November 1997 arXiv papers — page 11

Sankalpa Ghosh, R. Rajaraman

In this paper we report calculations of some pseudospin textures for bilayer quantum hall systems with filling factor $ ν=1$. The textures we study are isolated single meron solutions. Meron solutions have already been studied at great length by others by minimising the microscopic Hamiltonian between microscopic trial wavefunctions. Our approach is somewhat

Krzysztof Pomorski, Klaus Dietrich

We investigate the existence of stable charged metallic bubbles using the shell correction method. We find that for a given mesoscopic system of n atoms of a given metal and q less n (positive) elementary charges, a metallic bubble turns out to have a lower total energy than a compact spherical cluster, whenever the charge number q is larger than acritical c

J. -P. Bouchaud, P. Claudin, M. E. Cates, J. P. Wittmer

Stress patterns in static granular media exhibit unusual features when compared to either liquids or elastic solids. Qualitatively, we attribute these features to the presence of `stress paths', whose geometry depends on the construction history and controls the propagation of stresses. Stress paths can cause random focussing of stresses (large fluctuati

P. Claudin, J. -P. Bouchaud

In this paper we propose an extension of the model of Liu, Coppersmith et al., in order to allow for arch formation. This extended model qualitatively captures interesting properties of granular materials due to fluctuations of stress paths, such as stress fluctuations and stick-slip motion.

Marti Pi, Manuel Barranco, Agusti Emperador, Enrico Lipparini

Within Current Density Functional Theory, we have studied a quantum dot made of 210 electrons confined in a disk geometry. The ground state of this large dot exhibits some features as a function of the magnetic field (B) that can be attributed in a clear way to the formation of compressible and incompressible states of the system. The orbital and spin angula

Muktish Acharyya

The dynamical hysteresis is studied in the kinetic Ising model in the presence of a sinusoidal magnetic field both by Monte Carlo simulation and by solving the dynamical meanfield equation for the averaged magnetisation. The frequency variations of the dynamic coercive field are studied below the critical temperature. In both the cases, it shows a power law

Pablo Jensen, Bernd Niemeyer

Thin films are usually obtained by depositing atoms with a continuous flux. We show that using a chopped flux changes the growth and the morphology of the film. A simple scaling analysis predicts how the island densities change as a function of the frequency of the chopped flux in simple cases where aggregation is irreversible. These predictions are confirme

Pablo Jensen, Hernán Larralde, Muriel Meunier, Alberto Pimpinelli

We perform a comprehensive study of the formation of three dimensional (pyramidal) structures in a large range of conditions, including the possible evaporation of adatoms from the surface and the presence of surface defects. We compare our computer simulations to theoretical calculations of the growth and find good agreement between them. This work clarifie

W. H. Lee, W. Kluzniak

We present the results of hydrodynamic (SPH) simulations showing the coalescence of a black hole with a neutron star to be a promising theoretical source of short duration gamma-ray bursts. The favorable features of the process include rapid onset, millisecond variability, a duration much longer than the dynamical timescale, and a range of outcomes sufficien

Paul J. Groot, T. Galama, J. van Paradijs, C. Kouveliotou

We report on the results of R band observations of the error box of the gamma-ray burst of August 28, 1997, made between 4 hours and 8 days after this burst occurred. No counterpart was found varying by more than 0.2 magnitudes down to R = 23.8. We discuss the consequences of this non-detection for relativistic blast wave models of gamma-ray bursts, and the

H. S. Park, E. Ables, D. L. Band, S. D. Barthelmy

We are constructing a 0.6 meter telescope system to search for early time gamma-ray burst(GRB) optical counterparts. Super-LOTIS (Super-Livermore Optical Transient Imaging System) is an automated telescope system that has a 0.8 x 0.8 deg field-of-view, is sensitive to Mv ~ 19 and responds to a burst trigger within 5 min. This telescope will record images of

Henning Heiselberg, Sangyong Jeon, Larry McLerran, Hua-Bin Tang

We discuss the possibility that the sources for gamma ray bursts are hot neutron stars at cosmological distance scales. The temperature of such stars would be $T \sim 1 \MeV$. Such hot stars can produce an electromagnetic blast wave provided that the ratio of baryon and photon numbers $N_{B}/N_γ \le 10^{-6}$. The typical time scale for such blasts, the total

Wei Cui, Wan Chen, S. N. Zhang

It has been a long-standing puzzle what triggers the spectral transition between the hard and soft states in Cyg X-1. Also, the origin of the frequently observed X-ray flares in the source still remains a mystery. In this paper, we will make an attempt to address these issues in light of our recent work on black hole spin and its observational consequences.

