September 1998 arXiv papers — page 10

Lu-Ming Duan, Guang-Can Guo

A general theory of quantum error avoiding codes is established, and new light is shed on the relation between quantum error avoiding and correcting codes. Quantum error avoiding codes are found to be a special type of highly degenerate quantum error correcting codes. A combination of the ideas of correcting and avoiding quantum errors may yield better codes

M. Ardehali

A correlation inequality is derived from local realism and a supplementary assumption. This inequality is violated by a factor of 1.5 in the case of real experiments, whereas previous inequalities such as Clauser-Horne-Shimony-Holt inequality of 1969 and Clauser-Horne inequality of 1974 are violated by a factor of $\sqrt 2$. Thus the magnitude of violation o

M. Rakhmanov, M. Evans, H. Yamamoto

We propose a method for in-situ measurement of the length of kilometer size Fabry-Perot cavities in laser gravitational wave detectors. The method is based on the vernier, which occurs naturally when the laser incident on the cavity has a sideband. By changing the length of the cavity over several wavelengths we obtain a set of carrier resonances alternating

Boris A. Malomed

A general method to find an effective potential of interaction between far separated 2D and 3D solitons is elaborated, including the case of 2D vortex solitons. The method is based on explicit calculation of the overlapping term in the full Hamiltonian of the system (_without_ assuming that the ``tail'' of each soliton is not affected by its interact

Takehisa Fujita, Kaori Ito, Toshio Suzuki

A new result of investigations of the hyperfine structure (hfs) anomaly in Be isotopes is presented. The hfs constant for $^{11}$Be is obtained by using the core plus neutron type wave function: $ |2s_{1\over 2}>+|1d_{5\over2}\times 2^+ ; {1/2}^{+}> $. A large hfs anomaly of $^{11}$Be is found, which is mainly due to a large radius of the halo single particl

R. P. Martínez-y-Romero, A. L. Salas-Brito, Jaime Saldaña-Vega

A novel realization of the classical SU(2) algebra is introduced for the Dirac relativistic hydrogen atom defining a set of operators that, besides, allow the factorization of the problem. An extra phase is needed as a new variable in order to define the algebra. We take advantage of the operators to solve the Dirac equation using algebraic methods. To acomp

R. E. Borcherds

This is an informal write up of my talk in Berlin. It gives some background to Goddard's talk (math.QA/9808136) about the moonshine conjectures.

Katsunori Kawamura

We obtain a kind of structure theorem for the automorphism group ${\rm Aut}{\cal A}$ of a unital C$^{*}$-algebra ${\cal A}$. According to it, ${\rm Aut}{\cal A}$ can be regarded as a subgroup of the semi-direct product of direct product group consisting of some family of projective unitary groups and some permutation group on the spectrum of ${\cal A}$.

Jennifer Taback

We prove that PSL(2,Z[1/p]) gives the first example of groups which are not quasi-isometric to each other but have the same quasi-isometry group. Namely, PSL(2,Z[1/p]) and PSL(2,Z[1/q]) are not quasi-isometric unless p=q, and, independent of p, the quasi-isometry group of PSL(2,Z[1/p]) is PSL(2,Q). In addition, we characterize PSL(2,Z[1/p]) uniquely among al

Taro Kashiwa

The auxiliary field method, defined through introducing an auxiliary (also called as the Hubbard-Stratonovich or the Mean-) field and utilizing a loop-expansion, gives an excellent result for a wide range of a coupling constant. The analysis is made for Anharmonic-Oscillator and Double-Well examples in 0-(a simple integral) and 1-(quantum mechanics)dimension

D. L. Khokhlov

The weak interactions are described within the framework of electrodynamics. The massive vector field is considered as photon with the effective mass defined in the second order of the perturbation theory. Muon and tau-lepton are considered to be composite particles having the structure electron-positron-electron. The mass of muon is defined by the section o

P. Csizmadia, P. Levai, S. E. Vance T. S. Biro, M. Gyulassy

Hyperon and antihyperon production is investigated using two microscopical models: {\bf (1)} the fast hadronization of quark matter as given by the ALCOR model; {\bf (2)} string formation and fragmentation as in the HIJING/B model. We calculate the particle numbers and momentum distributions for Pb+Pb collisions at CERN SPS energies in order to compare the t

