September 1997 arXiv papers — page 16

Dario Vretenar, Peter Ring, Georgios A. Lalazissis, Wolfgang Poeschl

Isoscalar and isovector monopole oscillations that correspond to giant resonances in spherical nuclei are described in the framework of time-dependent relativistic mean-field theory. Time-dependent and self-consistent calculations that reproduce experimental data on monopole resonances in 208Pb, show that the motion of the collective coordinate is regular fo

S. Abbas, A. Abbas, S. Mohanty

Dark matter capture and annihilation in planets and their satellites, in addition to producing neutrinos (already the basis of several ongoing experiments), is shown to lead to more significant heat generation in these bodies for a uniform dark matter halo. This thermal output becomes more prominent when clumped dark matter passes through the solar system. T

S. A. Ramsey, B. L. Hu, A. M. Stylianopoulos

We present a detailed and systematic analysis of the coarse-grained, nonequilibrium dynamics of a scalar inflaton field coupled to a fermion field in the latter stages of the reheating period of inflationary cosmology. We derive coupled nonperturbative equations for the inflaton mean field and variance at two loops in a general curved spacetime, and show tha

Zhi-zhong Xing

We make an analysis of the phase-convention dependence of the CP-violating parameter ε_B and give some comments on the reported CLEO and OPAL constraints on Reε_B. It is emphasized that ε_B has little advantage for the study of CP violation in the B^0_d-\bar{B}^0_d system.

Kenji Morita, Shin Muroya, Hiroki Nakamura

We investigate HBT radii based on the numerical solutions of the hydrodynamical model which are so tuned as to reproduce the recent experimental data at the CERN SPS. Comparing the sizes of freeze-out hypersurface with HBT radii, we discuss dynamical effect of the systematic flow on the apparent HBT radii. Finally we compare HBT radii of the QGP phase transi

CS. Szabo

In this paper we show that Z_8 does not admit a natural duality. In fact, we show that 2Z_8 = {2, 4, 6, 8 | +,.} is not dualizable, and this will imply that the original ring is not dualizable, either. As a corollary we show that Sindi's conjecture does not hold. Our technique will be similar to one due to Quackenbush and Szabó, where non-dualizability i

Eric D'Hoker, D. H. Phong

The Seiberg-Witten curve and differential for ${\cal N}=2$ supersymmetric SU(N) gauge theory, with a massive hypermultiplet in the adjoint representation of the gauge group, are analyzed in terms of the elliptic Calogero-Moser integrable system. A new parametrization for the Calogero-Moser spectral curves is found, which exhibits the classical vacuum expecta

Vadim V. Varlamov

The physical fields (electromagnetic and electron fields) considered in the framework of Clifford algebras $\C_2$ and $\C_4$. The electron field described by the algebra $\C_4$ which in spinor representation is realized by well-known Dirac $γ$-matrices, and by force of isomorphism $\C_{4}\cong\C_{2}\otimes \C_{2}$ is represented as a tensor product of two ph

G. Costa, E. Lunghi

The problem of neutrino masses and mixing angles is analysed in a class of supersymmetric grand unified models, with SO(10) gauge symmetry and global U(2) flavour symmetry. Adopting the seesaw mechanism for the generation of the neutrino masses, one obtains a mass matrix for the left-handed neutrinos which is directly related to the parameters of the charged

D. Bardin, R. Kleiss, E. Accomando, H. Anlauf

The report summarizes the results of the activities of the Working Group on Event Generators for WW Physics at CERN during 1995.

A. A. Gvozdev, A. V. Kuznetsov, N. V. Mikheev, L. A. Vassilevskaya

The processes of the photon and electron-positron pair production by a neutrino propagating in a strong magnetic field are investigated in the framework of the Standard Model. The process probabilities and the mean values of the neutrino energy and momentum loss are calculated. Possible astrophysical manifestations of the processes considered are briefly ana

The OPAL Collaboration, K. Ackerstaff et al

This paper describes the measurement of the W boson mass, M_W, and decay width, Gamma_W, from the direct reconstruction of the invariant mass of its decay products in W pair events collected at a mean centre-of-mass energy of sqrt{s} = 172.12 GeV with the OPAL detector at LEP. Measurements of the W pair production cross-section, the W decay branching fractio

