October 1997 arXiv papers — page 9

Martin S. Kochman'ski

In this paper a new approach to solving the 2D and 3D Ising models in external magnetic field $H\neq0$ is developed. The general formalism for the approach to the problem is presented on the example of the 2D Ising model in the external magnetic field. The paper presents a new method obtaining the Onsager solution and computations of asymptotic forms of low-

Martin S. Kochman'ski

The paper presents new method for calculating the low-temperature asymptotics of free energy of the 3D Ising model in external magnetic field $(H\neq 0)$. The results obtained are valid in the wide range of temperature and magnetic field values fulfilling the condition: $[1-\tanh(h/2)]\simε,$ for $ε\ll 1$, where $h=βH$, $β$ - the inverse temperature and $H$

Peter Olsson, S. Teitel

We carry out Monte Carlo simulations of the three dimensional (3D) lattice London superconductor in zero applied magnetic field, making a detailed finite size scaling analysis of the Meissner transition. We find that the magnetic penetration length λ, and the correlation length ξ, scale as λ~ ξ~ |t|^{-ν}, with ν= 0.66 \pm 0.03, consistent with ordinary 3D XY

Andrei Manolescu, Vidar Gudmundsson

We investigate the FIR-absorption of short period parallel quantum wires in a perpendicular quantizing magnetic field. The external time-dependent electric field is linearly polarized along the wire modulation. The mutual Coulomb interaction of the electrons is treated self-consistently in the ground state and in the absorption calculation within the Hartree

Andrew Matacz

In recent studies the truncated Levy process (TLP) has been shown to be very promising for the modeling of financial dynamics. In contrast to the Levy process, the TLP has finite moments and can account for both the previously observed excess kurtosis at short timescales, along with the slow convergence to Gaussian at longer timescales. I further test the tr

Wenjun Zheng, Yue Yu

In an attempt to understand quantitatively the remarkable discoveries of metal-insulator transitions in two-dimensional systems, we generalize Mott's variable range hopping theory to the situation with strong Coulomb interaction. In our formulation, the Gaussian form is adopted into the expression of the hopping probability, and the effect of Coulomb gap

Zoltan Kovacs

Hierarchic properties of chaotic scattering in a model of satellite encounters, studied first by Petit and Henon, are examined by decomposing the dwell time function and comparing scattering trajectories. The analysis reveals an (approximate) ternary organization in the chaotic set of bounded orbits and the presence of a stable island. The results can open t

Slavek M. Rucinski, Hilmar W. Duerbeck

Hipparcos parallax data for 40 contact binary stars of the W UMa-type (with errors in M_V < 0.5) are used to derive a new, (B-V)-based absolute-magnitude calibration of the form M_V = M_V(logP,B-V). The calibration covers the ranges 0.26 < (B-V)_0 < 1.14, 0.24 < P < 1.15 day, and 1.4 < M_V < 6.1; it is based on a solution weighted by relative errors in the p

Z. Huang, C. L. Sarazin

We have analyzed the ROSAT HRI image and PSPC spectra of Abell~4059. The most striking feature of the X-ray image is the two X-ray holes and an orthogonal X-ray bar in the center of the cluster. It is likely that the radio plasma from the cD galaxy may have displaced the X-ray gas and created the X-ray holes, or we may be seeing a rotationally supported disk

Piet Hut, Lars Hernquist, George Lake, Jun Makino

We present the results from a two-day study in which we discussed various implementations of Smooth Particle Hydrodynamics (SPH), one of the leading methods used across a variety of areas of large-scale astrophysical simulations. In particular, we evaluated the suitability of designing special hardware extensions, to further boost the performance of the high

R. D. van der Meulen, H. Bloemen, K. Bennett, W. Hermsen

We report on a study of the gamma-ray continuum emission from the Crab supernova nebula and on a search for nuclear de-excitation gamma-ray lines. Crab is the brightest continuum source in the 1-10 MeV gamma-ray sky, and its continuum radiation is most likely of synchrotron origin. It is a likely source of cosmic rays through shock acceleration and thus a po

Simon F. Portegies Zwart, Christopher A. Tout, Hyung Mok Lee

Dynamical models of star clusters are maturing in the sense that effects other than simple point particle dynamics are taken into account. We summarize the relevance of and prospects for this new generation of N-body models.

