April 1999 arXiv papers

Guang-Hong Chen, M. E. Raikh, Yong-Shi Wu

We propose an experiment, which would allow to pinpoint the role of spin-orbit coupling in the metal-nonmetal transition observed in a number of two-dimensional systems at low densities. Namely, we demonstrate that in a parallel magnetic field the interplay between the spin-orbit coupling and the Zeeman splitting leads to a characteristic anisotropy of resis

M. Guidal, J. -M. Laget, M. Vanderhaeghen

A simple and elegant model, based on Reggeized t-channel exchanges is succesful in reproducing the main features of all existing data of the reactions ep->eKLambda and ep->eKSigma. In particular, the original way gauge invariance is taken into account is found to be essential to describe the ratio between the Coulomb and the Transverse cross-sections at larg

Burt Holzman

Two-particle correlations between pions in Au+Au collisions have been measured at beam kinetic energies of 6, 8, and 10.8 GeV/u at the Alternating Gradient Synchrotron (AGS) over a wide range of rapidities using a magnetic spectrometer. The data have been analyzed in the Hanbury-Brown and Twiss (HBT) framework to extract source parameters. The event-by-event

Kingman Cheung

We perform a global analysis of the lepton-quark neutral current data on the low scale gravity model, which arises from the extra dimensions. The global data include HERA neutral current deep-inelastic scattering, Drell-yan production at the Tevatron, and fermion pair production at LEPII. The Drell-yan production, due to the large invariant mass data, provid

C. Y. Peng, C. D. Impey, E. E. Falco, C. S. Kochanek

Deep HST/NICMOS H (F160W) band observations of the z=1.96 quasar pair Q 1634+267A,B reveal no signs of a lens galaxy to a 1 sigma threshold of approximately 22.5 mag. The minimum luminosity for a normal lens galaxy would be a 6L_* galaxy at z > 0.5, which is 650 times greater than our detection threshold. Our observation constrains the infrared mass-to-light

P. S. Kuhn, Marcia C. Barbosa, Y. Levin

Transfection of an anionic polynucleotide through a negatively charged membrane is an important problem in genetic engineering. The direct association of cationic surfactant to DNA decreases the effective negative charge of the nucleic acid, allowing the DNA-surfactant complex to approach a negatively charged membrane. The paper develops a theory for solutio

Peter Kaste

We discuss how to obtain an N=(2,2) supersymmetric SU(3) gauge theory in two dimensions via geometric engineering from a Calabi-Yau 4-fold and compute its non-perturbative twisted chiral potential. The relevant compact part of the 4-fold geometry consists of two intersecting P^1's fibered over P^2. The rigid limit of the local mirror of this geometry is

Hongwei Yu, L. H. Ford

The quantum lightcone fluctuations in flat spacetimes with compactified spatial dimensions or with boundaries are examined. The discussion is based upon a model in which the source of the underlying metric fluctuations is taken to be quantized linear perturbations of the gravitational field. General expressions are derived, in the transverse trace-free gauge

Ruben Minasian, Gregory Moore, Dimitrios Tsimpis

When an M-theory fivebrane wraps a holomorphic surface $\mathcal{P}$ in a Calabi-Yau 3-fold $X$ the low energy dynamics is that of a black string in 5 dimensional $\mathcal{N}=1$ supergravity. The infrared dynamics on the string worldsheet is an $\mathcal{N} = (0,4)$ 2D conformal field theory. Assuming the 2D CFT can be described as a nonlinear sigma model,

A. Pérez-Lorenzana, R. N. Mohapatra

The effects of extra dimensions on gauge coupling unification is studied. We start with a comparison between power law running of the gauge couplings in models with extra dimensions and logarithmic running that happens in many realistic cases. We then discuss the effect of extra dimensions on various classes of unification models. We identify products of evo

Elisa Prato

In this article we consider a generalization of manifolds and orbifolds which we call quasifolds; quasifolds of dimension k are locally isomorphic to the quotient of R^k by the action of a discrete group - tipically they are not Hausdorff topological spaces. The analogue of a torus in this geometry is a quasitorus. We define Hamiltonian actions of quasitori

R. Schack, C. M. Caves

We present a general method for constructing pure-product-state representations for density operators of $N$ quantum bits. If such a representation has nonnegative expansion coefficients, it provides an explicit separable ensemble for the density operator. We derive the condition for separability of a mixture of the Greenberger-Horne-Zeilinger state with the