Patrick R. Brady, Chris M. Chambers, Sergio M. C. V. Goncalves

We study critical behavior in the collapse of massive spherically symmetric scalar fields. We observe two distinct types of phase transition at the threshold of black hole formation. Type II phase transitions occur when the radial extent $(λ)$ of the initial pulse is less than the Compton wavelength ($μ^{-1}$) of the scalar field. The critical solution is th

Alexander Reznikov

I construct the real counterparts (which I call Borel-Bott classes) of the R/Z classes constructed in "Characteristic classes in symplectic topology", to appear, in the cohomology of volume-preserving and symplectomorhisms of a compact (symplectic) manifold.I show that, for the symplectic action of the mapping class group in the moduli space of stabl

Alexander Reznikov

the main theorem gives a sufficient condition for a n elements of SL(2,R) to generate a free group.The idea behind it is to use a nonorientable version of the Dehn-Wolpert-Goldman twist and to sew it with the original representation of a free group to get representation of the closed surfase group and then to apply Goldman' theorem.

H. Srikanth, Z. Zhai, S. Sridhar, A. Erb

Systematic microwave surface impedance measurements of YBCO single crystals grown in $BaZrO_3$ crucibles reveal new properties that are not directly seen in similar measurements of other YBCO samples. Two key observations obtained from complex conductivity are: a new normal conductivity peak at around 80K and additional pairing below 65K. High pressure oxyge

Hao Li, Chao Tang, Ned S. Wingreen

Protein structures are a very special class among all possible structures. It was suggested that a ``designability principle'' plays a crucial role in nature's selection of protein sequences and structures. Here we provide a theoretical base for such a selection principle, using a novel formulation of the protein folding problem based on hydropho

Dennis Zaritsky, D. N. C. Lin

We identify a vertical extension of the red clump stars in the color magnitude diagram (CMD) of a section of the Large Magellanic Cloud (LMC). After subtracting the principal red clump component, we find a peak in the residual stellar distribution that is ~ 0.9 mag brighter than the peak of the principal red clump distribution. We consider and reject the fol

Daniel J. Eisenstein

An analytic expression is given for the growth function for linear perturbations in a low-density universe made flat by a cosmological constant. The result involves elliptic integrals but is otherwise short and straight-forward.

Maxim Kontsevich

This is my talk on the Bourbaki seminar, November 1996. It contains an elementary introduction to Borcherds' product formulas.

A. Opfermann

We examine conformal rescaling and T-duality in the context of four-dimensional HKT geometries. The closure of the torsion forces the conformal factor to satisfy a modified harmonic equation. Because of this equation the conformal factors form non-commutative groups acting on the HKT geometries. Using conformal rescalings and T-duality transformations we gen

A. Stephan

We determine the allowed parameter space and the particle spectra of the minimal SUSY standard model (MSSM) and nonminimal SUSY standard model (NMSSM) imposing correct electroweak gauge-symmetry breaking and recent experimental constraints. The parameters of the models are evolved with the SUSY RGEs assuming universality at the GUT scale. Applying the new un

A. B. Balantekin, J. F. Beacom, M. A. Candido Ribeiro

The single-particle nuclear potential is intrinsically nonlocal. In this paper, we consider nonlocalities which arise from the many-body and fermionic nature of the nucleus. We investigate the effects of nonlocality in the nuclear potential by developing the Green's function for nonlocal potentials. The formal Green's function integral is solved anal

Sanatan Digal, Ajit M. Srivastava

We argue that disoriented chiral condensate (DCC) domains are not well defined for temperatures above the Ginzburg temperature $T_G$ ($\simeq 0.7 T_c$). Above $T_G$, the dynamics of DCC domains is dominated by thermal fluctuations leading to fluctuating orientation of the chiral field in a given domain. It implies that DCC domains may form even in relatively

F. A. Berends, C. G. Papadopoulos, R. Pittau

A study is made of the feasibility of maximum likelihood fits to determine M_W and triple gauge boson couplings using only those experimental kinematical variables that are well measured. A computational tool to calculate theoretical probabilities for those kinematical variables is discussed and then applied to samples of unweighted events produced by an eve

Ben Moore, Fabio Governato, Tom Quinn, Joachim Stadel

We examine the effects of mass resolution and force softening on the density profiles of cold dark matter halos that form within cosmological N-body simulations. As we increase the mass and force resolution, we resolve progenitor halos that collapse at higher redshifts and have very high densities. At our highest resolution we have nearly 3 million particles

