July 1996 arXiv papers — page 5

A. Riotto, E. Roulet, I. Vilja

The constraints imposed by the requirement that the scalar potential of supersymmetric theories does not have unbounded directions and charge or color breaking minima deeper than the usual electroweak breaking minimum (EWM) are significantly relaxed if one just allows for a metastable EWM but with a sufficiently long lifetime. For this to be acceptable one n

I. G. Aznauryan

In the framework of a relativistic quark model constructed in an infinite momentum frame, corrections of the order of $v^{2}/c^{2}$ are obtained in the formulas which express amplitudes of the transitions $ψ(ψ') \to η_{_{c}}(η'_{_{c}})γ$, $χ_{_{J}} \to ψγ$, $ψ' \to χ_{_{J}}γ$, $h_{_{c}} \to η_{_{c}}γ$, $η'_{_{c}} \to h_{_{c}}γ$ through overla

J. C. Romao, A. Ioannissyan, J. W. F. Valle

We show how R-parity can break spontaneously as a result of radiative corrections in unified N=1 supergravity models. We illustrate this with a concrete rank-four unified model, where the spontaneous breaking of R-parity is accompanied by the existence of a physical majoron. We determine the resulting supersymmetric particle mass spectrum and show that R-par

D. Comelli, J. R. Espinosa

In general electroweak models with weakly coupled (and otherwise arbitrary) Higgs sector there always exists in the spectrum a scalar state with mass controlled by the electroweak scale. A new and simple recipe to compute an analytical tree-level upper bound on the mass of this light scalar is given. We compare this new bound with similar ones existing in th

K. Golec-Biernat, J. Kwiecinski

The contribution of subleading reggeons to the diffractive structure function ${dF_{2}^D / dx_{\funp} dt}$ is estimated from the soft physics data. This contribution leads in a natural way to the violation of the factorization property of the diffractive structure function.

N. N. Achasov, A. A. Kozhevnikov

The results of an analysis are presented of some recent data on the reactions $e^+e^-\toπ^+π^-π^+π^-$, $e^+e^-\toπ^+π^-π^0π^0$ with the subtracted $ωπ^0$ events, $e^+e^-\toωπ^0$, $e^+e^-\toηπ^+π^-$, $e^+e^-\toπ^+π^-$, $J/ψ\toπ^+π^-π^0$ and $K^-p\toπ^+π^-Λ$, upon taking into account both the strong energy dependence of the partial widths on energy and the pre

Alfred Bartl, Helmut Eberl, Keisho Hidaka, Tadashi Kon

We present a detailed study of the decays of the neutral Higgs bosons $H^0$ and $A^0$ within the Minimal Supersymmetric Standard Model. We find that the supersymmetric modes ${\tilde{t}}\bar{\tilde{t}}$ and ${\tilde{b}}\bar{\tilde{b}}$ can dominate the $H^0$ and $A^0$ decays in a wide range of the model parameters due to large Yukawa couplings and mixings of

L. Del Debbio, M. Faber, J. Greensite, S. Olejnik

Some critical remarks are presented, concerning the abelian projection theory of quark confinement.

Hermann Dilger

The two-dimensional U(1)-gauged Higgs model is studied on an euclidean lattice of size $L_1\times L_2$, where the temperature $T=L_2^{-1}$ is of the order of the sphaleron mass. The simulation parameters are taken from zero temperature results. By comparison with classical and semiclassical results I discuss, whether the sphaleron transition rate can be extr

Karl Jansen

A summary of recent developments in the field of simulation algorithms for dynamical fermions is given.

S. Aid

First results on inclusive D0 and D* production in deep inelastic $ep$ scattering are reported using data collected by the H1 experiment at HERA in 1994. Differential cross sections are presented for both channels and are found to agree well with QCD predictions based on the boson gluon fusion process. A charm production cross section for 10 GeV$^2\le Q^2\le

M. F. A. da Silva, L. Herrera, F. M. Paiva, N. O. Santos

We consider two exact solutions of Einstein's field equations corresponding to a cylinder of dust with net zero angular momentum. In one of the cases, the dust distribution is homogeneous, whereas in the other, the angular velocity of dust particles is constant [1]. For both solutions we studied the junction conditions to the exterior static vacuum Levi-