Zoltan Haiman, Abraham Loeb

We study the observational signatures of a potential population of low-luminosity quasars at high redshifts in a LambdaCDM cosmology. We derive the evolution of the quasar luminosity function at fainter luminosities and higher redshifts than currently detected, based on three assumptions: (1) the formation of dark-matter halos follows the Press-Schechter the

Martin Kerscher

Using a measure of clustering derived from the nearest neighbour distribution and the void probability function we are able to distinguish between regular and clustered structures. With an example we show that regularity is a property of a point set, which may be invisible in the two point correlation function. Applying this measure to a supercluster catalog

Matts Roos, S. M. Harun-or-Rashid

Taking the Hubble constant to be in the range 60 - 75 km/s Mpc we show that three independent conditions strongly rule out the standard model of flat space with vanishing cosmological constant.

Garrelt Mellema, Alejandro C. Raga, Jorge Canto, Peter Lundqvist

We study the evolution of dense neutral clumps located in the outer parts of planetary nebulae. These clumps will be photo-ionized by the ionizing radiation from the central star and change their structure in the process. The main effect of the ionization process is the setting up of a photo-evaporation flow and a shock running through the clump. Once this s

J. Pando, P. Lipa, M. Greiner, L. Z. Fang

It is of fundamental importance to determine if and how hierarchical clustering is involved in large-scale structure formation of the universe. Hierarchical evolution is characterized by rules which specify how dark matter halos are formed by the merging of halos at smaller scales. We show that scale-scale correlations of the matter density field are direct

T. Totani, K. Sato, H. E. Dalhed, J. R. Wilson

Future detection of a supernova neutrino burst by large underground detectors would give important information for the explosion mechanism of collapse-driven supernovae. We studied the statistical analysis for the future detection of a nearby supernova by using a numerical supernova model and realistic Monte-Carlo simulations of detection by the Super-Kamiok

Boyle, R. J. Smith, T. Shanks, S. M. Croom

We describe the aims, strategy and status of the AAO 2dF QSO redshift survey. This goal of the survey is to obtain redshifts for 30000 QSOs in a homogeneous magnitude limited (B<21) survey. The survey began in early 1997 and should be complete by the end of 1999.

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

The estimate of the ionizing UV background through the proximity effect analysis is discussed. Taking into account the correct bending of the column density distribution which appears in high resolution high s/n data, a value of the UV background ~5x10^{-22} cgs is obtained in the redshift interval z=1.7-4 without indication of any appreciable redshift evolu

Stephan Endrass

We extend some results on even sets of nodes which have been proved for surfaces up to degree 6 to surfaces up to degree 10. In particular, we give a formula for the minimal cardinality of a nonempty even set of nodes.

S. Kallel, R. J. Milgram

In this paper we study the topology of the spaces Hol(M,P{n},k) of (basepoint preserving) holomorphic maps of a given degree k from a Riemann surface M of genus g>0 into the n-th complex projective space P{n}, n>0. Using symmetric products of the surface as well as the geometry of the associated Abel-Jacobi maps, we construct an explicit topological compacti

Indranil Dasgupta

We discuss new bounce-like (but non-time-reversal-invariant-) solutions to Euclidean equations of motion, which we dub boomerons. In the Euclidean path integral approach to quantum theories, boomerons make an imaginary contribution to the vacuum energy. The fake vacuum instabilty can be removed by cancelling boomeron contributions against contributions from

V. Avila-Reese, C. Firmani, X. Hernández

We use a semianalytical approach and a CDM cosmological model to study the gravitational collapse and virialization, the structure, as well as the global and statistical properties of isolated dark matter galactic halos which emerge from primordial Gaussian fluctuations. From the statistical properties of the density fluctuation field the possible mass aggre

Gaetano Fiore

We briefly summarize our systematic construction procedure of q-deforming maps for Lie group covariant Weyl or Clifford algebras.