G. Akemann, G. M. Cicuta, L. Molinari, G. Vernizzi

The two-point resolvent is calculated in the large-n limit for the generalized fixed and bounded trace ensembles. It is shown to disagree with the one of the canonical Gaussian ensemble by a non-universal part which is given explicitly for all monomial potentials $V(M)=M^{2p}$. Moreover, we prove that for the generalized fixed and bounded trace ensemble all

A. Jusufi, M. Watzlawek, H. Loewen

The distance-resolved effective interaction between two star polymers in a good solvent is calculated by Molecular Dynamics computer simulations. The results are compared with a pair potential proposed recently by Likos et al. [Phys. Rev. Lett. 1998, 80, 4450] which is exponentially decaying for large distances and crosses over, at the corona diameter of the

P. Thalmeier, A. N. Yaresko

An investigation of the spin excitation spectrum of charge ordered (CO) NaV2O5 is presented. We discuss several different exchange models which may be relevant for this compound, namely in- line and zig-zag chain models with weak as well as strong inter- chain coupling and also a ladder model and a CO/MV (mixed valent) model. We put special emphasis on the i

G. Lazarides

The standard big bang cosmological model and the history of the early universe according to the grand unified theories of strong, weak and electromagnetic interactions are summarized. The shortcomings of big bang are discussed together with their resolution by inflationary cosmology. Inflation and the subsequent oscillation and decay of the inflaton field ar

Geetha Basappa, Suneel, V. Kumaran, Prabhu R. Nott

We present important new results from light-microscopy and rheometry on a moderately concentrated lyotropic smectic, with and without particulate additives. Shear-treatment aligns the phase rapidly, except for a striking network of oily-streak defects, which anneals out much more slowly. If spherical particles several microns in diameter are dispersed in the

J. Zimanyi, T. S. Biro, T. Csorgo, P. Levai

The mischievous linear coalescence approach to hadronization of quark matter is shown to violate strangeness conservation in strong interactions. The simplest correct quark counting is shown to coincide with the non-linear algebraic coalescence rehadronization model, ALCOR. The non-linearity of the ALCOR model is shown to cancel from its simple predictions f

I. B. Khriplovich, R. V. Korkin

P odd anapole moment of the deuteron is found in the chiral limit, $m_π \to 0$. The contact current generated by the P odd pion exchange does not contribute to the deuteron anapole. Being combined with usual radiative corrections to the weak electron -- deuteron interaction, our calculation results in a sufficiently accurate theoretical prediction for the co

Iosif Polterovich

We present a new method for computation of the Korteweg-de Vries hierarchy via heat invariants of the 1-dimensional Schrodinger operator. As a result new explicit formulas for the KdV hierarchy are obtained. Our method is based on an asymptotic expansion of resolvent kernels of elliptic operators due to S.Agmon and Y.Kannai.

Willy Hereman, Unal Goktas

Discusses several integrability tests for nonlinear evolution equations.

Marek Czachor, Maciej Kuna, Sergiej B. Leble, Jan Naudts

We review some recent developments in the theory of nonlinear von Neumann equations. We distinguish between the von Neumann equation (which can be nonlinear) and the Liouville equation (which should be linear). Explicit examples illustrate the technique of binary Darboux integration of nonlinear density matrix equations and special attention is payed to the

Adonai S. Sant'Anna

We present an axiomatic framework for non-relativistic classical particle mechanics, inspired on Tati's ideas about a non-space-time description for physics. The main advantage of our picture is that it allows us to describe causality without any reference to elapsed time intervals.

I. Zakout, H. R. Jaqaman, S. Pal, H. Stöcker

Hot hypernuclear matter is investigated in an explicit SU(3) quark model based on a mean field description of nonoverlapping baryon bags bound by the self-consistent exchange of scalar $σ, ζ$ and vector $ω, ϕ$ mesons. The $σ, ω$ mean fields are assumed to couple to the u,d-quarks while the $ζ, ϕ$ mean fields are coupled to the s-quark. The coupling constants

J. Dukelsky, J. G. Hirsch, P. Schuck

A method is proposed which allows to calculate within the SCRPA theory the occupation numbers via the single particle Green function. This scheme complies with the Hugenholtz van Hove theorem. In an application to the Lipkin model it is found that this prescription gives consistently better results than two other commonly used approximations: lowest order bo