Ann A. Esin, Ramesh Narayan, Wei Cui, J. Eric Grove

We show that the model proposed by Esin, McClintock & Narayan (1997) for the low state, intermediate state and high state of the black hole soft X-ray transient, Nova Muscae 1991, is consistent with the spectral evolution of the black hole X-ray binary, Cyg X-1, during the hard-to-soft state transition observed in 1996. We also apply the model to the outburs

Wei Cui, S. N. Zhang, J. H. Swank, X. -M. Hua

We summarize recent observations of Cyg X-1 during its 1996 state transition. The results favor an emission geometry with a central optically thin corona surrounded by an optically thick, geometrically thin accretion disk. As the soft state is approached, the inner edge of the disk moves closer to the black hole, and the corona shrinks, perhaps due to more e

Duncan Forbes

Understanding the formation of globular clusters will help us to constrain the evolutionary history of galaxies. For mergers on-going today, it appears that the number of newly created proto-globulars varies with the progenitor types and that the percentage increase in the total cluster population is 100% or less. Elliptical galaxies, which are generally tho

Wei Cui, K. Ebisawa, T. Dotani, A. Kubota

We report results from simultaneous ASCA and RXTE observations of Cyg X-1 when the source made a rare transition from the hard (= low) state to the soft (= high) state in 1996. These observations together cover a broad energy range ~0.7--50 keV with a moderate energy resolution at the iron K-band, thus make it possible to disentangle various spectral compone

V. S. Dhillon

We review infrared (1-2.5 microns) observations of cataclysmic variables, a relatively unexplored part of the spectrum in which the dominant sources of emission are the secondary star, the outer regions of the accretion disc and the accretion column in magnetic systems. We describe the advances that have been made in our understanding of cataclysmic variable

Elcio Abdalla, Roya Mohayaee

It is shown that density fluctuations obey a scaling law in an open Friedmann universe. In a flat universe, the fluctuations are not scale-invariant. We compute the growth rate of adiabatic scale-invariant density fluctuations in flat, open and inflationary universes. We find that, given a sufficiently long time, the density perturbations decay away in the E

A. D. Challinor, A. N. Lasenby

We present an extension of the Kompaneets equation which allows relativistic effects to be included to any desired order. Using this, we are able to obtain simple analytic forms for the spectral changes due to the Sunyaev-Zel'dovich effect in hot clusters, correct to first and second order in the expansion parameter theta_e=k_B T_e/m c^2. These analytic

D. Syer, Shude Mao, H. J. Mo

We examine the global stability of an exponential stellar disk embedded in a dark matter halo and constrain the mass-to-light ratio of observed disks in the I-band, Y_I. Assuming only that the radial surface density distribution of disks is exponential, we derive an analytic upper limit: Y_I <~ 2.4h, for a Hubble constant of 100h~\kms\mpc^{-1}. Using N-body

S. Cristiani, S. D&#39;Odorico, V. D&#39;Odorico, A. Fontana

The observed clustering of Lyman-$α$ lines is reviewed and compared with the clustering of CIV systems. We argue that a continuity of properties exists between Lyman-$α$ and metal systems and show that the small-scale clustering of the absorbers is consistent with a scenario of gravitationally induced correlations. At large scales statistically significant o

W. N. Brandt, Th. Boller

We describe how recent X-ray surveys have led to advances in the understanding of ultrasoft narrow-line Seyfert 1 galaxies. The number of known ultrasoft narrow-line Seyfert 1s has increased greatly in recent years due to X-ray surveys, and it is now possible to obtain high quality 0.1--10 keV spectral and variability measurements for a large number of these

Rob P. Olling, Michael R. Merrifield

The local stellar kinematics of the Milky Way, parameterized by the Oort constants A and B, depend on the local gradient of the rotation curve, its absolute value (Theta_0), and the distance to the Galactic center (R_0). The surface density of interstellar gas in the Milky Way varies non-monotonically with radius, and so contributes significantly to the loca

M. Hattori

Looking for and studying very distant galaxy clusters, clusters at z>1, are one of the prime subjects of the modern observational cosmology. If the metallicity of the hot intra-cluster medium in very distant galaxy clusters is measured for example, it provides fruitful informations for us to understand the formation and evolution of galaxies. However, diffic

