June 1996 arXiv papers — page 6

Hartmut Wittig

The current status of lattice calculation of weak matrix elements for heavy quark systems is reviewed. After an assessment of systematic errors in present simulations, results for the B meson decay constant, the B-parameter B_B and semi-leptonic heavy-to-light and heavy-to-heavy transitions are discussed. The final topic are lattice results for heavy baryon

Mihoko M. Nojiri, Keisuke Fujii, Toshifumi Tsukamoto

Sleptons can easily be found at future linear e+e- colliders if kinematically accessible. Measurements of their masses and decay distributions would then determine MSSM parameters. This paper presents a detailed MC study of the production and decay of the lighter scalar tau lepton, stau1. We found that mstau1 and the left-right mixing angle of stau would be

N. Nakajima, M. Biyajima, N. Suzuki

Oscillatory behavior of cumulant moments obtained from the experimental data in $pp$ collisions and $\bar{p}p$ collisions are analyzed by the modified negative binomial distribution (MNBD) and the negative binomial distribution (NBD). Both distributions well describe the cumulant moments obtained from the data. This fact shows sharp contrast to the result in

T. Osada, S. Sano, M. Biyajima, G. Wilk

We applied an analytical formula for Bose-Einstein correlations (BEC) developed by us recently to high-energy heavy ion collisions, in particular to data on S+Pb$\toπ^+$-$π^+$+X reaction at energy $200$ GeV/nucleon reported by the NA44 Collaboration. It takes into account both Coulomb and strong ($π$-$π$~s-wave; I=2) final state interactions (FSI). We have f

T. Osada, S. Sano, M. Biyajima, G. Wilk

The recently reported data on the yield ratio $π^-/π^+$ in central rapidity region of heavy-ion collisions are analyzed by theoretical formula which accounts for Coulomb interaction between central charged fragment (CCF) consisting of nearly stopped nucleons with effective charge $Z_{\mbox{\scriptsize eff}}$ and charged pions produced in the same region of t

T. Osada, S. Sano, M. Biyajima

We present an analytical formula for the Bose-Einstein correlations (BEC) which includes effects of both Coulomb and strong final stateinteractions (FSI). It was obtained by using Coulomb wave function together with the scattering partial wave amplitude of the strong interactions describing data on the $s$-wave phase shift. We have proved numerically that th

P. P. Allport, P. S. L. Booth, C. Green, A. Greenall

The performace of an ATLAS-A silicon micro-strip detector prototype with FELIX 128 analogue read out chip has been studied. The noise level and the signal to noise ratio have been measured as a funtion of both detector bias and temperature. No evidence of micro-discharge was observed for detector bias voltages up to 300 V.

Piotr Bizoń

This is a brief review of critical phenomena in gravitational collapse. The conceptual issues are emphasized and some directions for future research are suggested. The paper is not addressed to the experts in the field -- for them little will be new. It is rather meant to introduce others into one of the most rapidly developing areas of research in general r

Eva K. Grebel

As part of an ongoing photometric survey of young Magellanic Cloud clusters we identified Be stars in NGC 1818 and a nearby smaller cluster in the Large Magellanic Cloud. The neighbouring cluster does not contain evolved stars, and its sparsely populated main sequence does not extend to stars as massive as in NGC 1818. Both clusters are younger than the surr

Kosaburo Hashiguchi

I show that all inertial systems are not equivalent, and the Lorentz transformation is not the space-time transformation over two inertial systems moving with relative constant velocity. To do this, I consider imaginary signals travelling over any inertial system K with arbitrarily large velocities. The travelling of an imaginary signal over K is just a time

Michael W. Deem

The behavior of a thin film of nematic liquid crystal with unequal Frank constants is discussed. Distinct Frank constants are found to imply unequal core energies for $+1/2$ and $-1/2$ disclinations. Even so, a topological constraint is shown to ensure that the bulk densities of the two types of disclinations are the same. For a system with free boundary con

B. Lussier, L. Taillefer, W. J. L. Buyers, T. E. Mason

A neutron diffraction experiment was performed to investigate the effect of a magnetic field on the antiferromagnetic order in the heavy fermion superconductor UPt_3. Our results show that a field in the basal plane of up to 3.2 Tesla, higher than H_c2(0), has no effect: it can neither select a domain nor rotate the moment. This has a direct impact on curren

