June 1997 arXiv papers — page 4

Giovanni Abbiendi

The study of photoproduction reactions has gained a unique opportunity with the HERA data. The high center of mass energy allows to carry out quantitative tests of QCD, to explore the substructure of both the photon and the proton and to shed new light on soft and diffractive processes. In this report we review the HERA results, comparing them with the reach

Eva-Maria Kabuss

The analysis of semi-inclusive data from deep inelastic scattering of polarized muons off polarized protons and deuterons by the SMC is presented. The resulting charged hadron asymmetries are used to determine polarized valence and sea quark distributions and their contributions to the nucleon spin. In addition, a new approach to derive inclusive asymmetries

CLEO Collaboration, T. Bergfeld et al

We have observed new channels for $τ$ decays with an $η$ in the final state. We study 3-prong tau decays, using the $η\toγγ$ and $η\to 3\piz$ decay modes and 1-prong decays with two $\piz$'s using the $η\toγγ$ channel. The measured branching fractions are $\B(τ^{-}\to π^{-}π^{-}π^{+}ην_τ) =(3.4^{+0.6}_{-0.5}\pm0.6)\times10^{-4}$ and $\B(τ^{-}\to π^{-}2\p

Arkadiusz Blaut, Jerzy Kowalski-Glikman

We consider the Wheeler-De Witt equation for canonical quantum gravity coupled to massless scalar field. After regularizing and renormalizing this equation, we find a one-parameter class of its solutions.

P. Wochner, J. M. Tranquada, D. J. Buttrey, V. Sachan

We report a detailed neutron scattering study of the ordering of spins and holes in oxygen-doped La(2)NiO(4.133). The single-crystal sample exhibits the same oxygen-interstitial order but better defined charge-stripe order than that studied previously in crystals with d = 0.125. In particular, charge order is observed up to a temperature at least twice that

M. P. Blencowe, A. P. Korte

We apply the linear $δ$-expansion (LDE), originally developed as a nonperturbative, analytical approximation scheme in quantum field theory, to problems involving noninteracting electrons in disordered solids. The initial idea that the LDE method might be applicable to disorder is suggested by the resemblance of the supersymmetric field theory formalism for

I. I. Mazin, A. I. Liechtenstein

Recent experiments by Mertz et al (Phys. Rev. B55, 9160, 1997) demonstrated that the loss of superconductivity upon Pr doping is associated with the change of the character of the oxygen holes from $p_σ$ to $p_π.$ This experiment sheds new light onto the long-standing problem of $T_{c}$ suppression by Pr, and helps to rule out a number of theoretical models,

Erik Luijten, Henk W. J. Blöte, Kurt Binder

We determine the scaling functions describing the crossover from Ising-like critical behavior to classical critical behavior in two-dimensional systems with a variable interaction range. Since this crossover spans several decades in the reduced temperature as well as in the finite-size crossover variable, it has up to now largely evaded a satisfactory numeri

G. Jug, K. Ziegler

We present a calculation for the second moment of the local density of states in a model of a two-dimensional quantum dot array near the quantum Hall transition. The quantum dot array model is a realistic adaptation of the lattice model for the quantum Hall transition in the two-dimensional electron gas in an external magnetic field proposed by Ludwig, Fishe

Isa Kh. Zharekeshev, Bernhard Kramer

The nearest-neighbor level spacing distribution is numerically investigated by directly diagonalizing disordered Anderson Hamiltonians for systems of sizes up to 100 x 100 x 100 lattice sites. The scaling behavior of the level statistics is examined for large spacings near the delocalization-localization transition and the correlation length exponent is foun

Th. Jolicoeur, J. C. Le Guillou

We show that current estimates of the critical exponents of the three-dimensional random-field Ising model are in agreement with the exponents of the pure Ising system in dimension 3 - theta where theta is the exponent that governs the hyperscaling violation in the random case.

