July 1997 arXiv papers — page 18

G. B. Lima Neto, V. Pislar, F. Durret, D. Gerbal

We present a new X-ray analysis mainly based on ROSAT HRI data. The HRI spatial resolution combined with an improved wavelet analysis method and with complementary radio and optical data provides new results compared to a previous paper based on ROSAT PSPC data (Pislar et al. 1997). We use also redshift data in order to identify galaxies dynamically belongin

M. G. Lattanzi, A. Spagna, A. Sozzetti, S. Casertano

We present the results of realistic end-to-end simulations of observations of nearby stars with the proposed global astrometry mission GAIA, recently recommended within the context of ESA's Horizon 2000 Plus long-term scientific program. We show that under realistic, if challenging, assumptions, GAIA will be capable of surveying the solar neighborhood wi

Virgo Consortium, :, Peter A. Thomas, J. M. Colberg

We investigate the internal structure of clusters of galaxies in high-resolution N-body simulations of 4 different cosmologies. There is a higher proportion of disordered clusters in critical-density than in low-density universes, although the structure of relaxed clusters is very similar in each. Crude measures of substructure, such as the shift in the posi

Michel Fioc, Brigitte Rocca-Volmerange

PEGASE is a new spectrophotometric evolution model for starbursts and evolved galaxies of the Hubble sequence. Its main originality is the extension to the near-infrared (NIR) of the atlas of synthetic spectra of Rocca-Volmerange & Guiderdoni (1988) with a revised stellar library including cold star parameters and stellar tracks extended to the TP-AGB and th

E. Cappellaro, P. A. Mazzali, S. Benetti, I. J. Danziger

The absolute V light curves of 5 SNe Ia, selected to represent the known range of absolute luminosities at maximum for this class of objects, are presented. Comparison of the long term luminosity evolution shows that the differences seen at maximum persist, and actually increase with time, einforcing the notion that intrinsic differences do exist among SNe I

Arnon Dar

The standard solar model (SSM) yield a $^8$B solar neutrino flux which is consistent within the theoretical and experimental uncertainties with that observed at Super-Kamiokande. The combined results from the Super- Kamiokande and the Chlorine solar neutrino experiments do not provide a solid evidence for neutrino properties beyond the minimal standard elect

M. D. Roberts, S. A. Dazeley, P. G. Edwards, T. Hara

Since 1992 the CANGAROO 3.8m imaging telescope has been used to search for sources of TeV gamma-rays. Results are presented here for observations of four Southern Hemisphere BL-Lacs - PKS0521-365, PKS2316-423, PKS2005-489 and EXO0423-084. In addition to testing for steady DC emission, a night by night burst excess search has been performed for each source.

T. Yoshikoshi, T. Kifune, S. A. Dazeley, P. G. Edwards

We have observed the Vela pulsar region at TeV energies using the 3.8 m imaging Cherenkov telescope near Woomera, South Australia every year since 1992. This is the first concerted search for pulsed and unpulsed emission from the Vela region, and the imaging technique also allows the location of the emission within the field of view to be examined. A signifi

T. Sako, S. A. Dazeley, P. G. Edwards, T. Hara

The data for VHE (~TeV) gamma rays from young gamma-ray pulsar PSR1509-58 observed in 1996 with the CANGAROO 3.8m Cerenkov imaging telescope are presented, as well as the additional data from March to June of 1997. The high spin-down luminosity of the pulsar and the plerionic feature around the pulsar observed with radio and X-rays suggest that VHE gamma-ray

K. L. Vaninsky

We consider classical particles on the line with the Weierstrass $\wp$ function as potential. This system parameterizes special solutions of the KP equation. We derive the trace formula which relates the Hamiltonian of the particle system to the residues of some Abelian differential (meromorphic one-form) on the spectral curve. Such formula is important for

Megan Donahue, G. Mark Voit, Isabella M. Gioia, Gerry Luppino

We have observed the most distant (z=0.829) cluster of galaxies in the Einstein Extended Medium Sensitivity Survey, with the ASCA and ROSAT satellites. We find an X-ray temperature of 12.3 +3.1/-2.2 keV for this cluster, and the ROSAT map reveals significant substructure. The high temperature of MS1054-0321 is consistent with both its approximate velocity di