M. F. A. da Silva, L. Herrera, F. M. Paiva, N. O. Santos

The physical and geometrical meaning of the four parameters of Lewis metric for the Lewis class are investigated. Matching this spacetime to a completely anisotropic, rigidly rotating, fluid cylinder, we obtain from the junction conditions that the four parameters are related to the vorticity of the source. Furthermore it is shown that one of the parameters

M. F. A. da Silva, L. Herrera, F. M. Paiva, N. O. Santos

We provide physical interpretation for the four parameters of the stationary Lewis metric restricted to the Weyl class. Matching this spacetime to a completely anisotropic, rigidly rotating, fluid cilinder, we obtain from the junction conditions that one of these parameters is proportional to the vorticity of the source. From the Newtonian approximation a se

Nils Andersson, Hisashi Onozawa

We present detailed calculations of the quasinormal modes of Reissner-Nordstrom black holes. While the first few, slowly damped, modes depend on the charge of the black hole in a relatively simple way, we find that the rapidly damped modes show several peculiar features. The higher modes generally spiral into the value for the extreme black hole as the charg

Donald E. Neville

The metric for plane gravitational waves is quantized within the Hamiltonian framework, using a Dirac constraint quantization and the self-dual field variables proposed by Ashtekar. The z axis (direction of travel of the waves) is taken to be the entire real line rather than the torus (manifold coordinatized by (z,t) is RxR rather than $S_1$ x R). Solutions

S. Schreckenberg

The basic ingredients of the `consistent histories' approach to quantum theory are a space $\UP$ of `history propositions' and a space $\D$ of `decoherence functionals'. In this article we consider such history quantum theories in the case where $\UP$ is given by the set of projectors $¶(\V)$ on some Hilbert space $\V$. We define the notion of a

S. Schreckenberg

The basic ingredients of the `consistent histories' approach to quantum theory are a space $\UP$ of `history propositions' and a space $\D$ of `decoherence functionals'. In this article we consider such history quantum theories in the case where $\UP$ is given by the set of projectors $¶(\V)$ on some Hilbert space $\V$. Using an analogue of Wigne

M. Khorrami, M. Mansouri, M. Mohazzab

Assuming a cellular structure for the space-time, we propose a model in which the expansion of the universe is understood as a decrumpling process, much like the one we know from polymeric surfaces. The dimension of space is then a dynamical real variable. The generalized Friedmann equation, derived from a Lagrangian, and the generalized equation of continui

Sudhansu S. Mandal, V. Ravishankar

We have determined the off-diagonal and diagonal conductivities for a quantum Hall effect system at exactly integer filling at finite temperatures and in the presence of weak short ranged disorder potential within the self consistent Born approximation. We find that there is a finite temperature contribution to off-diagonal conductivity $σ_{xy}$ which is `an

L. Frachebourg, P. L. Krapivsky

We investigate a 3-phase deterministic one-dimensional phase ordering model in which interfaces move ballistically and annihilate upon colliding. We determine analytically the autocorrelation function A(t). This is done by computing generalized first-passage type probabilities P_n(t) which measure the fraction of space crossed by exactly n interfaces during

J. H. Han, D. J. Thouless

We work out the dynamics of the compressible edge of the quantum Hall system based on the electrostatic model of Chklovskii et al.. We introduce a generalized version of Wen's hydrodynamic quantization approach to the dynamics of sharp edge and rederive Aleiner and Glazman's earlier result of multiple density modes. Bosonic operators of density excit

Adriaan M. J. Schakel

Starting from a standard description of an ideal, isentropic fluid, we derive the effective theory governing a gapless non-relativistic mode---the sound mode. The theory, which is dictated by the requirement of Galilei invariance, entails the entire set of hydrodynamic equations. The gaplessness of the sound mode is explained by identifying it as the Goldsto

Andrea Baldassarri

We present a numerical study of the non-equilibrium dynamics of the Sherrington-Kirkpatrick model. We analize the overlap distribution between the configurations visited at the time t and in particular its scaling behaviour with the size of the system. We find two different non-equilibrium dynamical regimes. The first is a proper Out of Equilibrium Regime, t

A. Kitazawa

Duality transformation, which relates a high-temperature phase to a low-temperature one, is used exactly to determine the critical point for several models (2D Ising, Potts, Ashkin-Teller, 8-vertex), as the self dual condition. By changing boundary condition, numerically we can determine the self-dual(critical) point of the Ashkin-Teller(or Gaussian) model.

