April 1999 arXiv papers — page 19

S. Bielefeld, J. Ihmels, H. C. Pauli

By their very nature, field-theoretical Hamiltonians are derived in momentum representation. To solve the corresponding integro-differential equations is more difficult than to solve the simpler differential equations in configuration space (`Schrödinger equation'). For the latter many different and very effective methods have been developed in the past.

Timo van Ritbergen, Robin G. Stuart

The determination of the Fermi coupling constant, G_F, is examined in the light of recently calculated 2-loop QED corrections and planned experiments to measure the muon lifetime to a level below 1ppm. The methods used in the calculation of the QED corrections are described in detail. Sources of the dominant theoretical and experimental uncertainties are ide

Feng Yuan, Kuang-Ta Chao

Following our recent paper on the calculations of diffractive quark jet production at hadron colliders, we present here the calculations of gluon jet production at hadron colliders in the two-gluon exchange parameterization of the Pomeron model. We use the helicity amplitude method to calculate the cross section formula. We find that for the gluon jet produc

Feng Yuan, Kuang-Ta Chao

Direct photon production at large transverse momentum in the coherent diffractive processes at hadron colliders is calculated in the two-gluon exchange model. We find that the amplitude for the production process is related to the differential off-diagonal gluon distribution function in the proton. We estimate the production rate at the Fermilab Tevatron by

Feng Yuan, Kuang-Ta Chao

Massless quark and antiquark jet production at large transverse momentum in the coherent diffractive processes at hadron colliders is calculated in the two-gluon exchange parametrization of the Pomeron model. We use the helicity amplitude method to calculate the cross section formula. We find that for the light quark jet production the diffractive process is

Lawrence Hall, Christopher Kolda

If spacetime contains large compact extra dimensions, the fundamental mass scale of nature, $Lambda$, may be close to the weak scale, allowing gravitational physics to significantly modify electroweak symmetry breaking. Operators of the form $(1/Lambda^2) |phi^* D phi|^2$ and $(1/Lambda^2) phi^* W B phi$, where $W$ and $B$ are the SU(2) and U(1) field streng

J. L. Lucio, G. Moreno, M. Napsuciale, J. J. Toscano

We work out predictions of the Linear Sigma Model for the $γγ\toπ^0 π^0$ cross section. We consider the sigma width, which is introduced in a consistent way with chiral Ward identities. The results of Chiral Perturbation Theory are recovered in the $m_σ\to \infty$ limit. A fit to existing experimental results is consistent with a light and broad $σ$ meson.

M. Engelhardt, K. Langfeld, H. Reinhardt, O. Tennert

By fixing lattice Yang-Mills configurations to the maximal center gauge and subsequently applying the technique of center projection, one can identify center vortices in these configurations. Recently, center vortices have been shown to determine the string tension between static quarks at finite temperatures (center dominance); also, they correctly reproduc

CRESST-Collaboration, :, M. Bravin, M. Bruckmayer

The current status of CRESST (Cryogenic Rare Event Search using Superconducting Thermometers) and new results concerning the detector development are presented. The basic technique of CRESST is to search for particle Dark Matter (WIMPS, Weakly Interacting Massive particles) by the measurement of non-thermal phonons as created by WIMP-induced nuclear recoils.

E. S. C. Ching, P. T. Leung, W. M. Suen, S. S. Tong

An open system is not conservative because energy can escape to the outside. An open system by itself is thus not conservative. As a result, the time-evolution operator is not hermitian in the usual sense and the eigenfunctions (factorized solutions in space and time) are no longer normal modes but quasinormal modes (QNMs) whose frequencies $ω$ are complex.