Tetsufumi Hirano

Based on the (3+1)-dimensional hydrodynamic model, the space-time evolution of hot and dense nuclear matter produced in non-central relativistic heavy-ion collisions is discussed. The elliptic flow parameter v_2 is obtained by Fourier analysis of the azimuthal distribution of pions and protons which are emitted from the freeze-out hypersurface. As a function

Miloslav Znojil

In the quantization scheme which weakens the hermiticity of a Hamiltonian to its mere PT invariance the superposition V(x) = x^2+ Ze^2/x of the harmonic and Coulomb potentials is defined at the purely imaginary effective charges (Ze^2=if) and regularized by a purely imaginary shift of x. This model is quasi-exactly solvable: We show that at each excited, (N+

R. Coquereaux, A. O. Garcia, R. Trinchero

The properties of Hopf star operations and twisted Hopf stars operations on quantum groups are discussed in relation with the theory of representations (star representations). Invariant Hermitian sesquilinear forms (scalar products) on modules or module-algebras are then defined and analyzed. Particular attention is paid to scalar products that can be associ

P. Zinn-Justin, J. -B. Zuber

Using matrix model techniques for the counting of planar Feynman diagrams, recent results of Sundberg and Thistlethwaite on the counting of alternating tangles and links are reproduced.

Ernest S. Croot

We answer several questions of P. Erdos and R. Graham by showing that for any rational number r > 0, there exist integers n1, n2, ..., nk, k variable, where N < n1 < n2 < ... < nk < (e^r + o_r(1) ) N, such that r = 1/n1 + 1/n2 + ... + 1/nk. Moreover, we obtain the best-possible error term for the o_r(1), which is O_r(loglog N/log N).

John Etnyre, Robert Ghrist

We consider the dynamics of vector fields on three-manifolds which are constrained to lie within a plane field, such as occurs in nonholonomic dynamics. On compact manifolds, such vector fields force dynamics beyond that of a gradient flow, except in cases where the underlying manifold is topologically simple. Furthermore, there are strong restrictions on th

Elisa Prato

Nous considérons un espace topologique qui est localement isomorphe au quotient de R^k par l&#39;action d&#39;un groupe discret et nous l&#39;appelons quasi-variété de dimension k. Les quasi-variétés généralisent les variétés et les V-variétés et représentent le cadre naturel pour la réduction symplectique par rapport à l&#39;action induite d&#39;un sous-gro

Ola Bratteli, Palle E. T. Jorgensen, Ki Hang Kim, Fred Roush

We first study situations where the stable AF-algebras defined by two square primitive nonsingular incidence matrices with nonnegative integer matrix elements are isomorphic even though no powers of the associated automorphisms of the corresponding dimension groups are isomorphic. More generally we consider neccessary and sufficient conditions for two such m

Carsten Michels

Given an infinite set Λof characters on a compact abelian group we show that Λis a Λ(p)-set for all p>2 if and only if the limit order of the ideal of all Λ-summing operators coincides with that of the ideal of all Gaussian-summing operators. This is a natural counterpart to a recent result of Baur which says that Λis a Sidon set if and only if even the two

Do Ngoc Diep, Phung Ho Hai, Aderemi O. Kuku

In this paper we construct and study the representation theory of a Hopf C^*-algebra with approximate unit, which constitutes quantum analogue of a compact group C^*-algebra. The construction is done by first introducing a convolution-product on an arbitrary Hopf algebra H with integral, and then constructing the L_2 and C^*-envelopes of H (with the new conv

D. Shklyarov, S. Sinel&#39;shchikov, L. Vaksman

We use Berezin&#39;s quantization procedure to obtain a formal $U_q su_{1,1}$-invariant deformation of the quantum disc. Explicit formulae for the associated q-bidifferential operators are produced.

Allan J. Macleod

We consider the practical computation of rational points on y^2=x(x^2+ax+b). The algebra necessary for a 4-descent procedure is described. A simple further descent is then described which only uses integer arithmetic. Numerous examples are given to illustrate the effectiveness of this extra descent. Currently, the largest point found has height 51.15 or 102.

Lieven Le Bruyn

Kontsevich and Rosenberg propose to study smooth noncommutative spaces by approximation at level n by representation spaces. In this note we make some comments about their proposal.