Carlos Simpson

Suppose $X$ is a 1-connected simplicial set with finitely many nondegenerate simplices. We give an effective algorithm to calculate a simplicial set with the $n$-type of the loop space $ΩX$. Iterating gives an algorithm to calculate the $π_i(X)$, different from the algorithms already known due to E. Brown and Kan-Curtis. The method is an effective version of

Zurab Kakushadze, Gary Shiu, S. -H. Henry Tye, Yan Vtorov-Karevsky

We review the construction and classification of three-family grand unified models within the framework of asymmetric orbifolds in perturbative heterotic superstring. We give a detailed survey of all such models which is organized to aid analysis of their phenomenological properties. We compute tree-level superpotentials for these models. These superpotentia

I. L. Aleiner, L. I. Glazman

We study the Coulomb blockade in a chaotic quantum dot connected to a lead by a single channel at nearly perfect transmission. We take into account quantum fluctuations of the dot charge and a finite level spacing for electron states within the dot. Mesoscopic fluctuations of thermodynamic and transport properties in the Coulomb blockade regime exist at any

O. M. Bulashenko, J. Mateos, D. Pardo, T. Gonzalez

Within a Monte Carlo simulation we investigate the statistical properties of an electron flow injected with a Poissonian distribution and transmitted under ballistic regime in the presence of long-range Coulomb interaction. Electrons are shown to exhibit a motional squeezing which tends to space them more regularly rather than strictly at random, and evidenc

K. Sheshadri, Rangan Lahiri Pushan Ayyub, Shobo Bhattacharya

We present a simple theory for structural transitions in displacive ferroelectrics of the perovskite type. In our theory, the competition between the elastic energy cost for the displacement of the homopolar ion from the centrosymmetric position, and the energy gain due to a ferroelectric ordering of the dipoles formed by the ionic displacements, leads natur

N. Gopalswamy, J. Zhang, M. R. Kundu, E. J. Schmahl

Transient microwave brightenings (TMBs) are small-scale energy releases from the periphery of sunspot umbrae, with a flux density two orders of magnitude smaller than that from a typical flare. Gopalswamy et al (1994) first reported the detection of the TMBs and it was pointed out that the radio emission implied a region of very high magnetic field so that t

Victor V. Batyrev, Ionunt Ciocan-Fontanine, Bumsig Kim, Duco van Straten

In this paper we show that conifold transitions between Calabi-Yau 3-folds can be used for the construction of mirror manifolds and for the computation of the instanton numbers of rational curves on complete intersection Calabi-Yau 3-folds in Grassmannians. Using a natural degeneration of Grassmannians $G(k,n)$ to some Gorenstein toric Fano varieties $P(k,n)

Orlando Alvarez, Luiz A. Ferreira, J. Sanchez Guillen

The zero curvature representation for two dimensional integrable models is generalized to spacetimes of dimension d+1 by the introduction of a d-form connection. The new generalized zero curvature conditions can be used to represent the equations of motion of some relativistic invariant field theories of physical interest in 2+1 dimensions (BF theories, Cher

Bai-lin Hao, Jun-xian Liu, Wei-mou Zheng

Recent progress of symbolic dynamics of one- and especially two-dimensional maps has enabled us to construct symbolic dynamics for systems of ordinary differential equations (ODEs). Numerical study under the guidance of symbolic dynamics is capable to yield global results on chaotic and periodic regimes in systems of dissipative ODEs which cannot be obtained

J. Harnad

The Hamiltonian approach to the theory of dual isomonodromic deformations is developed within the framework of rational classical R-matrix structures on loop algebras. Particular solutions to the isomonodromic deformation equations appearing in the computation of correlation functions in integrable quantum field theory models are constructed through the Riem

John A. Sidles

It is predicted that in force microscopy the quantum fluctuations responsible for the Casimir force can be directly observed as temperature-independent force fluctuations having spectral density $9π/(40\ln(4/e)) \hbar δk$, where $\hbar$ is Planck&#39;s constant and $δk$ is the observed change in spring constant as the microscope tip approaches a sample. For

Borge Nodland, C. J. McKinstrie

The propagation of an electromagnetic pulse in a plasma is studied for pulse durations that are comparable to the plasma period. When the carrier frequency of the incident pulse is much higher than the plasma frequency, the pulse propagates without distortion at its group speed. When the carrier frequency is comparable to the plasma frequency, the pulse is d