S. M. Merkowitz, J. A. Lobo, M. A. Serrano

A single spherical antenna is capable of measuring the direction and polarization of a gravitational wave. It is possible to solve the inverse problem using only linear algebra even in the presence of noise. The simplicity of this solution enables one to explore the error on the solution using standard techniques. In this paper we derive the error on the dir

Edward Seidel, Wai-Mo Suen

The astrophysics of compact objects, which requires Einstein's theory of general relativity for understanding phenomena such as black holes and neutron stars, is attracting increasing attention. In general relativity, gravity is governed by an extremely complex set of coupled, nonlinear, hyperbolic-elliptic partial differential equations. The largest par

Miguel Alcubierre, Gabrielle Allen, Bernd Bruegmann, Gerd Lanfermann

We demonstrate that evolutions of three-dimensional, strongly non-linear gravitational waves can be followed in numerical relativity, hence allowing many interesting studies of both fundamental and observational consequences. We study the evolution of time-symmetric, axisymmetric {\it and} non-axisymmetric Brill waves, including waves so strong that they col

Alexander Burinskii, Giulio Magli

Using a complex representation of the Debney-Kerr-Schild (DKS) solutions and the Kerr theorem we analyze the boosted Kerr geometries and give the exact and explicit expressions for the metrics, the principal null congruences, the coordinate systems and the location of the singularities for arbitrary value and orientation of the boost with respect to the angu

Daniel A. Stariolo, Jeferson J. Arenzon

We study by means of Monte Carlo simulations the off equilibrium properties of a model glass, the Frustrated Ising Lattice Gas (FILG) in three dimensions. We have computed typical two times quantities, like density-density autocorrelations and the autocorrelation of internal degrees of freedom. We find an aging scenario particularly interesting in the case o

A. Rochefort, F. Lesage, D. R. Salahub, Ph. Avouris

We have calculated the effects of structural distortions of armchair carbon nanotubes on their electrical transport properties. We found that the bending of the nanotubes decreases their transmission function in certain energy ranges and leads to an increased electrical resistance. Electronic structure calculations show that these energy ranges contain local

N. S. Branco

We study the Blume-Emery-Griffiths model in a random crystal field in two and three dimensions, through a real-space renormalization-group approach and a mean-field approximation, respectively. According to the two-dimensional renormalization-group calculation, non-symmetry-breaking first-order phase transitions are eliminated and symmetry-breaking discontin

B. Noheda, N. Duan, N. Cereceda, J. A. Gonzalo

A new experimental set-up controlled by computer has been made to measure the pyroelectric charge of ferroelectric materials with a relatively high conductivity at slow rates of temperature variation. It allowed us to obtain the polarisation vs. temperature behaviour of PZT with various compositions in the whole range of temperatures with a high accuracy. Th

Durga P. Choudhury, John S. Derov, S. Sridhar

Measurement of harmonic power on a suspended stripline microwave resonator patterned out of thin film YBa_2Cu_3O_7 (YBCO) has been carried out as a function of temperature and microwave power. The third harmonic power P_3 shows a subtle nonlinear dependence on the fundamental power P_1 on a log-log scale. Fit to a straight line yields slopes of P_3 vs. P_1 b

Marcelo R. Ubriaco

Starting with the fractal inspired distribution functions for Maxwell-Boltzmann, Bose-Einstein and Fermi systems, as reported by F. Büyükkiliç and D. Demirhan, we obtain the corresponding probability distributions and study their thermodynamic behavior. We compare our results with those corresponding to ideal gases (q=1), and Bose-Einstein and Fermi systems

Julie E. Millburn, John F. Mitchell, Dimitri N. Argyriou

We report the synthesis and room temperature crystal structures of the heretofore unknown, metastable manganites La2-2xSr1+2xMn2O7+delta (0.5 < x < 0.9) via high-temperature (T=1650 C) quenching followed by low-temperature (T=400 C) annealing to fill oxygen vacancies; this approach enables access to the electronic, magnetic, and structural properties of prev