Richard Berkovits

A comparison between an analytical calculation of the polarizability of a mesoscopic interacting system in the random phase approximation and numerical exact diagonalization results is presented. While for weak interactions the analytical calculation fits the numerical results rather well, deviations appear for stronger interactions. This is the result of th

Hamish Cunningham, Yorick Wilks, Robert J. Gaizauskas

The increasing use of `new methods' in NLP, which the NeMLaP conference series exemplifies, occurs in the context of a wider shift in the nature and concerns of the discipline. This paper begins with a short review of this context and significant trends in the field. The review motivates and leads to a set of requirements for support software of general

Stephen S. Eikenberry, Giovanni G. Fazio

We analyze the pulse shape of the Crab Nebula pulsar in the near-infrared, optical, ultraviolet, X-ray, and gamma-ray bands, including previously unpublished ROSAT HRI observations. We show that, in addition to the previously known trend for the fluences of the Bridge and Peak 2 to increase with energy relative to the fluence of Peak 1, there is a small but

Yu. I. Izotov, V. A. Lipovetsky, F. Chaffee, C. Foltz

The results of Multiple Mirror Telescope spectrophotometry of the extremely low-metallicity blue compact galaxy (BCG) SBS 0335-052 are presented. The oxygen abundance in central brightest part of the galaxy is found to be 12 + log(O/H) = 7.33+-0.01. The N/O, Ne/O, S/O and Ar/O abundance ratios are close to those derived in other BCGs, suggesting that heavy e

Luis C. Ho, Alexei V. Filippenko, Wallace L. W. Sargent

We describe a new sample of Seyfert nuclei discovered during the course of an optical spectroscopic survey of nearby galaxies. The majority of the objects, many recognized for the first time, have luminosities much lower than those of classical Seyferts and populate the faint end of the AGN luminosity function. A significant fraction of the nuclei emit broad

Thomas Liebscher, Rainer Kayser, Phillip Helbig

We reanalyse the spectra used by D.-E. Liebscher (no relation) et al with the same goal -- determining the cosmological parameters -- and basically the same assumptions but with a different statistical method, which does not rely on binning the data. Also, we correct for selection effects. We basically confirm their result, with somewhat larger but still ver

Lin Yan, J. G. Cohen

We carried out a radial velocity survey for spectroscopic binaries in the low density globular cluster NGC5053. Our sample contains a total of 77 cluster member giant and subgiant stars with visual magnitudes of 14.5-18.6. Of these 77 stars, 66 stars have on average of 3-4 measurements with a total of 236 velocities. A typical velocity error per measurement

Mark Hindmarsh, Mairi Sakellariadou, Graham R. Vincent

Cosmic strings provide a radically different paradigm for the formation of structure to the prevailing inflationary one. They afford some extra technical complications: for example, the calculation of the power spectrum of matter and radiation perturbations requires the knowledge of the history of the evolution of the defects in the form of two-time correlat

T. J. Ponman, P. D. Bourner, H. Ebeling, H. Bohringer

We report the results of an almost complete survey of the X-ray properties of Hickson's compact galaxy groups with the ROSAT PSPC. Diffuse X-ray emission is detected from 22 groups. We infer that hot intragroup gas is present in $\gtsimm 75\%$ of these systems and derive their X-ray luminosity function. Earlier reports that only spiral-poor systems exhib

A. Naim, O. Lahav

Following the recent surge of interest in peculiar galaxies at high redshifts we consider the definition, or lack thereof, of morphological peculiarities on a sample of local universe galaxies. Studying the morphology of local universe galaxies is also of interest in trying to understand galaxy dynamics and quantifying the relations between morphology and en

M. Berger, M. van der Klis, J. van Paradijs, W. H. G. Lewin

We present results of RXTE observations of the low-mass X-ray binary and atoll source 4U 1608$-$52 made over 9 days during the decline of an X-ray intensity outburst in March 1996. A fast-timing analysis shows a strong and narrow quasi periodic oscillation (QPO) peak at frequencies between 850 and 890 Hz on March 3 and 6, and a broad peak around 690 Hz on Ma