George Daskalakis, Aristoteles Kyriakis, Christos Markou, Hannelies Nowak

W-pair production in e+ e- annihilation at 500 GeV is studied using different Monte Carlo generators and the proposed detector for the Linear Collider in its TESLA version. Semileptonic W decays are used to give hints for the detector optimization and to determine the expected accuracy of the W mass determination and the measurement of the anomalous triple g

A. Bartl, H. Eberl, K. Hidaka, T. Kon

We present a detailed study of the decays of the Higgs bosons $H^+$, $H^0$, and $A^0$ within the Minimal Supersymmetric Standard Model including SUSY--QCD corrections. We find that the supersymmetric modes $\tilde t \bar{\tilde b}$ ($\tilde t \bar{\tilde t}$, and for large $\tanβ$ $\tilde b \bar{\tilde b}$) can dominate the $H^+$ ($H^0$, $A^0$) decays in a w

V. A. Dzuba, V. V. Flambaum, O. P. Sushkov

A semi-empirical calculation of the 6s - 7s Stark amplitude $α$ in Cs has been performed using the most accurate measurements and calculations of the electromagnetic amplitudes available. This is then used to extract the parameters of the electroweak theory from experimental data. The results are: $α= 269.0 (1.3) a_0^3$, weak charge of Cs $Q_W = -72.41(25)_{

S. Muroya, C. Nonaka

We numerically solve the (3+1)-dimensional relativistic hydrodynamical equation with a bag-model equation of state, which is one of the simplest models for the first order phase transition. Based on the numerical solution, we discuss the space-time evolution of the hot fluid produced in ultra relativistic nuclear collisions. Especially, the space-time struct

Stefano Mancini, Paolo Tombesi, Vladimir I. Man'ko

We show how the introduction of an algeabric field deformation affects the interference phenomena. We also give a physical interpretation of the developed theory.

Stefano Mancini, Paolo Tombesi, Vladimir I. Man'ko

We establish a general principle for the tomographic approach to quantum state reconstruction, till now based on a simple rotation transformation in the phase space, which allows us to consider other types of transformations. Then, we will present different realizations of the principle in specific examples.

Andrei Okounkov, Grigori Olshanski

In this paper we study the asymptotic behavior of the Jack rational functions as the number of variables grows to infinity. Our results generalize the results of A. Vershik and S. Kerov obtained in the Schur function case (theta=1). For theta=1/2,2 our results describe approximation of the spherical functions of the infinite-dimensional symmetric spaces $U(\

Bin Zhang

A Monte Carlo program solving Boltzmann equation for partons via cascade method is presented. At presented, only gluon-gluon elastic scattering is included. The scattering cross section is regulated by a medium generated screening mass. Three different geometric modes (3 dimension expansion, 1-d expansion, and scattering inside a box) are provided for theore

R. Rapp, M. Urban, M. Buballa, J. Wambach

A recently developed model for $ρ$-meson propagation in dense hadronic matter is applied to total photoabsorption cross sections in $γ$-proton and $γ$-nucleus reactions. Within the vector dominance model the photon coupling to the virtual pion cloud of the nucleon, two-body meson-exchange currents, as well as $γ$-nucleon resonances are included. Whereas the

J. Suhonen, J. Toivanen, A. Holt, T. Engeland

The microscopic quasiparticle-phonon model, MQPM, is used to study the energy spectra of the odd $Z=53 - 63$, N=82 isotones. The results are compared with experimental data, with the extreme quasiparticle-phonon limit and with the results of an unrestricted $2s1d0g_{7/2}0h_{11/2}$ shell model (SM) calculation. The interaction used in these calculations is a

Liang-gang Liu, Xiang-qian Luo, Qi-fa Zhou, Wei Chen

The particle-hole and Delta -hole excitations are well-known elementary excitation modes for the pion propagator in nuclear matter. But, the excitation also involves antiparticles, namely, nucleon-antinucleon, anti-Delta-nucleon and Delta-antinucleon excitations. These are important for high-energy momentum as well, and have not been studied before, to our k

Hector E. Lomeli, James D. Meiss

We study quadratic, volume preserving diffeomorphisms whose inverse is also quadratic. Such maps generalize the Hénon area preserving map and the family of symplectic quadratic maps studied by Moser. In particular, we investigate a family of quadratic volume preserving maps in three space for which we find a normal form and study invariant sets. We also give

András I. Stipsicz

In this note we show that there are 4-manifolds not containing Gompf nucleus $N_2$; in this way we answer Problem 4.98 of Kirby's problem list in the negative.