Elias Kiritsis, Boris Pioline

We obtain the exact non-perturbative thresholds of $R^4$ terms in IIB string theory compactified to eight and seven dimensions. These thresholds are given by the perturbative tree-level and one-loop results together with the contribution of the D-instantons and of the (p,q)-string instantons. The invariance under U-duality is made manifest by rewriting the s

Duiliu-Emanuel Diaconescu, Jaume Gomis

Certain limits of the duality between M-theory on ${T^5/Z_2}$ and IIB on K3 are analyzed in Matrix theory. The correspondence between M-theory five-branes and ALE backgrounds is realized as three dimensional mirror symmetry. Non-critical strings dual to open membranes are explicitly described as gauge theory excitations. We also comment on Type IIA on K3 and

Andrew A. de Laix, Glenn Starkman

The multipole moments of the power spectrum of large scale structure, observed in redshift space, are calculated for a finite sample volume including the effects of both the linear velocity field and geometry. A variance calculation is also performed including the effects of shot noise. The sensitivity with which a survey with the depth and geometry of the S

Eric M. Rains

One of the fundamental concepts of quantum information theory is that of entanglement purification; that is, the transformation of a partially entangled state into a smaller-dimensional, more completely entangled state. Of particular interest are protocols for entanglement purification (EPPs) that alternate purely local operations with one- or two-way classi

P. Pronin, K. Stepanyantz

We explicitly calculate one-loop divergences for an arbitrary field theory model using the higher derivative regularization and nonsingular gauge condition. They are shown to agree with the results found in the dimensional regularization and do not depend on the form of regularizing term. So, the consistency of the higher derivative regularization is proven

Didier Sornette

We discuss the concept of discrete scale invariance and how it leads to complex critical exponents (or dimensions), i.e. to the log-periodic corrections to scaling. After their initial suggestion as formal solutions of renormalization group equations in the seventies, complex exponents have been studied in the eighties in relation to various problems of phys

Chanyong Park, Sang-Jin Sin

We study the effect of the solitonic degrees of freedom in string cosmology following the line of Rama. The gas of solitonic p-brane is treated as a perfect fluid in a Brans-Dicke type theory. In this paper, we find exact cosmological solutions for any Brans-Dicke parameter $ω$ and for general parameter $γ$ of equation of state and classify the cosmology of

G. Franzese, V. Cataudella, A. Coniglio

The Invaded Cluster (IC) dynamics introduced by Machta et al. [Phys. Rev. Lett. 75 2792 (1995)] is extended to the fully frustrated Ising model on a square lattice. The properties of the dynamics which exhibits numerical evidence of self-organized criticality are studied. The fluctuations in the IC dynamics are shown to be intrinsic of the algorithm and the

G. German

We suggest that the $ϕ^4$ model is only a polynomial approximation to a more fundamental theory. As a consequence the high temperature regime might not be correctly described by this model. If this turns out to be true then several results concerning e.g., critical temperatures, symmetry restoration at high temperature and high temperature expansions should

Paul S. Aspinwall

If one begins with the assertion that the type IIA string compactified on a K3 surface is equivalent to the heterotic string on a four-torus one may try to find a statement about duality in ten dimensions by decompactifying the four-torus. Such a decompactification renders the K3 surface highly singular. The resultant K3 surface may be analyzed in two quite

Kenji Mohri

We investigate a (0,2) gauge theory realized on the world volume of the type IIB D1-brane at the singular point of a Calabi-Yau fourfold. It is argued that the gauge anomaly can be canceled via coupling to the R-R chiral bosons in bulk IIB string. We find that for a generic choice of the Fayet-Iliopoulos parameters on the world volume, the Higgs moduli space

I. Antoniadis, S. Ferrara, R. Minasian, K. S. Narain

We discuss several implications of R^4 couplings in M theory when compactified on Calabi-Yau (CY) manifolds. In particular, these couplings can be predicted by supersymmetry from the mixed gauge-gravitational Chern-Simons couplings in five dimensions and are related to the one-loop holomorphic anomaly in four-dimensional N=2 theories. We find a new contribut