Lawrence M. Krauss

In a recent striking discovery, Dunlop {\bf \it et al} observed a galaxy at redshift z=1.55 with an estimated age of 3.5 Gyr. This is incompatible with age estimates for a flat matter dominated universe unless the Hubble constant is less than $ 45 kms^{-1}Mpc^{-1}$. While both an open universe, and a universe with a cosmological constant alleviate this probl

R. Pandharipande

Let H(d) be the (open) Hilbert scheme of rational normal curves of degree d in P^d. A presentation of the integral Chow ring of H(d) is given via equivariant Chow ring computations. Included also in the paper are algebraic computations of the integral equivariant Chow rings of the algebraic groups O(n), SO(2k+1). The results for S0(3)=PGL(2) are needed for t

R. Pandharipande

The integral equivariant Chow ring of S0(4) is computed via the geometry of ruled quadric surfaces in P^3.

Pedro Luis del Angel, Stefan Müller-Stach

We construct projectors in the ring of correspondences of a complex uniruled 3-fold $X$ which lift the Kuenneth components of the diagonal in singular cohomology and have other properties which were conjectured by J. Murre. Such Murre decompositions have been already obtained for curves, surfaces, abelian varieties and varieties with cell decompositions by t

Sean Scully, Michel Cassé, Keith A. Olive, Elisabeth Vangioni-Flam

The predictions of the abundances of D and \he3 from Big Bang Nucleosynthesis (BBN) and recent observations of these two isotopes suggest the need to develop new chemical evolution models. In particular, we examine the role of an early episode of massive star formation that would induce a strong destruction of D and a galactic wind. We discuss the ability of

Gene F. Mazenko, Robert A. Wickham

The theory of phase ordering kinetics for the O(2) model using the gaussian auxiliary field approach is reexamined from two points of view. The effects of fluctuations about the ordering field are included and we organize the theory such that the auxiliary field correlation function is analytic in the short-scaled distance (x) expansion. These two points are

J. M. Aroca, H. Fort, R. Gambini

The worldsheet formulation is introduced for lattice gauge theories with dynamical fermions. The partition function of lattice compact QED with staggered fermions is expressed as a sum over surfaces with border on self-avoiding fermionic paths. The surfaces correspond to the world sheets of loop-like pure electric flux excitations and meson-like configuratio

A. Ali, D. London

We review and update the constraints on the parameters of the quark flavour mixing matrix $V_{CKM}$ in the standard model and estimate the resulting CP asymmetries in $B$ decays, taking into account recent experimental and theoretical developments. With the updated CKM matrix we present the currently-allowed range of the ratios $|V_{td}/V_{ts}|$ and $|V_{td}

G. E. Arutyunov, S. A. Frolov, P. B. Medvedev

It is shown that the elliptic Ruijsenaars-Schneider model can be obtained from the affine Heisenberg Double by means of the Poisson reduction procedure. The dynamical $r$-matrix naturally appears in the construction.

B. Allés, G. Boyd, M. D'Elia, A. Di Giacomo

We investigate the performance of the hybrid Monte Carlo algorithm, the standard algorithm used for lattice QCD simulations involving fermions, in updating non-trivial global topological structures. We find that the hybrid Monte Carlo algorithm has serious problems decorrelating the global topological charge at the values of $β$ and $m$ currently simulated,

P. Taxil, J. -M. Virey

The production of high-transverse energy jets in hadron-hadroncollisions is sensitive to the presence of new contact interactions between quarks. If proton polarization were available, the measurement of some parity violating spin asymmetries in one-jet production at large transverse energy would complement the usual search for deviations from the expected Q

K. Shizuya

The current distribution is studied for a finite-width two-dimensional system of Hall electrons, with a clear distinction drawn between the equilibrium edge current and the Hall current. It is pointed out that both the distribution and direction of the equilibrium edge current change dramatically as the number of electron edge states increases, and that this

Prakash Mathews, V. Ravindran, Sridhar K

Deep Inelastic scattering experiments using transversely polarised targets yield information on the structure function $g_2$. By means of a free-field analysis, we study the operator structure of $g_2$ and demonstrate the need for retaining the twist three mass terms in order to maintain current-conservation. We show that the structure function $g_T=g_1+g_2$