Xiang-Song Chen, Fan Wang

We prove that the {\em gauge dependent} gluon spin, gluon and quark orbital angular momenta operators have {\em gauge invariant} expectation values on hadron states with {\em definite} momentum and polarization, therefore the conventional decomposition of nucleon spin into contributions from the spin and orbital angular momentum of quark and gluon is {\em ga

G. Burgio, F. Di Renzo, C. Parrinello, C. Pittori

We investigate the occurrence of power terms $(Lambda^2/p^2$ in the running QCD coupling by analysing non-perturbative measurements of $α_s(p)$ at quite low momenta obtained from the lattice three-gluon vertex. Our study provides some evidence for such a contribution. The phenomenological implications of such a presence are reviewed.

Rainer Mankel, Alexander Spiridonov

The Concurrent Track Evolution method, which was introduced in a previous paper (DESY 97-054), has been further explored by applying it to the propagation of track candidates into an inhomogeneous magnetic field volume equipped with tracking detectors, as is typical for forward B spectrometers like HERA-B or LHCb. Compared to the field-free case, the method

Matthias H. Hettler, P. J. Hirschfeld

Nonmagnetic impurities in d-wave superconductors cause strong local suppressions of the order parameter. We investigate the observable effects of the scatterigng off such suppressions in bulk samples by treating the order parameter "hole" as a pointlike off-diagonal scatterer treated within a self-consistent t-matrix approximation. Strong scattering

G. A. Ummarino, R. S. Gonnelli

In this work we calculate the direct solution of the equations for the retarded electron-boson interaction in the case of d-wave symmetry for the pair wave function and in the real axis formulation. We use a spectral function containing an isotropic part and an anisotropic one: alpha^2(Omega,phi,phi')F(Omega)=[alpha^2]_s*F(Omega)+[alpha^2]_d*F(Omega)*cos

Kazusumi Ino

We study the persistent edge current in the fractional quantum Hall effect. We give the grand partition functions for edge excitations of hierarchical states coupled to an Aharanov-Bohm flux and derive the exact formula of the persistent edge current. For $m$-th hierarchical states with $m>1$, it exhibits anomalous oscillations in its flux dependence at low

T. N. LaRosa, Steven N. Shore, Loris Magnani

We present the results of a velocity correlation study of the high latitude cloud MBM16 using a fully sampled $^{12}$CO map, supplemented by new $^{13}$CO data. We find a correlation length of 0.4 pc. This is similar in size to the formaldehyde clumps described in our previous study. We associate this correlated motion with coherent structures within the tur

A. Fassia, W. P. S. Meikle

We use early-time observations of He I 10830 Åto measure the extent of upward mixing of radioactive material in SN 1987A. This work develops and extends the work of Graham (1988), and places constraints on actual explosion models. The presence of the He I 10830 Å(2s^{3}S--2p^{3}P) line at $\geq 10$ days post-explosion implies re-ionisation by $γ$-rays from u

D. L. Khokhlov

The model of the homogenous and isotropic universe is considered in which the coordinate system of reference is not defined by the matter but is a priori specified. The scale factor of the universe changes following the linear law. The scale of mass changes proportional to the scale factor of the universe. The model under consideration avoids the flatness an

R. D. Hoffman, S. E. Woosley, T. A. Weaver, T. Rauscher

We explore the sensitivity of the nucleosynthesis of intermediate mass elements (28 < A < 80) in supernovae derived from massive stars to the nuclear reaction rates employed in the model. Two standard sources of reaction rate data (Woosley et al. 1978; and Thielemann et al. 1987) are employed in pairs of calculations that are otherwise identical. Both includ

M. B. Hastings

The large N sigma model, in D<4 space-time dimensions, with disorder a function of d space dimensions, is analyzed via a renormalization group treatment. Critical exponents for average quantities are calculated, first to lowest order and then to all orders, in $ε=D-2 - d/2$. In particular, it is found that $νd =2$. When D=d+1, this model is equivalent to a l

Gustav W. Delius

We give a new integrable boundary condition in affine Toda theory which is soliton-preserving in the sense that a soliton hitting the boundary is reflected as a soliton. All previously known integrable boundary conditions forced a soliton to be converted into an antisoliton upon reflection. We prove integrability of our boundary condition using a generalizat