Charles A. Nelson, Brian T. Kress, Marco Lopes, Thomas P. McCauley

The modularity property of the helicity formalism is used to provide amplitude expressions and stage-two spin-correlation functions which can easily be used in direct experimental searches for electro-weak symmetries and dynamics in the decay processes $t \to W^+ b$, $\bar t \to W^- \bar b$. The formalism is used to describe the decay sequences $t\to W^{+}b\

A. Brignole, L. E. Ibañez, C. Muñoz

We review the origin of soft supersymmetry-breaking terms in N=1 supergravity models of particle physics. We first consider general formulae for those terms in general models with a hidden sector breaking supersymmetry at an intermediate energy scale. The results for some simple models are given. We then consider the results obtained in some simple superstri

Boris Tomasik, Ulrich Heinz

A comprehensive model study of Bose-Einstein correlation radii in heavy ion collisions is presented. The starting point is a longitudinally and transversally expanding fireball, represented at freeze-out by an azimuthally symmetric emission function. The freeze-out temperature is allowed to feature transverse and temporal gradients. Their effects on the corr

P. Coleman, A. M. Tsvelik

We discuss how local moment physics is modified by the presence of interactions in the conduction sea. Interactions in the conduction sea are shown to open up new symmetry channels for the exchange of spin with the localized moment. We illustrate this conclusion in the strong-coupling limit by carrying out a Schrieffer Wolff transformation for a local moment

N. Andrei, P. Coleman, H. Y. Kee, A. M. Tsvelik

We discuss how the properties of a single-channel Kondo lattice model are modified by additional screening channels. Contrary to current wisdom, additional screening channels appear to constitute a relevant perturbation which destabilizes the Fermi liquid. When a heavy Fermi surface develops, it generates zero modes for Kondo singlets to fluctuate between sc

Jose D. Edelstein, Marta L. Trobo, Francisco A. Brito, Dionisio Bazeia

We study a variety of supersymmetric systems describing sixth-order interactions between two coupled real superfields in 2+1 dimensions. We search for BPS domain ribbon solutions describing minimum energy static field configurations that break one half of the supersymmetries. We then use the supersymmetric system to investigate the behavior of mesons and fer

Masafumi Koike, Joe Sato

We examine how large CP- and T-violation effects are allowed in long baseline neutrino experiments with three generations of neutrinos, considering both the solar neutrino deficit and the atmospheric neutrino anomaly. We considerd two cases: When we attribute only the atmospheric neutrino anomaly to neutrino oscillation and assume the constant transition pro

T. R. Kirkpatrick, D. Belitz

Zero-temperature or quantum phase transitions in itinerant electronic systems both with and without quenched disordered are discussed. Phase transitions considered include, the ferromagnetic transition, the antiferromagnetic transition, the superconductor-metal transition, and various metal-insulator transitions. Emphasis is placed on how to determine the un

T. Pellizzari

I propose a scheme which allows for reliable transfer of quantum information between two atoms via an optical fibre in the presence of decoherence. The scheme is based on performing an adiabatic passage through two cavities which remain in their respective vacuum states during the whole operation. The scheme may be useful for networking several ion-trap quan

Roger Picken

(Talk presented at the XVth Workshop on Geometric Methods in Physics, Quantizations, Deformations and Coherent States, in Bialowieza, Poland, July 1-7, 1996.) The aim of this article is to introduce some basic notions of Topological Quantum Field Theory (TQFT) and to consider a modification of TQFT, applicable to embedded manifolds. After an introduction bas

T. H. Baker, P. J. Forrester

The theory of non-symmetric Jack polynomials is developed independently of the theory of symmetric Jack polynomials, and this theory together with the relationship between the non-symmetric, symmetric and anti-symmetric Jack polynomials is used to deduce the corresponding results for the symmetric Jack polynomials.