U. Nowak, J. Heimel, T. Kleinefeld, D. Weller

We study the magnetic properties of nanoscale magnetic films with large perpendicular anisotropy comparing polarization microscopy measurements on Co_28Pt_72 alloy samples based on the magneto-optical Kerr effect with Monte Carlo simulations of a corresponding micromagnetic model. We focus on the understanding of the dynamics especially the temperature and f

F. Y. Wu, H. Y. Huang

It is shown that certain sum rule identities exist which relate correlation functions for $n$ Potts spins on the boundary of a planar lattice for $n\geq 4$. Explicit expressions of the identities are obtained for $n=4,5$. It is also shown that the identities provide the missing link needed for a complete determination of the duality relation for the $n$-poin

S. S. Manna, D. Giri

A new sandpile model is studied in which bonds of the system are inhibited for activity after a certain number of transmission of grains. This condition impels an unstable sand column to distribute grains only to those neighbours which have toppled less than m times. In this non-Abelian model grains effectively move faster than the ordinary diffusion (super-

T. Sh. Misirpashaev, P. W. Brouwer, C. W. J. Beenakker

The spontaneous emission rate Γof a two-level atom inside a chaotic cavity fluctuates strongly from one point to another because of fluctuations in the local density of modes. For a cavity with perfectly conducting walls and an opening containing N wavechannels, the distribution of Γis given by P(Γ) \propto Γ^{N/2-1}(Γ+Γ_0)^{-N-1}, where Γ_0 is the free-spac

H. Alt, C. Dembowski, H. -D. Graef, R. Hofferbert

Based on very accurate measurements performed on a superconducting microwave resonator shaped like a desymmetrized three-dimensional (3D) Sinai billiard, we investigate for the first time spectral properties of the vectorial Helmholtz, i.e. non-quantum wave equation for a classically totally chaotic and theoretically precisely studied system. We are thereby

Thomas J. Loredo, Eanna E. Flanagan, Ira M. Wasserman

A recent study of the rotation of the plane of polarization of light from 160 cosmological sources claims to find significant evidence for cosmological anisotropy. We point out methodological weaknesses of that study, and reanalyze the same data using Bayesian methods that overcome these problems. We find that the data always favor isotropic models for the d

A. B. Balantekin

This review covers a subset of the astrophysical phenomena where neutrinos play a significant role and where the underlying microphysics is nuclear physics. The current status of the solar neutrino problem, atmospheric neutrino experiments, the role of neutrinos in determining the dynamics of type-II supernovae, and recent developments in exploring neutrino

A. J. Connolly, A. S. Szalay, Mark Dickinson, M. U. SubbaRao

The Hubble Deep Field (HDF) is the deepest set of multicolor optical photometric observations ever undertaken, and offers a valuable data set with which to study galaxy evolution. Combining the optical WFPC2 data with ground-based near-infrared photometry, we derive photometrically estimated redshifts for HDF galaxies with J<23.5. We demonstrate that incorpo

G. Ghisellini, M. Villata, C. M. Raiteri, S. Bosio

We monitored the BL Lac object S5 0716+714 in the optical band during the period November 1994-April 1995, which includes the time of a gamma-ray observation by the Energetic Gamma Ray Experiment Telescope (EGRET) on February 14--28, 1995. The light curves in the R and B bands show fast fluctuations superimposed on longer timescale variations. The color inde

A. C. Baker, D. L. Clements

Essentially all Ultra-Luminous IR Galaxies (ULIRGs) are in disturbed, interacting or merging systems. It is known that interactions tend to induce galactic starbursts. Thus, elliptical galaxies which are formed in mergers will tend to have high metallicity, low dust and molecular gas content, and faint structural distortions, as observed for the bone fide el

F. Macchetto, A. Marconi, D. J. Axon, A. Capetti

We have obtained long-slit observations of the circumnuclear region of M87 at three different locations, with a spatial sampling of 0.028&#34; using the Faint Object Camera f/48 spectrograph on board HST. These data allow us to determine the rotation curve of the inner ~1&#34; of the ionized gas disk in [OII]3727 to a distance as close as 0.07&#34; (~5pc) to

Amir Levinson, David F. Chernoff, Edwin E. Salpeter

We study molecular hydrogen formation in and on solids. We construct a model with surface sites and bulk sites capable of describing (1) the motion and exchange of H and H_2 between surface and bulk, (2) the recombination of H and dissociation of H_2 in and on the solid, and (3) the injection of H from the gas phase and the loss of H and H_2 from the solid.