Sharmanthie Fernando, Freydoon Mansouri

We construct super AdS black holes in 2+1 dimensions in terms of Chern Simons gauge theory of N=(1,1) super AdS group coupled to a (super)source. We take the source to be a super AdS state specified by its Casimir invariants. We show that the corresponding space-time is a supermultiplet of AdS space-times related to each other by supersymmetry transformation

Alessio Filippetti, Warren E. Pickett

Ab-initio results for structural and electronic properties of NaCl-type FeN are presented in a framework of plane-wave and ultrasoft pseudopotentials. Competition among different magnetic ordering is examined. We find the ferromagnetic phase stable overall. Stabilization over the unpolarized phase is obtained by splitting one flat t_2g-type band crossing the

Ph. de Forcrand

The short-range modes of the fermionic determinant can be absorbed in the gauge action using the loop expansion. The coefficients of this expansion and the zeroes of the polynomial approximating the remainder can be optimized by a simple, practical method. When the multiboson approach is used, this optimization results in a faster simulation with fewer auxil

D. Novikov, Hume A. Feldman, Sergei F. Shandarin

We suggest novel statistics for the CMB maps that are sensitive to non-Gaussian features. These statistics are natural generalizations of the geometrical and topological methods that have been already used in cosmology such as the cumulative distribution function and genus. We compute the distribution functions of the Partial Minkowski Functionals for the ex

John Cantwell, Lawrence Conlon

David Gabai showed that disk decomposable knot and link complements carry taut foliations of depth one. In an arbitrary sutured 3-manifold M, such foliations F, if they exist at all, are determined up to isotopy by an associated ray [F] issuing from the origin in H^1(M;R) and meeting points of the integer lattice H^1(M;Z). Here we show that there is a finite

Laurent Lellouch, C. -J. David Lin, UKQCD Collaboration

We present preliminary results for B_K, B_7^{3/2} and B_8^{3/2} from two high-statistics lattice computations. These calculations are performed at beta=6.0 and 6.2 in the quenched approximation, using mean-field-improved Sheikholeslami-Wohlert fermionic actions.

Y. Ishikawa, H. Fukuyama

The effect of a magnetic field on Josephson current has been studied for a superconductor/normal-metal/superconductor (SNS) system, where N is a two-dimensional electron gas in a confining potential. It is found that the dependence of Josephson currents on the magnetic field are sensitive to the width of the normal metal. If the normal metal is wide and cont

D. Yu. Ivanov, A. Schiller, V. G. Serbo

We consider the Coulomb correction (CC) to the $e^+e^-$ pair production related to multiphoton exchange of the produced $e^{\pm}$ with nuclei. The contribution of CC to the energy distribution of $e^+$ and $e^-$ as well as to the total pair production cross section are calculated with an accuracy of the order of 1%. The found correction to the total Born cro

A. Gabrielli, F. Sylos Labini, S. Pellegrini

We study the (newtonian) gravitational force distribution arising from a fractal set of sources. We show that, in the case of real structures in finite samples, an important role is played by morphological properties and finite size effects. For dimensions smaller than d-1 (being $d$ the space dimension) the convergence of the net gravitational force is assu

A. Hombach, W. Cassing, U. Mosel

We study the mixing and the kinetic equilibration of projectile and target nucleons in relativistic heavy-ion collisions in the energy regime between 150~AMeV and 2~AGeV in a coupled-channel BUU (CBUU) approach. We find that equilibrium in the projectile-target degrees of freedom is in general not reached even for large systems at low energy where elastic nu

Y. G. Joh, R. Orbach, G. G. Wood, J. Hammann

The peak of the spin glass relaxation rate, S(t)=d{-M_{TRM}(t,t_w)}/H/{d ln t}, is directly related to the typical value of the free energy barrier which can be explored over experimental time scales. A change in magnetic field H generates an energy E_z={N_s}{X_fc}{H^2} by which the barrier heights are reduced, where X_{fc} is the field cooled susceptibility

Ziv Ran

Nagata has conjectured that the following statement (N_r) holds for all $r\geq 10$: (N_r) if $P_1,...P_r \in {\mathbb P}^2$ are generic points then any plane curve $C$ satisfies $\sum_1^r mult_{P_i}(C)\leq \sqrt{r} deg(C)$. Nagata proved (N_r) whenever $r$ is a perfect square. Here we prove (N_r) provided $r=k^2+α,1\leqα\leq2k,k\geq 3$ and either (i) $α$ is

Robert R. Tucci

In a previous paper, we described a computer program called Qubiter which can decompose an arbitrary unitary matrix into elementary operations of the type used in quantum computation. In this paper, we describe a method of reducing the number of elementary operations in such decompositions.

