular sizes and absolute luminosities (5 arcmin $\leq $D

Aneta Siemiginowska, Jill Bechtold, Thomas L. Aldcroft, K. K. McLeod

We present a high-resolution spectrum of the high redshift, lensed quasar Q1208+1101, obtained with the echellette spectrograph on the Multiple Mirror Telescope. We examine the new and published spectra and provide an updated list of high-confidence metal-line absorption systems at z=1.1349, 2.8626, 2.9118, 2.9136, 2.9149. Combining this with a simple model

Shiv K. Sethi, Simon Prunet, F. R. Bouchet

We estimate the dust polarized emission in our galaxy at high galactic latitudes, which is the dominant foreground for measuring CMB polarization using the high frequency instrument (HFI) aboard Planck surveyor. We compare it with the level of CMB polarization and conclude that, for angular scales $\le 1^{\circ}$, the scalar-induced CMB polarization and temp

Pavel Kroupa

The effects which star cluster concentration and binarity have on observable parameters, that characterise the dynamical state of a population of stars after their birth aggregate dissolves, are investigated. To this end, the correlations between ejection velocity, binary proportion, mean system mass, binary orbital period and mass ratio are quantified for s

Veronique Buat, Denis Burgarella

We study the FIR and UV-visible properties of nearby star forming galaxies. This comparison is performed using the local luminosity functions at UV and FIR wavelengths and on individual starburst galaxies for which photometric data from UV to NIR and FIR are available. The comparison of the FIR and UV local luminosity functions argues for a moderate extincti

B. Altieri, L. Metcalfe, A. Biviano, K. Leech

We report on the mid-infrared imaging at 5, 7, 10 and 15 microns of the galaxy cluster Abell 2218 obtained with the ISOCAM instrument onboard ESA&#39;s Infrared Space Observatory (ISO), as part of an on-going program to image gravitational arcs and arclets in distant clusters. Several cluster galaxies as well as field galaxies are detected. We discuss their

C. J. Pethick, A. Y. Potekhin

Recent calculations indicate that in the outer parts of neutron stars nuclei are rod-like or slab-like, rather than roughly spherical. We consider the elastic properties of these phases, and argue that they behave as liquid crystals, rather than rigid solids. We estimate elastic constants and discuss implications of our results for neutron star behavior.

Andrew R Liddle

I discuss the interplay between inflation and microwave background anisotropies, stressing in particular the accuracy with which inflation predictions need to be made, and the importance of inflation as an underlying paradigm for cosmological parameter estimation.

M. Guainazzi, G. Matt, L. A. Antonelli, F. Fiore

We present evidence of flux variability, on both short (hours) and long (months) time scales of the Seyfert 2 galaxy NGC 7172. These results are based on the ASCA observation of NGC 7172 performed on May 1996. The source was detected at a rather low flux level, about 3 times fainter than its usual state (including one year before, when it was also observed b