Nigel J. Kalton

We give a brief proof of a recent result of Avron, Seiler and Simon.

Gary T. Horowitz, Simon F. Ross

We investigate the properties of a class of near-extreme static black hole solutions called naked black holes. These black holes, which occur in string theory, have small curvature invariants but large tidal forces outside their event horizons. We show that these large tidal forces are due to a concentration of dilaton stress-energy near the horizon. We stud

John Ellis, Alon E. Faraggi, D. V. Nanopoulos

We study the problem of baryon stability in M theory, starting from realistic four-dimensional string models constructed using the free-fermion formulation of the weakly-coupled heterotic string. Suitable variants of these models manifest an enhanced custodial gauge symmetry that forbids to all orders the appearance of dangerous dimension-five baryon-decay o

Haru-Tada Sato

We present a twisted commutator deformation for $N=1,2$ super Virasoro algebras based on $GL_q(1,1)$ covariant noncommutative superspace.

G. M. Prosperi

A Schwinger-Dyson equation for the quark propagator is derived in the context of a Bethe-Salpeter second order formalism developped in preceding papers and of the Minimal Area Law model for the evaluation of the Wilson loop. We discuss how the equal time straight line approximation has to be modified to include correctly trajectories going backwards in time.

Enrico Meggiolaro

The high-energy quark-quark scattering amplitude is calculated first in the case of scalar QCD, using Fradkin's approach to derive the scalar quark propagator in an external gluon field and computing it in the eikonal approximation. The results are then extended to the case of ``real'' (i.e., fermion) QCD. The high-energy quark-quark scattering a

Kazuo Fujikawa, Kazumi Okuyama

An $SO(9,1)$ invariant formulation of an 11-dimensional supermembrane is presented by combining an $SO(10,1)$ invariant treatment of reparametrization symmetry with an $SO(9,1)$ invariant $θ_{R} = 0$ gauge of $κ$-symmetry. The Lagrangian thus defined consists of polynomials in dynamical variables (up to quartic terms in $X^μ$ and up to the eighth power in $θ

Vincenzo Branchina, Janos Polonyi

It is shown that in the Effective Standard Model new phenomena can arise due to the presence of small instanton configurations. The chief result is that under certain conditions new hidden coupling constants could exist in the model. In the Electroweak sector that might result in the possibility of observing B+L violating processes due to a highly non pertur

G. Lopez Castro, J. H. Munoz, G. Toledo Sanchez

We consider the isospin breaking corrections to charmless semileptonic decays of B mesons. Both, the recently measured branching ratios of exclusive decays by the CLEO Collaboration and the end-point reion of the inclusive lepton spectrum in form factor models, can be affected by these corrections. Isospin corrections can affect the determination of |V_ub| f

V. Barger, S. Pakvasa, X. Tata

We show that current experimental constraints already severely restrict what might be observable at $eμ$ colliders. We identify some cases where it may be possible to probe physics beyond what might be possible at other facilities and make some remarks about physics capability of high energy $eμ$ colliders.

C. M. Hung, E. Shuryak

We have shown that recent experimental data on radial flow, both from AGS and SPS energies, are in agreement with the Equation of State (EOS) including the QCD phase transition. New hydro-kinetic model (HKM) is developed, which incorporates hydrodynamical treatment of expansion and proper kinetics of the freeze-out. We show that the freeze-out surfaces for d

Alan Kostelecky

In this talk, I review the possibility that CPT and Lorentz symmetry might be spontaneously broken in nature by effects originating in a theory beyond the standard model, and I discuss some existing and future experimental tests.

Bernd A. Kniehl

We review recent developments in the theoretical description of inclusive single-hadron production at next-to-leading order in the parton model of quantum chromodynamics. Fragmentation functions are extracted from fits to data of inclusive pion and kaon production in e^+e^- annihilation at different centre-of-mass energies. Exploiting sensitivity to the scal

A. M. Kotzinian

Different phenomenological approaches for Lambda and Lambda-bar polarization in polarized semi-inclusive deep inelastic scattering and electron-positron annihilation at Z^0 pole are considered. Current and future experiments will soon provide accurate enough data to study spin phenomena in these reactions and distinguish between various models.