Th. Gallay, G. Raugel

We consider the damped hyperbolic equation in one space dimension $εu_{tt} + u_t = u_{xx} + F(u)$, where $ε$ is a positive, not necessarily small parameter. We assume that $F(0)=F(1)=0$ and that $F$ is concave on the interval $[0,1]$. Under these assumptions, our equation has a continuous family of monotone propagating fronts (or travelling waves) indexed by

I. Vidaña, A. Polls, A. Ramos, M. Hjorth-Jensen

s- and p-wave $Λ$ single-particle enrgies are obtained for a variety of $Λ$ hypernuclei from the relevant self-energy constructed within the framework of a perturbative many-body approach. Results are presented for present realistic hyperon-nucleon interactions such as Jülich B and Nijmegen SC models. Effects of the non-locality and energy-dependence of the

C. Hanhart, K. Nakayama

We clarify under what circumstances the nucleon--nucleon final state interaction fixes the energy dependence of the total cross--section for the reaction $NN \to NNx$ close to production threshold, where $x$ can be any meson whose interaction with the nucleon is not too strong. We strongly criticize the procedure used recently by several authors to include t

Z. -L. Zhou, M. Bouwhuis, M. Ferro-Luzzi, E. Passchier

We report on a first measurement of tensor analyzing powers in quasi-elastic electron-deuteron scattering at an average three-momentum transfer of 1.7 fm$^{-1}$. Data sensitive to the spin-dependent nucleon density in the deuteron were obtained for missing momenta up to 150 MeV/$c$ with a tensor polarized $^2$H target internal to an electron storage ring. Th

V. A. Malyshev

In this paper we study stochastic dynamics which leaves quantum gravity equilibrium distribution invariant. We start theoretical study of this dynamics (earlier it was only used for Monte-Carlo simulation). Main new results concern the existence and properties of local correlation functions in the thermodynamic limit. The study of dynamics constitutes a thir

Ralph Greenberg

We study this subject by first proving that the p-primary subgroup of the classical Selmer group for an elliptic curve with good, ordinary reduction at a prime p has a very simple and elegant description which involves just the Galois module of p-power torsion points. We then prove theorems of Mazur, Schneider, and Perrin-Riou on the basis of this descriptio

A. Silverberg, Yu. G. Zarhin

Suppose $\ell$ is a prime number, ${\mathbf Q}_\ell$ is the field of $\ell$-adic numbers, ${\mathbf F}_\ell$ is the finite field of $\ell$ elements, and $d$ is a positive integer. Suppose $G$ is a finite subgroup of a symplectic group $Sp_{2d}({\mathbf Q}_\ell)$. We prove that $G$ can be embedded in $Sp_{2d}({\mathbf F}_\ell)$ in such a way that the characte

Kirti Joshi, Eugene Z. Xia

Let $X$ be a projective curve of genus 2 over an algebraically closed field of characteristic 2. The Frobenius map on X induces a rational map on the moduli space of rank-2 bundles. We show that up to isomorphism, there is only one (up to tensoring by an order two line bundle) semi-stable vector bundle of rank 2 with determinant equal to a theta characterist

Lawrence Breen

We show that the obstruction to the existence of a strict symmetric monoidal structure on a monoidal stack $\cal C$ is determined by a commutator biextension associated to $\cal C$, and that this biextension is alternating under an additional hypothesis. The analogous construction for monoidal 2-stacks is described, together with the corresponding generaliza

Vladimir O. Soloviev

It is shown that the new formula for the field theory Poisson brackets arise naturally in the extension of the formal variational calculus incorporating divergences. The linear spaces of local functionals, evolutionary vector fields, functional forms, multi-vectors and differential operators become graded with respect to divergences. The bilinear operations,

Lajos Molnar

As a continuation of the work on linear maps between operator algebras which preserve certain subsets of operators with finite rank, or corank, here we consider the problem inbetween, that is, we treat the question of preserving operators with infinite rank and infinite corank. Since, as it turns out, in this generality our preservers cannot be written in a

