September 1998 arXiv papers — page 8

U. K. Yang, A. Bodek

A re-analysis of the NMC and SLAC data leads to a great improvement in our knowledge of the valence d and u parton distribution functions at high x. Standard parton distributions with our modifications are in good agreement with QCD predictions for d/u at x=1, and with the CDHSW nu p and nubar p data, the HERA charged current cross section data, the collider

Paolo Zanardi

We introduce quantum procedures for making $\cal G$-invariant the dynamics of an arbitrary quantum system S, where $\cal G$ is a finite group acting on the space state of S. Several applications of this idea are discussed. In particular when S is a N-qubit quantum computer interacting with its environment and $\cal G$ the symmetric group of qubit permutation

W. A. Atkinson, A. H. MacDonald

We report on a microscopic evaluation of electrodynamic response for the vortex lattice state of a model s-wave superconductor. Our calculation accounts self-consistently for both quasiparticle and order parameter response and establishes the collective nature of linear response in the clean limit. We discuss the effects of homogeneous and inhomogeneous pinn

C. R. Allton, L. Conti, A. Donini, V. Gimenez

We present the first lattice measurement, using Non Perturbative Renormalization Method, of the B-parameters of the dimension-six four-fermion operators relevant for the supersymmetric corrections to the $ΔS=2$ transitions.

E. Caurier, G. Martinez-Pinedo, F. Nowacki, A. Poves

Binding energies and other global properties of nuclei in the middle of the $pf$ shell, such as M1, E2 and Gamow-Teller sum rules, have been obtained using a new Shell Model code (NATHAN) written in quasi-spin formalism and using a $j-j$-coupled basis. An extensive comparison is made with the recently available Shell Model Monte Carlo results using the effec

B. Zeini, A. Freimuth, B. Büchner, R. Gross

Measurements of the transverse (k_{xy}) and longitudinal (k_{xx}) thermal conductivity in high magnetic fields are used to separate the quasiparticle thermal conductivity (k_{xx}^{el}) of the CuO_2-planes from the phononic thermal conductivity in YBa_2Cu_3O_{7-δ}. k_{xx}^{el} is found to display a pronounced maximum below T_c. Our data analysis reveals disti

Brian P. Dolan

An analytic form for the conductivity tensor in crossover between two quantum Hall plateaux is derived, which appears to be in good agreement with existing experimental data. The derivation relies on an assumed symmetry between quantum Hall states, a generalisation of the law of corresponding states from rational filling factors to complex conductivity, whic

David Wands

I show that cosmological perturbation spectra produced from quantum fluctuations in massless or self-interacting scalar fields during an inflationary era remain invariant under a two parameter family of transformations of the homogeneous background fields. This relates slow-roll inflation models to solutions which may be far from the usual slow-roll limit. F

Nathan Roche, Steve Eales, Hans Hippelein, Chris Willott

On five K-band Omega camera images, covering a total of 162.2 sq. arcmin to K=19.5, we investigate (i) the clustering environment of 5 radio galaxies at 0.7<z<0.8 and (ii) the galaxy angular correlation function. We detect a cluster of estimated Abell richness class 1 or 2, centred on the radio galaxy 5C6.75 at z=0.775. Of the other radio galaxies, two appea

Takayuki Nakajima, Jun Nishimura

We study the two-dimensional Eguchi-Kawai model as a toy model of the IIB matrix model, which has been recently proposed as a nonperturbative definition of the type IIB superstring theory. While the planar limit of the model is known to reproduce the two-dimensional Yang-Mills theory, we find through Monte Carlo simulation that the model allows a different l

Christian R. Kaiser, Paul Alexander

We present an analytical model for the cosmological evolution of the FRII source population. Based on an earlier model for the intrinsic radio luminosity - linear size evolution of these objects, we construct theoretical source samples. The source distributions in the radio power - linear size plane of these samples are then compared with that of an observed

Ariel Caticha

In this note I expand further on the main assumptions leading to the consistent-amplitude approach to quantum theory and I offer a reply to Jerry Finkelstein&#39;s recent comment (quant-ph/9809017) concerning my argument for the linearity of quantum mechanics (Phys. Rev. A57, 1572 (1998)).