Uma Mahanta

Tev scale new heavy physics could significantly affect the cross-section for the rare process $e^+e^-\to H\gm $ through non-renormalizable operators involving the light SM fields. In this article we show that for $\sqs =500$ Gev and $\lam =1$ Tev some of these operators, which are only weakly constrained by the latest LEP and SLD data, could produce an obser

G. Grindhammer

The expectations for and the measurements of transverse energy flows, single particle p_T spectra, and the rate of forward jets in deep inelastic ep events from the H1 and ZEUS experiments at HERA are reported and discussed. It is shown that together they offer a good chance to establish deviations from the DGLAP paradigm. At the present level of limited sta

Leszek Motyka, Kacper Zalewski

A nonrelativistic Hamiltonian with plausible spin dependent corrections is proposed for the quarkonia below their respective strong decay thresholds. With only six free parameters this model reproduces the nine known masses of the bottomonia within about 1 MeV, the six known masses of the charmonia within a few MeV and the five known leptonic decay widths of

A. Bartl, H. Eberl, T. Gajdosik, S. Kraml

We present numerical predictions for the decay branching ratios of the heavier stop and sbottom mass eigenstates. We estimate the precision to be expected for the determination of the underlying supersymmetry parameters of the stop and sbottom systems.

G. V. Dass, K. V. L. Sarma

We study the EPR correlation implied by the entangled wavefunction of the $B^0\bar{B}^0$ pair created by the $Υ$(4S) resonance. The analysis uses the basis provided by the mass eigenstates $B_1,B_2$ rather than the flavour states $B^0, \bar{B}^0$. Data on the inclusive dilepton charge ratio are close to the expectation of quantum mechanics, but nearly 8 stan

F. Karsch, J. Engels, T. Scheideler

By matching Wilson loop ratios on anisotropic lattices we measure the coefficients $\cs$ and $\ct$, which are required for the calculation of the energy density. The results are compared to that of an indirect method of determination. We find similar behaviour, the differences are attributed to different discretization errors.

Shoji Hashimoto, Kenichi Ishikawa, Hideo Matsufuru, Tetsuya Onogi

We report results on $f_B$ and semi-leptonic $B$ decay form factors using NRQCD. We investigate $1/M$ scaling behavior of decay amplitudes. For $f_B$ Effect of higher order relativistic correction terms are also studied.

C. Adloff

The double-differential inclusive di-jet cross section in photoproduction processes is measured with the H1 detector at HERA. The cross section is determined as a function of the average transverse jet energy E_T^jets for ranges of the fractional energy x_gamma^jets of the parton from the photon side. An effective leading order parton distribution in the pho

The OPAL Collaboration, K. Ackerstaff et al

This paper describes a search for the Standard Model Higgs boson using data from e^+e^- collisions collected at center-of-mass energies of 161, 170 and 172 GeV by the OPAL detector at LEP. The data collected at these energies correspond to integrated luminosities of 10.0, 1.0 and 9.4 pb^-1, respectively. The search is sensitive to the main final states from

The OPAL Collaboration, K. Ackerstaff et al

The process e^+e^- -> gamma gamma (gamma) is studied using data recorded with the OPAL detector at LEP. The data sample corresponds to a total integrated luminosity of 25.38 pb^{-1} taken at centre-of-mass energies of 130-172 GeV. The measured cross-sections agree well with the expectation from QED. In a combined fit using data from all centre-of-mass energi

Ronald Dickman, Adriana G. Moreira

We study the two-dimensional contact process (CP) with quenched disorder (DCP), and determine the static critical exponents beta and nu_perp. The dynamic behavior is incompatible with scaling, as applied to models (such as the pure CP) that have a continuous phase transition to an absorbing state. We find that the survival probability (starting with all site

A. Raghav Chari, F. D. M. Haldane

In this note, we discuss the effective mass of quasiparticles in finite sized $ν= 1/2$ systems in the lowest Landau level, given a natural notion we have of the Fermi surface in these finite sized systems. The effective mass is related to the difference between instantaneous density-density response functions of the ground state and excited states of the sys