J. K. Jain, R. K. Kamilla

We construct a new representation of composite fermion wave functions in the lowest Landau level which enables Monte Carlo computations at arbitrary filling factors for a fairly large number of composite fermions, thus clearing the way toward a more detailed quantitative investigation of the fractional quantum Hall effect. As an illustrative application, the

H. Kurki-Suonio, M. Laine

We study numerically the real-time history of the cosmological electroweak phase transition, as it may take place in the Standard Model or in MSSM for m_H < m_W according to recent lattice results. We follow the nucleated bubbles from the initial stages of acceleration and rapid growth, through collisions with compression waves resulting in slowing down and

Leung Chim

From the equivalence of the bosonic and fermionic representations of finitized characters in conformal field theory, one can extract mathematical objects known as Bailey pairs. Recently Berkovich, McCoy and Schilling have constructed a `generalized&#39; character formula depending on two parameters $\ra$ and $\r2$, using the Bailey pairs of the unitary model

John R. Klauder

Based on the results of a recent reexamination of the quantization of systems with first-class and second-class constraints from the point of view of coherent-state phase-space path integration, we give additional examples of the quantization procedure for reparameterization invariant Hamiltonians, for systems for which the original set of Lagrange multiplie

John R. Klauder

We outline the principal results of a recent examination of the quantization of systems with first- and second-class constraints from the point of view of coherent-state phase-space path integration. Two examples serve to illustrate the procedures.

Jean Cleymans, Azwinndini Muronga

We investigate the dependence of hadronic ratios on the number of projectile participants using a thermal model incorporating exact baryon number and strangeness conservation. A comparison is made with results from $Au-Au$ collisions obtained at the BNL-AGS.

Th. Rubehn, K. X. Jing, L. G. Moretto, L. Phair

Fission excitation functions of He-3 and He-4 induced compound nuclei are shown to scale exactly according to the Bohr-Wheeler transition state prediction once the shell effects are accounted for. The presented method furthermore allows one to model-independently extract values for the shell effects which are in good agreement to those obtained from liquid-d

Marcelo R. Ubriaco

We consider the simplest $SU_{q}(2)$ invariant fermionic hamiltonian and calculate the low and high temperature behavior for the two distinct cases $q>1$ and $q<1$. For low temperatures we find that entropy values for the Fermi case are an upper bound for those corresponding to $q\neq 1$. At high temperatures we find that the sign of the second virial coeffi

P. Binetruy, E. A. Dudas

We study gaugino condensation in presence of an anomalous $U(1)$ gauge group and find that global supersymmetry is dynamically broken. An example of particular interest is provided by effective string models with 4-dimensional Green-Schwarz anomaly cancellation mechanism. The structure of the hidden sector is constrained by the anomaly cancellation condition

Paolo Pasti, Dmitrij Sorokin, Mario Tonin

We demonstrate that an action proposed by A. Khoudeir and N. R. Pantoja in {\sl Phys. Rev.} {\bf D53}, 5974 (1996) for endowing Maxwell theory with manifest electric--magnetic duality symmetry contains, besides the Maxwell field, additional propagating vector degrees of freedom. Hence it cannot be considered as a duality symmetric action for a {\it single} a

Sergei Gukov, Igor Polyubin

The low energy effective actions of the $N=2$ SUSY $SU(N_c)$ QCD are considered at the symmetric point on the moduli space. The classes of such theories have similar spectral curves. This fact allows us to show that all these models have the same structure of the coupling matrix and to show that the $N_f=2N_c$ spectral curve can not be presented as a double

J. R. Morris, D. Bazeia

A simple model is presented where the disappearance of domain walls and the associated production of ``Fermi balls&#39;&#39;, which have been proposed as candidates for cold dark matter, are features which arise rather naturally in response to softly broken supersymmetry.