Andrea Ferrara

I review some of the evidences for dust in the Local Bubble and in galactic halos and show that a general mechanism based on radiation pressure is capable of evacuating dust grains from regions dominated by massive star energy input and thus originate huge dusty halos. A Monte Carlo/particle model has been developed to study the dust dynamics above HII chimn

Giuseppe Lanzafame, D. Molteni, S. K. Chakrabarti

Viscous Keplerian discs become sub-Keplerian close to a black hole since they pass through sonic points before entering into it. We study the time evolution of polytropic viscous accretion discs (both in one and two dimensional flows) using Smoothed Particle Hydrodynamics. We discover that for a large region of the parameter space, when the flow viscosity pa

Donu Arapura, Madhav Nori

This is a long overdue write up of the following: If the fundamental group of a normal complex algebraic variety (respectively Zariski open subset of a compact Kähler manifold) is a solvable group of matrices over Q (respectively polycyclic group), then it is virtually nilpotent. This should be interpreted as saying that a large class of solvable groups will

Biswajoy Brahmachari

In the presence of ${\bf 126 + \bar{126}}$ Higgs multiplets in a SO(10) theory, the fermion masses get contributions from an induced vacuum expectation value (VEV) of a $SU(2)_L$ doublet residing in ${\bf 126}$ which differentiates between quarks and leptons by a relative sign leading to a significant correction to the prediction of the mass ratio of the bot

Norbert Dragon, Sergei M. Kuzenko, Ulrich Theis

We describe the vector-tensor multiplet and derive its Chern-Simons couplings to the N=2 Yang-Mills gauge superfield in harmonic superspace.

J. A. Oller, E. Oset

We present a unified picture which studies simultaneously the gamma gamma-->pi^+ pi^-, pi^0 pi^0, K^+ K^-, K^0 bar{K}^0, pi^0 eta reactions up to about sqrt(s)=1.4 GeV reproducing the experimental cross sections. The present work implements in an accurate way the final state interactions of the meson-meson system, which is shown to be essential in order to r

Paul Hoyer, Stephane Peigne

We study eta_c and J/psi hadroproduction induced by multiple scattering off fixed centres in the target. We determine the minimum number of hard scatterings required and show that additional soft scatterings may be factorized, at the level of the production amplitude for the eta_c and of the cross section for the J/psi. The J/psi provides an interesting exam

A. I. Posazhennikova, M. V. Sadovskii

Ginzburg-Landau expansion for superconductors with anisotropic $s-$ and $d-$wave pairing is derived in the presence of anisotropic normal impurity scattering which makes $d-$pairing state more stable under disordering. It is demonstrated that the slope of the upper critical field $|dH_{c2}/dT|_{T_{c}}$ in superconductors with $d-$wave pairing has nonlinear d

B. Blok, M. Lublinsky

Motivated by recent work on three-point QCD sum rules in heavy quark physics, we use the simple quantum mechanical models to study the basic issue of duality in three-point sum rules. We show that while in all of these models the duality in two-point sum rules works fine, the duality in three-point sum rules may be 100%- violated, leading to completely unrel

Anjan S. Joshipura, V. Ravindran, Sudhir K. Vempati

R parity violating trilinear couplings $λ&#39;_{1jk}$ of the minimal supersymmetric standard model (MSSM) are constrained from the limit on the electron neutrino mass. Strong limits on these couplings follow from the earlier neglected contribution due to sneutrino vacuum expectation values. The limits on most of the $λ&#39;_{1jk}$ couplings derived here are

Roberto Casadio, Fabio Finelli, Giovanni Venturi

The semiclassical collapse of a sphere of quantized dust is studied. A Born-Oppenheimer decomposition is performed for the wave function of the system and the semiclassical limit is considered for the gravitational part. The method of adiabatic invariants for time dependent Hamiltonians is then employed to find (approximate) solutions to the quantum dust equ

Shibaji Roy

It has been shown recently that the toroidally compactified type IIB string effective action possesses an SL(2, R) invariance. Using this symmetry we construct an infinite family of macroscopic string-like solutions permuted by SL(2, Z) group for type II superstrings in $4 \leq D < 10$. These solutions, which formally look very similar to the corresponding s

Peter Kopietz, Axel Voelker

We re-examine the effect of electron-electron interactions on the persistent current in mesoscopic metal rings threaded by an Aharonov-Bohm flux. The exchange contribution to the current is shown to be determined by the weak localization correction to the polarization. We explicitly calculate the contribution from exchange interactions with momentum transfer