J. J. Rodríguez-Núñez, S. Schafroth

We explore the effect of the imaginary part of the self-energy, $ImΣ(\vec{k},ω)$, having a single pole, $Ω(\vec{k},ω)$, with spectral weight, $α(\vec{k})$, and quasi-particle lifetime, $Γ(\vec{k})$, on the density of states. We solve the set of parameters, $Ω(\vec{k},ω$), $α(\vec{k})$, and $Γ(\vec{k})$ by means of the moment approach (exact sum rules) of Nol

Romualdo Pastor-Satorras

We study the properties of time sequences extracted from a self-organized critical system, within the framework of the mathematical multifractal analysis. To this end, we propose a fixed-mass algorithm, well suited to deal with highly inhomogeneous one dimensional multifractal measures. We find that the fixed mass (dual) spectrum of generalized dimensions de

H. J. Bussemaker, D. Thirumalai, J. K. Bhattacharjee

By balancing the average energy gap with its typical change due to mutations for protein-like heteropolymers with M residues, we show that native states are unstable to mutations on a scale M* ~ (lambda/sigma_mu)^(1/zeta_s), where lambda is the dispersion in the interaction free energies and sigma_mu their typical change. Theoretical bounds and numerical est

William J. Mullin

We examine the possibility of Bose-Einstein condensation (BEC) in two-dimensional (2D) system of interacting particles in a trap. We use a self-consistent mean-field theory of Bose particles interacting by a contact interaction in the Popov and WKB approximations. The equations show that the normal state has a phase transition at some critical temperature (T

B. Partoens, V. A. Schweigert, F. M. Peeters

The groundstate configuration and the eigenmodes of two parallel two-dimensional classical atoms are obtained as function of the inter-atomic distance (d). The classical particles are confined by identical harmonic wells and repel each other through a Coulomb potential. As function of d we find several structural transitions which are of first or second orde

M. Wilkinson, B. Mehlig, P. N. Walker

We give a theoretical treatment of magnetic dipole absorption of electromagnetic radiation in small conducting particles, at photon energies which are large compared to the single particle level spacing, and small compared to the plasma frequency. We discuss both diffusive and ballistic electron dynamics for particles of arbitrary shape. The conductivity bec

Michael R. Geller, Daniel Loss

Edge states of the quantum Hall fluid provide an opportunity to study mesoscopic effects in a highly correlated electron system that is both experimentally accessible and theoretically tractable. In this paper we review recent work on the persistent current and Aharonov-Bohm magnetoconductance oscillations in the fractional quantum Hall effect regime.

E. Lai, R. J. Gooding

An extensive experimental and theoretical effort has led to a largely complete mapping of the magnetic phase diagram of La_(2-x)Sr_xCuO_4, and a microscopic model of the spin textures produced in the x < 0.05 regime has been shown to be in agreement with this phase diagram. Here we use this same model to derive a theory of the impurity-dominated, low tempera

Rolf Menne, Rolf R. Gerhardts

On the basis of Boltzmann&#39;s equation, and including anisotropic scattering in the collision operator, we investigate the effect of one-dimensional superlattices on two-dimensional electron systems. In addition to superlattices defined by static electric and magnetic fields, we consider mobility superlattices describing a spatially modulated density of sc

J. Kötzler, M. Kaufmann

The ac-conductivity along the CuO$_2$-layers of epitaxial films and single crystals of thicknesses 0.2$μ$m$\leq L_z \leq130μ$m reveals clear signatures for 2D-ordering. In particular, at $T_c$ the screening length assumes the universal value $L_zΛ_{T_c}/2ν_s$ predicted by the Kosterlitz-Thouless theory, which indicates that binding of long vortex strings nuc

P. Leboeuf, G. Iacomelli

The time evolution of a bounded quantum system is considered in the framework of the orthogonal, unitary and symplectic circular ensembles of random matrix theory. For an $N$ dimensional Hilbert space we prove that in the large $N$ limit the return amplitude to the initial state and the transition amplitude to any other state of Hilbert space are Gaussian di

S. Flach, K. Kladko

We present a perturbation theory of kink solutions of discrete Klein-Gordon chains. The unperturbed solutions correspond to the kinks of the adjoint partial differential equation. The perturbation theory is based on a reformulation of the discrete chain problem into a partial differential equation with spatially modulated mass density. The first order correc