A. Alekseev, V. Cheianov, A. P. Dmitriev, V. Yu. Kachorovskii

In the paper we dscuss experimental results of M. Grayson et al. on tunneling $I$-$V$ characteristics of the quantum Hall edge. We suggest a two step tunneling mechanism involving localized electron states near the edge, which might account for discrepancy between the experimental data and the predictions of the chiral Luttinger liquid theory of the quantum

R. Melzi, P. Carretta

We present a careful analysis of the temperature dependence of the nuclear spin-lattice relaxation rate $1/T_1$ in gapped quasi-1D Heisenberg antiferromagnets. It is found that in order to estimate the value of the gap correctly from $1/T_1$ the peculiar features of the dispersion curve for the triplet excitations must be taken into account. The temperature

D. H. E. Gross, E. Votyakov

It is discussed how phase transitions of first order (with phase separation and surface tension), continuous transitions and (multi)-critical points can be defined and classified for finite systems from the topology of the energy surface $e^{S(E,N)}$ of the mechanical N-body phase space or more precisely of the curvature determinant $D(E,N)=\partial^2S/\part

V. Janis

We present a general framework how to investigate stability of solutions within a single self-consistent renormalization scheme being a parquet-type extension of the Baym-Kadanoff construction of conserving approximations. To obtain a consistent description of one- and two-particle quantities, needed for the stability analysis, we impose equations of motion

V. Janis

The question of thermodynamic consistence and $Φ$-derivability of the asymptotic limit of high spatial dimensions for quantum itinerant models is addressed. It is shown that although the irreducible $n$-particle Green functions are local, reducible vertex functions retain different momentum dependence. As a consequence, the vertex corrections to conductivity

S. M. Reimann, M. Koskinen, M. Manninen, B. R. Mottelson

Quantum dots in magnetic fields are studied within the current spin density functional formalism avoiding any spatial symmetry restrictions of the solutions. We find that the maximum density droplet reconstructs into states with broken internal symmetry: The Chamon-Wen edge co-exists with a modulation of the charge density along the edge. The phase boundarie

Jurgen Horbach, Walter Kob

We investigate the structure and dynamics of sodium disilicate by means of molecular dynamics computer simulation. We show that the structure is described by a partially destroyed tetrahedral SiO_4 network and a spherical super structure formed by the silicon and sodium atoms. The static structure factor of our simulation is in very good agreement with one f

C. Bauer, S. Dietrich, A. O. Parry

Using an interface displacement model derived from a microscopic density functional theory we investigate thin liquidlike wetting layers adsorbed on flat substrates with an embedded chemical heterogeneity forming a stripe. For a wide range of effective interface potentials we find first-order phase transitions as well as continuous changes between lateral in

Rajiv R. P. Singh, Zheng Weihong, C. J. Hamer, J. Oitmaa

Ground state energies for plaquette and dimer order in the $J_1-J_2$ square-lattice spin-half Heisenberg model are compared using series expansion methods. We find that these energies are remarkably close to each other at intermediate values of $J_2/J_1$, where the model is believed to have a quantum disordered ground state. They join smoothly with those obt

Kazuhiko Kuroki, Ryotaro Arita, Hideo Aoki

A link between the spin fluctuation and the &#34;fermiology&#34; is explored for the single-band Hubbard model within the fluctuation exchange (FLEX) approximation. We show that the experimentally observed peak position of the spin structure in the high T_C cuprates can be understood from the model that reproduces the experimentally observed Fermi surface. I

I. L. Drichko, A. M. Diakonov, V. D. Kagan, I. Yu. Smirnov

High frequency (hf) conductivity in the form $σ^{hf} = σ_1^{hf} - iσ_2^{hf}$ was obtained from the measurement of Surface Acoustic Waves (SAW) attenuation and velocity (f=30 MHz) in GaAs/AlGaAs heterostructures ($n=1.3-7\cdot 10^{11}cm^{-2}$). It has been shown that in the Integer Quantum Hall Effect (IQHE) regime for all the samples at magnetic fields corre

Ken Kiyono, Nobuko Fuchikami

An improved mass-spring model for a dripping faucet is presented. The model is constructed based on the numerical results which we recently obtained from fluid dynamical calculations. Both the fluid dynamical calculations and the present mass-spring model exhibit a variety of complex behavior including transition to chaos in good agreement with experiments.