E. V. Ferapontov

We continue the investigation of the correspondence between systems of conservation laws and congruences of lines in projective space. Relationship between &#34;additional&#34; conservation laws and hypersurfaces conjugate to a congruence is established. This construction allows us to introduce, in a purely geometric way, the Lévy transformations of semihami

R. Holman, T. W. Kephart

We construct the N=1 supergravity analog of the Green-Schwarz and heterotic superstring theories in 10D. We find the SO(8) theory previously found by compactification of 10D on $K3$. We also find eleven $G_2\times G_2$ theories, two with symmetric matter content. It is not obvious how ten of the $G_2\times G_2$ theories can be gotten from 10D.

S. S. Shahverdiyev, I. V. Tyutin, B. L. Voronov

We propose and develop a new calculus for local variational differential operators. The main difference of the new formalism with the canonical differential calculus is that the image of higher order operators on local functionals does not contain indefinite quantities like $δ(0)$. We apply this formalism to BV formulation of general gauge field theory and t

Mark B. Wise

The appropriate power counting for the effective field theory of NN interactions is reviewed. It is more subtle than in most effective field theories since in the limit that the S-wave NN scattering lengths go to infinity it is governed by a nontrivial fixed point. The leading two body terms in the effective field theory for nucleon self interactions are sca

Robert Bluhm

The CPT theorem has been tested to very high precision in a variety of experiments involving particles and antiparticles confined within Penning traps. These tests include comparisons of anomalous magnetic moments and charge-to-mass ratios of electrons and positrons, protons and antiprotons, and hydrogen ions and antiprotons. We present a theoretical analysi

Nikolaos Kidonakis

We discuss the resummation of threshold logarithms for heavy quark and dijet cross sections in hadronic collisions. The resummed cross sections are presented at next-to-leading logarithmic accuracy in terms of anomalous dimension matrices which describe the factorization of soft gluons from the hard scattering. We apply our formalism to the calculation of th

Bogdan B. Niczyporuk

One principal motivation for studying exclusive reactions is that they provide a new class of observables, called off-diagonal parton distributions, for the internal structure of the nucleon. The study of exclusive reactions provides a probe of nucleon structure complementary to purely inclusive studies. The simplest, and possibly the most promising, type of

V. S. Fadin, A. D. Martin

We demonstrate, to next-to-leading order accuracy, the cancellation of the infrared singularities in the impact factors which arise in the QCD description of high energy processes A + B -> A&#39; + B&#39; of colourless particles. We study the example where A is a virtual photon in detail, but show that the result is true in general.

Gabor Papp, George Fai, Peter Levai

In order to fix the parameters for predictions of hard photon and pion production in $Au+Au$ collisions at $\sqrt{s}=200$ GeV, proton-proton and proton-nucleus data are analyzed in perturbative QCD in the energy range $\sqrt{s} \approx 20-60$ GeV and a prediction at RHIC energy is given.

N. Kauer, L. Reina, J. Repond, D. Zeppenfeld

The transverse momentum flow inside jets is a sensitive measure of internal jet structure. For the current jets in deep inelastic scattering this jet shape measure is determined at order alpha_s^2, i.e. with up to three partons inside a single jet. The scale dependence of jet shapes in various jet algorithms is discussed. Results agree well with recent measu

Craig J. Copi, Junseong Heo, Lawrence M. Krauss

Distinguishing the signals due to scattering of WIMP dark matter off of nuclear targets from those due to background noise is a major challenge. The Earth&#39;s motion relative to the galactic halo should produce halo-dependent seasonal modulation in the event rate, but it also should produce an angular signal that is both far stronger and less ambiguous. Di

M. Kirchbach

It is argued that the only three-flavor symmetry which is consistent with the Okubo-Zweig-Iizuka (OZI) rule, and is therefore dictated by the gluon gauge dynamics, is the heavy c quark limit of a certain U(4)_F subgroup (called S_OZI here) and defined as S_OZI= \lim_(m_c\to Λ_c) SU(2)_ud * SU(2)_cd * U(1) with the two SU(2) groups acting in turn onto the 1st

C. Gutsfeld, H. A. Kastrup, K. Stergios

We calculate numerically scattering phases for elastic meson-meson scattering processes in the strongly coupled massive Schwinger-model with an SU(2) flavour symmetry. These calculations are based on Luescher&#39;s method in which finite size effects in two-particle energies are exploited. The results from Monte-Carlo simulations with staggered fermions for