Tohru Koma, Hal Tasaki

In a general class of one and two dimensional Hubbard models, we prove upper bounds for the two-point correlation functions at finite temperatures for electrons, for electron pairs, and for spins. The upper bounds decay exponentially in one dimension, and with power laws in two dimensions. The bounds rule out the possibility of the corresponding condensation

Gerardo Ortiz, Ivo Souza, Richard M. Martin

We present a simple and direct proof that the exchange-correlation hole, and therefore the exchange-correlation energy, in a polarized insulator is not determined by the bulk density alone. It is uniquely characterized by the density and the macroscopic electric polarization of the dielectric medium.

Jeff Secker, William E. Harris, Pat Cote, J. B. Oke

We have used deep R- and B-band CCD images (with ~1.2 arcsec seeing) of the central ~700 arcmin^2 of the Coma cluster core (and an associated ~270 arcmin^2 control field) to study the early-type dwarf elliptical (dE) galaxy population. Analysis of the color-restricted control-field-corrected color-magnitude diagram (CMD) shows that the dE galaxy sequence is

F. De Paolis, G. Ingrosso, Ph. Jetzer, M. Roncadelli

MACHOs (Massive Astrophysical Compact Halo Objects) - as discovered by microlensing experiments towards the LMC - provide a natural explanation for the galactic halo dark matter. A realistic possibility is that MACHOs are brown dwarfs of mass $\sim 0.1 M_{\odot}$. Various arguments suggest that brown dwarfs should have a coronal X-ray emission of $\sim 10^{2

Raul Jimenez, A. F. Heavens, M. R. S. Hawkins, P. Padoan

Gravitational lensing studies suggest that the Universe may contain a population of dark galaxies; we investigate this intriguing possibility and propose a mechanism to explain their nature. In this mechanism a dark galaxy is formed with a low density disk in a dark halo of high spin parameter; such galaxies can have surface densities below the critical Toom

M. R. S. Hawkins, D. Clements, J. W. Fried, A. F. Heavens

We report the discovery of a new gravitational lens candidate Q2138-431AB, comprising two quasar images at a redshift of 1.641 separated by 4.5 arcsecs. The spectra of the two images are very similar, and the redshifts agree to better than 115 km.sec$^{-1}$. The two images have magnitudes $B_J = 19.8$ and $B_J = 21.0$, and in spite of a deep search and image

Jordi Gomez-Gomar, Jordi Isern, Pierre Jean

The explosion mechanism associated with thermonuclear supernovae (SNIa) is still a matter of debate. There is a wide agreement that high amounts of of radioactive nuclei are produced during these events and they are expected to be strong gamma-ray emitters. In the past, several authors have investigated the use of this gamma-ray emission as a diagnostic tool

Elena Pierpaoli, Stefano Borgani, Antonio Masiero, Masahiro Yamaguchi

We analyse the formation of cosmic structures in models where the dark matter is dominated by light gravitinos with mass of $ 100$ eV -- 1 keV, as predicted by gauge-mediated supersymmetry (SUSY) breaking models. After evaluating the number of degrees of freedom at the gravitinos decoupling ($g_*$), we compute the transfer function for matter fluctuations an

Antoinette Songaila

Column density distribution functions of CIV with 12.05 < log (N) < 14.35 and SiIV with 11.70 < log (N) < 13.93 have been obtained using 81 CIV absorbers and 35 SiIV absorbers redward of the Ly alpha forest in the lines of sight to seven quasars with 2.518 < z(em) < 3.78. These distribution functions have been directly integrated to yield ion densities at z

Ravi Vakil

We study the geometry of varieties parametrizing degree d rational and elliptic curves in P^n intersecting fixed general linear spaces and tangent to a fixed hyperplane H with fixed multiplicities along fixed general linear subspaces of H. As an application, we derive recursive formulas for the number of such curves when the number is finite. These recursive

Eduardo Esteves

The Jacobian $J$ of a complete, smooth, connected curve $X$ admits a canonical divisor $Θ$, called the Theta divisor. It is well-known that $Θ$ is ample and, in fact, $3Θ$ is very ample. For a general complete, integral curve $X$, D&#39;Souza constructed a compactification $\bar J$ of the Jacobian $J$ by considering torsion-free, rank 1 sheaves on $X$. Souca