T. P. Dominici, R. Teixeira, J. E. Horvath, G. A. Medina Tanco

We present in this work secondary catalogs up to $m_{Val} \sim 13$ based on the Tycho reference frame (ESA, 1997) for 12 selected low-extinction fields towards the galactic bulge. The observations have been performed with the Askania-Zeiss Meridian Circle equiped with a CCD camera, located at the Abrahão de Moraes Observatory (Valinhos, Brazil) and operated

F. P. Pijpers

An unbiased method for improving the resolution of astronomical images is presented. The strategy at the core of this method is to establish a linear transformation between the recorded image and an improved image at some desirable resolution. In order to establish this transformation only the actual point spread function and a desired point spread function

P. G. Ferreira, M. Davis, H. A. Feldman, A. H. Jaffe

The mean pairwise velocity of galaxies has traditionally been estimated from the redshift space galaxy correlation function. This method is notorious for being highly sensitive to the assumed model of the pairwise velocity dispersion. Here we propose an alternative method to estimate the streaming velocity directly from peculiar velocity samples, which conta

P. G. Ferreira, K. M. Gorski, J. Magueijo

I review our recent claim that there is evidence of non-Gaussianity in the 4 Year COBE DMR data. I describe the statistic we apply, the result we obtain and make a detailed list of the systematics we have analysed. I finish with a qualitative understanding of what it might be and its implications.

B. Ricci, F. L. Villante, M. Lissia

We derive a lower limit on the Beryllium neutrino flux on earth, $Φ(Be)_{min} = 1\cdot 10^9 cm^{-2} s^{-1}$, in the absence of oscillations, by using helioseismic data, the B-neutrino flux measured by Superkamiokande and the hydrogen abundance at the solar center predicted by Standard Solar Model (SSM) calculations. We emphasize that this abundance is the on

K. Iwasawa, A. C. Fabian, K. Nandra

We report on simultaneous ASCA and ROSAT observations of the Seyfert galaxy NGC5548 made during the ASCA Performance Verification phase. Spectral features due to a warm absorber and reflection are clearly seen in the X-ray spectra. We find that the continuum spectral shape differs between the ASCA and ROSAT datasets. The photon-index obtained from the ROSAT

S. Siegler, H. Riffert

We present a fully Lagrangian conservation form of the general relativistic hydrodynamic equations for perfect fluids with artificial viscosity in a given arbitrary background spacetime. This conservation formulation is achieved by choosing suitable Lagrangian time evolution variables, from which the generic fluid variables rest-mass density, 3-velocity, and

P. Saracco, S. D&#39;Odorico, A. Moorwood, J. G. Cuby

Deep J and Ks band images covering a $5\times5$ arcmin area centered on the NTT Deep Field have been obtained during the Science Verification of SOFI at the NTT. These images were made available via the Web in early June. The preliminary results we have obtained by the analysis of these data are the following: 1) the counts continue to rise with no evidence

G. Giovannini, G. B. Taylor, E. Arbizzani, M. Bondi

We report on centimeter VLA and VLBI observations of the giant, low power radio galaxy 1144+35. These observations are sensitive to structures on scales from less than 1 parsec to greater than 1 megaparsec. Diffuse steep spectrum lobes on the megaparsec scale are consistent with an age of $\sim$ 10$^8$ years. On the parsec scale, a complex jet component is s

Jihn E. Kim

From the present cosmic abundance of the light elements, one can obtain a lifetime bounds of LSP. From the consideration of deuterium, we obtain $τ_χ \ge 10^6$ s.