W. Ootani, M. Minowa, K. Miuchi, Y. Inoue

An experiment to search for hypothetical particle dark matter using cryogenic thermal detector, or bolometer is ongoing. The bolometer consists of eight pieces of 21 g LiF absorbers and sensitive NTD germanium thermistors attached to them and is installed in the Nokogiriyama underground cell which is a shallow depth site ($\sim 15$ m w.e.). We report on the

Ian H. Redmount

Recent evidence indicates that the Universe is open, i.e., spatially hyperbolic, longstanding theoretical preferences to the contrary notwithstanding. This makes it possible to select a vacuum state, Fock space, and particle definition for a quantized field, by requiring concordance with ordinary flat-spacetime theory at late times. The particle-number basis

G. Yu. Bogoslovsky, H. F. Goenner

It is shown that the problem of a possible violation of the Lorentz transformations at Lorentz factors $γ>5\times 10^{10} ,$ indicated by the situation which has developed in the physics of ultra-high energy cosmic rays (the absence of the GZK cutoff), has a nontrivial solution. Its essence consists in the discovery of the so-called generalized Lorentz trans

W. Wernsdorfer, R. Sessoli, D. Gatteschi

Current theories still fail to give a satisfactory explanation of the observed quantum phenomena in the relaxation of the magnetisation of the molecular cluster Mn12 acetate. In the very low temperature regime, Prokof&#39;ev and Stamp recently proposed that slowly changing dipolar fields and rapidly fluctuating hyperfine fields play a major role in the tunne

Ya. M. Blanter, E. V. Sukhorukov

Conductance and shot noise of an open cavity with diffusive boundary scattering are calculated within the Boltzmann-Langevin approach. In particular, conductance contains a non-universal geometric contribution, originating from the presence of open contacts. Subsequently, universal expressions for multi-terminal conductance and noise valid for all chaotic ca

A. Mourachkine

We present experimental data obtained by different techniques. Some of them are not easy to explain by any theoretical model presented in the literature. However, a MCS model of the superconductivity in hole-doped cuprates, proposed in our previous work, is capable to explain them. Thus, we present an evidence in favor of the MCS model.

A Calogeracos

The interaction of a fast moving sine-Gordon soliton with an external periodic potential is examined. The resulting equation of motion for the collective coordinate representing the position of the soliton is given in relativistic form. We examine the radiation emitted due to the interaction of the soliton with the potential and we calculate the potential de

Tetsuya Mutou, Hiroshi Kontani

We propose the origin of the charge-ordered stripe structure with the orbital ordering observed experimentally in La_(1-x)Ca_(x)MnO_(3) (x=1/2, 2/3), in which the long-range Coulomb interaction plays an essential role. We study a Hubbard model with doubly-degenerate e_g orbitals, and treat the on-site Coulomb interaction (U) and the nearest-neighbor one (V)

Baruch Rosenstein

Consistent perturbation theory for thermodynamical quantities in type II superconductors in magnetic field at low temperatures is developed. It is complementary to the existing expansion valid at high temperatures. Magnetization and specific heat are calculated to two loop order and compare well to existing Monte Carlo simulations and experiments.

Kedar Damle, S. E. Nagler

Recent inelastic neutron scattering experiments on (VO)_2P_2O_7 (VOPO) have seen previously unanticipated sharp peaks in the dynamic structure factor in addition to the pair of triplet modes observed earlier. We argue that the additional features are in essence `shadows&#39; of the previously studied features arising due to umklapp scattering, and suggest ex

B. Mathiesen, A. E. Evrard, J. J. Mohr

We examine an ensemble of 48 simulated clusters to determine the effects of small-scale density fluctuations and large-scale substructure on X-ray measurements of the intracluster medium (ICM) mass. We measure RMS density fluctuations in the ICM which can be characterized by a mean mass-weighted clumping factor C = <rho^2>/<rho>^2 between 1.3 and 1.4 within

D. Calzetti, C. J. Conselice, J. S. Gallagher, A. L. Kinney

(Abridged) We investigate the interplay between starbursts and host galaxies by studying the structure and physical characteristics of the ionized gas surrounding the central starbursts in the two nearby galaxies NGC5253 and NGC5236. The two systems represent very different galactic environments, NGC5253 being a metal-poor dwarf, and NGC5236 being a metal-ri