G. G. Williams, H. S. Park, E. Ables, D. L. Band

LOTIS (Livermore Optical Transient Imaging System) is a gamma-ray burst optical counterpart search experiment located near Lawrence Livermore National Laboratory in California. The system is linked to the GCN (GRB Coordinates Network) real-time coordinate distribution network and can respond to a burst trigger in 6-15 seconds. LOTIS has a total field-of-view

O. Almaini, T. Shanks, B. J. Boyle, I. Georgantopoulos

We summarise our recent work on the faint galaxy contribution to the cosmic X-ray background (XRB). At bright X-ray fluxes (in the ROSAT pass band), broad line QSOs dominate the X-ray source population, but at fainter fluxes there is evidence for a significant contribution from emission-line galaxies. Here we present statistical evidence that these galaxies

I. F. Mirabel, V. Dhawan, S. Chaty, L. F. Rodriguez

We report simultaneous observations in the X-ray, infrared, and radio wavelengths of the galactic superluminal source GRS 1915+105. During episodes of rapid disappearance and follow up replenishment of the inner accretion disk evidenced by the X-ray oscillating flux, we observe the ejection of relativistic plasma clouds in the form of synchrotron flares at i

B. Russo, M. Teixidor i Bigas

Let C be a projective smooth curve of genus g> 1. Let E be a vector bundle of rank r on C. For each integer r&#39;<r, associate to E the invariant s_{r&#39;}(E)=r&#39;deg(E)-rdeg(E&#39;) where E&#39;is a subbundle of E of rank r&#39; and maximal degree. For every r&#39;, one can stratify the moduli space of stable vector bundles according to the value of the

Sean M. Carroll, Mark Trodden

We propose a class of field theories featuring solitonic solutions in which topological defects can end when they intersect other defects of equal or higher dimensionality. Such configurations may be termed ``Dirichlet topological defects&#39;&#39;, in analogy with the D-branes of string theory. Our discussion focuses on defects in scalar field theories with

B. Alles, M. D&#39;Elia, A. Di Giacomo, R. Kirchner

A detailed comparison is made between the field-theoretic and geometric definitions of topological charge density on the lattice. Their renormalizations with respect to continuum are analysed. The definition of the topological susceptibility, as used in chiral Ward identities, is reviewed. After performing the subtractions required by it, the different latti

A. A. Likhoded, G. Valencia, O. P. Yushchenko

We study the sensitivity of a 500 GeV $e^+e^-$ Linear Collider to $CP$ violating anomalous couplings. We find that with 50~fb$^{-1}$, and taking only one non-zero coupling at a time, the process $e^+e^-\to W^+ W^-$ can be used to place the 95% confidence level bounds $|\tildeκ_γ|\leq0.1$, $|\tildeκ_Z|\leq 0.1$ and $|g_4^Z|\leq 0.1$ from CP even observables.

Jean Letessier, Jan Rafelski, Ahmed Tounsi

Imposing an equilibrium between the thermal pressure of deconfined quarks and gluons and the dynamical compression pressure exercised by in-flowing nuclear matter, we study the initial thermal conditions reached in a quark-gluon plasma fireball formed in a relativistic heavy ion collision. We show that entropy is produced primarily in the pre-equilibrium sta

K. Bora, R. L. Jaffe

We study the tensor structure function $b_1\xq$ in deep inelastic scattering (DIS) of an electron from a polarized deuteron target. We model the electron-nucleon cross section at the starting point for $Q^2$ evolution by vector-meson-dominance (VMD). Shadowing due to the double-scattering of vector mesons, along with the presence of a d-state admixture in gr

W. Hollik, J. I. Illana, S. Rigolin, D. Stoeckinger

A minimal supersymmetric version of the Standard Model with complex parameters allows contributions to the weak-electric dipole moments of fermions at the one-loop level. Assuming generation-diagonal trilinear soft-susy-breaking terms and the usual GUT constraint, a set of CP-violating physical phases can be introduced. In this paper the general expressions

Jean Letessier, Jan Rafelski, Ahmed Tounsi

We study the chemical conditions at freeze-out associated with the production of strange-particles in Si-Au collisions at 14.6 GeV A. We obtain freeze-out chemical potentials and temperature, and determine the entropy as well as the final particle abundance. We also consider in detail the alternative evolution scenarios involving the hadronic gas and the dec

Poul H. Damgaard, Shinsuke M. Nishigaki

Based on random matrix theory in the unitary ensemble, we derive the double-microscopic massive spectral correlators corresponding to the Dirac operator of QCD_3 with an even number of fermions N_f. We prove that these spectral correlators are universal, and demonstrate that they satisfy exact massive spectral sum rules of QCD_3 in a phase where flavor symme