Frank Eisenmenger, Ulrich H. E. Hansmann

The multicanonical ansatz is used to study variations in the energy landscape of a small peptide, Met-enkephalin, under a change from the ECEPP/2 force field to ECEPP/3. Local minima with energies up to 5 kcal/mol higher than the global minima are sampled and classified according to H-bridges and backbone angles. The distribution and relative weight for vari

Ulrich H. E. Hansmann, Yuko Okamoto

We compare numerically the effectiveness of three recently proposed algorithms, multicanonical simulations, simulations in a 1/k-ensemble, and simulated tempering for the protein folding problem. For this we perform simulations with high statistics for one of the simplest peptides, Met-enkephalin. While the performances of all three approaches is much better

Ulrich H. E. Hansmann, Yuko Okamoto, Frank Eisenmenger

We demonstrate that the multicanonical approach is not restricted to Monte Carlo simulations, but can also be applied to simulation techniques such as molecular dynamics, Langevin, and hybrid Monte Carlo algorithms. The effectiveness of the methods are tested with an energy function for the protein folding problem. Simulations in the multicanonical ensemble

G. G. Adamian, N. V. Antonenko, W. Scheid, V. V. Volkov

Using the dinuclear system concept we present calculations of production cross sections for the heaviest nuclei. The obtained results are in a good agreement with the experimental data. The experimentally observed rapid fall-off of the cross sections of the cold fusion with increasing charge number $Z$ of the compound nucleus is explained. Optimal experiment

G. G. Adamian, N. V. Antonenko, W. Scheid, V. V. Volkov

A model of competition between complete fusion and quasifission channels in fusion of two massive nuclei is extended to include the influence of dissipative effects on the dynamics of nuclear fusion. By using the multidimensional Kramers-type stationary solution of the Fokker-Planck equation, the fusion rate through the inner fusion barrier in mass asymmetry

Kirill Ilinski

We give a brief introduction to the Gauge Theory of Arbitrage. Treating a calculation of Net Present Values (NPV) and currencies exchanges as a parallel transport in some fibre bundle, we give geometrical interpretation of the interest rate, exchange rates and prices of securities as a proper connection components. This allows us to map the theory of capital

D. _U. Jungnickel, C. Wetterich

We review the formalism of the effective average action in quantum field theory which corresponds to a coarse grained free energy in statistical mechanics. The associated exact renormalization group equation and possible nonperturbative approximations for its solution are discussed. This is applied to QCD where one observes the consecutive emergence of meson

L. N. Epele, C. A. Garcia Canal, William A. Ponce

Under the assumption that there exists a local gauge horizontal symmetry $G_H$ wich allows only for a top quark mass at tree level, we look for the constraints that charge quatization and the family structure of the standard model imposes on that symmetry.

Glennys R. Farrar

Gauginos may be nearly massless at tree level, with loop corrections giving a gluino mass of order 100 MeV and a photino mass of order 1 GeV. Relic photinos can naturally account for the observed dark matter, but their detection is more difficult than for conventional WIMPs. The lightest gluino-containing baryon could account for the recently observed ultra-

F. Berruto, G. Grignani, G. W. Semenoff, P. Sodano

We revisit the strong coupling limit of the Schwinger model on the lattice using staggered fermions and the hamiltonian approach to lattice gauge theories. Although staggered fermions have no continuous chiral symmetry, they posses a discrete axial invari ance which forbids fermion mass and which must be broken in order for the lattice Schwinger model to exh

Carmen Molina-Paris

For a quantum field in a curved background the choice of the vacuum state is crucial. We exhibit a vacuum state in which the expectation values of the energy and pressure allow an intuitive interpretation. We apply this general result to the de Sitter universe.

S. Bouarroudj, V. Ovsienko

The first group of differentiable cohomology of $\Diff(S^1)$, vanishing on the Möbius subgroup $PSL(2,R)\subset\Diff(S^1)$, with coefficients in modules of linear differential operators on $S^1$ is calculated. We introduce three non-trivial $PSL(2,R)$-invariant 1-cocycles on $\Diff(S^1)$ generalizing the Schwarzian derivative.