Yi-Jen Lee

We construct the Seiberg-Witten theory on 3-manifolds with Euclidean ends (connected sums of $\R^3$ and a compact manifold) with perturbations which approximate $*dx_3$ at infinity, and describe the structure of the moduli spaces. The setup is inspired by Taubes&#39;s program of relating the 4-dimensional Seiberg-Witten invariant with `singular Gromov invari

Michael Hutchings, Yi-Jen Lee

Let X be a closed manifold with zero Euler characteristic, and let f: X --> S^1 be a circle-valued Morse function. We define an invariant I which counts closed orbits of the gradient of f, together with flow lines between the critical points. We show that our invariant equals a form of topological Reidemeister torsion defined by Turaev [Math. Res. Lett. 4 (1

Kiyoshi Okuyama, Hiroshi Suzuki

We propose a new formulation of chiral fermions on a lattice, on the basis of a lattice extension of the covariant regularization scheme in continuum field theory. The species doublers do not emerge. The real part of the effective action is just one half of that of Dirac-Wilson fermion and is always gauge invariant even with a finite lattice spacing. The gau

T. Tanaka

The variational perturbation theory for wave functions, which has been shown to work well for bound states of the anharmonic oscillator, is applied to resonance states of the anharmonic oscillator with negative coupling constant. We obtain uniformly accurate wave functions starting from the bound states.

Paul Fendley

We study multi-soliton states in two-dimensional N=2 supersymmetric theories. We calculate their energy exactly as a function of mass and volume in the simplest integrable N=2 theory, the sine-Gordon model at a particular coupling. These energies are related to the expectation value $I= tr [\exp(inπF) \exp(-H/T)]$, where F is the fermion number. For n=1, thi

Ross H. McKenzie

The nature of the low-temperature phase of the quasi-two-dimensional conductors $α-(BEDT-TTF)_2{M}Hg(SCN)_4$[{M}=K,Rb,Tl] is considered. It is argued that the magnetic field dependence of the phase diagram is more consistent with a charge-density wave, rather than a spin-density wave ground state. The phase diagram of a charge-density wave in a magnetic fiel

Gyula Bene

Using a new approach to quantum mechanics we revisit Hardy&#39;s proof for Bell&#39;s theorem and point out a loophole in it. We also demonstrate on this example that quantum mechanics is a local realistic theory.

Emanuel Knill, Isaac Chuang, Raymond Laflamme

In bulk quantum computation one can manipulate a large number of indistinguishable quantum computers by parallel unitary operations and measure expectation values of certain observables with limited sensitivity. The initial state of each computer in the ensemble is known but not pure. Methods for obtaining effective pure input states by a series of manipulat

Wladyslaw Marcinek

An algebraic formalism for description of quantum states of charged particle with spin moving in two-dimensional space under influence of singular magnetic field is developed in terms of graded algebras. The fundamental assumption is that the particle is transformed into a composite system which consists quasiparticles, quasiholes and magnetic fluxes. Such s

Raja Ramanna, Anju Sharma

In this review, a new method is proposed based on Cantor&#39;s theory of Cardinality to analyze the experimental data on unstable nuclear systems which includes fundamental particles and their flavours, $β$-decay including spin and parity, $α$-decay and the systematics of the energy levels of light nuclei. The method also derives a formula for the Binding En

R. C. Hwa, J. Pisut, N. Pisutova

The nonlinear effect of gluon depletion in the collision of large nuclei can be large. It is due to multiple scatterings among comoving partons initiated by primary scattering of partons in the colliding nuclei. The effect can give rise to substantial suppression of $J/ψ$ production in very large nuclei, even if the linear depletion effect is insignificant f

Alejandro Kievsky

The three-nucleon ground state and the N--d scattering states are obtained using variational principles. The wave function of the system is decomposed into angular-spin-isospin channels and the corresponding two dimensional spatial amplitudes are expanded in a correlated polynomial basis. For the scattering states, the complex form of the Kohn variational pr

K. Hagino, N. Takigawa, A. B. Balantekin

Eigen-channel approach to heavy-ion fusion reactions is exact only when the excitation energy of the intrinsic motion is zero. In order to take into account effects of finite excitation energy, we introduce an energy dependence to weight factors in the eigen-channel approximation. Using two channel problem, we show that the weight factors are slowly changing

A. N. Kvinikhidze, B. Blankleider

We show how to attach an external photon to a system of three strongly interacting nucleons described by three-body scattering equations. Our method involves the idea of gauging the scattering equations themselves, and results in electromagnetic amplitudes where the external photon is effectively coupled to every part of every strong interaction diagram in t