Stefan Weigert

State reconstruction for quantum spins is reviewed. Emphasis is on non-tomographic approaches which are based on measurements performed with a Stern-Gerlach apparatus. Two consequences of successfully implemented state reconstruction are pointed out. First, it allows one to determine experimentally the expectation value of an arbitrary operator without a dev

Frank Antonsen

We define Sturmian basis functions for the harmonic oscillator and investigate whether recent insights into Sturmians for Coulomb-like potentials can be extended to this important potential. We also treat many body problems such as coupling to a bath of harmonic oscillators. Comments on coupled oscillators and time-dependent potentials are also made. It is a

Marek Czachor, Jan Naudts

Combination of the Liouville equation with the q-averaged energy $U_q = <H>_q$ leads to a microscopic framework for nonextensive q-thermodynamics. The resulting von Neumann equation is nonlinear: $i\dotρ=[H,ρ^q]$. In spite of its nonlinearity the dynamics is consistent with linear quantum mechanics of pure states. The free energy $F_q=U_q-TS_q$ is a stabilit

R. E. Kastner

Recent authors have raised objections to the counterfactual interpretation of the Aharonov-Bergmann-Lebowitz (ABL) rule of time symmetrized quantum theory (TSQT). I distinguish between two different readings of the ABL rule, counterfactual and non-counterfactual, and confirm that TSQT advocate L. Vaidman is employing the counterfactual reading to which these

A. Manwani, C. Koch

Here we analyze synaptic transmission from an information-theoretic perspective. We derive closed-form expressions for the lower-bounds on the capacity of a simple model of a cortical synapse under two explicit coding paradigms. Under the ``signal estimation&#39;&#39; paradigm, we assume the signal to be encoded in the mean firing rate of a Poisson neuron. T

Stephan I. Tzenov

In the present paper we study the role of particle interactions on the evolution of a high energy beam. The interparticle forces taken into account are due to space charge alone. We derive the collision integral for a charged particle beam in the form of Balescu-Lenard and Landau and consider its further simplifications. Finally, the transition to the genera

H. D. Dahmen, E. Gjonaj, T. Stroh

We discuss applications of the quantile concept of trajectories and velocities to the propagation of electromagnetic signals in wave guides of varying cross section. Quantile motion is a general description of the transport properties of measurable conserved quantities in quantum mechanics as well as in classical electrodynamics. In the latter case we consid

Thomas Mehen, Iain W. Stewart

We introduce a momentum subtraction scheme which obeys the power counting of Kaplan, Savage, and Wise (KSW), developed for systems with large scattering lengths, $a$. Unlike the power divergence subtraction scheme, coupling constants in this scheme obey the KSW scaling for all $μ_R > 1/a$. We comment on the low-energy theorems derived by Cohen and Hansen. We

B. R. Schlei, D. Strottman, J. P. Sullivan, H. W. van Hecke

Within a relativistic hydrodynamic framework, we use four different equations of state of nuclear matter to compare to experimental spectra from CERN/SPS experiments NA44 and NA49. Freeze-out hypersurfaces and Bose-Einstein correlation functions for identical pion pairs are discussed. We find that two-pion Bose-Einstein interferometry measures the relationsh

R. Machleidt

After a historical review, I present the progress in the field of realistic NN potentials that we have seen in recent years. A new generation of very quantitative (high-quality/high-precision) NN potentials has emerged. These potentials will serve as reliable input for microscopic nuclear structure calculations and will allow for a systematic investigation o

Hartmuth Arenhoevel

A set of 13 linearly independent invariant amplitudes for the electromagnetic production of a pseudoscalar particle from a spin-one particle is derived which respect Lorentz and gauge invariance. The $T$-matrix can be represented by a linear superposition of these amplitudes with invariant functions as coefficients, which depend on the Mandelstam variables o

H. Nakada, Y. Alhassid

We calculate microscopically total and parity-projected level densities for $β$-stable even-even nuclei between Fe and Ge, using the shell model Monte Carlo methods in the complete $(pf+0g_{9/2})$-shell. A single-particle level density parameter $a$ and backshift parameter $Δ$ are extracted by fitting the calculated densities to a backshifted Bethe formula,

J. L. Friar, D. Hüber, U. van Kolck

After a brief review of the role three-nucleon forces play in the few-nucleon systems, the chiral-perturbation-theory approach to these forces is discussed. Construction of the (nominal) leading- and subleading-order Born terms and pion-rescattering graphs contributing to two-pion-exchange three-nucleon forces is reviewed, and comparisons are made of the typ

V. G. Bagrov, B. F. Samsonov, L. A. Shekoyan

It is proved that the Darboux transformation of the system of coherent states of a free particle leads to the states that may be treated as coherent states of soliton-like potentials.