C. A. Hayward, D. Poilblanc, L. P. Lévy

We study the magnetization of a Heisenberg spin ladder using exact diagonalization techniques, finding three distinct magnetic phases. We consider the results in relation to the experimental behaviour of the new copper compound Cu_2(C_5H_{12}N_2)_2Cl_4 and deduce that the compound is well described by such a model with a ratio of `chain' to `rung' bo

Stephan Haas, Elbio Dagotto

Photoemission spectra for the isotropic two-leg t-J ladder are calculated at various hole-doping levels using exact diagonalization techniques. Low-energy sharp features caused by short-range antiferromagnetic correlations are observed at finite doping levels close to half-filling, above the naive Fermi momentum. These features should be observable in angle-

Kazuhiko Kuroki, Hideo Aoki, Takashi Hotta, Yasutami Takada

Quantum Monte Carlo method is used to re-examine superconductivity in the single-band Hubbard model in two dimensions. Instead of the conventional pairing, we consider a `correlated pairing', $\langle \tilde{c}_{i\uparrow} \tilde{c}_{i'\downarrow} %\tilde{c}_{j'\downarrow}^\dagger \tilde{c}_{j \uparrow}^\dagger \rangle$ with $\tilde{c}_{iσ} \equi

Hisatoshi Yokoyma, Shinya Tokizaki

Magnetization process of the Gutzwiller wave function is studied accurately by a variational Monte Carlo method. We apply it to the one-dimensional (1D) and 2D Hubbard models (HM), and to the 1D periodic Anderson model (PAM) without orbital degeneracy. For the HM, magnetization varies discontinuously to the full moment, as the magnetic field increases. For t

D. Olguin, R. Baquero

In this work we present the electronic band structure for (001)--CdTe interfaces with some other II--VI zinc blende semiconductors. We assume ideal interfaces. We use tight binding Hamiltonians with an orthogonal basis ($s p^3 s^*$). We make use of the well--known Surface Green's Function Matching method to calculate the interface band structure. In our

G. Garcia-Calderon, J. L. Mateos, M. Moshinsky

In this paper we study the time evolution of the decay process for a particle confined initially in a finite region of space, extending our analysis given recently (Phys. Rev. Lett. 74, 337 (1995)). For this purpose, we solve exactly the time-dependent Schroedinger equation for a finite-range potential. We calculate and compare two quantities: (i) the surviv

Anthony Hartley, Cecile Paris

This paper presents an analysis conducted on a corpus of software instructions in French in order to establish whether task structure elements (the procedural representation of the users' tasks) are alone sufficient to control the grammatical resources of a text generator. We show that the construct of genre provides a useful additional source of control

Somnath Bharadwaj

We investigate whether it is possible to study perturbatively the transition in cosmological clustering between a single streamed flow to a multi streamed flow. We do this by considereing a system whose dynamics is governed by the Zel'dovich approximation (ZA) and calculating the evolution of the two point correlation function using two methods: 1.Distri

Jack O. Burns, Michael J. Ledlow, Chris Loken, Anatoly Klypin

We present the first X-ray Luminosity Function (XLF) for an optically-selected sample of 49 nearby poor clusters of galaxies and a sample of 67 Abell clusters with z < 0.15. We have extended the measured cluster XLF by more than a factor of 10 in X-ray luminosity. Our poor cluster sample was drawn from an optical catalog of groups with 0.01<z<0.03 composed o

J. Craig Wheeler

The observations and theory of the exciting new class of galactic black hole X-ray transients is reviewed. Seven of these systems have measured mass functions or mass estimates in excess of stable neutron stars, making them excellent black hole candidates. Two of them have revealed ``superluminal&#34; radio jets. Study of the hard and soft radiation from the

K. A. Pounds, W. N. Brandt

Seyfert-type AGN that exhibit unusually strong and steep soft X-ray spectra are reviewed, building on observations made during the ROSAT all-sky survey. Two individual cases are described in brief detail, both being identified initially in the small sample of Seyferts detected in the Wide Field Camera (WFC) survey. In one case the similarity in X-ray appeara

R. Trasarti Battistoni, G. Invernizzi, S. Bonometto

We investigate the clustering properties of loose groups in the Perseus--Pisces redshift Survey (PPS). Previous analyses based on CfA and SSRS surveys led to apparently contradictory results. We investigate the source of such discrepancies, finding satisfactory explanations for them. Furthermore, we find a definite signal of group clustering, whose amplitude