D. G. Luchinsky, R. S. Maier, R. Mannella, P. V. E. McClintock

We consider noise-driven exit from a domain of attraction in a two-dimensional bistable system lacking detailed balance. Through analog and digital stochastic simulations, we find a theoretically predicted bifurcation of the most probable exit path as the parameters of the system are changed, and a corresponding nonanalyticity of the activation energy. We al

D. Cinabro

Using the silicon strip detector of the CLEO experiment operating at the Cornell Electron-positron Storage Ring (CESR), we have observed that the horizontal size of the luminous region decreases in the presence of the beam-beam interaction from what is expected without the beam-beam interaction. The dependence on the bunch current agrees with the prediction

L. Engvik, M. Hjorth-Jensen, R. Machleidt, H. Muether

We study the symmetry energy in infinite nuclear matter employing a non-relativistic Brueckner-Hartree-Fock approach and using various new nucleon-nucleon (NN) potentials, which fit np and pp scattering data very accurately. The potential models we employ are the recent versions of the Nijmegen group, Nijm-I, Nijm-II and Reid93, the Argonne $V_{18}$ potentia

Laurentiu Paunescu, Alexandru Zaharia

The Lojasiewicz exponent at infinity of an entire function measures of the infimal rate of growth of its gradient. The authors compute the Lojasiewicz exponents at infinity of the 3-variable complex polynomials x - 3 x^{2n+1} y^{2q} + 2 x^{3n+1} y^{3q} + y z

Alexander Fedotov, Frédéric Klopp

This work is devoted to the study of a family of almost periodic one-dimensional Schrödinger equations. We define a monodromy matrix for this family. We study the asymptotic behavior of this matrix in the adiabatic case. Therefore, w develop a complex WKB method for adiabatic perturbations of periodic Schrödinger equations. At last, the study of the monodrom

Xinhui Jiang

Let Z denote the simple limit of prime dimension drop algebras that has a unique tracial state. Let A != 0 be a unital C^*-algebra with A = A tensor Z. Then the homotopy groups of the group U(A) of unitaries in A are stable invariants, namely, π_i(U(A)) = K_{i-1}(A) for all integers i >= 0. Furthermore, A has cancellation for full projections, and satisfies

Jean Taylor

Suppose curves are moving by curvature in a plane, but one embeds the plane in $R^3$ and looks at the plane from an angle. Then circles shrinking to a round point would appear to be ellipses shrinking to an ``elliptical point,'' and the surface energy would appear to be anisotropic as would the mobility. The result of this paper is that if one uses t

Sergei K. Suslov

In a recent paper Ismail, Masson, and Suslov have established a continuous orthogonality relation and some other properties of a $_2φ_1$-Bessel function on a $q$-quadratic grid. Dick Askey suggested that the ``Bessel-type orthogonality'' at the $_2φ_1$-level has really a general character and can be extended up to the $_8φ_7$-level. Very-well-poised

Victor A. Vassiliev

We propose a new method of computing cohomology groups of spaces of knots in $\R^n$, $n \ge 3$, based on the topology of configuration spaces and two-connected graphs, and calculate all such classes of order $\le 3.$ As a byproduct we define the higher indices, which invariants of knots in $\R^3$ define at arbitrary singular knots. More generally, for any fi

H. Pierre Noyes

This paper starts with a personal memoir of how some significant ideas arose and events took place during the period from 1972, when I first encountered Ted Bastin, to 1979, when I proposed the foundation of ANPA. I then discuss program universe, the fine structure paper and its rejection, the quantitative results up to ANPA 17 and take a new look at the han

Luis Alvarez-Gaume, Marcos Marino, Frederic Zamora

We analyze the vacuum structure of N=2, SU(2) QCD with massive quark hypermultiplets, once supersymmetry is softly broken down to N=0 with dilaton and mass spurions. We give general expressions for the low energy couplings of the effective potential in terms of elliptic functions to have a complete numerical control of the model. We study in detail the possi

Yolanda Lozano

We find an eleven dimensional description of the D-2-brane of the massive type IIA theory as a first step towards an understanding of this theory in eleven dimensions. By means of a world-volume IIA/M theory duality transformation we show that the massive D-2-brane is equivalent to the dimensional reduction of the eleven dimensional membrane coupled to an au

A. Patrascioiu, E. Seiler

We comment on the recent paper by Balog and Niedermaier [hep-th/9701156].

Paul Sutcliffe

We review classical BPS monopoles, their moduli spaces, twistor descriptions and dynamics. Particular emphasis is placed upon symmetric monopoles, where recent progress has been made. Some remarks on the role of monopoles in S-duality and Seiberg-Witten theory are also made.