F. Bergeron, G. Garsia

This work studies the remarkable relationships that hold among certain m-tuples of the Garsia-Haiman modules $ {\bf M}_μ$ and corresponding elements of the Macdonald basis. We recall that ${\bf M}_μ$ is defined for a partition $μ\part n$, as the linear span of derivatives of a certain bihomogeneous polynomial $Δ_ μ(x,y)$ in the variables $x_1,x_2,..., x_n, y

F. Bergeron, N. Bergeron, A. M. Garsia, M. Haiman

The lattice cell in the ${i+1}^{st}$ row and ${j+1}^{st}$ column of the positive quadrant of the plane is denoted $(i,j)$. If $μ$ is a partition of $n+1$, we denote by $μ/ij$ the diagram obtained by removing the cell $(i,j)$ from the (French) Ferrers diagram of $μ$. We set $Δ_{μ/ij}=\det \| x_i^{p_j}y_i^{q_j} \|_{i,j=1}^n$, where $(p_1,q_1),... ,(p_n,q_n)$ a

Wolfram Koepf

In the last decade major steps towards an algorithmic treatment of orthogonal polynomials and special functions (OP & SF) have been made, notably Zeilberger&#39;s brilliant extension of Gosper&#39;s algorithm on algorithmic definite hypergeometric summation. By implementations of these and other algorithms symbolic computation has the potential to change the

Hans U. Boden, Christopher M. Herald

We derive a gauge theoretic invariant of integral homology 3-spheres which counts gauge orbits of irreducible, perturbed flat SU(3) connections with sign given by spectral flow. To compensate for the dependence of this sum on perturbations, the invariant includes contributions from the reducible, perturbed flat orbits. Our formula for the correction term gen

Philippe Carmona, Laure Coutin

Fractional Brownian motion belongs to a class of long memory Gaussian processes that can be represented as linear functionals of an infinite dimensional Markov process. This representation leads naturally to: - An efficient algorithm to approximate the process. - An infinite dimensional ergodic theorem which applies to functionals of the type $integral_0^t p

Peter Goddard

Laudation delivered at the International Congress of Mathematicians in Berlin following the award of the Fields Medal to Richard Borcherds.

W. Kummer, H. Liebl, D. V. Vassilevich

General 2d dilaton theories, containing spherically symmetric gravity and hence the Schwarzschild black hole as a special case, are quantized by an exact path integral of their geometric (Cartan-) variables. Matter, represented by minimally coupled massless scalar fields is treated in terms of a systematic perturbation theory. The crucial prerequisite for ou

G W Gibbons

The Geroch-Wald-Jang-Huisken-Ilmanen approach to the positive energy problem to may be extended to give a negative lower bound for the mass of asymptotically Anti-de-Sitter spacetimes containing horizons with exotic topologies having ends or infinities of the form $Σ_g \times {\Bbb R}$, in terms of the cosmological constant. We also show how the method gives

C. Klimcik

I compute the cohomology of a non-commutative complex underlying the notion of the gauge field on the fuzzy sphere.

F. Antonuccio, O. Lunin, S. Pinsky

In recent years a supersymmetric form of discrete light-cone quantization (hereafter `SDLCQ&#39;) has emerged as a very powerful tool for solving supersymmetric field theories. In this scheme, one calculates the light-cone supercharge with respect to a discretized light-cone Fock basis, instead of working with the light-cone Hamiltonian. This procedure has t

J. Rahmfeld, A. Rajaraman

We derive the classical kappa-symmetric Type IIB string action on AdS(3) x S(3) by employing the SU(1,1|2)^2 algebra. We then gauge fix kappa-symmetry in the background adapted Killing spinor gauge and present the action in a very simple form.