Lin Yan, Patrick J. McCarthy, Wolfram Freudling, Harry I. Teplitz

We present a luminosity function for H$α$ emission from galaxies at redshifts between 0.7 and 1.9 based on slitless spectroscopy with NICMOS on HST. The luminosity function is well fit by a Schechter function over the range $6 \times 10^{41} < L(Hα) < 2 \times 10^{43} erg/sec$ with $L^* = 7 \times 10^{42} erg/sec$ and $ϕ^* = 1.7 \times 10^{-3} Mpc^{-3}$ for

Sidney van den Bergh

The small Antlia-Sextans clustering of galaxies is located at a distance of only 1.36 Mpc from the Sun, and 1.72 Mpc from the adopted barycenter of the Local Group. The latter value is significantly greater than the radius of the zero- velocity surface of the Local Group which, for an assumed age of 14 Gyr, has Ro = 1.18 &#34; 0.15 Mpc. This, together with t

Qingjuan Yu, Scott Tremaine

Plutinos are Kuiper-belt objects that share the 3:2 Neptune resonance with Pluto. The long-term stability of Plutino orbits depends on their eccentricity. Plutinos with eccentricities close to Pluto (fractional eccentricity difference |e-e_p|/e_p<=0.1) can be stable because the longitude difference librates, in a manner similar to the tadpole and horseshoe l

Fabian Walter, Andreas Heithausen

We present the discovery of a giant molecular complex (r=350 pc, M_ vir=10^7 M_sun) in the tidal arms south-east of NGC 3077, a member of the M 81 triplet. The complex is clearly detected in the 12CO (J=1-0) transition at five independent positions. The position relative to NGC 3077, the systemic velocity (v_hel=14km/s) and the cloud averaged line width (15k

R. Gilli, G. Risaliti, M. Salvati

The synthesis model for the cosmic X-ray background (XRB) -based on the integrated emission of Active Galactic Nuclei (AGNs)- is complemented with new observational results. We adopt the most recent estimates of the AGN X-ray luminosity function and evolution. We adopt the column density distribution of type 2 AGNs observed in the local Universe, instead of

D. A. Moffett, T. H. Hankins

New polarimetric observations of the Crab pulsar at frequencies between 1.4 and 8.4 GHz are presented. Additional pulse components discovered in earlier observations (Moffett & Hankins 1996, astro-ph/9604163) are found to have high levels of linear polarization, even at 8.4 GHz. No abrupt sweeps in position angle are found within pulse components; however, t

Carlos Abia, Yakiv Pavlenko, Patrick de Laverny

The formation of lithium lines in the atmosphere of C-rich giants is discussed. LTE and NLTE approximations are used to model lithium lines in the spectra of super Li-rich AGB stars. The system of equations of the statistical balance of neutral Li in plane-parallel model atmospheres is solved for a 20-level atom model. JOLA and line-by-line models of molecul

Guillermo Abramson, Jose Luis Vega

We propose a model for co-evolving ecosystems that takes into account two levels of description of an organism, for instance genotype and phenotype. Performance at the macroscopic level forces mutations at the microscopic level. These, in turn, affect the dynamics of the macroscopic variables. In some regions of parameter space, the system self-organises int

Achille Corsetti, Pran Nath

Predictions for the out-going muon fluxes from the annihilation of neutralinos in the center of the Sun and the Earth in supergravity unification are given. Effects of uncertainties of the input data are analysed. It is shown that the out-going muon flux measurements from the Sun and the Earth are complementary, with the Earth providing a larger flux for low

R. Altendorfer, J. Bagger

The partial breaking of supersymmetry in flat space can be accomplished using any one of three dual representations for the massive N=1 spin-3/2 multiplet. Each of the representations can be ``unHiggsed&#39;&#39;, which gives rise to a set of dual N=2 supergravities and supersymmetry algebras.