Yoshiaki Taniguchi, Youichi Ohyama, D. B. Sanders

It is known that merging galaxies with luminous starbursts and high far-infrared luminosities tend to have higher $R_{1-0} =^{12}CO(J=1-0)/^{13}CO(J=1-0)$ integrated line intensity ratios ($R_{1-0} \simeq 20-50$) than normal spiral galaxies ($R_{1-0} \simeq 5-15$). Comparing far-infrared luminosities [L(FIR)] with those of ^{12}CO(J=1-0) and ^{13}CO(J=1-0) f

K. L. Rhode, J. J. Salzer, D. J. Westpfahl, L. A. Radice

The nearby irregular galaxy Holmberg II has been extensively mapped in HI using the Very Large Array (VLA), revealing intricate structure in its interstellar gas component (Puche et al. 1992). An analysis of these structures shows the neutral gas to contain a number of expanding HI holes. The formation of the HI holes has been attributed to multiple supernov

A. Udalski, I. Soszynski, M. Szymanski, M. Kubiak

We present a sample of 13 candidates for single-mode second overtone Cepheids discovered in the 2.4 square degree area of the SMC bar during the OGLE microlensing search. All candidates passed four photometric tests: analysis of Fourier parameters of the light curve, R_21 and ϕ_21, position in the period-luminosity diagram and location in the color-magnitude

D. P. Snowden-Ifft, C. J. Martoff, J. M. Burwell

Weakly Interacting Massive Particles (WIMPs) are an attractive candidate for the dark matter thought to make up the bulk of the mass of our universe. We explore here the possibility of using a low pressure negative ion drift chamber to search for WIMPs. The innovation of drifting ions, instead of electrons, allows the design of a detector with exceptional se

Matthew D. Duez, Eric T. Engelhard, John M. Fregeau, Kevin M. Huffenberger

We improve and extend Shapiro&#39;s model of a relativistic, compact object which is stable in isolation but is driven dynamically unstable by the tidal field of a binary companion. Our compact object consists of a dense swarm of test particles moving in randomly-oriented, initially circular, relativistic orbits about a nonrotating black hole. The binary com

Prakash Mathews, Sreerup Raychaudhuri, K. Sridhar

Dijet production at the Tevatron including effects of virtual exchanges of spin-2 Kaluza-Klein modes in theories with large extra dimensions is considered. The experimental dijet mass and angular distribution are exploited to obtain stringent limits ($\sim 1.2$ TeV) on the effective string scale $M_S$.

F. Antonuccio, O. Lunin, S. Pinsky

We consider a two dimensional SU(N) gauge theory coupled to an adjoint Majorana fermion, which is known to be supersymmetric for a particular value of fermion mass. We investigate the `soft&#39; supersymmetry breaking of the discrete light cone quantization (DLCQ) of this theory. There are several DLCQ formulations of this theory currently in the literature

Stefano Liberati, Matt Visser, Francesco Belgiorno, Dennis Sciama

Several years ago Schwinger proposed a physical mechanism for sonoluminescence in terms of changes in the properties of the quantum-electrodynamic (QED) vacuum state. This mechanism is most often phrased in terms of changes in the Casimir Energy: changes in the distribution of zero-point energies and has recently been the subject of considerable controversy.

Sidi Cherkawi Benzahra

I consider the dissociation of the upsilon meson due to absorption of a thermal gluon. I discuss the dissociation rate in terms of the energy density, the number density, and the temperature of the quark-gluon plasma. I compare this to the effect due to screening.