Z. Bern, L. Dixon, D. C. Dunbar, M. Perelstein

We discuss nontrivial examples illustrating that perturbative gravity is in some sense the `square&#39; of gauge theory. This statement can be made precise at tree-level using the Kawai, Lewellen and Tye relations between open and closed string tree amplitudes. These relations, when combined with modern methods for computing amplitudes, allow us to obtain lo

Stuart Kauffman, Lee Smolin

We describe the application of methods from the study of discrete dynanmical systems to the problem of the continuum limit of evolving spin networks. These have been found to describe the small scale structure of quantum general relativity and extensions of them have been conjectured to give background independent formulations of string theory. We explain wh

Ioannis Giannakis, James T. Liu, Massimo Porrati

In this paper we study three point functions of the Type II superstring involving one graviton and two massive states, focusing in particular on the spin-7/2 fermions at the first mass level. Defining a gravitational quadrupole ``h-factor&#39;&#39;, we find that the non-minimal interactions of string states in general are parametrized by $h\ne1$, in contrast

A. Berkovich, B. M. McCoy

We demonstrate the equality between the universal chiral partition function, which was first found in the context of conformal field theory and Rogers-Ramanujan identities, and the exclusion statistics introduced by Haldane in the study of the fractional quantum Hall effect. The phenomena of multiple representations of the same conformal field theory by diff

B. Dressler, K. Goeke, P. V. Pobylitsa, M. V. Polyakov

We summarize recent attempts to calculate the flavor asymmetry of the nucleon&#39;s sea quark distributions in the large-$N_c$ limit, where the nucleon can be described as a soliton of an effective chiral theory. We discuss the leading-twist longitudinally polarized and transversity antiquark distributions, $Δ\bar u (x) - Δ\bar d (x)$ and $δ\bar u (x) - δ\ba

W. Kilian, P. M. Zerwas

Recent developments in prospects of searching for Higgs particles and testing their properties at the LHC and at TeV e+e- linear colliders are summarized. The discovery limits of supersymmetric particles at the LHC are presented and the accuracy is explored with which the fundamental SUSY parameters in the context of supergravity models can be determined at

S. L. Dubovsky, D. S. Gorbunov, S. V. Troitsky

We consider constraints on gauge mediated supersymmetry breaking models imposed by the requirement of grand unification. In particular, we demonstrate several ways to reduce the number of parameters coming from the dynamical supersymmetry breaking sector. One of approaches exploits nonperturbative unification of gauge couplings in multi-messenger models.

I. M. Dremin, C. S. Lam

It is shown that the high-energy expansion of the scattering amplitude calculated from Feynman diagrams factorizes in such a way that it can be reduced to the eikonalized form up to the terms of inverse power in energy in accordance with results obtained by solving the Klein-Gordon equation. Therefore the two approaches when applied to the suppression of the

Robert D. Pisarski, T. L. Trueman, Michel H. G. Tytgat

I consider the low temperature correction to the anomalous coupling of a neutral pion to two photons from an effective Lagrangian point of view.

Tran N. Truong

The first three coefficients of the Taylor&#39;s series expansion of the vector pion form factor as a function of the momentum transfer are evaluated using experimental data on the pion form factor and the P-wave pi pi phase shifts. The real part of the form factor as a function of energy is also calculated by dispersion relation. Comparisons these results w

C. Panagiotakopoulos, K. Tamvakis

We reconsider the Next to Minimal Supersymmetric Standard Model (NMSSM) as a natural solution to the $μ$-problem and show that both the stability and the cosmological domain wall problems are eliminated if we impose a ${\cal {Z}}_2$ $R$-symmetry on the non-renormalizable operators.

H. Navelet, R. Peschanski

We derive the analytic expression of the two one-loop dipole contributions to the elastic 4-gluon amplitude in QCD. The first one corresponds to the double QCD pomeron exchange, the other to an order alpha^2 correction to one-pomeron exchange. Both are expressed in terms of the square of the recently derived triple QCD pomeron vertex and involve a summation

Tamas G. Kovacs, Zsolt Schram

We investigate the monopole-instanton correlation in SU(2) lattice gauge theory using a renormalisation group inspired smoothing technique. We look at the properties of monopole clusters and their correlation with instantons. Since the action of the smoothed configurations is dominated by instantons we compare the smoothed Monte Carlo lattices to artificiall

V. F. Andreev, A. S. Belousov, A. M. Fomenko, L. A. Gorbov

Measures taken to extend the acceptance of the H1 detector at HERA for photoproduction events are described. These will enable the measurement of electrons scattered in events in the high y range 0.85 < y < 0.95 in the 1998 and 1999 HERA run period. The improvement is achieved by the installation of an electromagnetic calorimeter, the ET8, in the HERA tunnel