G. G. Adamian, N. V. Antonenko, W. Scheid

Based on the general form of the master equation for open quantum systems the tunneling is considered. Using the path integral technique a simple closed form expression for the tunneling rate through a parabolic barrier is obtained. The tunneling in the open quantum systems strongly depends on the coupling with environment. We found the cases when the dissip

B. Mombelli, O. Kahn, J. Leandri, Y. Leroyer

Various types of mixed spin two-dimensional Heisenberg networks are investigated by means of Monte Carlo simulations. This study aims at interpreting quantitatively the thermodynamical properties of two-dimensional molecule-based magnets recently synthesized. The proposed model requires that: (i) one of the two magnetic centers has a spin large enough to be

Ulrich H. E. Hansmann

We discuss the use of Tsallis generalized mechanics in simulated annealing algorithms. For a small peptide it is shown that older implementations are not more effective than regular simulated annealing in finding ground state configurations. We propose a new implementation which leads to an improvement over regular simulated annealing.

G. A. Ummarino, R. S. Gonnelli

In this article we quantify the possible effects of the breakdown of Migdal&#39;s theorem on the electron-phonon (e-p) coupling constant, on the critical temperature and on the superconducting gap by examining different kinds of superconducting materials either with low and high critical temperature. We use the theoretical approach developed by Grimaldi, Pie

G. A. Ummarino, R. S. Gonnelli, C. Bravi, V. A. Stepanov

An intrinsic gap depression at the Superconductor-Insulator interface due to the very short value of the coherence length in High-Tc Superconductors [HTSs] is considered, in the framework of a mixed (s+id)-wave pair symmetry for the order parameter ranging from pure s to pure d-wave. This gap depression acts as the main physical agent causing the relevant re

Fabrizio Brighenti, William G. Mathews

X-ray emitting gaseous halos, such as that in elliptical galaxies like NGC 4472, cannot have been produced solely from gas expelled from galactic stars. In traditional models for the evolution of hot interstellar gas (cooling flows) in ellipticals, the galaxies are assumed to have been cleared of gas by SNII-driven winds at some early time then gas is subseq

Ioseph L. Buchbinder, Sergei M. Kuzenko, Burt A. Ovrut

Using the harmonic superspace background field formulation for general D=4, N=2 super Yang-Mills theories, with matter hypermultiplets in arbitrary representations of the gauge group, we present the first rigorous proof of the N=2 non-renormalization theorem; specifically, the absence of ultraviolet divergences beyond the one-loop level. Another simple conse

Norman Margolus, Lev B. Levitin

We discuss the problem of counting the maximum number of distinct states that an isolated physical system can pass through in a given period of time---its maximum speed of dynamical evolution. Previous analyses have given bounds in terms of the standard deviation of the energy of the system; here we give a strict bound that depends only on E-E0, the system&#

M. Pernici, M. Raciti, F. Riva

The Wilsonian exact renormalization group gives a natural framework in which ultraviolet and infrared divergences can be treated separately. In massless QED we introduce, as the only mass parameter, a renormalization scale $Ł_R > 0$. We prove, using the flow equation technique, that infrared convergence is a necessary consequence of any zero-momentum renorma

E. Buffenoir, Ph. Roche

This work begins with a review of complexification and realification of Hopf algebras. We emphasize the notion of multiplier Hopf algebras for the description of different classes of functions (compact supported, bounded, unbounded) on complex quantum groups and the construction of the associated left and right Haar measure. Using a continuation of $6j$ symb

S. M. Hayden, G. Aeppli, P. Dai, H. A. Mook

We review recent measurements of the high-frequency dynamic magnetic susceptibility in the high-$T_c$ superconducting systems La$_{2-x}$Sr$_{x}$CuO$_4$ and YBa$_2$Cu$_3$O$_{6+x}$. Experiments were performed using the chopper spectrometers HET and MARI at the ISIS spallation source. We have placed our measurements on an absolute intensity scale, this allows s

D. V. Antonov

Making use of the duality transformation, we derive in the Londons&#39; limit of the Abelian Higgs Model string representation for the &#39;t Hooft loop average defined on the string world-sheet, which yields the values of two coefficient functions parametrizing the bilocal correlator of the dual field strength tensors. The asymptotic behaviours of these fun