L. L. Frankfurt, E. Piasetzky, M. M. Sargsian, M. I. Strikman

The deuteron disintegration at high energies and large angles in the $d(p,2p)n$ reaction, is calculated in kinematical conditions where the dominant contributions are due to soft rescatterings of the initial and final nucleons, which accompany the hard $pp$ reaction. The eikonal approximation, which accounts for relativistic kinematics as dictated by Feynman

G. Marchesini, B. R. Webber, G. Abbiendi, I. G. Knowles

HERWIG (Hadron Emission Reactions With Interfering Gluons) is a multipurpose Monte Carlo event generator for the simulation of hard collisions between hadrons, leptons and photons. This note describes the new features of version 5.9. These include adding over 100 new particles, 1800 new decay modes and supporting new decay types. A complete space-time pictur

C. W. Kim

In this lecture we review some of the basic properties of neutrinos, in particular their mass and the oscillation behavior. First we discuss how to describe the neutrino mass. Then, under the assumption that neutrinos are massive and mixed, the fundamentals of the neutrino oscillations are discussed with emphasis on subtle aspects which have been overlooked

Yuan-Ben Dai, Chao-Shang Huang, Han-Wen Huang

The inclusive rate and forward-backward asymmetry of dilepton angular distribution for a B-meson to decay to strange hadronic final states and a $τ^+τ^-$ pair in a two Higgs doublet model are computed. In particular, contributions of neutral Higgs bosons to the decay are included. QCD corrections to the effective Hamiltonian for $B\rightarrow X_sτ^+τ^-$ are

C. S. Kim, Jae Kwan Kim, Yeong Gyun Kim, Kang Young Lee

We investigate the form factors for exclusive semileptonic decays of $B$-meson to $D,~D^*$, based on the parton picture and helped by the results of the HQET. We obtain the numerical results for the slope of the Isgur-Wise function, which is consistent with the experimental results, and we extracte the dependences of hadronic form factors on $q^2$ by varying

S. Yu. Khlebnikov, M. E. Shaposhnikov

We discuss the computation of the grand canonical partition sum describing hot matter in systems with the Higgs mechanism in the presence of non-zero conserved global charges. We formulate a set of simple rules for that computation in the high-temperature approximation in the limit of small chemical potentials. As an illustration of the use of these rules, w

Robert Eckardt, J&#34;org Hansper, Manfred F. Gari

We review the consequences of the sensitivity of the relation between the moments of a model for the nucleon quark distribution amplitude and the coefficients of its polynomial expansion. Criteria for a simpler approach to constructing a model for the quark distribution amplitude are formulated. We describe how such a simpler (or &#34;haplousterotic&#34;) mo

Hermann Dilger, Jochen Heitger

We study the continuum limit of the $2D$ U(1)--Higgs model with variable scalar field length, which is qualitatively different from the fixed length case. Our simulations concentrate on the scaling behaviour of the topological susceptibility, and an instanton-induced confinement mechanism of fractional charges is numerically confirmed.

Daniel J. Loranz, William A. Hiscock

The stress-energy tensor of a quantized scalar field is computed in the reduced two-dimensional charged dilatonic black hole spacetime of Garfinkle, Horowitz, and Strominger. In order for the stress-energy of quantized fields to be regular on the event horizon in both the extreme string metric and the conformally associated physical metric, it is necessary t

François Goy

Clock synchronisation is conventional when inertial systems are involved. This statement is no longer true in accelerated systems. A demonstration is given in the case of a rotating platform. We conclude that theories based on the Einstein&#39;s clock synchronisation procedure are unable to explain, for example, the Sagnac effect on the platform. Implication

A. R. Prasanna

We define a new parameter `cumulative drag index&#39; for a particle in circular orbit in a stationary, axisymmetric gravitational field and study its behaviour in the two well known solutions of general relativity {\it viz.}, the Kerr spacetime and the Gödel spacetime, wherein the inertial frame dragging has an important role. As it shows similar behaviour

A. M. Tikofsky

We describe paired quantum Hall states at filling fractions $ν$, where $ν^{-1}$ is an integer, and present explicit wavefunctions for these states. Experiments are proposed to distinguish between paired states of singlet and triplet symmetry. It is argued from existing experimental data that the $ν=1/2$ state observed in double layer quantum wells is a singl

G. T. Barkema, Normand Mousseau

A computational approach is presented to obtain energy-minimized structures in glassy materials. This approach, the activation-relaxation technique (ART), achieves its efficiency by focusing on significant changes in the microscopic structure (events). The application of ART is illustrated with two examples: the structure of amorphous silicon, and the struct