R. A. Chevalier, Z. -Y. Li

Likely progenitors for the GRBs (gamma-ray bursts) are the mergers of compact objects or the explosions of massive stars. These two cases have distinctive environments for the GRB afterglow: the compact object explosions occur in the ISM (interstellar medium) and those of massive stars occur in the preburst stellar wind. We calculate the expected afterglow f

S. Allen, H. Touchette, S. Moukouri, Y. M. Vilk

The attractive Hubbard model in d=2 is studied through Monte Carlo simulations at intermediate coupling. There is a crossover temperature $T_X$ where a pseudogap appears with concomitant precursors of Bogoliubov quasiparticles that are not local pairs. The pseudogap in $A(k,ω)$ occurs in the renormalized classical regime when the correlation length is larger

Paul B. Slater

We report the results of certain integrations of quantum-theoretic interest, relying, in this regard, upon recently developed parameterizations of Boya et al of the n x n density matrices, in terms of squared components of the unit (n-1)-sphere and the n x n unitary matrices. Firstly, we express the normalized volume elements of the Bures (minimal monotone)

Zurab Kakushadze

We consider non-perturbative four dimensional N=1 space-time supersymmetric orientifolds corresponding to Type I compactifications on (generalized) Voisin-Borcea orbifolds. Some states in such compactifications arise in ``twisted&#39;&#39; open string sectors which lack world-sheet description in terms of D-branes. Using Type I-heterotic duality as well as t

B. Monreal, S. A. Bass, M. Bleicher, S. Esumi

Using a microscopic transport model together with a coalescence after-burner, we study the formation of deuterons in Au + Au central collisions at $\sqrt{s}=200 AGeV$. It is found that the deuteron transverse momentum distributions are strongly affected by the nucleon space-momentum correlations, at the moment of freeze-out, which are mostly determined by th

Hilmar Forkel, Fernando S. Navarra, Marina Nielsen

A crucial input for recent meson hyperon cloud model estimates of the nucleon matrix element of the strangeness current are the nucleon-hyperon-K* (NYK*) form factors which regularize some of the arising loops. Prompted by new and forthcoming information on these form factors from hyperon-nucleon potential models, we analyze the dependence of the loop model

Cécile Renault, Nicolas Renaud, Gilles Henri

The CAT imaging telescope on the site of the former solar plant Th'emis in southern France observed gamma-rays from the BL Lac object Mkn501 above 250 GeV for more than 60 usable hours on-source from March to October 1997. This source was in a state of high activity during all this period. By studying the correlation between the photons of different energies

Joachim Hainz, Hermann Grabert

A systematic semiclassical expansion of the hydrogen problem about the classical Kepler problem is shown to yield remarkably accurate results. Ad hoc changes of the centrifugal term, such as the standard Langer modification where the factor l(l+1) is replaced by (l+1/2)^2, are avoided. The semiclassical energy levels are shown to be exact to first order in $

Nathan Isgur

Flux tube zero-point motion produces quark displacements transverse to the flux tube which make significant contributions to hadronic charge radii. In heavy quark systems, these contributions can be related by Bjorken&#39;s sum rule to the rates for semileptonic decay to hybrid mesons. This connection can be generalized to other leptoproduction processes, wh

R. Mélin, S. Peysson

A Bethe-Peierls treatment to dilution in frustrated magnets and spin liquids is given. A spin glass phase is present at low temperatures and close to the percolation point as soon as frustration takes a finite value in the dilute magnet model; the spin glass phase is reentrant inside the ferromagnetic phase. An extension of the model is given, in which the s

V. V. Lebedev

We examine high-order dynamical correlations of defects (vortices, disclinations etc) in thin films starting from the Langevin equation for the defect motion. We demonstrate that dynamical correlation functions $F_{2n}$ of vorticity and disclinicity behave as $F_{2n}\sim y^2/r^{4n}$ where $r$ is the characteristic scale and $y$ is the fugacity. As a conseque

V. A. Gani, A. E. Kudryavtsev

The process of collision of two parallel domain walls in a supersymmetric model is studied both in effective Lagrangian approximation and by numerical solving of the exact classical field problem. For small initial velocities we find that the walls interaction looks like elastic reflection with some delay. It is also shown that in such approximation internal

P. Bozhilov

We consider null bosonic p-branes in curved space-times. Some exact solutions of the classical equations of motion and of the constraints for the null membrane in general stationary, axially symmetrical, four dimensional, gravity background are found.

Damir Becirevic, Alexei B. Kaidalov

We propose a simple parametrization for the form factors in heavy to light decays which satisfies the heavy quark scaling laws and avoids introducing the explicit &#34;dipole&#34; form. The illustration is provided on the set of lattice data for B -> pi, semileptonic decay. The resulting shape of the form factor also agrees with the QCD sum rule predictions.