Vladimir G. Troitsky

We show that the celebrated Lomonosov theorem cannot be improved by increasing the number of commuting operators. Specifically, we prove that if T is the operator on l_1 without a non-trivial closed invariant subspace constructed by C.J.Read, then there are three operators S_1, S_2 and K (non-multiples of the identity) such that T commutes with S_1, S_1 comm

Emili Bagan, Robin Horan, Martin Lavelle, David McMullan

If constituent quarks are to emerge from QCD they must have well defined colour and be energetically favoured. After reviewing the general properties of charges in gauge theories, a method for constructing charges is presented and applied to the infra-red structure of the theory and to the interquark potential. Both of these applications supply a physical in

Alfredo Herrera-Aguilar, Oleg Kechkin

We present extremal stationary solutions that generalize the Israel-Wilson-Perjes class for the d+3-dimensional low-energy limit of heterotic string theory with n >= d+1 U(1) gauge fields compactified on a d-torus. A rotating axisymmetric dyonic solution is obtained using the matrix Ernst potential formulation and expressed in terms of a single d+1 X d+1-mat

Clovis Wotzasek

We study the two-fold dimensional dependence of the electromagnetic duality groups. We introduce the dual projection operation that systematically discloses the presence of an internal space of potentials where the group operation is defined. A two-fold property of the kernel in the projection is shown to define the dimensional dependence of the duality grou

Yi-Yen Wu

We study Maldacena&#39;s conjecture and the AdS/SYM correspondence on the Coulomb branch. Several interesting aspects of this conjectured AdS/SYM correspondence on the Coulomb branch are pointed out and clarified.

J. W. Moffat

The basic features of a quantum field theory which is Poincaré invariant, gauge invariant, finite and unitary to all orders of perturbation theory are reviewed. Quantum gravity is finite and unitary to all orders of perturbation theory. The Bekenstein-Hawking entropy formula for a black hole is investigated in a conical Rindler space approximation to a black

D. Pocanic

This work reviews the available experimental information on the pi-pi scattering lengths, especially the recent near-threshold pi N -> pi pi N data from several laboratories and the related application of the Chew-Low-Goebel (CLG) technique well below 1 GeV/c momentum. At this time uncertainties stemming from non-pion-exchange backgrounds in near-threshold C

E. Predazzi

Hadronic diffraction has become a hot and fashionable subject in recent years due to the great interest triggered by the HERA and Tevatron data. These data have helped to put the field in a different perspective paving the road to a hopefully more complete understanding than hitherto achieved. The forthcoming data in the next few years from even higher energ

Daniel J. H. Chung, Edward W. Kolb, Antonio Riotto

What is commonly called the reheat temperature, $T_{RH}$, is not the maximum temperature obtained after inflation. The maximum temperature is, in fact, much larger than $T_{RH}$. As an application of this we consider the production of massive stable dark-matter particles of mass $M_X$ during reheating, and show that their abundance is suppressed as a power o

Gennaro Corcella, Michael H. Seymour

Parton showers are accurate for soft and/or collinear emission, but for a good description of the whole of phase space they need to be supplemented by matrix element corrections. In this paper, we discuss matrix element corrections to the decay t->Wb and apply our results to the HERWIG Monte Carlo event generator. The phenomenological results show marked imp

G. Burgio, F. Di Renzo, C. Parrinello, C. Pittori

We study deviations from the perturbative asymptotic behaviour in the running QCD coupling by analysing non-perturbative measurements of alpha_s (p) at low momenta as obtained from the lattice three-gluon vertex. Our exploratory study provides some evidence for power corrections to the perturbative running proportional to 1/p^2.

A. Di Giacomo

A number of observables are constructed which can give useful information on instanton ensembles.The basic properties used are : (1) Instantons are SU(2) configurations ,(2)They are self-dual or antiself-dual.

S. M. H. Wong

We show that although there is no infrared divergence in exclusive P-wave quarkonium decays, the colour octet contribution is no less important than in the inclusive decay. Results from more proper calculations with only colour singlet contribution are not sufficient to account for the measured partial decay widths and so the next higher Fock state must be i

Ulf-G. Meißner, Guido Müller, Sven Steininger

The complete renormalization of the generating functional for Green functions of quark currents between one-nucleon states in two flavor heavy baryon chiral perturbation theory is performed to order $q^4$. We show how the heat kernel method has to be extended for operators orthogonal to the heavy fermion four-velocity. A method is developed to treat the mult

G. Quznetsov

The simplest massive Lagrangian, invariant for the global SU(2) transformation, is constructed.