A. Balfagon, X. Jaen

We are presenting an algorithm capable of simplifying tensor polynomials with indices when the building tensors have index symmetry properties. These properties include simple symmetry, cyclicity and those due to the presence of partial and covariant derivatives. We are also including some examples using the Riemann tensor as a paradigm. The algorithm is par

J. W. Moffat

A theory is developed which attempts to reconcile the measurements of nonlocal quantum observables with special relativity and quantum mechanics. The collapse of a wave function, which coincides with a nonlocal measurement by some macroscopic measuring device, is associated with the triggering of an absorber mechanism due to the interaction of the apparatus

Bobby Vandalore, Shivkumar Kalyanaraman, Raj Jain, Rohit Goyal

ATM (asynchronous transfer mode) is the technology chosen for the Broadband Integrated Services Digital Network (B-ISDN). The ATM ABR (available bit rate) service can be used to transport ``best-effort&#39;&#39; traffic. In this paper, we extend our earlier work on the buffer requirements problem for TCP over ABR. Here, a worst case scenario is generated suc

Bobby Vandalore, Sonia Fahmy, Raj Jain, Rohit Goyal

In this paper we give a general definition of weighted fairness and show how this can achieve various fairness definitions, such as those mentioned in the ATM Forum TM 4.0 Specifications. We discuss how a pricing policy can be mapped to general weighted (GW) fairness. The GW fairness can be achieved by calculating the $ExcessFairshare$ (weighted fairshare of

Bobby Vandalore, Raj Jain, Rohit Goyal, Sonia Fahmy

The main goals of a switch scheme are high utilization, low queuing delay and fairness. To achieve high utilization the switch scheme can maintain non-zero (small) queues in steady state which can be used if the sources do not have data to send. Queue length (delay) can be controlled if part of the link capacity is used for draining queues in the event of qu

Bobby Vandalore, Sonia Fahmy, Raj Jain, Rohit Goyal

An explicit rate switch scheme monitors the load at each link and gives feedback to the sources. We define the overload factor as the ratio of the input rate to the available capacity. In this paper, we present four overload based ABR switch schemes which provide MCR guarantees. The switch schemes proposed use the overload factor and other quantities to calc

Sonia Fahmy, Raj Jain

Multipoint capabilities are essential for ATM networks to efficiently support many applications, including IP multicasting and overlay applications. The current signaling and routing specifications for ATM define point-to-multipoint capabilities. Multipoint-to-point connection support is also being discussed by the signaling and PNNI groups, and will be defi

Yu. S. Barash, A. A. Svidzinsky

Effect of surface pair breaking, entirely neglected by M. Samanta and S. Datta [Phys. Rev. B v. 57, 10972 (1998)], is quite important in considering surface (or interface) quasiparticle bound states and associated characteristics of junctions involving unconventional superconductors. The whole class of bound states with nonzero energy is simply omitted withi

R. A. Serota, B. Goodman

We evaluate the electric dipole absorption in small metal particles in a longitudinal electric field taking into account the Fermi-Thomas screening. When either the level broadening or the frequency of the field are larger than the mean energy-level spacing, the main contribution to absorption is classical, with quantum corrections. When both the broadening

Reka Albert, Albert-Laszlo Barabasi, Nathan Carle, Andrew Dougherty

While there have been important theoretical advances in understanding the universality classes of interfaces moving in porous media, the developed tools cannot be directly applied to experiments. Here we introduce a method that can identify the universality class from snapshots of the interface profile. We test the method on discrete models whose universalit

S. Sitotaw, R. A. Serota

We use the exact correlation function of the density of energy levels in the magnetic field to evaluate persistent currents in mesoscopic metals. We also analyze the perturbation theory limit of the correlation function vis-a-vis the perturbation theory limit of the orbital response.