S. Pastor, V. B. Semikoz, J. W. F. Valle

We consider the sensitivity of future neutrino experiments in the low energy region, such as BOREXINO or HELLAZ, to a solar electron antineutrino signal. We show that, if neutrino conversions within the Sun result in partial polarization of initial solar neutrino fluxes, then a new opportunity arises to observe the electron antineutrinos and thus to probe th

Attilio Cucchieri

We study numerically the so-called fundamental modular region Lambda, a region free of Gribov copies, in the minimal Landau gauge for pure SU(2) lattice gauge theory. To this end we evaluate the influence of Gribov copies on several quantities --- such as the smallest eigenvalue of the Faddeev-Popov matrix, the third and the fourth derivatives of the minimiz

K. Belczynski, J. Mikolajewska

The amplitude of the ellipsoidal variability, the mass function, and the evolutionary limits on the component masses have been used to constrain the binary system parameters. Contrary to all previous studies, our analysis shows that the mass ratio of T CrB q(M_giant/M_hot)=0.6, which implies a low mass binary system, with the stellar masses M_giant=0.7 solar

Tomomi Muto

We consider D-branes on an orbifold $C^3/Z_n$ and investigate the moduli space of the D-brane world-volume gauge theory by using toric geometry and gauged linear sigma models. For $n=11$, we find that there are five phases, which are topologically distinct and connected by flops to each other. We also verify that non-geometric phases are projected out for $n

S. Keller, J. Womersley

We explore the ability of the Large Hadron Collider to measure the mass of the W boson. We believe that a precision better than 15 MeV could be attained, based on a year of operation at low luminosity (10^{33} cm^-2 s^-1). If this is true, this measurement will be the world&#39;s best determination of the W mass

N Linden, S Popescu

We build, using group-theoretic methods, a general framework for approaching multi-particle entanglement. As far as entanglement is concerned, two states of n spin-1/2 particles are equivalent if they are on the same orbit of the group of local rotations (U(2)^n). We give a method for finding the number of parameters needed to describe inequivalent n spin-1/

Michael Martin Nieto

The time evolution of even and odd squeezed states, as well as that of squeezed number states, has been given in simple, analytic form. This follows experimental work on trapped ions which has demonstrated even and odd coherent states, number states, and squeezed (but not displaced) ground states. We review this situation and consider the extension to even a

Anatol N. Kirillov, Atsuo Kuniba, Tomoki Nakanishi

The spectral decomposition of the path space of the vertex model associated to the level $l$ representation of the quantized affine algebra $U_q(\hat{sl}_n)$ is studied. The spectrum and its degeneracy are parametrized by skew Young diagrams and what we call nonmovable tableaux on them, respectively. As a result we obtain the characters for the degeneracy of

M. Blaauboer, A. E. Kozhekin, A. G. Kofman, G. Kurizki

We theoretically analyze wave packet transmission through a phase-conjugating mirror and show that the transmission of a suitably chosen input pulse is superluminal, i.e. the peak of the pulse emerges from the mirror before the time it takes to travel the same distance in vacuum. This pulse reshaping effect can be attributed directly to the dispersion relati

P. Navratil, B. R. Barrett

We use Faddeev&#39;s decomposition to solve the shell-model problem for three nucleons. The dependence on harmonic-oscillator excitations allowed in the model space, up to $32 \hbarΩ$ in the present calculations, and on the harmonic-oscillator frequency is studied. Effective interactions derived from Nijmegen II and Reid93 potentials are used in the calculat

Xin-Nian Wang

Hard QCD processes in ultrarelativistic heavy-ion collisions become increasingly relevant and they can be used as probes of the dense matter formed during the violent scatterings. We will discuss how one can use these hard probes to study the properties of the dense matter and the associated phenomenologies. In particular, we study the effect of jet quenchin

Jean-Yves Ollitrault

Azimuthal distributions of particles produced in nucleus-nucleus collisions are measured with respect to an estimated reaction plane which, because of finite multiplicity fluctuations, differs in general from the true reaction plane. It follows that the measured distributions do not coincide with the true ones. I propose a general method of reconstructing th

O. Bergman, M. R. Gaberdiel, G. Lifschytz

The BPS spectrum of type I&#39; string theory in a generic background is derived using the duality with the nine-dimensional heterotic string theory with Wilson lines. It is shown that the corresponding mass formula has a natural interpretation in terms of type I&#39;, and it is demonstrated that the relevant states in type I&#39; preserve supersymmetry. By