M. Schroeder, R. Urbanczik

We use a binary search tree and the simplex algorithm to measure the fraction of patterns that can be stored by an Ising perceptron. The algorithm is much faster than exhaustive search and allows us to obtain accurate statistics up to a system size of N=42. The results show that the finite size scaling ansatz Nadler and Fink suggest in [1] cannot be applied

M. Raidal, A. Santamaria

Using an effective lagrangian description we analyze possible new physics contributions to the most relevant muon number violating processes: $μ\to e γ$ and $μ$--$e$ conversion in nuclei. We identify a general class of models in which those processes are generated at one loop level and in which $μ$--$e$ conversion is enhanced with respect to $μ\to e γ$ by a

Imre Varga, Etienne Hofstetter, Janos Pipek

Based on the spectral statistics obtained in numerical simulations on three dimensional disordered systems within the tight--binding approximation, a new superuniversal scaling relation is presented that allows us to collapse data for the orthogonal, unitary and symplectic symmetry ($β=1,2,4$) onto a single scaling curve. This relation provides a strong evid

A. A. Varlamov, G. Balestrino, E. Milani, D. V. Livanov

HTS show many puzzling anomalies in their normal state properties. Among them are: - the presence of a peak in the c-axis resistance and its growth in external magnetic field - the anomalous negative magnetoresistance observed above Tc - the deviation from the Korringa law in the temperature dependence of the NMR relaxation rate - the opening of a large pseu

Asish K. Dhara, Kewal Krishan, Chandana Bhattacharya, Sailjananda Bhattacharya

The dynamics of fission has been studied by solving Euler-Lagrange equation with dissipation generated through one and two body nuclear friction. The average kinetic energies of the fission fragments, prescission neutron multiplicities and the mean energies of the prescission neutrons have been calculated and compared with experimental values and they agree

Anthony J. Bracken, Xiang-Yu Ge, Yao-Zhong Zhang, Huan-Qiang Zhou

The integrable open-boundary conditions for the model of three coupled one-dimensional XY spin chains are considered in the framework of the quantum inverse scattering method. The diagonal boundary K-matrices are found and a class of integrable boundary terms is determined. The boundary model Hamiltonian is solved by using the coordinate space Bethe ansatz t

H. W. Braden

A new spectral parameter independent R-matrix (that depends on all of the dynamical variables) is proposed for the elliptic Calogero-Moser models. Necessary and sufficient conditions for this R-matrix to exist reduce to an equality between determinants of matrices involving elliptic functions. The needed identity appears new and is still unproven in full gen

Naihuan Jing

We construct level one representations of the quantum affine algebra $U_q(G_2^{(1)})$ by vertex operators from bosonic fields.

S. Veseli

We consider several issues related to the multidimensional integration using a network of heterogeneous computers. Based on these considerations, we develop a new general purpose scheme which can significantly reduce the time needed for evaluation of integrals with CPU intensive integrands. This scheme is a parallel version of the well-known adaptive Monte C

Reijiro Kubo, Waichi Ogura, Takesi Saito, Yukinori Yasui

The Relationship between the Neumann system and the Jacobi system in arbitrary dimensions is elucidated from the point of view of constrained Hamiltonian systems. Dirac brackets for canonical variables of both systems are derived from the constrained Hamiltonians. The geodesic equations corresponding to the Rosochatius system are studied as an application of

J. A. Minahan, D. Nemeschansky, N. P. Warner

We derive modular anomaly equations from the Seiberg-Witten-Donagi curves for softly broken N=4 SU(n) gauge theories. From these equations we can derive recursion relations for the pre-potential in powers of m^2, where m is the mass of the adjoint hypermultiplet. Given the perturbative contribution of the pre-potential and the presence of ``gaps&#39;&#39; we

V. A. Slobodenyuk

The Schwinger - DeWitt expansion for the evolution operator kernel of the Schrodinger equation is studied for convergence. It is established that divergence of this expansion which is usually implied for all continuous potentials, excluding ones of the form V(q)=aq^2+bq+c, really takes place only if the coupling constant g is treated as independent variable.