R. Chitra, T. Giamarchi, P. Le Doussal

The effects of weak point-like disorder on periodic systems at their upper critical dimension D_c for disorder are studied. The systems studied range from simple elastic systems with D_c=4 to systems with long range interactions with D_c=2 and systems with D_c=3 such as the vortex lattice with dispersive elastic constants. These problems are studied using th

Marta Chaves, Maria Augusta Santos

A geometric approach to critical fluctuations of a nonequilibrium model is reported. The two-dimensional majority vote model was investigated by Monte Carlo simulations on square lattices of various sizes and a detailed scaling analysis of cluster statistical and geometric properties was performed. The cluster distribution exponents and fractal dimension wer

M. D. Todorov, T. L. Boyadjiev

A direct method for calculating the minimal length of ``one-dimensional&#39;&#39; Josephson junctions is proposed, in which the specific distribution of the magnetic flux retains its stability. Since the length of the junctions is a variable quantity, the corresponding nonlinear spectral problem as a problem with free boundaries is interpreted. The obtained

Rosa Lopez, Ramon Aguado, Gloria Platero, Carlos Tejedor

A theory of the Kondo effect in quantum dots at zero temperature in the presence of arbitrary intense AC potentials is presented.We generalize the Friedel-Langreth sum rule to take care of charge conservation and propose a consistent procedure to study a time dependent Anderson Hamiltonian. The effect of the AC potential on both the quantum dot density of st

A. Minguzzi, M. P. Tosi

A recently developed local-density current functional formalism for confined Bose-condensed superfluids requires visco-elastic spectra which are defined through a finite-frequency extension of the dissipative coefficients entering the linearized hydrodynamic equations of the two-fluid model. We evaluate these spectra for a superfluid with contact interaction

Tota Nakamura

A localization length of a free-spin soliton from a non-magnetic impurity is deduced in a general double-spin-chain model ($J_0-J_1-J_2-J_3$ model). We have solved a variational problem which employs the nearest-neighbor singlet-dimer basis. The wave function of a soliton is expressed by the Airy function, and the localization length $(ξ)$ is found to obey a

Toru Sakai, Yasumasa Hasegawa

The magnetization process of the $S$=1/2 antiferromagnetic spin ladder with the four-spin cyclic exchange interaction at T=0 is studied by the exact diagonalization of finite clusters and size scaling analyses. It is found that a magnetization plateau appears at half the saturation value if the ratio of the four- and two-spin exchange coupling constants $J_4

D. Braak, N. Andrei

A simple picture for the spectrum of the one-dimensional Hubbard model is presented using a classification of the eigenstates based on an intuitive bound-state Bethe-Ansatz approach. This approach allows us to prove a &#34;string hypothesis&#34; for complex momenta and derive an exact formulation of the Bethe-Ansatz equations including all states. Among othe

P. Lemmens, M. Fischer, M. Grove, G. Els

Magnetic bound states are a general phenomenon in low dimensional antiferromagnets with gapped singlet states. Using Raman scattering on three compounds as dedicated examples we show how exchange topology, dimensionality, defects and thermal fluctuations influence the properties and the spectral weight of these states.

Piotr Garbaczewski

We make a detailed analysis of both phenomenological and analytic background for the &#34;Brownian recoil principle&#34; hypothesis (Phys. Rev. A 46, (1992), 4634). A corresponding theory of the isothermal Brownian motion of particle ensembles (Smoluchowski diffusion process approximation), gives account of the environmental recoil effects due to locally ind

K. Ishikawa, N. Maeda, T. Ochiai, H. Suzuki

Quantum Hall Dynamics is formulated on von Neumann lattice representation where electrons in Landau levels are defined on lattice sites and are treated systematically like lattice fermions. We give a proof of the integer Hall effect, namely the Hall conductance is the winding number of the propagator in the momentum space and is quantized exactly as integer

J. T. Chalker, S. L. Sondhi

We consider the two-dimensional chiral metal, which exists at the surface of a layered, three-dimensional sample exhibiting the integer quantum Hall effect. We calculate its magnetoresistance in response to a component of magnetic field perpendicular to the sample surface, in the low temperature, but macroscopic, regime where inelastic scattering may be negl

Marcus Metzler

We numerically investigate the influence of classical percolation on the quantum Hall localization-delocalization transition. This is accomplished within the framework of the generalized Chalker--Coddington network model which allows us to control the number of {\em classical} saddle points by setting the width $W$ of the saddle point distribution. It is fou

Gwang-Hee Kim, Mincheol Shin

Within the framework of the path-integral approach we study the quantum vortex creep for the situation where both the Hall and the dissipative dynamics are simultaneously present. We calculate the relaxation rate and the crossover temperature separating the thermal activation and the quantum tunneling processes for anisotropic or multilayer superconductors.