M. Asorey, F. Falceto

We show that the vacuum functional of 3+1 dimensional non-abelian gauge theories vanishes for some classical field configurations $ψ_0(A)=0$ when the coefficient of the CP violating $θ$--term becomes $θ=π$ (mod. $2π$). Some of these classical configurations are explicitly identified and include sphalerons. The results shed new light into the non-perturbative

Keshav Dasgupta, Sunil Mukhi

We study BPS-saturated classical solutions for the world-sheet theory of a D-string in the presence of a point charge. These solutions are interpreted as describing planar 3-string junctions, which arise because the original D-string is deformed by the presence of the inserted charge. We compute the angles of the junctions and show that the vector sum of str

M. Cadoni

We study the BPS black hole solutions of the (truncated) action for heterotic string theory compactified on a six-torus. The O(3,Z) duality symmetry of the theory, together with the bound state interpretation of extreme black holes, is used to generate the whole spectrum of the solutions. The corresponding spacetime structures, written in terms of the string

Yong-Wan Kim, Young-Jai Park, K. D. Rothe

Following systematically the generalized Hamiltonian approach of Batalin, Fradkin and Tyutin (BFT), we embed the second-class non-abelian SU(2) Higgs model in the unitary gauge into a gauge invariant theory. The strongly involutive Hamiltonian and constraints are obtained as an infinite power series in the auxiliary fields. Furthermore, comparing these resul

Ling-Lie Chau, Oleg Zaboronsky

We study the structure of the normal matrix model (NMM). We show that all correlation functions of the model with axially symmetric potentials can be expressed in terms of holomorphic functions of one variable. This observation is used to demonstrate the exact solvability of the model. The two-point correlation function is calculated in the scaling limit by

V. Barger, Chung Kao

The prospects at the CERN LHC are investigated for the discovery via decays into muon pairs of neutral Higgs bosons in the minimal supergravity model. Promising results are found for the CP-odd pseudoscalar ($A^0$) and the heavier CP-even scalar ($H^0$) Higgs bosons at large $\tanβ\equiv v_2/v_1$. For $\tanβ\agt 10$ and 100 GeV $\alt m_A,m_H \alt$ 550 GeV, t

K. G. Chetyrkin, A. H. Hoang, J. H. Kühn, M. Steinhauser

Recent analytical and numerical results for the three-loop polarization function allow to present a phenomenological analysis of the cross section for massive quark production in electron positron annihilation to order $α_s^2$. Numerical predictions based on fixed order perturbation theory are presented for charm and bottom production above 5 and 11.5 GeV, r

Bo-Qiang Ma, Ivan Schmidt

Two new sum rules for the quark tensor charges of the nucleon are proposed, based on a relation connecting the quark transversity distributions to the quark helicity distributions and the quark model spin distributions, and on the sum rules for the quark helicity distributions. The two sum rules are useful for an estimate of the values of the quark tensor ch

V. A. Petrov, A. V. Prokudin

It is demonstrated that the &#34;soft pomeron&#34; (together with a secondary reggeon) describing cross-sections of hadron-hadron collisions is fairly able to describe the energy dependence of cross-sections of exclusive (virtual) photoproduction of vector mesons $(ρ^0, ϕ, J/ψ)$ obtained at HERA. However these poles are insufficient for description of the to

V. V. Anisovich, Yu. D. Prokoshkin, A. A. Kondashov, S. A. Sadovsky

We perform the K-matrix analysis of meson partial waves with IJ^{PC} =00^{++}, 10^{++}, 02^{++}, 12^{++} basing on GAMS data on π^-p -> π^0π^0 n, ηηn, ηη&#39; n together with BNL data on π^-p -> K\bar K n and Crystal Barrel data on p\bar p (at rest) -> π^0π^0π^0, π^0ηη, π^0π^0η. The positions of the amplitude poles (physical resonances) are determined as wel

T. Binoth, A. Ghinculov, J. J. van der Bij

We present the result of a calculation of the next-to-leading correction to the Higgs propagator in the 1/N expansion, where the Higgs sector is treated as an O(N) symmetric sigma-model. The results are compared with two-loop perturbation theory. The existing discrepancy between the lowest order of the 1/N expansion and perturbation theory is dramatically re

Bing An Li

A new dynamical symmetry breaking of $SU(2)_{L}\times U(1)$ caused by the combination of the axial-vector component and the fermion mass is found in electroweak theory. We obtain (m^{2}_{W}={1/2}g^{2}m^{2}_{t}) and (m^{2}_{Z}=ρm^{2}_{W}/cos^{2}θ_{W}) with (ρ\simeq 1), (G_{F}={1/2 \sqrt{2}m^{2}_{t}})}}). Two fixed gauge fixing terms for W and Z boson fields a