Harold U. Baranger, Pier A. Mello

We show that reflection symmetry has a strong influence on quantum transport properties. Using a random S-matrix theory approach, we derive the weak-localization correction, the magnitude of the conductance fluctuations, and the distribution of the conductance for three classes of reflection symmetry relevant for experimental ballistic microstructures. The S

N. M. Salem, R. J. Gooding

We determine where a given concentration of ferromagnetic (FM) bonds doped into a square lattice antiferromagnet must go to minimize the system&#39;s total magnetic energy. We find (i) an infinite degeneracy of ground--state arrangements of FM bonds that correspond to completely unfrustrated configurations for classical spins, and (ii) this degeneracy is lif

D-H Lee, Y. Krotov, J. Gan, S. A. Kivelson

We show that in the limit of vanishing bare electron effective mass, and in the presence of particle-hole symmetric disorder (which can be of vanishing strength), the composite fermion Hall conductance is constrained to be $-{1\over 2}\frac{e^2}{h}$. We discuss the implications of this results for the existence and nature of a composite Fermi liquid in the l

Roberto Iengo, Giancarlo Jug

We present a theory for the decay of a supercurrent through nucleation of vortex-antivortex pairs in a two-dimensional superconductor in the presence of dissipation and of a periodic pinning potential. Through a powerful quantum electrodynamics formulation of the problem we show that the nucleation rate develops oscillations in its current-density dependence

D. H. E. Gross, A. Ecker, X. Z. Zhang

Phase transitions of first and second order can easily be distinguished in small systems in the microcanonical ensemble. Configurations of phase coexistence, which are suppressed in the canonical formulation, carry important information about the main characteristics of first order phase transitions like the transition temperature, the latent heat, and the i

Yuval Oreg, Alexander M. Finkel&#39;stein

The influence of electron--electron interaction on two terminal DC conductance of one--dimensional quantum wires is studied. A cancelation between the effect of the electron--electron interaction on the current and on the external electric field is the reason for the universal value, $e^2/2π\hbar $ per mode, of the DC conductance of a clean wire. The effect

Neil Turok

How unique are the inflationary predictions for the cosmic microwave anisotropy pattern? In this paper, it is asked whether an arbitrary causal source for perturbations in the standard hot big bang could effectively mimic the predictions of the simplest inflationary models. A surprisingly simple example of a `scaling&#39; causal source is found to closely re

S. S. Eikenberry, G. G. Fazio, S. M. Ransom, J. Middleditch

We present evidence of wavelength-dependent variations within the infrared, optical, and ultraviolet pulse profile peaks of the Crab Nebula pulsar. The leading and trailing edge half-width half-maxima of the peaks display clear differences in their wavelength dependences. In addition, phase-resolved infrared-to-ultraviolet color spectra show significant vari

S. S. Eikenberry, G. G. Fazio, S. M. Ransom

We describe the design, operation, and performance of a new high-speed infrared photometer using the Solid-State Photomultiplier (SSPM) detector. The SSPM was developed by Rockwell International Science Center and has single-photon counting capability over the 0.4-28 micron wavelength range, intrinsic time response of order 1 ns, and low detector noise (Petr

A. G. Gubanov, H. Andernach

Radio measurements of rich Abell clusters of galaxies have been collected both from radio source catalogues and dedicated publications. By gathering these data for every cluster, complemented by optical data, an overall picture of each cluster may be obtained and samples may be drawn suitable for statistical studies.

H. Andernach, S. A. Trushkin, A. G. Gubanov, O. V. Verkhodanov

We have collected the largest existing set of radio source lists in machine-readable form: 320 tables with 1.75 million records. Only a minor fraction of these is accessible via public databases. We describe our plans to make this huge amount of heterogeneous data accessible in a homogeneous way via the World Wide Web, with reliable cross-identifications, an

Yasushi Suto, Takahiko Matsubara

We discuss the two potentially important effects which should be taken into account in the analysis of the cosmological redshift-space distortion especially at high redshifts; the effect of inhomogeneities in the light propagation and the evolution of bias. Although such inhomogeneities affect significantly the degree of the cosmological redshift distortion,

Flavio Angelini

We give a condition for certain divisors on the blow up of P^3 at points in general position to be ample. The result extends a theorem of G. Xu on the blow up of the projective plane.