Hitoshi Nishino

We present a lagrangian formulation for recently-proposed supersymmetric Yang-Mills theory in twelve dimensions. The field content of our multiplet has an additional auxiliary vector field in the adjoint representation. The usual Yang-Mills field strength is modified by a Chern-Simons form containing this auxiliary vector field. This formulation needs no con

L. Martina, O. K. Pashaev, G. Soliani

The Jackiw-Teitelboim gauge formulation of the 1+1 dimensional gravity allows us to relate different gauge fixing conditions with integrable hierarchies of evolution equations. We show that the equations for the Zweibein fields can be written as a pair of time reversed evolution equations of the reaction-diffusion type, admitting dissipative solutions. The s

Debashis Gangopadhyay, Soumitra Sengupta

We show that the usual physical meaning of maximal symmetry can be made to remain unaltered even if torsion is present. All that is required is that the torsion fields satisfy some mutually consistent constraints. We also give an explicit realisation of such a scenario by determining the torsion fields, the metric and the associated Killing vectors.

Debashis Gangopadhyay, Soumitra Sengupta

We construct new maximally symmetric solutions for the metric. We then show that for a string moving in a background consisting of maximally symmetric gravity, dilaton field and second rank antisymmetric tensor field, the O(d) $\otimes$ O(d) transformation on the vacuum solutions, in general, gives inequivalent solutions that are not maximally symmetric.

Shin&#39;ichi Nojiri, Sergei D. Odintsov

We calculate the one-loop effective potential for the toroidal non-abelian D-brane in the constant magnetic SU(2) gauge field. The study of its properties shows that the potential is unbounded below. This fact indicates the instability of the non-abelian D-brane in the background under consideration like the instability of chromomagnetic vacuum in SU(2) gaug

C. T. H. Davies

I discuss the spectrum of hadrons containing heavy quarks ($b$ or $c$), and how well the experimental results are matched by theoretical ideas. Useful insights come from potential models and applications of Heavy Quark Symmetry and these can be compared with new numerical results from the ab initio methods of Lattice QCD.

C. D. Froggatt, H. B. Nielsen

We present two rather differently based predictions for the quark and lepton spectrum: One provides a rather successful fit to the mass suppressions---the well known fermion mass hierarchy---interpreted as due to most mass terms needing to violate approximately conserved quantum numbers corresponding to the AGUT group $ SMG^3\times U(1)_f$. This is actually,

Dietmar Ebert, Thomas Jurke

The approach of path integral hadronization, applied to a quark-diquark toy model, is used to derive an effective chiral meson-baryon Lagrangian. In this approach the Goldberger-Treiman relation, found at the quark-meson level, is re-established at the composite hadron level. For illu- strations, electromagnetic low energy characteristics of composite nucleo

C. Munoz

A review of the soft supersymmetry-breaking parameters and the $μ$ term arising in superstring models is performed paying special attention to their phenomenological implications. In particular, the violation of the scalar mass universality which may lead to dangerous flavor changing neutral current phenomena and the existence of charge and color breaking mi

S. V. Chekanov

Some aspects of applications of bunching parameters are discussed. It is investigated to what extent Monte-Carlo models, which have been tuned to reproduce global event-shape variables and single-particle inclusive distributions, agree with each other.

I. Royzen

A simple relativistic model is suggested that elucidates qualitatively the quark-antiquark distribution within virtual photon. The diffractive hadroproduction in DIS initiated by highly virtual photon $γ^{*}(Q^2)$ is discussed in more detail. The main result is that the contribution of large transverse scale $q\bar q$-fluctuations of the photon is just suffi

Thorsten Feldmann

The eta(c)-gamma transition form factor is calculated within a perturbative approach. It is shown that the Q^2 dependence of the form factor is well determined in the region where experimental data is expected in the near future.

I. M. Dremin

It is shown that Sudakov form factors for a colour dipole in a QCD-inspired model of leptoproduction of vector mesons reduce the value of the cross section of the process by an order of magnitude. They suppress the large size quark- antiquark pairs and unequal sharing of energy among the components of the dipole. Some freedom in the choice of the model param

Xue-Qian Li, Zhijian Tao

We demonstrate that if the universe is dominated by the massive cold dark matter, then besides the generally believed thermal distribution of the dark matter relics, there may exist some very energetic non-thermal relics of the dark matter particles in the universe from some unknown sources, such as from decay of supermassive X particle released from topolog

A. Donini, M. Guagnelli, P. Hernandez, A. Vladikas

We consider the lattice regularization of N=1 supersymmetric Yang--Mills theory with Wilson fermions. This formulation breaks supersymmetry at any finite lattice spacing; we discuss how Ward identities can be used to define a supersymmetric continuum limit, which coincides with the point where the gluino becomes massless. As a first step towards the understa

Aida X. El-Khadra

We present an exploratory study for the nonperturbative determination of the coefficient of the ${\cal O}(a)$ improvement term to the Wilson action, $c_{SW}$. Following the work by Lüscher et al., we impose the PCAC relation as a nonperturbative improvement condition on $c_{SW}$, without, however, using the Schrödinger functional in our calculation.