Javier Borlaf

A "reduced" differential geometry adapted to the presence of abelian isometries is constructed.Classical T-duality diagonalizes in this setting, allowing us to get conveniently the transformation of the relevant geometrical objects such as connections, pullbacks and generalized curvatures.Moreover we can induce privileged maps from the viewpoint of t

Alexander A. Vlasov

There are known problems of Lorentz-Dirac equation for moving with acceleration charged particle in classical electrodynamics. The model of extended in one dimension particle is proposed and shown that electromagnetic self-interaction can lead (with appropriate choice of retarded and advanced interactions) to zero change in particle momentum. The hypothesis

Kenichi Konishi, Haruhiko Terao

Several dynamical aspects of the SU(2) Seiberg-Witten models with N_f quark hypermultiplets are explored. We first clarify the meaning of the number of the singularities of the space of vacua. CP invariance of the theories are then studied and periodicities of theories in θwith and without bare quark masses are obtained ((4-N_f)πand π, respectively). CP noni

R. P. Malik, A. K. Mishra, G. Rajasekaran

Dynamics has been generalized to a noncommutative phase space. The noncommuting phase space is taken to be invariant under the quantum group $GL_{q,p}(2)$. The $q$-deformed differential calculus on the phase space is formulated and using this, both the Hamiltonian and Lagrangian forms of dynamics have been constructed. In contrast to earlier forms of $q$-dyn

Tamiaki Yoneya

The purpose of this talk is to review some considerations by the present author on the possible role of a simple space-time uncertainty relation toward nonperturbative string theory. We first motivate the space-time uncertainty relation as a simple space-time characterization of the fundamental string theory. We then argue that the relation captures some of

Seung-geun Lee, Sang-Jin Sin

We study the effect of the solitonic degree of freedom in string cosmology following the line of Rama. The gas of solitonic p-brane is treated as a perfect fluid in a Brans-Dicke type theory. In this paper, we find analytic solutions for a few solvable cases of equation of states with general Brans-Dicke parameter $ω$ and study the cosmology of the solutions

Howard E. Haber

The Higgs sector of the Minimal Supersymmetric Model (MSSM) is a CP-conserving two-Higgs doublet model that depends, at tree-level, on two Higgs sector parameters. In order to accurately determine the phenomenological implications of this model, one must include the effects of radiative corrections. The leading contributions to the one-loop radiative correct

Arjun Berera, Thomas W. Kephart, Marc Sher

An attractive alternative to the standard model of CP violation is the aspon model. In this model, CP is spontaneously broken, automatically solving the strong CP problem. Recently, it has been shown that CP violation in the B system is much smaller in the aspon model than in the standard model. Here we provide a complementary study by considering $K_L\to π^

Lorenz von Smekal, Almut Mecke, Reinhard Alkofer

The pseudo-scalar flavor-singlet meson mixes with two gluons. A dimensional argument by Kogut and Susskind shows that this can screen the Goldstone pole of the chiral limit in this channel, if the gluon correlations are infrared enhanced. Using a gluon propagator as singular as sigma/k^4 for k^2 -> 0 we relate the screening mass to the string tension sigma.

A. Hayashigaki, Y. Kanazawa, Yuji Koike

We present a calculation of the two-loop anomalous dimension for the transversity distribution h_1(x,Q^2), $γ^{h(1)}_n$, in the MS scheme of the dimensional regularization. Due to the chiral-odd nature, h_1 does not mix with the gluon distributions, and thus our result is the same for the flavor-singlet and nonsinglet distributions. At small n (moment of h_1

M. Hirsch, H. V. Klapdor-Kleingrothaus, S. G. Kovalenko

We consider contributions of R-parity conserving softly broken supersymmetry (SUSY) to neutrinoless double beta ($\znbb$) decay via the (B-L)-violating sneutrino mass term. The latter is a generic ingredient of any weak-scale SUSY model with a Majorana neutrino mass. The new R-parity conserving SUSY contributions to $\znbb$ are realized at the level of box d

S. P. Klevansky, R. H. Lemmer

The validity of Weinberg's two sum rules for massless QCD, as well as the six additional sum rules introduced into chiral perturbation theory by Gasser and Leutwyler, are investigated for the extended Nambu-Jona-Lasinio chiral model that includes vector and axial vector degrees of freedom. A detailed analysis of the vector, axial vector and coupled pion