Amand Faessler, Sergey Kovalenko, Fedor Simkovic, Joerg Schwieger

We examine the pion exchange mode of neutrinoless double beta decay induced by the R-parity violating quark-lepton operators of the supersymmetric (SUSY) extensions of the standard model of the electroweak interactions. The corresponding nuclear matrix elements are evaluated within the renormalized quasiparticle random phase approximation with proton-neutron

D. Schildknecht

We review the empirical evidence for the validity of the Standard Electroweak Theory in Nature. The experimental data are interpreted in terms of an effective Lagrangian for Z physics, allowing for potential sources of SU(2) violation and containing the predictions of the Standard Electroweak Theory as a special case. Particular emphasis is put on discrimina

Stephen C. Davis, Anne C. Davis, Mark Trodden

We investigate the microphysics of cosmic strings in Nonabelian gauge theories with N=1 supersymmetry. We give the vortex solutions in a specific example and demonstrate that fermionic superconductivity arises because of the couplings and interactions dictated by supersymmetry. We then use supersymmetry transformations to obtain the relevant fermionic zero m

Jean Letessier, Jan Rafelski, Ahmed Tounsi

We study as function of the collision energy and stopping the thermal conditions reached in a quark-gluon plasma fireball formed in a relativistic heavy ion collision. We explore strange particle yields for the current round of Pb-Pb and Au-Au experiments.

S. M. Bilenky, C. Giunti, W. Grimus

We show that the existing neutrino oscillation data are in favour of the schemes with mixing of four massive neutrinos and that only two of these schemes, with two pairs of neutrinos with close masses separated by a gap of about 1 eV, are compatible with all data. Possible implications of these schemes for future experiments are discussed.

Chao-Hsi Chang, Hui-Shi Dong, Xi-Chen Feng, Xue-Qian Li

To describe possible effects of medium, besides the hamiltonian introduced by Mikheev, Smirnov and Wolfenstein (MSW), in principle, there may exist new terms in the evolution equation for the neutrino oscillation due to the environment. Considering a two-energy-level quantum system: $ν_1-ν_2$, two-species neutrino system which is embedded in a matter environ

G. Boyd, B. Alles, M. D&#39;Elia, A. Di Giacomo

Topology on the lattice is reviewed. In quenched QCD topological susceptibility chi is fully understood. The Witten-Veneziano mechanism for the eta&#39; mass is confirmed. The topological susceptibility drops to zero at the deconfining phase transition. Preliminary results are also presented for chi and chi&#39; in full QCD, and for the spin content of the p

Tereza Mendes

We report the results of our quenched lattice simulations of the Wilson action with a nonperturbatively determined clover term at beta=6.2 and compare them with those of the standard Wilson action at the same beta value.

M. Laine, O. Philipsen

Gauge-invariant non-local scalar and field strength operators have been argued to have significance, e.g., as a way to determine the behaviour of the screened static potential at large distances, as order parameters for confinement, as input parameters in models of confinement, and as gauge-invariant definitions of light constituent masses in bound state sys

JLQCD Collaboration, S. Aoki, M. Fukugita, S. Hashimoto

We present our study of the dependence of the heavy-to-light semileptonic B decay form factors on the heavy-light meson mass $M_{PS}$. Simulations are made over a range of the heavy quark mass covering both the charm and bottom quarks using the $O(a)$-improved clover action at $β=5.9$ on a $16^3\times 40$ and $24^3\times 64$ lattice. We find that a weak depe

Gabriele Gionti

We discuss the elongated phase of 4D simplicial quantum gravity by exploiting recent analytical results. In particular using Walkup&#39;s theorem we prove that the dominating configurations in the elongated phase are tree-like structures called &#34;stacked spheres&#34;. Such configurations can be mapped into branched polymers and baby universes arguments ar

C. Adloff

A thrust analysis of Large-Rapidity-Gap events in deep-inelastic ep collisions is presented, using data taken with the H1 detector at HERA in 1994. The average thrust of the final states X, which emerge from the dissociation of virtual photons in the range 10 < Q2 < 100 GeV2, grows with hadronic mass M_X and implies a dominant 2-jet topology. Thrust is found

Jean-Pierre De Villiers, Valeri P. Frolov

The gravitational interaction of an infinitely long cosmic string with a Schwarzschild black hole is studied. We consider a straight string that is initially at a great distance and moving at some initial velocity v (0 < v < c) towards the black hole. The equations of motion of the string are solved numerically to obtain the dependence of the capture impact

Rodrigo M Aros, Nelson Zamorano

We study a solution of Einstein&#39;s equations that describes a straight cosmic string with a variable angular deficit, starting with a $2 π$ deficit at the core. We show that the coordinate singularity associated to this defect can be interpreted as a traversible wormhole lodging at the the core of the string. A negative energy density gradually decreases

G. Sardanashvily

Every Dirac spin structure on a world manifold is associated with a certain gravitational field, and is not preserved under general covariant transformations. We construct a composite spinor bundle such that any Dirac spin structure is its subbundle, and this bundle admits general covariant transformations.