R. S. Bhalerao, V. Ravishankar

We consider pair production in a space-time-dependent background field and derive a source term, i.e., production rate in the one-particle phase space. Such a source term is required in Boltzmann-equation-based models of quark-gluon plasma formation and evolution. We compare the source term derived here with the one that has been used in the literature so fa

G. Q. Li, C. -H. Lee, G. E. Brown

The recent past witnesses the growing interdependence between the physics of hadrons, the physics of relativistic heavy-ion collisions, and the physics of compact objects in astrophysics. A notable example is the kaon which plays special roles in all the three fields. In this paper, we first review the various theoretical investigations of kaon properties in

Tom Banks

This is a brief description of what has been accomplished and what remains to be done in the construction of a nonperturbative formulation of &#34;The Theory Formerly Known as String&#34;. It is culled from two short talks given by the author at SUSY 97 and Strings 97.

Hitoshi Miyazaki, Izumi Tsutsui

It is argued that, in the two dimensional principal chiral model, the Wess-Zumino term can be induced quantum mechanically, allowing the model with the critical value of the coupling constant $λ^2 = 8π/|k|$ to turn into the Wess-Zumino-Novikov-Witten model at the quantum level. The Wess-Zumino term emerges from the inequivalent quantizations possible on a sp

R. J. Cova, W. J. Zakrzewski

Using numerical simulations, the stability and scattering properties of the O(3) model on a two-dimensional torus are studied. Its solitons are found to be unstable but can be stabilized by the addition of a Skyrme term to the Lagrangian. Scattering at right angles with respect to the initial direction of motion is observed in all cases considered. The model

A. Shafiekhani, M. Khorrami

The exactly and quasi-exactly solvable problems for spin one-half in one dimension on the basis of a hidden dynamical symmetry algebra of Hamiltonian are discussed. We take the supergroup, $OSP(2|1)$, as such a symmetry. A number of exactly solvable examples are considered and their spectrum are evaluated explicitly. Also, a class of quasi-exactly solvable p

Carl R. Schmidt

We compare different schemes for the treatment of heavy quark production in Deep-Inelastic Scattering (DIS). For fully-integrated quantities such as $F_{2}(x,Q^{2})$, we advocate the use of the General-Massive Variable-Flavor-Number (GM-VFN) scheme; we present some results showing the progress of a Next-to-Leading Order calculation in this scheme. For differ

Biswajoy Brahmachari

We note that the recent direct measurement of the top quark mass at $173.3 \pm 5.6 (stat) \pm 6.2 (syst)$ by D0 collaboration severely constrains the theoretically attractive infra-red fixed point scenario of the top quark Yukawa coupling in supersymmetric GUTs. For one-step unified models the above mentioned measurement bounds the arbitrary but experimental

Anatoly V. Radyushkin

Applications of perturbative QCD to deeply virtual Compton scattering process require a generalization of usual parton distributions for the case when long-distance information is accumulated in nonforward matrix elements of quark and gluon operators. We discuss two types of functions parametrizing such matrix elements: double distributions F(x,y;t) and nonf

Anatoly V. Radyushkin

Applications of perturbative QCD to hard exclusive electroproduction processes in the Bjorken limit at small invariant momentum transfer t bring in a new type of parton distributions which have hybrid properties, resembling both the parton distribution functions and the distribution amplitudes. Their t-dependence is analogous to that of hadronic form factors

Anatoly D. Adamov, Gary R. Goldstein

A perturbative QCD calculation of heavy flavor quark fragmentation into heavy flavor baryons is developed along the lines of corresponding heavy meson models. The non-perturbative formation of the baryon is accomplished by implementing the quark-diquark model of the baryons. Diquark color form factors are used to enable the integration over the virtual heavy

M. A. Doncheski, R. W. Robinett

The contribution of axigluons (the massive color-octet gauge bosons in all chiral color models) to top quark pair production in hadronic collisions is considered. The agreement between the experimental values of the ttbar production cross-section at the TEVATRON and recent QCD predictions is used to discuss limits on the axigluon mass. Specifically,intermedi

B. Grzadkowski, B. Lampe, K. J. Abraham

In order to observe a signal of possible CP violation in top-quark couplings, we study top-quark production and decay under the conditions of the Tevatron upgrade. Transverse energy asymmetries sensitive to CP violation are defined. Applying the recently proposed optimal method, we calculate the statistical significance for the direct observation of CP viola