Roger Coziol

In a diagram of metallicity (z) vs. luminosity (M$_B$), the different types of nearby (Z $< 0.05$) starburst galaxies seem to follow the same linear relationship as the normal spiral and irregular galaxies. However, for comparable luminosities the more massive starburst nucleus galaxies (SBNGs) show a slight metallic defficiency as compared to the giant spir

F. Courbin, D. Hutsemekers, G. Meylan, P. Magain

We report on imaging and spectroscopic observations of the radio-loud, highly polarized quasar PKS 1610-771 (z = 1.71). Our long-slit spectroscopy of the companion 4.55 arcseconds NW of the quasar confirms the stellar nature of this object, so ruling out the previously suspected gravitationally lensed nature of this system. PKS 1610-771 looks fuzzy on our su

M. L. Markevitch, C. L. Sarazin, M. J. Henriksen

We use ASCA data to obtain two-dimensional maps of the gas temperature in three clusters: A754, A3558 and Triangulum Australis (the maps of A2256, A2319, A2163 and A665, also presented at the conference, have since appeared in [5]). All clusters from our sample show considerable temperature decline with radius at r ~ 0.5-1 h^{-1} Mpc, most prominently in dis

H. Dreiner, S. Lola, P. Morawitz

We study the pair production of charginos in e+e- collisions followed by the decay via R-parity violating LQD operators. We determine the complete matrix element squared for chargino decays via LQD or LLE operators. We find regions in MSSM parameter space where the chargino mass is 52.5GeV and the R-parity violating decays of the charginos dominate the gauge

Hirosi Ooguri, Yaron Oz, Zheng Yin

We study the boundary states of D-branes wrapped around supersymmetric cycles in a general Calabi-Yau manifold. In particular, we show how the geometric data on the cycles are encoded in the boundary states. As an application, we analyze how the mirror symmetry transforms D-branes, and we verify that it is consistent with the conjectured periodicity and the

Paul Federbush

We consider theories with gauged chiral fermions in which there are abelian anomalies, and no nonabelian anomalies (but there may be nonabelian gauge fields present). We construct an associated theory that is gauge-invariant, renormalizable, and with the same particle content, by adding a finite number of terms to the action. Alternatively one can view the n

David Tytler, Scott Burles

The primordial D/H ratio now provides the best measure of the cosmological density of baryons. We describe in detail how we deduce the D/H ratio from absorption lines in the spectra of quasars, and we present our first two measurements of D/H in different QSOs, which agree to within the random errors. We describe how we correct D/H for blending with Lyman al

R. Kaminski, L. Lesniak, K. Rybicki

A new analysis of S-wave production amplitudes for the reaction $π^- p_{\uparrow} \rightarrow π^+ π^- n$ on a transversely polarized target is performed. It is based on the results obtained by the CERN-Cracow -Munich collaboration in the pion-pion energy range from 600 MeV to 1600 MeV at 17.2 GeV/c $π^-$ momentum. Energy-independent separation of the S-wave

F. A. Brito, D. Bazeia

In this paper we deal with defects inside defects in systems of two scalar fields in 3+1 dimensions. The systems we consider are defined by potentials containing two real scalar fields, and so we are going to investigate domain ribbons inside domain walls. After introducing some general comments on the possibility of finding defects that support internal str

F. Sefkow

Recent results from the experiments ZEUS and H1 on charm production in $ep$ collisions are reviewed. The topics are elastic and inelastic $J/ψ$ photoproduction, $D^*$ photoproduction differential cross sections and a first look at the proton structure function F_2^{c\bar{c}}.

A. Casher, F. Englert, N. Itzhaki, S. Massar

It is generally admitted that gravitational interactions become large at an invariant distance of order $1$ from the black hole horizon. We show that due to the ``atmosphere&#39;&#39; of high angular particles near the horizon strong gravitational interactions already occur at an invariant distance of the order of $\sqrt[3]{M}$. The implications of these res

Raphael Bousso, Stephen W. Hawking

Black holes came into existence together with the universe through the quantum process of pair creation in the inflationary era. We present the instantons responsible for this process and calculate the pair creation rate from the no boundary proposal for the wave function of the universe. We find that this proposal leads to physically sensible results, which

T. E. Browder, K. Honscheid, Daniele Pedrini

We review recent experimental results on lifetimes and hadronic decays of hadrons that contain $c$ and $b$ quarks. The theoretical implications of these results are also considered. An understanding of hadronic decays of heavy quarks is required to interpret the CP violating asymmetries in $B$ decays that will be observed in experiments planned for the near

R. Carroll

The nature of the BA function and its adjoint for KP-Toda is traced through the averaging method in generating the Whitham equations, differentials, and symplectic forms, with connections to EM duality.