Dmitriy S. Kalyuzhniy

The theorem on the existence of three commuting contractions on a Hilbert space and of a linear homogeneous matrix function of three independent variables for which the generalized von Neumann inequality fails is proved.

Mark Friesen, Paul Muzikar

Recent theoretical work has derived the correct form of the Ginzburg-Landau differential equations, for the superconducting order parameter and vector potential, in the presence of a small defect. Here, these equations are applied to the case of a single vortex line pinned on such a defect. We develop the coupled set of partial differential equations, and sh

C. Pryor, J. Kim, L. W. Wang, A. J. Williamson

The electronic structure of interfaces between lattice-mismatched semiconductor is sensitive to the strain. We compare two approaches for calculating such inhomogeneous strain -- continuum elasticity (CE, treated as a finite difference problem) and atomistic elasticity (AE). While for small strain the two methods must agree, for the large strains that exist

M. Guerrero, J. E. Gubernatis, Shiwei Zhang

We simulated the 3-band Hubbard model using the Constrained Path Monte Carlo (CPMC) method in search for a possible superconducting ground state. The CPMC is a ground state method which is free of the exponential scaling of computing time with system size. We calculated the binding energy of a pair of holes for systems up to $6 \times 4$ unit cells. We also

G. Chaboussant, Y. Fagot-Revurat, M. -H. Julien, M. E. Hanson

We present an extensive NMR study of the spin-1/2 antiferromagnetic Heisenberg ladder Cu2(C5H12N2)2Cl4 in a magnetic field range 4.5 - 16.7 T. By measuring the proton NMR relaxation rate 1/T_1 and varying the magnetic field around the critical field H_c1 = Delta / gμ_B = 7.5 T, we have studied the transition from a gapped spin liquid ground state to a gaples

David Hanon, Jean Pierre Boon

We present an analysis of diffusion in terms of the spontaneous density fluctuations in a non-thermal two-species fluid modeled by a lattice gas automaton. The power spectrum of the density correlation function is computed with statistical mechanical methods, analytically in the hydrodynamic limit, and numerically from a Boltzmann expression for shorter time

Giorgio Parisi, Federico Ricci-Tersenghi, Juan J. Ruiz-Lorenzo

We study the four dimensional Gaussian spin glass in presence of a magnetic field. Using off-equilibrium numerical simulations we have found that the probability distribution of the overlaps is built in the same way as that of the Mean Field approximation with replica symmetry breaking. Finally we have studied the violation of the fluctuation-dissipation the

P. Link, I. N. Goncharenko, J. -M. Mignot, T. Matsumura

Neutron diffraction experiments on TmTe at pressures up to 7 GPa are reported. The semiconductor-to-metal transition occurring at 2 GPa in this compound is accompanied by the appearance of strong ferromagnetic exchange interactions producing a Curie temperature as high as 14 K. This behavior is characteristic for the incipient mixed-valence regime just above

Thomas J. Pollehn, Arno Schindlmayr, R. W. Godby

We investigate the performance of the GW approximation by comparison to exact results for small model systems. The role of the chemical potentials in Dyson&#39;s equation as well as the consequences of numerical resonance broadening are examined, and we show how a proper treatment can improve computational implementations of many-body perturbation theory in

J. -Q. Liang, H. J. W. Mueller-Kirsten, A. V. Shurgaia, F. Zimmerschied

The tunneling splitting of the energy levels of a ferromagnetic particle in the presence of an applied magnetic field - previously derived only for the ground state with the path integral method - is obtained in a simple way from Schroedinger theory. The origin of the factors entering the result is clearly understood, in particular the effect of the asymmetr

Sudhansu S. Mandal, Muktish Acharyya

We have studied the integer quantum Hall effect at finite temperatures by diagonalizing a single body tight binding model Hamiltonian including Aharonov-Bohm phase. We have studied the energy dependence of the specific heat and the Hall conductivity at a given temperature. The specific heat shows a sharp peak between two consecutive Hall plateaus. At very lo