H. D. Chen, W. P. Bai, D. L. Yin, Y. L. Zhu

The vortices in a high-Tc superconductor with strong correlated pinning centers have been studied numerically using the mapping to charged bosons in two-dimensions(2D) and the Monte-Carlo algorithm. Considering the viscous dissipation of moving vortices we derived a nonlinear voltage response expression which describes different regimes and their crossover u

Kenji Harada, Matthias Troyer, Naoki Kawashima

The temperature dependence of the correlation length, susceptibilities and the magnetic structure factor of the two-dimensional spin-1 square lattice quantum Heisenberg antiferromagnet are computed by the quantum Monte Carlo loop algorithm (QMC). In the experimentally relevant temperature regime the theoretically predicted asymptotic low temperature behavior

F. Yusef-Zadeh, D. A. Roberts, W. M. Goss, D. A. Frail

High-resolution VLA observations of 1720 MHz OH maser emission from Sgr A East and the circumnuclear disk with spatial and spectral resolutions of $\approx$ 2\dasec5 $\times$ 1\dasec3 and 0.27 \kms are reported. This follow-up observational study focuses on the recent discovery of a number of such OH maser features and their intense circularly polarized mase

Eric Hooper, Belinda Wilkes, Kim McLeod, Jonathan McDowell

Observations for the U.S. key project on quasars using ISO were completed in April when the satellite&#39;s cryogen supply expired. This proceeding presents an update of the project, including information on the final sample, a discussion of some of the data reduction challenges and current efforts to meet them, plus a comparison of preliminary results with

Ata Sarajedini, Doug Geisler, Paul Harding, Robert Schommer

We have constructed color-magnitude diagrams (CMDs) for ten globular clusters in the halo of the nearby spiral galaxy M33 based on Hubble Space Telescope Wide-Field Planetary Camera 2 observations in the F555W (~V) and F814W (~I) filters. These data reveal the morphology of the HB and allow us to estimate the cluster metallicity using the shape and color of

M. Berger, M. van der Klis

We studied the fast timing behaviour of the atoll source 4U 1705-44 using the entire EXOSAT dataset, four observations covering a total of 230,000 seconds of 1-20 keV spectral and timing data. In one of the observations, 4U 1705-44 was in a low intensity &#34;island&#34; state and had an unusually hard spectrum. The fast timing analysis of this hard island s

M. Gl&#34;uck, S. Kretzer, E. Reya

Neutrino-nucleon total cross sections for neutrino energies up to ultrahigh energies (UHE), E_ν=10^12 GeV, are evaluated within the framework of the dynamical (radiative) parton model. The expected uncertainties of these predictions do not exceed the level of about 20 % at the highest energies where contributions of parton distributions in the yet unmeasured

Andrew R Liddle, Robert J Scherrer

An attractive method of obtaining an effective cosmological constant at the present epoch is through the potential energy of a scalar field. Considering models with a perfect fluid and a scalar field, we classify all potentials for which the scalar field energy density scales as a power-law of the scale factor when the perfect fluid density dominates. There

J. Marti&#39;, S. Mereghetti, S. Chaty, I. F. Mirabel

We report the results of a deep search for the optical and near infrared counterpart of the microquasar source GRS1758-258. At least two possible candidate counterparts of the binary star companion have been recognized on the basis of astrometric coincidence to within 1&#34;. Our photometric study shows that the brightest of them would be consistent with a K

N. Kaiser, G. Wilson, G. Luppino, L. Kofman

We perform a weak lensing and photometric study of the z=0.42 supercluster MS0302+17 using deep I and V band images taken with the UH8K CCD mosaic camera at the CFHT. We use archival ROSAT HRI data to estimate fluxes, gas masses and, in one case, the binding mass of the three major clusters. We then use our CCD data to determine the optical richness and lumi

Chung-Pei Ma

This paper presents an analytical formula that closely approximates the fully nonlinear power spectrum of matter fluctuations for redshift $z\approx 5$ to 0 over a wide range of cosmologically interesting flat models with varying matter density $Ω_m$ and neutrino fraction $Ω_ν$. The functional form is motivated by analytical solutions in asymptotic regimes,

M. E. J. Newman, Gunther J. Eble

We show that the decline in the extinction rate during the Phanerozoic can be accurately parameterized by a logarithmic fit to the cumulative total extinction. This implies that extinction intensity is falling off approximately as the reciprocal of time. We demonstrate that this observation alone is sufficient to explain the existence of the proposed power-l

TW Donnelly, Ingo Sick

We investigate the degree to which the scaling functions $F(ψ&#39;)$ derived from cross sections for inclusive electron-nucleus quasi-elastic scattering define the same function for different nuclei. In the region where the scaling variable $ψ&#39;< 0$, we find that this superscaling is experimentally realized to a high degree.