S. G. Bondarenko, V. V. Burov, M. Beyer, S. M. Dorkin

We discuss polarization characteristics of the deuteron disintegration near the threshold energy. Due to the small relative energy of the outgoing $np$ pair, the dominant amplitude for this process is a 1+ -> 0^+ transition. Relativistic covariance requires only one electromagnetic transition form factor for this amplitude. Subsequently this leads to substan

C. Ciofi degli Atti, S. Scopetta

Nuclear effects in polarized inelastic electron scattering off polarized $^3He$ are discussed; in the kinematics of future experiments at CEBAF, Fermi motion effects are found to be much larger than in deep inelastic scattering. It is shown that improperly describing nuclear dynamics would lead to the extraction of unreliable neutron spin structure functions

S. A. Voloshin, W. E. Cleland

Utilizing the Lorentz invariance of the correlation function we study the effects of anisotropic transverse flow on the HBT correlation function. In particular we show that directed flow would evidence itself by non zero ``side--long&#39;&#39; and ``side--out&#39;&#39; terms in the correlation function. We also show that the study of ratios of the correlatio

P. Bozek

We estimate the importance of the nonlinear terms in the Vlasov equation for the development of the unstable modes. The results allow to identify the region of wavelength where the linear evolution is justified.

A. Schuettauf, W. D. Kunze, A. Woerner, M. Begemann-Blaich

Multi-fragment decays of 129Xe, 197Au, and 238U projectiles in collisions with Be, C, Al, Cu, In, Au, and U targets at energies between E/A = 400 MeV and 1000 MeV have been studied with the ALADIN forward-spectrometer at SIS. By adding an array of 84 Si-CsI(Tl) telescopes the solid-angle coverage of the setup was extended to θ_lab = 16 degree. This permitted

Mitch Rudominer

In this paper we explore a connection between descriptive set theory and inner model theory. From descriptive set theory, we will take a countable, definable set of reals, A. We will then show that A is equal to the reals of M, where M is a canonical model from inner model theory. In technical terms, M is a &#39;&#39;mouse&#39;&#39;. Consequently, we say tha

Gary T. Horowitz, Donald Marolf

We extend our recent analysis of the entropy of extremal black strings with traveling waves. We previously considered waves carrying linear momentum on black strings in six dimensions. Here we study waves carrying angular momentum on these strings, and also waves carrying linear momentum on black strings in five dimensions. In both cases, we show that the ho

Adel Bilal, Frank Ferrari

In these notes, we emphasize the rôle of spontaneous broken global discrete symmetries acting on the moduli space of $N=2$ susy Yang-Mills theories and show how they can be used, together with the BPS condition, as a spectrum generating symmetry. In particular, in the strong-coupling region, all BPS states come in multiplets of this broken symmetry. This pla

S. J. Gates

Within a four dimensional N = 1 superspace, we present a new ansatz for the Skyrme term and for the gauged WZNW term embedded into a superaction. We use the new chiral-nonminimal (CNM) formulation for the effective low-energy action of 4D, N = 1 supersymmetric QCD constructed by assigning right-handed components of Dirac fields to chiral multiplets and left-

R. Dhanawittayapol, S. James Gates, Lubna Rana

Extending prior investigations, we study three of the the four distinct minimal (4,0) scalar multiplets coupled to (4,0) supergravity. It is found that the scalar multiplets manifest their differences at the component level by possessing totally different couplings to the supergravity fields. Only the SM-I multiplet possesses a conformal coupling. For the re

S. J. Gates

Utilizing (2,0) superfields, we write a supersymmetry-squared action and partially relate it to the new formulation of the Green-Schwarz action given by Berkovits and Siegel. Recent results derived from this new formulation are discussed within the context of some prior proposals in the literature. Among these, we note that 4D, N = 1 beta-FFC superspace geom

Michael Duetsch

We continue the investigation of quantized Yang-Mills theories coupled to matter fields in the framework of causal perturbation theory which goes back to Epstein and Glaser. In this approach gauge invariance is expressed by a simple commutator relation for the S-matrix and the corresponding gauge transformations are simple transformations of the free fields