Jishnu Dey, Mira Dey, T. Frederico, Lauro Tomio

The baryon- coupling to its current ($λ_{B}$), in conventional QCD sum rule calculations (QCDSR), is shown to scale as the cubic power of the baryon mass, $M_B$. Some theoretical justification for it comes from a simple light-cone model and also general scaling arguments for QCD. But more importantly, taken as a phenomenological ansatz for the present, this

W. Ochs, T. Shimada

We calculate the probability for rapidity gaps in the parton cascade for different approximations within the perturbative QCD and compare the results with recent measurements. The aim is to find out whether the dual connection between the parton and hadron final states -- observed so far in various inclusive measurements -- holds as well for the extreme kine

F. J. Yndurain

We consider possible mechanical masses that could appear in supersymmetry, other than by direct Higgs coupling to fermions and we speculate that the existence of such a type of mass would allow one to have the Higgs mass of the $u$ quark zero, and the Higgs mass of the $d$ quark (at 1 \gev) of $\approx 1 \to 2 MeV$, thus solving at the same time the strong C

Chun Liu

The original results for the baryon-pion couplings in the large $N_c$ QCD can be understood in a simpler way in the Hartree-Fock picture. The large $N_c$ relation and its $1/N_c$ correction between the heavy baryon-meson coupling and the light baryon-meson coupling are emphasized. Application to the baryon-$ρ$ meson interactions is straightforward. The impli

Wu-Ki Tung

Conventional perturbative QCD calculations on the production of a heavy quark ``$H$&#39;&#39; consist of two contrasting approaches: the usual QCD parton formalism uses the zero-mass approximation ($m_H=0$) once above threshold, and treats $H$ just like the other light partons; on the other hand, most recent ``NLO&#39;&#39; heavy quark calculations treat $m_

Shaaban Khalil, Tatsuo Kobayashi

We study Yukawa unification in string models with moduli-dominant SUSY breaking. This type of SUSY breaking in general leads to non-universal soft masses, i.e., soft scalar masses and gaugino masses. Such non-universality is important for phenomenological aspects of Yukawa unification, i.e., successful electroweak breaking, SUSY corrections to the bottom mas

L. Randall, E. Katz, S. Su

We discuss a potential new probe of supersymmetric physics. In particular, we discuss the possibility of measuring hard supersymmetry violation which occurs at one loop through &#34;super-oblique&#34; corrections to the gauge and gaugino propagators. In models with heavy scalar partners, or with many gauge-charged particles which participate in supersymmetry

Tiehui, Liu

The search for $D^0\bar{D}^0$ mixing may carry a large discovery potential for new physics since the $D^0\bar{D}^0$ mixing rate is expected to be small in the Standard Model. This paper gives a brief review of the experimental techniques which can be used to search for $D^0\bar{D}^0$ mixing in the future. Some ideas, applicable to future mixing searches at h

Simon Hands

I review dynamical chiral symmetry breaking in four-fermi models, including results of Monte Carlo simulations with dynamical fermions. For 2<d<4, where the phase transition defines an ultraviolet fixed point of the renormalisation group, the continuum theory may either be describable using the large-N_f expansion, as in the case of the Gross-Neveu model, or

Laurel E. Sinclair

The HERA experiments H1 and ZEUS have recently presented a number of interesting results from studies of the hadronic final state produced in $ep$ collisions. These studies have focussed on deep inelastic scattering events and on the photoproduction of jets, and also on the comparison of the final states produced in these two regimes. Some of these results a

Nils Andersson

The first numerical study of axial (toroidal) pulsation modes of a slowly rotating relativistic star is presented. The calculation includes terms of first order in $ε\equiv Ω\sqrt{R^3/M}<<1$ ($R$ is the radius, $M$ is the mass and $Ω$ is the rotation frequency of the star), and accounts for effects due to the coriolis force. Effects due to the centrifugal fl

F. Woynarovich, P. Forgacs

The scaling limit of the higher level Bethe Ansatz (HLBA) equations for a macroscopically half-filled Hubbard chain is considered. These equations practically decouple into three disjoint sets which are again of the BA type, and correspond to the secular equations of three different kinds of dressed particles (one massive and two massless). The finite size c