C. D. Froggatt, H. B. Nielsen, D. J. Smith

The multiple point criticality principle is applied to the pure Standard Model (SM), with a desert up to the Planck scale. We are thereby led to impose the constraint that the effective Higgs potential should have two degenerate minima, one of which should have a vacuum expectation value of order unity in Planck units. In this way we predict a top quark mass

I. Antoniadis, K. Benakli

The original paper (hep-th/9209020) contains an early example of gauge mediated supersymmetry breaking motivated by string model building. In this erratum we point out an important misprint in the abstract of the published version (Phys. Lett. B295 (1992) 219) which may confuse the reader. We also correct the computation of scalar masses and the numerical ex

G. Lopez Castro, G. Toledo Sanchez

We consider the effects of anomalous magnetic dipole moments of vector mesons in the decay distribution of photons emitted in two-pseudoscalar decays of charged vector mesons. By choosing a kinematical configuration appropriate to isolate these effects from model-dependent and dominant bremsstrahlung contributions, we show that this method can provide a vali

K. -I. Izawa, M. Kawasaki, T. Yanagida

We point out that for a class of `new inflation' models in supergravity the required initial value of the inflaton field is dynamically set if there is another inflation (`pre-inflation') before the `new inflation'. We study the dynamics of both inflatons by taking a hybrid inflation model for the `pre-inflation' as an example. We find out th

S. Dusini, F. Ferrari, I. Lazzizzera, A. Sartori

We show that neural network classifiers can be helpful in discriminating Higgs production events from the huge background at LHC, assuming the case of a mass value $M_H \sim 200$ GeV. We use the high performance neurochip TOTEM, trained by the Reactive Tabu Search algorithm (RTS), which could be used for on-line purposes. Two different sets of input variable

A. M. Rooke

It has already been shown that the energy flow distributions in tagged events disagree with those predicted by QCD models, generating serious systematic errors in the unfolding of the photon structure function $F_{2}^γ$. This new analysis uses the jet structure in the hadronic final state to identify the class of events which is in worst agreement with the m

J. A. Lauber, L. Lonnblad, M. H. Seymour

Monte Carlo models of DIS e-gamma scattering must describe hard emissions as well as the soft and collinear limits. Comparison with the observed experimental hadronic energy flow has shown that various models underestimate the high-p_T contribution, in particular at low-x. We have attempted to tune the Herwig, Pythia and Ariadne models to improve the agreeme

J. M. Butterworth

The status of HERA data on jet photoproduction is reviewed, and some suggestions and prospects for further work are given.

E. Fabri, R. Giannitrapani

In this short note we briefly review some recent mathematical results relevant to the classical Regge Calculus evolution problem.

S. Ansoldi, A. Aurilia, R. Balbinot, E. Spallucci

We introduce an effective Lagrangian which describes the classical and semiclassical dynamics of spherically symmetric, self-gravitating objects that may populate the Universe at large and small (Planck) scale. These include wormholes, black holes and inflationary bubbles. We speculate that such objects represent some possible modes of fluctuation in the pri

J. Y. Halpern

Starting with a likelihood or preference order on worlds, we extend it to a likelihood ordering on sets of worlds in a natural way, and examine the resulting logic. Lewis earlier considered such a notion of relative likelihood in the context of studying counterfactuals, but he assumed a total preference order on worlds. Complications arise when examining par

T. Drakengren, P. Jonsson

This paper combines two important directions of research in temporal resoning: that of finding maximal tractable subclasses of Allen's interval algebra, and that of reasoning with metric temporal information. Eight new maximal tractable subclasses of Allen's interval algebra are presented, some of them subsuming previously reported tractable algebras

D. L. Mammen, T. Hogg

The easy-hard-easy pattern in the difficulty of combinatorial search problems as constraints are added has been explained as due to a competition between the decrease in number of solutions and increased pruning. We test the generality of this explanation by examining one of its predictions: if the number of solutions is held fixed by the choice of problems,