S. Mrenna, C. -P. Yuan

We study the kinematic distributions of top--antitop quark pairs produced at the Tevatron, including the effects of initial state and final state multiple soft gluon emission, using the Collins--Soper--Sterman resummation formalism. The resummed results are compared with those predicted by the showering event generator PYTHIA for various distributions involv

S. W. Ham, H. Genten, B. R. Kim, S. K. Oh

We investigate the Higgs sector of a nonlinear supersymmetric standard model at LEP 1 and LEP 2, as well as at future linear $e^+ e^-$ colliders with $\sqrt s = 500$, 1000, and 2000 GeV. The LEP 1 data do not put any constraints on the parameters of the model, and allow a massless Higgs boson in particular. For LEP 2, there are remarkable differences between

Ernest Ma

The totality of present neutrino data seems to require four light neutrinos, but only three of them can be the neutral components of left-handed lepton doublets. To accommodate one or more naturally light singlet neutrino(s), an extra U(1) gauge factor is proposed to implement an analogous seesaw mechanism which accounts for the light doublet neutrinos. Usin

Utpal Sarkar

The lepton number violating interactions generated by the light Majorana neutrinos can erase the primordial baryon asymmetry of the universe during the electroweak phase transition. The Majorana masses of the left-handed neutrinos are constrained to avoid this problem. These constraints do not depend on the $(B-L)$ symmetry breaking mechanism.

Mikulaas Blazek

We propose to verify relations between quantities which characterize scaling properties of high energy density fluctuations in terms of factorial moments and newly introduced associated frequency moments. Typical examples are presented in frame of systematics developed in the present paper. It involves also several sorts of moments applied so far in the sear

Jens O. Andersen

We study the screening of static electric fields in massless scalar electrodynamics at high temperature and zero chemical potential. Effective field theory methods are used to separate the contributions from the momentum scales T and eT to the electric screening mass. The effects of the distance scale 1/T are encoded in the parameters of an effective three-d

P. Poulose, Saurabh D. Rindani

We study two simple $CP$-violating asymmetries of leptons coming from the decay of $t$ and $øt$ in $e^+e^- \ra \tt$, which do not need the full reconstruction of the $t$ or $øt$ for their measurement. They can arise when the top quark possesses nonzero electric and weak dipole form factors in the couplings to the photon and $Z$, respectively. Together, these

Andree Blotz, Edward Shuryak

We have calculated the 3-point correlation function for the electromagnetic interaction of the pion in an ensembles of instantons and anti-instantons, modelling the QCD vacuum. The results are well described by a pion pole and the pion formfactor is extracted, nicely following a standard monopole fit. The experimental data on the formfactor are well reproduc

A. B. Balantekin, J. F. Beacom

The matter-enhanced oscillations of two neutrino flavors are studied using a uniform semiclassical approximation. Unlike some analytic studies which have focused on certain exactly-solvable densities, this method can be used for an arbitrary monotonic density profile. The method is applicable to a wider range of mixing parameters than previous approximate me

Colin Morningstar, Mike Peardon

The low-lying glueball masses and the hadronic scale $r_0$ are computed in lattice SU(3) gauge theory with the aim of establishing the effectiveness of the improved action approach in removing finite-spacing artifacts. The use of anisotropic lattices in which the temporal spacing is much smaller than that in the spatial directions allows much more efficient

Erez Etzion

This thesis describes a new a measurement of the tau lepton polarization and its forward-backward asymmetry at the Z resonance using the OPAL detector. This measurement is based on analyses of the tau->electron, muon and pion (Kaon) decays from a sample of 30663 tau-pair events collected in the polar angle range of Abs(cos(theta)) <0.68 during the 1990-1992

L. E. Sinclair

Recent results obtained from studies of diffractive processes in hard photoproduction performed by the ZEUS collaboration using data delivered by HERA in 1993 and 1994 are presented. In particular, we have found that $(7 \pm 3)$\% of events with two jets at a pseudorapidity interval of 3.5 to 4 are inconsistent with a non-diffractive production mechanism. Th

Steven L. Liebling, Matthew W. Choptuik

We study the collapse of a free scalar field in the Brans-Dicke model of gravity. At the critical point of black hole formation, the model admits two distinctive solutions dependent on the value of the coupling parameter. We find one solution to be discretely self-similar and the other to exhibit continuous self-similarity.