N. N. Nikolaev, A. V. Pronyaev, B. G. Zakharov

We calculate the diffraction slope $B_{D}$ for diffractive DIS. We find a counterintuitive rise of $B_{D}$ from exclusive diffractive excitation of vector mesons to excitation of continuum states with $M^{2} \sim Q^{2}$. For the small-mass continuum we predict a rapid variation of $B_{D}$ with $M^{2}$ on the scale $m_{V}^{2}$ and a sharp drop of $B_{D}$ for

Masashi Wakamatsu, Takanori Kubota

We carry out a systematic investigation of twist-two spin dependent structure functions of the nucleon within the framework of the chiral quark soliton model (CQSM) by paying special attention to the role of chiral symmetry of QCD. The importance of chiral symmetry is illustrated through the good reproduction of the recent SLAC data for the neutron spin stru

Jianwei Qiu, James P. Vary, Xiaofei Zhang

We propose a model for the production and suppression of J/ψmesons in high-energy hadronic collisions. We factorized the process into a production of the $c\bar{c}$ pairs of relative momentum $k=k_c-k_{\bar{c}}$ convoluted with a transition probability from the produced $c\bar{c}$ pairs into the observed J/$ψ$ mesons. As the produced $c\bar{c}$ pairs exit th

A. H. Hoang

We review the theoretical ideas and tools required to arrive at a next-to-next-to-leading order (NNLO) description of the heavy quark-antiquark production cross section in $e^+e^-$ annihilation for the case that the center of mass kinetic energy of the quarks is larger than $Λ_{QCD}$. In this case the NNLO cross section can be calculated with purely perturba

Kostas Orginos, Doug Toussaint

Improved Kogut-Susskind quark actions containing repeatedly smeared links are studied to address the issue of flavor symmetry restoration. As a measure of the flavor symmetry restoration the mass spectrum of all the pions is computed. We present results for several variants of the &#34;fat&#34; actions that are suitable for full QCD simulations.

W. Bardeen, A. Duncan, E. Eichten, H. B. Thacker

Using the pole shifting procedure of the modified quenched approximation (MQA) to cure the exceptional configuration problem, accurate hadron hadron spectrum calculations can be obtained at very light quark mass. Here we use the MQA to extend and improve our previous investigation of chiral logs in the pion mass. At beta=5.7 for Wilson fermion, we see clear

PACS Collaboration, S. Aoki, G. Boyd, R. Burkhalter

We report the final results of the CP-PACS calculation for the quenched light hadron spectrum with the Wilson quark action. Our data support the presence of quenched chiral singularities, and this motivates us to use mass formulae based on quenched chiral perturbation theory in order to extrapolate hadron masses to the physical point. Hadron masses and decay

A. Duncan, E. Eichten, H. Thacker

Virtual quark effects in lattice QCD are studied in an approach where the infrared modes are included in a precise and gauge-invariant manner. At fixed physical volume the required number of modes does not increase in the continuum limit, and the acceptance is tolerable even for very light quark masses. Topological charge distributions at varying quark mass,

J. F. Markham, T. D. Kieu

Current algorithms used to put a lattice gauge configuration into Landau gauge either suffer from the problem of critical slowing-down or involve an additional computational expense to overcome it. Evolutionary Algorithms (EAs), which have been widely applied to other global optimisation problems, may be of use in gauge fixing. Also, being global, they shoul

H. B. Thacker

For purposes of regularization as well as numerical simulation, the discretization of Lorentz invariant continuum field theories on a space-time lattice is often convenient. In general, this discretization destroys the rotational or Lorentz-frame independence of the theory, which is only recovered in the continuum limit. The Baxter 8-vertex model may be inte

A. Ali Khan, in collaboration with T. Bhattacharya, S. Collins, C. Davies

Preliminary results from an extensive lattice calculation of the B, B_c, and Υspectrum at quenched β= 6.0 are presented. The study includes radially and orbitally excited mesons, and baryons containing b quarks. The b quarks are formulated using NRQCD; for light and c quarks, a tadpole-improved clover action is used.