The MILC Collaboration, C. Bernard, T. Blum, T. A. DeGrand

We present an update on the MILC Collaboration&#39;s light hadron spectrum calculation with two flavors of dynamical, staggered quarks. We present extrapolations of the nucleon to rho mass ratio to the continuum limit for fixed values of the pi to rho mass ratio including the physical one.

Raymond E. Frey

Key electroweak measurements performed by the SLD collaboration at the SLC are described and recent results given. The left-right cross-section asymmetry, $A_{LR}$, has been updated to include the 1996 data. It remains the single most precise measurement of $\sin^2θ_W^{eff}$, and it is compared to the LEP results. The polarized differential cross section for

The WA98 Collaboration, M. M. Aggarwal et al

The restoration of chiral symmetry and its subsequent breaking through a phase transition has been predicted to create regions of Disoriented Chiral Condensates (DCC). This phenomenon has been predicted to cause anomalous fluctuations in the relative production of charged and neutral pions in high-energy hadronic and nuclear collisions. The WA98 experiment h

F. Sefkow

Recent results from the H1 and ZEUS collaborations on hard QCD processes in ep interactions are reviewed. The topics cover jet shapes, the structure of real and virtual photons, and the production of J/Psi mesons and open charm.

M. C. Lima, I. Damião Soares

A relativistic model for the emission of gravitational waves from an initially unperturbed Schwarzschild black hole, or spherical collapsing configuration, is completely integrated. The model consists basically of gravitational perturbations of the Robinson-Trautman type on the Schwarzschild spacetime. In our scheme of perturbation, gravitational waves may e

U. Guenther, A. Zhuk

We study inhomogeneous multidimensional cosmological models with a higher dimensional space-time manifold under dimensional reduction. Stability due to different types of effective potentials is analyzed for specific configurations of internal spaces. Necessary restrictions on the parameters of the models are found and masses of gravitational excitons (small

U. Guenther, A. Zhuk

We study inhomogeneous multidimensional cosmological models with a higher dimensional space-time manifold under dimensional reduction and show that small inhomogeneous excitations of the scale factors of the internal spaces near minima of effective potentials should be observable as massive scalar particles (gravitational excitons) in the external space-time

J. Acacio de Barros, N. Pinto-Neto, M. A. Sagioro-Leal

We apply the causal interpretation of quantum mechanics to homogeneous and isotropic quantum cosmology where the sources of the gravitational field are either dust or radiation perfect fluids. We find non-singular quantum trajectories which tends to the classical one when the scale factor becomes much larger then the Planck length. In this situation, the qua

S. Jhingan

We will describe here the structure of singularity forming in gravitational collapse of spherically symmetric inhomogeneous dust. Such a collapse is described by the Tolman-Bondi-Lema{î}tre metric. The main new result here relates, in a general way, the formation of black holes and naked shell-focusing singularities resulting as the final fate of such a coll

Ralf Meyer

The matrix normed structure of the unitization of a (non-selfadjoint) operator algebra is determined by that of the original operator algebra. This yields a classification up to completely isometric isomorphism of two-dimensional unital operator algebras. This allows to define invariant distances on the spectrum of commutative operator algebras analogous to

François Lalonde, Dusa McDuff, Leonid Polterovich

This paper studies the question of when a loop $ϕ$ in the group Symp$(M,ω)$ of symplectomorphisms of a symplectic manifold $(M,ω)$ is isotopic to a loop that is generated by a time-dependent Hamiltonian function. (Loops with this property are said to be Hamiltonian.) Our main result is that Hamiltonian loops are rigid in the following sense: if $ϕ$ is Hamilt