F. M. Paiva, M. J. Rebouças, A. F. F. Teixeira

A limiting diagram for the Segre classification in 5-dimensional space-times is obtained, extending a recent work on limits of the energy-momentum tensor in general relativity. Some of Geroch&#39;s results on limits of space-times in general relativity are also extended to the context of five-dimensional Kaluza-Klein space-times.

R. Beig

We study transverse-tracefree (TT)-tensors on conformally flat 3-manifolds $(M,g)$. The Cotton-York tensor linearized at $g$ maps every symmetric tracefree tensor into one which is TT. The question as to whether this is the general solution to the TT-condition is viewed as a cohomological problem within an elliptic complex first found by Gasqui and Goldschmi

V. Burdyuzha, O. Lalakulich, Yu. Ponomarev, G. Vereshkov

We propose that the Universe created from "nothing" with relatively small particles number and quickly relaxed to quasiequilibrium state at the Planck parameters. The classic cosmological solution for this Universe with Lambda-term has two branches divided by the gap. The quantum process of tunneling between the cosmological solution branches and kinetic of

Francois Lalonde, Dusa McDuff

A positive path in the linear symplectic group $\Sp(2n)$ is a smooth path which is everywhere tangent to the positive cone. These paths are generated by negative definite (time-dependent) quadratic Hamiltonian functions on Euclidean space. A special case are autonomous positive paths, which are generated by time-independent Hamiltonians, and which all lie in

Dusa McDuff

These are notes of lectures given at the NATO Summer School, Montreal 1995. Taubes&#39;s recent spectacular work setting up a correspondence between $J$-holomorphic curves in symplectic 4-manifolds and solutions of the Seiberg-Witten equations counts $J$-holomorphic curves in a somewhat new way. The &#34;standard&#34; theory concerns itself with moduli space

Erik Koch, Olle Gunnarsson

We present the results of self-consistent calculations of the electronic shell and supershell structure for clusters having up to 6000 valence electrons. The ionic background is described in terms of a homogeneous jellium. The calculations were performed for a series of different electron densities, resembling Cs, Rb, K, Na, Li, Au, Cu, Tl, In, Ga, and Al, r

L. Yin, S. Chakravarty, P. W. Anderson

Recent neutron scattering experiments in YBCO exhibit an unusual magnetic peak that appears only below the superconducting transition temperature. The experimental observations are explained within the context of the interlayer tunneling theory of high temperature superconductors.

Giuseppe Albertini, Silvio Renato Dahmen, Birgit Wehefritz

We consider the asymmetric six--vertex model, {\it i.e.} the symmetric six--vertex model in an external field with both horizontal and vertical components, and the relevant asymmetric $XXZ$ chain. The model is widely used to describe the equilibrium shape of a crystal. By means of the Bethe Ansatz solution we determine the exact free energy singularity, as f

A. M. Gutin, V. I. Abkevich, E. I. Shakhnovich

The relation between cooperativity of protein folding and the Random-Field Ising Model (RFIM) is established. Generalization of the Imry-Ma argument predicts cooperative folding transition for small heterogeneity of the interactions stabilizing the native structure. Monte Carlo simulation of a lattice model shows that starting from some finite heterogeneity

Christian Helm, Franz Forsthofer, Joachim Keller

We investigate a double layer system with tight-binding hopping, intra-layer and inter-layer interactions, as well as a Josephson like coupling. We find that an antiferromagnetic spin polarization induces additional spin-triplet pairing (with $S_z =0$) to the singlet order parameter. This causes an undamped collective mode in the superconducting state below

R. R. Levitskii, S. I. Sorokov

The method for calculation of the correlation functions of the Ising-type systems with short-range interaction and with arbitrary value of spin is developed within cluster approximation. For the Ising model (spin $S^z=\pm1$) the expressions for pair and ternary correlation functions within two-particle approximation in $\set{q}$-space are obtained for the hy

R. R. Levitskii, S. I. Sorokov, R. O. Sokolovskii

Spin relaxation in a site-disordered Ising model within master equation approach is studied. The $\vec{q},ω$-dependent susceptibility of the model is calculated and investigated. Effects described by the two-site cluster approximation and lost by the mean field approximation are discussed. Comparison of obtained results with dielectric measurements in $Cs(H_