M. Imachi, S. Kanou, H. Yoneyama

CP(N-1) model with topological term is numerically studied. The topological charge distribution P(Q) is calculated and then transformed to the partition function Z($θ$) as a function of $θ$ parameter. In the strong coupling region, P(Q) shows a gaussian behavior, which indicates a first order phase transition at $θ=π$. In the weak coupling region, P(Q) devia

L. Moscoso

Neutrino telescopes offer an alternative way to explore the Universe. Several projects are in operation or under construction. A detector under the ocean is very promising because of the very accurate angular resolution that it provides. The ANTARES project is intended to demonstrate the feasibilty of such a detector.

Stuart L. Shapiro

The head-on collision of identical neutron stars from rest at infinity requires a numerical simulation in full general relativity for a complete solution. Undaunted, we provide a relativistic, analytic argument to suggest that during the collision, sufficient thermal pressure is always generated to support the hot remnant in quasi-static stable equilibrium a

Jose M. Martin-Garcia, Carsten Gundlach

We study the nonspherical linear perturbations of the discretely self-similar and spherically symmetric solution for a self-gravitating scalar field discovered by Choptuik in the context of marginal gravitational collapse. We find that all nonspherical perturbations decay. Therefore critical phenomena at the threshold of gravitational collapse, originally fo

Vladimir O. Soloviev

We consider the algebra of spatial diffeomorphisms and gauge transformations in the canonical formalism of General Relativity in the Ashtekar and ADM variables. Modifying the Poisson bracket by including surface terms in accordance with our previous proposal allows us to consider all local functionals as differentiable. We show that closure of the algebra un

Yannis Labrou, Tim Finin

We address the issues of semantics and conversations for agent communication languages and the Knowledge Query Manipulation Language (KQML) in particular. Based on ideas from speech act theory, we present a semantic description for KQML that associates ``cognitive&#39;&#39; states of the agent with the use of the language&#39;s primitives (performatives). We

Victor W. Marek, Miroslaw Truszczynski

In this paper we reexamine the place and role of stable model semantics in logic programming and contrast it with a least Herbrand model approach to Horn programs. We demonstrate that inherent features of stable model semantics naturally lead to a logic programming system that offers an interesting alternative to more traditional logic programming styles of

William Aiello, Mihir Bellare, Giovanni Di Crescenzo, Ramarathnam Venkatesan

We investigate, in the Shannon model, the security of constructions corresponding to double and (two-key) triple DES. That is, we consider F_{k1}(F_{k2}(.)) and F_{k1}(F_{k2}^{-1}(F_{k1}(.))) with the component functions being ideal ciphers. This models the resistance of these constructions to ``generic&#39;&#39; attacks like meet in the middle attacks. We o

Vern Paxson

Recent network traffic studies argue that network arrival processes are much more faithfully modeled using statistically self-similar processes instead of traditional Poisson processes [LTWW94,PF95]. One difficulty in dealing with self-similar models is how to efficiently synthesize traces (sample paths) corresponding to self-similar traffic. We present a fa

Anoop Sarkar

This paper describes the incremental generation of parse tables for the LR-type parsing of Tree Adjoining Languages (TALs). The algorithm presented handles modifications to the input grammar by updating the parser generated so far. In this paper, a lazy generation of LR-type parsers for TALs is defined in which parse tables are created by need while parsing.

Anoop Sarkar

In this paper we present a new tree-rewriting formalism called Link-Sharing Tree Adjoining Grammar (LSTAG) which is a variant of synchronous TAGs. Using LSTAG we define an approach towards coordination where linguistic dependency is distinguished from the notion of constituency. Such an approach towards coordination that explicitly distinguishes dependencies

Anoop Sarkar

Much of the power of probabilistic methods in modelling language comes from their ability to compare several derivations for the same string in the language. An important starting point for the study of such cross-derivational properties is the notion of _consistency_. The probability model defined by a probabilistic grammar is said to be _consistent_ if the

Mark-Jan Nederhof, Anoop Sarkar, Giorgio Satta

Language models for speech recognition typically use a probability model of the form Pr(a_n | a_1, a_2, ..., a_{n-1}). Stochastic grammars, on the other hand, are typically used to assign structure to utterances. A language model of the above form is constructed from such grammars by computing the prefix probability Sum_{w in Sigma*} Pr(a_1 ... a_n w), where