J. Gaite, J. Margalef-Roig, S. Miret-Artés

We analyze the thermodynamical potential of a lattice gas model with three components and five parameters using the methods of Catastrophe Theory. We find the highest singularity, which has codimension five, and establish its transversality. Hence the corresponding seven-degree Landau potential, the canonical form Wigwam or $A_6$, constitutes the adequate st

S. Drewes, S. R. Renn, F. Guinea

We consider a model for electron tunneling between a pair of ultrasmall metallic grains. Under appropriate circumstances, non-equilibrium final state effects can strongly enhance tunneling and produce electron-hole coherence between the grains. The model displays a quantum phase transition between a Coulomb blockaded state to a coherent state exhibiting subo

Kamal K. Bhattacharya, James P. Sethna

We applied a multicanonical algorithm (entropic sampling) to a two-dimensional and a three-dimensional Lennard-Jones system with quasicrystalline and glassy ground states. Focusing on the ability of the algorithm to locate low lying energy states, we compared the results of the multicanonical simulations with standard Monte Carlo simulated annealing and mole

Hiroshi Kontani, Morio Miyazawa, Kosaku Yamada

In a heavy fermion system, there exists the anomalous Hall effect caused by localized $f$-orbital freedom, in addition to the normal Hall effect due to the Lorentz force. In 1994, we found that the Hall coefficient caused by the anomalous Hall effect ($R_H^{AHE}$) is predominant and the relation $R_H^{AHE} \propto ρ^2$ ($ρ$ is the electrical resistivity) hol

R. Bulla, Th. Pruschke, A. C. Hewson

We use the numerical renormalization group method to study an Anderson impurity in a conduction band with the density of states varying as rho(omega) \propto |omega|^r with r>0. We find two different fixed points: a local-moment fixed point with the impurity effectively decoupled from the band and a strong-coupling fixed point with a partially screened impur

J. L. Lebowitz, A. Mazel, P. Nielaba, L. Samaj

We use Monte Carlo techniques and analytical methods to study the phase diagram of multicomponent Widom-Rowlinson models on a square lattice: there are M species all with the same fugacity z and a nearest neighbor hard core exclusion between unlike particles. Simulations show that for M between two and six there is a direct transition from the gas phase at z

Mark Burgess, Haarek Haugerud, Are Strandlie

We present a generalized framework for cellular/lattice based visualizations in two dimensions based on state of the art computing abstractions. Our implementation takes the form of a library of reusable functions written in C++ which hides complex graphical programming issues from the user and mimics the algebraic structure of physics at the Hamiltonian lev

M. Houbiers, R. Ferwerda, H. T. C. Stoof, W. I. McAlexander

We report on a study of the superfluid state of spin-polarized atomic Li6 confined in a magnetic trap. Density profiles of this degenerate Fermi gas, and the spatial distribution of the BCS order parameter are calculated in the local density approximation. The critical temperature is determined as a function of the number of particles in the trap. Furthermor

B. Eynard

It has been observed that the statistical distribution of the eigenvalues of random matrices possesses universal properties, independent of the probability law of the stochastic matrix. In this article we find the correlation functions of this distribution in two classes of random hermitian matrix models: the one-matrix model, and the two-matrix model, altho

Sang Boo Nam

It is shown that there are three kinds of vortices in a superconductor; a vortex with the fluxoid quantum 1 (VF), a new vortex with 0 (VZF), and a vortex with -1 (VAF), respectively. The Hall field via three vortices is studied and found to change its sign, depending of the relative strength of contributions via VF and VAF, similar to that of a system with t

Franz-Josef Elmer

The dynamical behavior caused by dry friction is studied for a spring-block system pulled with constant velocity over a surface. The dynamical consequences of a general type of phenomenological friction law (stick-time dependent static friction, velocity dependent kinetic friction) are investigated. Three types of motion are possible: Stick-slip motion, cont

Adrienne L. Fairhall, Barak Galanti, Victor S. L'vov, Itamar Procaccia

We present results from direct numerical simulations of the Kraichnan model for passive scalar advection by a rapidly-varying random scaling velocity field for intermediate values of the velocity scaling exponent. These results are compared with the scaling exponents predicted for this model by Kraichnan. Further, we test the recently proposed fusion rules w