David Eppstein

We present an algorithm for maintaining the width of a planar point set dynamically, as points are inserted or deleted. Our algorithm takes time O(kn^epsilon) per update, where k is the amount of change the update causes in the convex hull, n is the number of points in the set, and epsilon is any arbitrarily small constant. For incremental or decremental upd

Z. Bern, L. Dixon, M. Perelstein, J. S. Rozowsky

We present an ansatz for all one-loop amplitudes in pure Einstein gravity for which the n external gravitons have the same outgoing helicity. These loop amplitudes, which are rational functions of the momenta, also arise in the quantization of self-dual gravity in four-dimensional Minkowski space. Our ansatz agrees with explicit computations via D-dimensiona

NuTeV Collaboration, D. Naples, A. Romosan

We present new limits on nu_e to nu_tau and nu_e to nu_sterile oscillations by searching for electron neutrino dissappearance in the high-energy wide-band CCFR neutrino beam. Sensitivity to nu_tau appearance comes from tau decay modes in which a large fraction of the energy deposited is electromagnetic. The beam is composed primarily of muon neutrinos but th

Nina Amenta, Marshall Bern, David Eppstein, Shang-Hua Teng

We show that, for any set of n points in d dimensions, there exists a hyperplane with regression depth at least ceiling(n/(d+1)). as had been conjectured by Rousseeuw and Hubert. Dually, for any arrangement of n hyperplanes in d dimensions there exists a point that cannot escape to infinity without crossing at least ceiling(n/(d+1)) hyperplanes. We also appl

R. Sekhar Chivukula, Bogdan A. Dobrescu, Howard Georgi, Christopher T. Hill

We study electroweak symmetry breaking involving the seesaw mechanism of quark condensation. These models produce a composite Higgs boson involving the left-handed top quark, yet the top mass arises naturally at the observed scale. We describe a schematic model which illustrates the general dynamical ideas. We also consider a generic low-energy effective the

Igor Pesando

We describe the type IIB supergravity background on AdS_{3} x S_{3} x T^{4} using the potentials of AdS_{3|4} x S_{3} x T^{4} and we use the supersolvable algebra associated to AdS_{3|4} to compute the kappa gauge fixed type IIB string action. From the explicit form of the action we can clearly see how passing from pure NSNS backgrounds to pure RR background

E. Chereul, M. Crézé, O. Bienaymé

This paper presents the detailed results obtained in the search of density- velocity inhomogeneities in a volume limited and absolute magnitude limited sample of A-F type dwarfs within 125 parsecs of the Sun. A 3-D wavelet analysis is used to extract inhomogeneities, both in the density and velocity distributions. Having established a real picture of the pha

Daniele Fargion, Rostislav Konoplich, Marco Grossi, Maxim Khlopov

The diffused gamma halo around our Galaxy recently discovered by EGRET could be produced by annihilations of relic neutrinos N (of fourth generation), whose mass is within a narrow range (Mz /2 < M < Mz). Neutrino annihilations in the halo may lead to either ultrarelativistic electron pairs whose inverse Compton Scattering on infrared or optical galactic pho

Tom Bridgeland

We give a condition for an exact functor between triangulated categories to be an equivalence. Applications to Fourier-Mukai transforms are discussed. In particular, we obtain a large number of such transforms for K3 surfaces.

Kazuyuki Fujii, Yasushi Homma, Tatsuo Suzuki

In the preceding paper(hep-th/9806084), we constructed submodels of nonlinear Grassmann sigma models in any dimension and, moreover, an infinite number of conserved currents and a wide class of exact solutions. In this paper, we first construct almost all conserved currents for the submodels and all ones for the one of ${\bf C}P^1$-model. We next review the

Zurab Kakushadze, S. -H. Henry Tye

In string theory, the brane world scenario, where the Standard Model gauge and matter fields live inside some branes while gravitons live in the bulk, can be a viable description of our universe. In this note we argue that the brane world actually is a likely description of nature. Our discussion includes a revisit of certain issues, namely, coupling unifica