R. R. Levitskii, S. I. Sorokov

Spin correlation functions (up to the 3-site one) of disordered Ising model with the nearest neighbour interaction are calculated and investigated within a two-site cluster approximation for both quenched and annealed cases. The approach yields the exact results for the one-dimensional system. The long-range interaction is taken into account in the mean fiel

R. K. Bhaduri, M. V. N. Murthy

A Bose-Einstein condensate of atoms, trapped in an axially symmetric harmonic potential, is considered. By averaging the spatial density along the symmetry direction over a length that preserves the aspect ratio, the system may be mapped on to a zero temperature noninteracting Fermi-like gas. The ``mock fermions&#39;&#39; have a state occupancy factor $(>>1)

Viktor K. Horváth, H. Eugene Stanley

To better understand the temporal behavior of a roughening meniscus driven by capillary forces during the imbibition of a viscous fluid in porous media, we measure the height-height autocorrelation function $C(t)$ using a constant driving force. We find $C(t)\sim t^β$, with $β= 0.56\pm 0.03$, and provide the first experimental evidence for driving force inde

J. Ambjorn, G. Akemann

We study the universal properties of distributions of eigenvalues of random matrices in the large $N$ limit. The distributions fall in universality classes characterized entirely by the support of the spectral density.

Yasuhiro Saiga, Yusuke Kato, Yoshio Kuramoto

A new anisotropic t-J model in one dimension is proposed which has long-range hopping and exchange. This t-J model is only partially solvable in contrast to known integrable models with long-range interaction. In the high-density limit the model reduces to the XXZ chain with the long-range exchange. Some exact eigenfunctions are shown to be of Jastrow-type i

Kiyohide Nomura, Atsuhiro Kitazawa

It was a difficult problem to determine the Gaussian fixed line from the numerical data, because close to the Berezinskii-Kosterlitz-Thouless multicritical point the divergence of the correlation length becomes very slow. Considering the renormalization group behavior, we find an efficient method to determine the Gaussian fixed line.

Seungoh Ryu, M. Hellerqvist, S. Doniach, A. Kapitulnik

Using Langevin dynamics, we have investigated the dynamics of vortices in a disordered two dimensional superconductor subjected to a uniform driving current. The results provide direct numerical evidence for a dynamical phase transition between a plastic flow regime and a moving ``hexatic glass.&#34; The simulated current-voltage characteristics are in excel

Rens Bod, Remko Bonnema, Remko Scha

In Data-Oriented Parsing (DOP), an annotated language corpus is used as a stochastic grammar. The most probable analysis of a new input sentence is constructed by combining sub-analyses from the corpus in the most probable way. This approach has been succesfully used for syntactic analysis, using corpora with syntactic annotations such as the Penn Treebank.

James F. Allen, Bradford W. Miller, Eric K. Ringger, Teresa Sikorski

This paper describes a system that leads us to believe in the feasibility of constructing natural spoken dialogue systems in task-oriented domains. It specifically addresses the issue of robust interpretation of speech in the presence of recognition errors. Robustness is achieved by a combination of statistical error post-correction, syntactically- and seman

Robert Popham, Scott Kenyon, Lee Hartmann, Ramesh Narayan

We present solutions for the accretion disks and boundary layers in pre-main-sequence stars undergoing FU Orionis outbursts. These solutions differ from earlier disk solutions in that they include a self-consistent treatment of the boundary layer region. In a previous paper (Popham 1996), we showed that these stars should stop accreting angular momentum once

Xiang-Ping Wu, Li-Zhi Fang

Gravitational lensing by clusters of galaxies has been detected on scales ranging from $\sim10^{-1}$ Mpc to $\sim10$ Mpc, namely, arcs/arclets, weak lensing and quasar-cluster associations. This allows us to derive an overall radius matter distribution of clusters of galaxies. While the dynamical analysis of the X-ray observations has yielded a great number

F. Fusi Pecci, M. Bellazzini, F. R. Ferraro, R. Buonanno

We review the most outstanding issues related to the study of the morphology of the Horizontal Branch (HB) in the Color-Magnitude Diagrams of Galactic Globular Clusters and its use as age indicator. It is definitely demonstrated (see also Bolte, this meeting) that age cannot be the only 2nd-P driving the HB morphology. Other candidate 2nd-Ps are briefly exam

Dante Minniti, Albert Zijlstra

We present evidence for the existence of an old stellar halo in the dwarf irregular galaxy WLM, an isolated member of the Local Group. The halo consists of population-II stars, with low metallicities and age $\geq 10^{10}$yr. The finding of a halo in a dwarf irregular galaxy argues for a generic mode of galaxy formation that requires a halo in the presence o