D. Mardones, P. C. Myers, M. Tafalla, D. J. Wilner

We report observations of 47 candidate protostars in two optically thick lines (H2CO 212-111 and CS 2-1) and one optically thin line (N2H+ 1-0) using the IRAM 30-m, SEST 15-m, and Haystack 37-m radio telescopes. The sources were selected from the redness of their spectra (Tbol < 200 K) and their near distance (d < 400 pc). Most of the sources have asymmetric

D. Munshi, F. Bernardeau, A. L. Melott, R. Schaeffer

Perturbation Theory (PT) applied to a cosmological density field with Gaussian initial fluctuations suggests a specific hierarchy for the correlation functions when the variance is small. In particular quantitative predictions have been made for the moments and the shape of the one-point probability distribution function (PDF) of the top-hat smoothed density

A. S. Trotter, J. M. Moran, L. J. Greenhill, X. -W. Zheng

We present a parsec-scale image of the OH maser in the nucleus of the active galaxy IIIZw35, made using the Very Long Baseline Array at a wavelength of 18 cm. We detected two distinct components, with a projected separation of 50 pc (for D=110 Mpc) and a separation in Doppler velocity of 70 km/s, which contain 50% of the total maser flux. Velocity gradients

A. Crider, E. P. Liang, I. A. Smith, D. Lin

Using Monte Carlo methods to simulate the inverse Compton scattering of soft photons, we model the spectrum of the Galactic black hole candidate Cyg X-1, which shows evidence of a nonthermal tail extending beyond a few hundred keV. We assume an ad hoc sphere of leptons, whose energy distribution consists of a Maxwellian plus a high energy power-law tail, and

Marc Balcells

I report on the discovery of two faint (~ 26.8 Rmag/arcsec^2) tidal tails around the shell elliptical NGC 3656 (Arp 155). This galaxy had previously been interpreted as a case of accretion, or minor merger. The two tidal tails are inconsistent with a minor merger, and point instead to a disk-disk major merger origin. NGC 3656 extends Toomre&#39;s merger sequ

Andres Meza, Nelson Zamorano

We have investigated the stability of a set of non-rotating anisotropic spherical models with a phase-space distribution function of the Osipkov-Merritt type. The velocity distribution in these models is isotropic near the center and becomes radially anisotropic at large radii. They are special members of the family studied by Dehnen and Tremaine et al. wher

Stefanie Komossa, Henner Fink

We have analyzed survey and pointed \ros PSPC observations of the Seyfert galaxy NGC 3227. Large amplitude X-ray variability is detected, with a factor $\sim$ 15 change in count rate within about 3 years. Smaller changes are seen on the timescale of days, the largest being a factor of 3.5. No strong spectral variability is found throughout the pointed observ

K. Sakurazawa, T. Tanimori, S. A. Dazeley, P. G. Edwards

The CANGAROO experiment has observed gamma-ray above 7TeV from the Crab pulsar/nebula at large zenith angle in Woomera, South Australia. We report the CANGAROO data taken in 1992, 1993 and 1995, from which it appears that the energy spectrum extends at least up to 50 TeV. The observed integral spectrum is (8.4+-1.0) x 10^{-13}(E/7 TeV)^(-1.53+-0.15)cm^{-2}s^

T. Kifune, S. A. Dazeley, P. G. Edwards, T. Hara

We report recent results of the CANGAROO Collaboration on very high energy gamma ray emission from pulsars, their nebulae, SNR and AGN in the southern sky. Observations are made in South Australia using the imaging technique of detecting atmospheric Cerenkov light from gamma rays higher than about 1 TeV. The detected gamma rays are most likely produced by th

Aaron Bertram

This paper has two parts. In the first part, we review stable pairs and triples on curves, leading up to Thaddeus&#39; diagram of flips and contractions starting from the blow-up of projective space along a curve embedded by a complete linear series of the form K + ample. In the second part, we identify log canonical divisors which exhibit Thaddeus&#39; flip

Aaron Bertram

Given an embedded smooth projective variety Y in CP^n, we show how the existence of a hypersurface with high multiplicity along Y, but of relatively low degree and log canonical near Y implies vanishing of higher cohomology for certain twists of powers of the ideal sheaf of Y. This is applied to get rather non-trivial vanishing in case Y is a universal deter