F. Catanese, M. Franciosi, K. Hulek, M. Reid

We prove a general embedding theorem for Cohen--Macaulay curves (possibly nonreduced), and deduce a cheap proof of the standard results on pluricanonical embeddings of surfaces, assuming vanishing H^1(2K_X)=0.

Patrick Dorey, Roberto Tateo

We suggest an approach to the problem of finding integral equations for the excited states of an integrable model, starting from the Thermodynamic Bethe Ansatz equations for its ground state. The idea relies on analytic continuation through complex values of the coupling constant, and an analysis of the monodromies that the equations and their solutions unde

Gia Dvali, Alex Pomarol

We point out that an anomalous gauge U(1) symmetry is a natural candidate for being the mediator and messenger of supersymmetry breaking. It facilitates dynamical supersymmetry breaking even in the flat limit. Soft masses are induced by both gravity and the U(1) gauge interactions giving an unusual mass hierarchy in the sparticle spectrum which suppresses fl

Wolfgang Eholzer, Nils-Peter Skoruppa

We describe several infinite series of rational conformal field theories whose conformal characters are modular units, i.e. which are modular functions having no zeros or poles in the upper complex half plane, and which thus possess simple product expansions. We conjecture that certain infinite series of rational models of Casimir W-algebras always have this

Alex Kumjian

The author provides some definitions and structural results about Fell bundles, defined as C^*-algebra bundles over topological groupoids. Such bundles are a mutual generalization of semi-direct products of groups with C^*-algebras and C^*-algebra bundles over topological spaces. In particular a Morita equivalence theorem with semi-direct products is establi

Sergey Solodukhin

We discuss the statistical-mechanical entropy of black hole calculated according to &#39;t Hooft. It is argued that in presence of horizon the statistical mechanics of quantum fields depends on their UV behavior. The ``brick wall&#39;&#39; model was shown to provide a correct description when the ``brick wall&#39;&#39; parameter is less than any UV cut-off.

V. Ravindran

The $Q^2$ evolution of polarised parton fragmentation functions is discussed using Altarelli-Parisi evolution equations. The first moments of both polarised quark and gluon fragmentation functions are shown to behave in a similar fashion at very high energies. This analysis is applicable to any hard processes involving production of polarised hadrons. The po

I. Royzen

A simple relativistic model is suggested that elucidates the qualitative difference in valence quark distributions of bosons in ground and virtual states. The inelastic diffraction of highly virtual photon in DIS is discussed.

She-Sheng Xue

We analyze the dynamics of an $SU_L(2)\otimes U_R(1)$ chiral theory on the lattice with a strong multifermion coupling. It is shown that no spontaneous symmetry breaking occurs; the ``spectator&#39;&#39; fermion $ψ_R$ is a free mode; doublers are decoupled as massive Dirac fermions consistently with the chiral symmetries. In 1+1 dimension, we show that the r

P. C. Aichelburg, H. Balasin

We generalize previous \cite{AiBa2} work on the classification of ($C^\infty$) symmetries of plane-fronted waves with an impulsive profile. Due to the specific form of the profile it is possible to extend the group of normal-form-preserving diffeomorphisms to include non-smooth transformations. This extension entails a richer structure of the symmetry algebr

Hugo A. Morales-Tecotl, Luis F. Urrutia, J. David Vergara

We show that the reality conditions to be imposed on Ashtekar variables to recover real gravity can be implemented as second class constraints a la Dirac. Thus, counting gravitational degrees of freedom follows accordingly. Some constraints of the real theory turn out to be non-polynomial, regardless of the form, polynomial or non-polynomial, taken for the r

Don H. Kim, Derek K. K. Lee, Patrick A. Lee

A simple model of a degenerate two-dimensional Bose liquid interacting with a fluctuating gauge field is investigated as a possible candidate to describe the charge degree of freedom in the normal state of the cuprate superconductors. We show that the fluctuating gauge field destroys superfluidity even in the Bose degenerate regime. We discuss the nature of

Yuval Oreg, Yuval Gefen

The scattering phase shift of an electron transferred through a quantum dot is studied within a model Hamiltonian, accounting for both the electron--electron interaction in the dot and a finite temperature. It is shown that, unlike in an independent electron picture, this phase may exhibit a phase lapse of $ π$ {\em between } consecutive resonances under gen