T. W. Jones, Dongsu Ryu, I. L. Tregillis

We report an extensive set of two-dimensional MHD simulations exploring the role and evolution of magnetic fields in the dynamics of supersonic plasma clumps. We examine the influence of both ambient field strength and orientation on the problem. Of those two characteristics, field orientation is far more important in the cases we have considered with $β_0 =

A. Leclair, F. Lesage, H. Saleur

A single impurity in the 1D Luttinger model creates a local modification of the charge density analogous to the Friedel oscillations. In this paper, we present an exact solution of the case $g={1\over 2}$ (the equivalent of the Toulouse point) at any temperature $T$ and impurity coupling, expressing the charge density in terms of a hypergeometric function. W

Anatoly Malevanets, Raymond Kapral

The existence of stable links and knots is demonstrated in three-dimensional, bistable, chemical media. The reaction-diffusion medium segregates into regions of high and low concentration separated by sharp interfaces. The interfaces repel at short distances so that domains with various topologies are possible depending on the initial conditions and system p

Dusa McDuff

Let $X$ be an oriented 4-manifold which does not have simple SW-type, for example a blow-up of a rational or ruled surface. We show that any two cohomologous and deformation equivalent symplectic forms on $X$ are isotopic. This implies that blow-ups of these manifolds are unique, thus extending work of Biran. We also establish uniqueness of structure for cer

S. Nishigaki

We prove the universality of correlation functions of chiral complex matrix models in the microscopic limit (N->\infty, z->0, N z=fixed) which magnifies the crossover region around the origin of the eigenvalue distribution. The proof exploits the fact that the three-term difference equation for orthogonal polynomials reduces into a universal second-order dif

P. V. Moniz

In this paper we investigate whether conserved currents can be sensibly defined in supersymmetric minisuperspaces. Our analysis deals with k=1 FRW and Bianchi class--A models. Supermatter in the form of scalar supermultiplets is included in the former. Moreover, we restrict ourselves to the first-order differential equations derived from the Lorentz and supe

N. Brambilla, A. Vairo

The $Q \bar{Q}$ semirelativistic interaction in QCD can be simply expressed in terms of the Wilson loop and its functional derivatives. In this approach we present the $Q \bar{Q}$ potential up to order $1/m^2$ using the expressions for the Wilson loop given by the Wilson Minimal Area Law (MAL), the Stochastic Vacuum Model (SVM) and Dual QCD (DQCD). We confir

Matthias Wulf

The algebra of constraints arising in the canonical quantization of N=1 supergravity in four dimensions is investigated. Using the holomorphic action, the structure functions of the algebra are given and it is shown that the algebra does not close formally for two chosen operator orderings.

J. Cruz, J. Navarro-Salas, M. Navarro, C. F. Talavera

We study finite-dimensional extra symmetries of generic 2D dilaton gravity models. Using a non-linear sigma model formulation we show that the unique theories admitting an extra (conformal) symmetry are the models with an exponential potential $V \propto e^{βϕ}$ ($ S ={1\over2π} \int d^2 x \sqrt{-g} [ R ϕ+ 4 λ^2 e^{βϕ} ]$), which include the CGHS model as a

D. H. Cobden, E. Kogan

We study experimentally the reproducible conductance fluctuations between the quantum Hall plateaus in the conductance of two-terminal submicron silicon MOSFETs. For the dramatic fluctuations at the insulator-to-first-plateau transition we find a conductance distribution that is approximately uniform between zero and $e^2/h$. We point out that this is consis

Takashi Torii, Hiroki Yajima, Kei-ichi Maeda

We discuss black holes in an effective theory derived from a superstring model, which includes a dilaton field, a gauge field and the Gauss-Bonnet term. Assuming U(1) or SU(2) symmetry for the gauge field, we find four types of spherically symmetric solutions, i.e., a neutral, an electrically charged, a magnetically charged and a ``colored&#39;&#39; black ho

Arthur Jabs

.We expound an alternative to the Copenhagen interpretation of the formalism of nonrelativistic quantum mechanics. The basic difference is that the new interpretation is formulated in the language of epistemological realism. The {\psi} function is no longer interpreted as a probability amplitude of the observed behaviour of elementary particles but as an obj