J. Retzlaff, S. Borgani, S. Gottloeber, A. Klypin

Using extensive N-body simulations we estimate redshift space power spectra of clusters of galaxies for different cosmological models (SCDM, TCDM, CHDM, Lambda-CDM, OCDM, BSI, tau-CDM) and compare the results with observational data for Abell-ACO clusters. Our mock samples of galaxy clusters have the same geometry and selection functions as the observational

Sidney van den Bergh

Properties of 53 globular cluster systems are investigated. Strong correlations are found between parent galaxy luminosity and both the slope of the radial density profile for clusters and the width of the cluster color (metallicity) distribution. These correlations are in the sense that the most luminous early-type galaxies are embedded in cluster systems t

Jose&#39; P. S. Lemos

Gravitational collapse of non-spherical symmetric matter leads inevitably to non-static external spacetimes. It is shown here that gravitational collapse of matter with toroidal topology in a toroidal anti-de Sitter background proceeds to form a toroidal black hole. According to the analytical model presented, the collapsing matter absorbs energy in the form

Siegfried Grossmann, Martin Holthaus

After discussing the key idea underlying the Maxwell&#39;s Demon ensemble, we employ this idea for calculating fluctuations of ideal Bose gas condensates in traps with power-law single-particle energy spectra. Two essentially different cases have to be distinguished. If the heat capacity remains continuous at the condensation point in the large-N-limit, the

Hsiang-nan Li

We propose a modified Balitskii-Fadin-Kuraev-Lipatov equation from the viewpoint of the resummation technique, which satisfies the unitarity bound. The idea is to relax the strong rapidity ordering and to restrict phase space for real gluon emissions in the evaluation of the BFKL kernel. It is found that the gluon distribution function rises as a power of th

Silvano Simula

The spin-averaged binding energy and the hyperfine mass splitting of heavy-light mesons are investigated within the constituent quark model as a function of the inverse heavy-quark mass. It is shown that the so-called heavy-quark kinetic energy, -lambda1 / 2mQ, may differ remarkably from the non-relativistic expectation <p**2> / 2mQ, thanks to relativistic e

Jörg Main, Michael Schwacke, Günter Wunner

For the hydrogen atom in combined magnetic and electric fields we investigate the dependence of the quantum spectra, classical dynamics, and statistical distributions of energy levels on the mutual orientation of the two external fields. Resonance energies and oscillator strengths are obtained by exact diagonalization of the Hamiltonian in a complete basis s

R. Ketzmerick, K. Kruse, T. Geisel

We show that avoided crossings of energy bands may give rise to a variety of phenomena such as transitions from metal to insulator and vice versa, changes in localization lengths, and changes in the fractal dimension of energy spectra. We explain the occurrence of these phenomena in the kicked Harper model under classically chaotic conditions and predict the

E. Bagan, P. Ball, V. M. Braun

We calculate radiative corrections to the light-cone sum rule for the semileptonic form factor in $B\toπeν$ decays and thus remove the major uncertainty in determining the CKM mixing angle $|V_{ub}|$ by this method. We discuss the remaining uncertainties and perspectives for further studies. The structure of the radiative corrections suggests factorization o

Arkady Berenstein, Anatol N. Kirillov

We define an action of the symmetric group on the set of domino tableaux, and prove that the number of domino tableaux of a given weight does not depend on the permutation of components of the last. A bijective proof of the well-known result due to J. Stembridge that the number of self-evacuating tableaux of a given shape is equal to that of domino tableaux

G. Michalek, M. Ostrowski, R. Schlickeiser

Energetic particle transport in a finite amplitude magnetosonic and Alfvenic turbulence is considered using Monte Carlo particle simulations, which involve an integration of particle equation of motion. We show that in a low-Betha plasma cosmic ray can be the most important damping process for magnetosonic waves. Assuming such conditions we derive the moment

Chang-Yeong Lee

Using the formalism of noncommutative geometric gauge theory based on the superconnection concept, we construct a new type of vector gauge theory possessing a shift-like symmetry and the usual gauge symmetry. The new shift-like symmetry is due to the matrix derivative of the noncommutative geometric gauge theory, and this gives rise to a mass term for the ve