Bernardo A. Huberman, Lada A. Adamic

The World Wide Web is fast becoming a source of information for a large part of the world&#39;s population. Because of its sheer size and complexity users often resort to recommendations from others to decide which sites to visit. We present a dynamical theory of recommendations which predicts site visits by users of the World Wide Web. We show that it leads

XTAG Research Group

This document describes a sizable grammar of English written in the TAG formalism and implemented for use with the XTAG system. This report and the grammar described herein supersedes the TAG grammar described in an earlier 1995 XTAG technical report. The English grammar described in this report is based on the TAG formalism which has been extended to includ

Davood Rafiei, Alberto Mendelzon

We study a set of linear transformations on the Fourier series representation of a sequence that can be used as the basis for similarity queries on time-series data. We show that our set of transformations is rich enough to formulate operations such as moving average and time warping. We present a query processing algorithm that uses the underlying R-tree in

P. Fendley, H. Saleur

We study the current in a multi-channel quantum wire and the magnetization in the multi-channel Kondo problem. We show that at zero temperature they can be written simply in terms of contour integrals over a (two-dimensional) hyperelliptic curve. This allows one to easily demonstrate the existence of weak-coupling to strong-coupling dualities. In the Kondo p

J. M. Eroles, C. D. Batista, S. B. Bacci, E. R. Gagliano

We study the $B_{1g}$ and $A_{1g}$ Raman profiles of M$_{2}$Cu$O_{4}$ (with M= La, Pr, Nd, Sm, Gd), Bi$_{2}$Sr$_{2}$Ca$_{0.5}$Y$_{0.5}$Cu$_{2}$O$_{8+y}$%, YBa$_{2}$Cu$_{3}$O$_{6.2}$ and PrBa$_{2}$Cu$_{2.7}$Al$_{0.3}$O$_{7}$ insulating cuprates within the Loudon-Fleury theory, in the framework of an extended Hubbard model for moderate on-site Coulomb interact

M. P. Anantram, T. R. Govindan

We study the conductance of carbon nanotube wires in the presence of disorder, in the limit of phase coherent transport. For this purpose, we have developed a simple numerical procedure to compute transmission through carbon nanotubes and related structures. Two models of disorder are considered, weak uniform disorder and isolated strong scatterers. In the c

S. Lukyanov

We proposed an analytical expression for the amplitude defining the long distance asymptotic of the correlation function <σ^z_k σ^z_{k+n}>.

Martin Weigel, Wolfhard Janke

In a MC study using a cluster update algorithm we investigate the finite-size scaling (FSS) of the correlation lengths of several representatives of the class of three-dimensional classical O(n) symmetric spin models on a column geometry. For all considered models we find strong evidence for a linear relation between FSS amplitudes and scaling dimensions whe

Saurabh Basu

Two-magnon Raman scattering intensity is obtained for two-dimensional spin-1/2 antiferromagnets in presence of hopping disorder. A consistent mode assignment scheme is prescribed which essentially establishes a correspondence between the hopping-disordered and the pure system. It is seen that a minute amount of disorder in hopping leads to a good agreement o

P. Viot, G. Tarjus

We study a 3-dimensional Ising model in which the tendency to order due to short-range ferromagnetic interactions is frustrated by competing long-range (Coulombic) interactions. Complete ferromagnetic ordering is impossible for any nonzero value of the frustration parameter, but the system displays a variety of phases characterized by periodically modulated

A. B. van Oosten, F. Mila

We report ab initio quantum chemical cluster calculations of the chain (J_a) and the largest interchain (J_b) Heisenberg exchange of the chain cuprates Ca_2CuO_3 and Sr_2CuO_3. We find that J_a is comparable to the in-plane J in layered cuprates and J_a/J_b ~250-400. Using recent theory we obtain close agreement with experiment for the staggered moments and

L. Schweitzer, H. Potempa

We investigate the influence of the boundary conditions on the scale invariant critical level statistics at the metal insulator transition of disordered three-dimensional orthogonal and two-dimensional unitary and symplectic tight-binding models. The distribution of the spacings between consecutive eigenvalues is calculated numerically and shown to be differ

Zhigang Zheng, Bambi Hu, Gang Hu

Brownian motion of an array of harmonically coupled particles subject to a periodic substrate potential and driven by an external bias is investigated. In the linear response limit (small bias), the coupling between particles may enhance the diffusion process, depending on the competition between the harmonic chain and the substrate potential. An analytical