H. Nikolic

Although there is no relative motion among different points on a rotating disc, each point belongs to a different noninertial frame. This fact, not recognized in previous approaches to the Ehrenfest paradox and related problems, is exploited to give a correct treatment of a rotating ring and a rotating disc. Tensile stresses are recovered, but, contrary to t

Tim Gebbie, Peter Dunsby, George Ellis

This is the second of a series of papers extending the 1+3 covariant and gauge invariant treatment of kinetic theory to an examination of Cosmic Microwave Background temperature anisotropies arising from inhomogeneities in the early universe. The first paper dealt with algebraic issues. Here we derive the mode form of the integrated Boltzmann equations, firs

Richard P. Sear

A simple model of globular proteins which incorporates anisotropic attractions is proposed. It is closely related to models used to model simple hydrogen-bonding molecules such as water. Theories for both the fluid and solid phases are presented, and phase diagrams calculated. The model protein exhibits a fluid-fluid transition which is metastable with respe

Sasanka Ghosh, Sudipta Nandy

A generalised inverse scattering method has been developed for arbitrary n dimensional Lax equations. Subsequently, the method has been used to obtain N soliton solutions of a vector higher order nonlinear Schrodinger equation, proposed by us. It has been shown that under suitable reduction, vector higher order nonlinear Schrodinger equation reduces to highe

Somnath Bharadwaj, Varun Sahni, B. S. Sathyaprakash, Sergei F. Shandarin

We apply Shapefinders, statistical measures of `shape&#39; constructed from two dimensional partial Minkowski functionals, to study the degree of filamentarity in the Las Campanas Redshift Survey (LCRS). In two dimensions, three Minkowski functionals characterise the morphology of an object, they are: its perimeter (L), area (S), and genus. Out of L and S a

Ken-Ichiro Imura

Effects of backward scattering between fractional quantum Hall (FQH) edge modes are studied. Based on the edge-state picture for hierarchical FQH liquids, we discuss the possibility of the transitions between different plateaux of the tunneling conductance $G$. We find a selection rule for the sequence which begins with a conductance $G=m/(mp\pm 1)$ ($m$: in

Yoshiaki Himemoto, Takahiro Tanaka

The Hawking radiation is one of the most interesting phenomena predicted by the theory of quantum field in curved space. The origin of Hawking radiation is closely related to the fact that a particle which marginally escapes from collapsing into a black hole is observed at the future infinity with infinitely large redshift. In other words, such a particle ha

E. Allahyarov, I. D&#39;Amico, H. Löwen

The effective interaction between charged colloidal particles confined between two planar like-charged walls is investigated using computer simulations of the primitive model describing asymmetric electrolytes. In detail, we calculate the effective force acting onto a single macroion and onto a macroion pair in the presence of slit-like confinement. For mode

L. Lusanna, M. Materassi

The canonical decomposition of a real Klein-Gordon field in collective and relative variables proposed by Longhi and Materassi is reformulated on spacelike hypersurfaces. This allows to obtain the complete canonical reduction of the system on Wigner hyperplanes, namely in the rest-frame Wigner-covariant instant form of dynamics. From the study of Dixon&#39;s

Thomas R. Hemmert, Bastian Kubis, Ulf-G. Meißner

We investigate the strange electric and magnetic form factors of the nucleon in the framework of heavy baryon chiral perturbation theory to third order in the chiral expansion. All counterterms can be fixed from data. In particular, the two unknown singlet couplings can be deduced from the parity-violating electron scattering experiments performed by the SAM

I. I. Bigi, A. I. Sanda

Data from the CPLEAR collaboration coupled with the assumption that the Bell-Steinberger relation holds have provided {\em direct} evidence for \ot~violation. In this note we investigate what we can say about \ot~violation {\em without} such an assumption. We show that both the modulus and the phase of $η_{+-}$ can be reproduced with \ot~{\em invariant} dyna

S. Anantha Ramakrishna, K. Divakara Rao

The suitability of using the angular peak shape of the coherent backscattered light for estimating the light transport parameters of biological media has been investigated. Milk and methylene blue doped milk were used as tissue phantoms for the measurements carried out with a He-Ne laser (632.8nm). Results indicate that while the technique accurately estimat

Yuri S. Kivshar, Tristram J. Alexander, Solomon Saltiel

We introduce a novel class of parametric optical solitons supported simultaneously by two second-order nonlinear cascading processes, second-harmonic generation and sum-frequency mixing. We obtain, analytically and numerically, the solutions for three-wave spatial solitons and show that the presence of an additional cascading mechanism can change dramaticall