Steven R. White, D. J. Scalapino

Results for a doped 3-leg t-J ladder obtained using the density matrix renormalization group are reported. At low hole doping, the holes form a dilute gas with a uniform density. The momentum occupation of the odd band shows a sharp decrease at a large value of k_F similar to the behavior of a lightly doped t-J chain, while the even modes appear gapped. The

M. C. Fauré, P. Bassereau, M. A. Carignano, I. Szleifer

We have studied both experimentally and theoretically the surface pressure isotherms of copolymers of polystyrene-polyethyleneoxide (PS-PEO) at the air-water interface. The SCMF (single chain mean-field) theory provides a very good agreement with the experiments for the entire range of surface densities and shows that the adsorption energy per PEO monomer at

R. Meyer, P. Entel

We have performaed molecular dynamics simulations of Fe(80)Ni(20) alloys using an inter-atomic potential of the EAM-type which allows the simulation of the martensite-austenite transition. We present results, showing the development of an inhomogeneous shear system on a nanoscale during the thermally induced austenitic transition. In addition to this we obta

Branko P. Stojkovic, David Pines

We present a study of the normal state optical conductivity in the cuprate superconductors using the nearly antiferromagnetic Fermi liquid (NAFL) description of the magnetic interaction between their planar quasiparticles. We find that the highly anisotropic scattering rate in different regions of the Brillouin zone, both as a function of frequency and tempe

H. A. Blom, A. Kadigrobov, A. M. Zagoskin, R. I. Shekhter

We consider the conductance of an Andreev interferometer, i.e., a hybrid structure where a dissipative current flows through a mesoscopic normal (N) sample in contact with two superconducting (S) &#34;mirrors&#34;. Giant conductance oscillations are predicted if the superconducting phase difference $ϕ$ is varied. Conductance maxima appear when $ϕ$ is on odd

V. Martisovits, D. L. Cox

We apply the staggered-pairing Ginzburg-Landau phenomenology to describe superconductivity in UPd_2Al_3 and UNi_2Al_3. The phenomenology was applied successfully to UPt_3 so it explains why these materials have qualitatively different superconducting phase diagrams although they have the same point-group symmetry. UPd_2Al_3 and UNi_2Al_3 have a two-component

Theo M. Nieuwenhuizen, Felix Ritort

We examine the phase diagram of the $p$-interaction spin glass model in a transverse field. We consider a spherical version of the model and compare with results obtained in the Ising case. The analysis of the spherical model, with and without quantization, reveals a phase diagram very similar to that obtained in the Ising case. In particular, using the stat

Holger Koehler, Matthias Vojta, Klaus W. Becker

Current methods to describe the thermodynamic behavior of many-particle systems are often based on perturbation theory with an unperturbed system consisting of free particles. Therefore, only a few methods are able to describe both strongly and weakly correlated systems along the same lines. In this article we propose a cumulant approach which allows for the

D. B. Saakian, Th. M. Nieuwenhuizen

A Gaussian variational approximation is often used to study interfaces in random media. By considering the 1+1 dimensional directed polymer in a random medium, it is shown here that the variational Ansatz typically leads to a negative variance of the free energy. The situation improves by taking into account more and more steps of replica symmetry breaking.

S. Suzuki, O. Sakai, Y. Shimizu

The resistivity for an extended two channel Anderson model is calculated. When the temperature decreases, it decreases logarithmically, and has T^1/2 anomaly at very low temperatures, as seen in some dilute U alloys. The single-particle and the spin excitation spectra are also calculated.

H. Schulz-Baldes, J. Bellissard

We develop a mathematical framework allowing to study anomalous transport in homogeneous solids. The main tools characterizing the anomalous transport properties are spectral and diffusion exponents associated to the covariant Hamiltonians describing these media. The diffusion exponents characterize the spectral measures entering in Kubo&#39;s formula for th

Brian P. Dolan

A metric is introduced on the two dimensional space of parameters describing the Ising model on a Bethe lattice of co-ordination number q. The geometry associated with this metric is analysed and it is shown that the Gaussian curvature diverges at the critical point. For the special case q=2 the curvature reduces to an already known result for the one dimens

S. V. Iordanskii, S. G. Plyasunov

Using gradient expansion method the particle density, the energy and the action were calculated at the formation of a vortex-skyrmion at high magnetic field. No approximation of single Landau level was used contrary to other papers on the subject. Taking into account the nearest Landau levels essentially changes the expression for the vortex energy and gives