D. Scalapino, Shou-Cheng Zhang, W. Hanke

We construct an SO(5) symmetric electron model on a two-chain ladder with purely local interactions on a rung. The ground state phase diagram of this model is determined in the strong-coupling limit. The relationship between the spin-gap magnon mode of the spin-gap insulator and the $π$ resonance mode of the d-wave pairing phase is discussed. We also present

A. S. Moskvin, A. S. Ovchinnikov

High-$T_c$ cuprates like $La_{2-x}Sr_{x}CuO_{4}$ and $YBa_{2-x}Cu_{3}O_{6+x}$ are considered as a system of the electron and hole polar pseudo-Jahn-Teller $CuO_{4}$ centers $[{CuO}_{4}^{7-}]_{JT}$ and $[CuO_{4}^{5-}]_{JT}$, respectively, or a system of the local bosons moving in a lattice of the hole centers. Ground manifold of the polar centers includes thr

M. Hilke, J. C. Flores, F. Dominguez-Adame

There are no periodic wave-functions in the RDM but close to the critical energies there exist periodic envelopes. These envelopes are given by the non-disordered properties of the system.

A. Zee

There has been much recent work on the spectrum of the random non-hermitean Hamiltonian which models the physics of vortex line pinning in superconductors. This note is loosely based on the talk I gave at the conference &#34;New Directions in Statistical Physics&#34; held in Taipei, August 1997. We describe here new results in spatial dimensions higher than

Jakub Zakrzewski, Dominique Delande, Andreas Buchleitner

A simple example of quantum transport in a classically chaotic system is studied. It consists in a single state lying on a regular island (a stable primary resonance island) which may tunnel into a chaotic sea and further escape to infinity via chaotic diffusion. The specific system is realistic : it is the hydrogen atom exposed to either linearly or circula

Wolfram Just

A simple construction is presented, which generalises piecewise linear one-dimensional Markov maps to an arbitrary number of dimensions. The corresponding coupled map lattice, known as a simplicial mapping in the mathematical literature, allows for an analytical investigation. Especially the spin Hamiltonian, which is generated by the symbolic dynamics is ac

R. D. Preece, G. N. Pendleton, M. S. Briggs, R. S. Mallozzi

We report on the temporal behavior of the high-energy power law continuum component of gamma-ray burst spectra with data obtained by the Burst and Transient Source Experiment. We have selected 126 high fluence and high flux bursts from the beginning of the mission up until the present. Much of the data were obtained with the Large Area Detectors, which have

L. Drissen, M. M. Shara

We report the discovery of a variable blue straggler in the core of the globular cluster M5, based on a 12-hour long series of images obtained with the Planetary Camera aboard the Hubble Space Telescope. In addition, we present the light curves of 28 previously unknown or poorly studied large-amplitude variable stars (all but one are RR Lyrae) in the cluster

H. Wozniak, D. Friedli, L. Martinet, D. Pfenniger

We present ISOCAM images (1.5&#34;/px) in the LW2 (6.75 microns) and LW3 (15 microns) broad band filters of the circumnuclear starburst of NGC 4321 (M 100). A detailed comparison with the emission at other wavelengths (U, B, Halpha, and CO) is also presented. The nature and intensity of the mid-infrared emission is shown to be remarkably different from one s

L. Amendola, H. Di Nella, M. Montuori, F. Sylos Labini

We present the statistical properties of large scale galaxy distribution in the LEDA redshift database. This catalog contains more than 40,000 redshifts over all the sky. We find that LEDA, although seriously affected by incompleteness, shows quite stable statistical properties. In particular, we have considered the behaviour of the two points correlation fu

D. Lennon, S. Mao, J. Reetz, T. Gehren

We describe a real-time spectroscopic program to observe bright gravitational microlensing events toward the Galactic Bulge. The program is carried out using the NTT at ESO. We present the preliminary analysis of the microlensing events we have observed thus far. We demonstrate that these data provide detailed information on the intrinsic properties of the s

G. Malaguti, G. G. C. Palumbo, M. Cappi, A. Comastri

The Seyfert 2 galaxy NGC 7674 has been observed within the BeppoSAX Core Programme with the onboard narrow field instruments between 0.1 and 100 keV. The broad-band spectrum shows four most relevant spectral components: a) a soft excess below ~2 keV; b) a prominent (EW~1 keV) Fe line; c) a flat (Gamma~1.1) 2-10 keV continuum; d) a 4.5sigma detection above 13