I. Dan Melamed

Automatic segmentation of text into minimal content-bearing units is an unsolved problem even for languages like English. Spaces between words offer an easy first approximation, but this approximation is not good enough for machine translation (MT), where many word sequences are not translated word-for-word. This paper presents an efficient automatic method

I. Dan Melamed

Many multilingual NLP applications need to translate words between different languages, but cannot afford the computational expense of inducing or applying a full translation model. For these applications, we have designed a fast algorithm for estimating a partial translation model, which accounts for translational equivalence only at the word level. The mod

I. Dan Melamed

The first step in most empirical work in multilingual NLP is to construct maps of the correspondence between texts and their translations ({\bf bitext maps}). The Smooth Injective Map Recognizer (SIMR) algorithm presented here is a generic pattern recognition algorithm that is particularly well-suited to mapping bitext correspondence. SIMR is faster and sign

Fernando P. Simonotti, Eduardo Vergini, Marcos Saraceno

We construct a semiclassically invariant function on the boundary of the billiard, taken as the Poincare section in Birkhoff coordinates, based on periodic orbit information, as an ansatz for the normal derivative of the eigenfunction. Defining an appropriate scalar product on the section, we can compute the scar intensity of a given periodic orbit on an eig

Marko Robnik, Jure Dobnikar, Andrea Rapisarda, Tomaz Prosen

We study some new universal aspects of diffusion in chaotic systems, especially such having very large Lyapunov coefficients on the chaotic (indecomposable, topologically transitive) component. We do this by discretizing the chaotic component on the Surface-of-Section in a (large) number $N$ of simplectically equally big cells (in the sense of equal relative

Noam Soker

Based on the large number of elliptical planetary nebulae I argue that about 55 per cent of all progenitors of planetary nebulae have planets around them. The planets spin up the stars when the later evolve along the red giant branch or along the asymptotic giant branch. The arguments, which were presented in several of my earlier works, and are summarized i

Andrew Ulmer

Tidal disruption flares are differentiated into two classes -- those which are sub-Eddington and those which radiate near the Eddington limit. Flares from black holes above ~2 x 10^7 M_\odot will generally not radiate above the Eddington limit. For a Schwarzschild black hole, the maximum bolometric luminosity of a tidal disruption is ~L_Edd(5 x 10^7 M_\odot)

A. Marconi, D. J. Axon, F. D. Macchetto, A. Capetti

We present the first HST long-slit spectrum of a gaseous disk around a candidate super-massive black-hole. The results of this study on the kinematics of the gaseous disk in M87 are a considerable improvement in both spatial resolution and accuracy over previous observations and requires a projected mass of M_{BH}(sin i)^2 = (2.0+/- 0.5) 10^9 M_{sun} (M_{BH}

Heino Falcke, W. M. Goss, L. C. Ho, H. Matsuo

We report first results from a multiwavelength campaign to measure the simultaneous spectrum of Sgr A* from cm to mm wavelengths. The observations confirm that the previously detected submm-excess is not due to variability; the presence of an ultracompact component with a size of a few Schwarzschild radii is inferred. In a VLA survey of LINER galaxies, we fo

G. G. Pooley, R. P. Fender

Monitoring with the Ryle Telescope at 15 GHz of the Galactic X-ray transient source GRS 1915+105 has revealed a remarkable range of rapid and extended flares which appear to be related to the X-ray emission as recorded by the RXTE all-sky monitor. Quasi-periodic oscillations in the range 20 - 40 min have been found and are probably related to oscillations in

M. Maisack, K. Mannheim, R. D. Geckeler, M. Hillas

We report preliminary results of a multi-frequency campaign on the TeV candidate blazar W Comae (z=0.102). Flux limits by Whipple and HEGRA show that the TeV flux must be considerably below an E^-2 extrapolation of the EGRET flux. In the framework of proton-initiated cascade models, this implies a moderate amount of gamma-ray attenuation due to pair producti

R. Fux

Many 3D N-body barred models of the Galaxy extending beyond the Solar circle are realised by self-consistent evolution of various bar unstable axisymmetric models. The COBE/DIRBE K-band map, corrected for extinction, is used to constrain the location of the observer in these models, assuming a constant mass-to-light ratio. The resulting view points in the be