Arnold Roessl

In the context of chiral SU(2) perturbation theory, pion-kaon scattering is analysed near the threshold to fourth chiral order. The scattering amplitude is calculated both in the relativistic framework and by using an approach similar to heavy baryon chiral perturbation theory. Both methods lead to equivalent results. We obtain relations between threshold pa

Z. Bern, A. K. Grant

We demonstrate that QCD gluon amplitudes can be used to construct a Lagrangian for gravity. This procedure makes use of perturbative `squaring&#39; relations between gravity and gauge theory that follow from string theory. We explicitly carry out the construction for up to five-point interactions and discuss a set of field variables in the Einstein-Hilbert L

Ana Achucarro, Tanmay Vachaspati

We review a class of non-topological defects in the standard electroweak model, and their implications. Starting with the semilocal string, which provides a counterexample to many well known properties of topological vortices, we discuss electroweak strings and their stability with and without external influences such as magnetic fields. Other known properti

Kun Yang, A. H. MacDonald

We show in this paper that the boundary condition averaged nondissipative drag conductance of two coupled mesoscopic rings with no tunneling, evaluated in a particular many-particle eigenstate, is a topological invariant characterized by a Chern integer. Physical implications of this observation are discussed.

Roh Suan Tung

We propose a gauge theory of gravitation. The gauge potential is a connection of the Super SL(2,C) group. A MacDowell-Mansouri type of action is proposed where the action is quadratic in the Super SL(2,C) curvature and depends purely on gauge connection. By breaking the symmetry of the Super SL(2,C) topological gauge theory to SL(2,C), a spinor metric is nat

Amit Giveon, Martin Rocek

String backgrounds of the form AdS_3 x N that give rise to two dimensional spacetime superconformal symmetry are constructed.

Piotr Garstecki, Trinh Xuan Hoang, Marek Cieplak

Dynamical connectivity graphs, which describe dynamical transition rates between local energy minima of a system, can be displayed against the background of a disconnectivity graph which represents the energy landscape of the system. The resulting supergraph describes both dynamics and statics of the system in a unified coarse-grained sense. We give examples

M. K. Volkov, V. L. Yudichev

First radial excitations of the isoscalar and isovector scalar mesons f_0(400-1200), f_0(980) and a_0(980) are investigated in the framework of a nonlocal version of a chiral quark model of the Nambu--Jona-Lasinio type. It is shown that f_0(1370), f_J(1710) and a_0(1450) are the first radially excited states of f_0(400-1200), f_0(980) and a_0(980) which are

V. Berezinsky, G. Fiorentini, M. Lissia

The excess of solar-neutrino events above 13 MeV that has been recently observed by Superkamiokande can be explained by the vacuum oscillation solution to the Solar Neutrino Problem (SNP). If the boron neutrino flux is 20% smaller than the standard solar model (SSM) prediction and the chlorine signal is assumed 30% (or 3.4 sigmas) higher than the measured on

L. V. Fil&#39;kov, V. L. Kashevarov, E. S. Konobeevski, M. V. Mordovskoy

The reaction pd-->pX at 305 MeV is studied with the aim to search for supernarrow dibaryons, the decay of which into two nucleons is forbidden by the Pauli exclusion principle. The experiment was carried out at the Moscow Meson Factory using the spectrometer TAMS, which detected the scattered proton in coincidence with another charged particle (either p or d

Oded Schramm

The uniform spanning tree (UST) and the loop-erased random walk (LERW) are related probabilistic processes. We consider the limits of these models on a fine grid in the plane, as the mesh goes to zero. Although the existence of scaling limits is still unproven, subsequential scaling limits can be defined in various ways, and do exist. We establish some basic

Jayaram N. Chengalur, A. G. de Bruyn, D. Narasimha

We report on WSRT observations of HI and OH absorption at z=0.885 towards the radio lens PKS 1830-21, mm wave transitions of several molecular species have already been observed at this redshift. At mm wavelengths the source structure is dominated by two extremely compact components, the northeast (NE) and southwest (SW) components. At lower frequencies the

Anna Pla-Dalmau, Alan D. Bross, Kerry L. Mellott

As a way to lower the cost of plastic scintillation detectors, commercially available polystyrene pellets have been used in the production of scintillating materials that can be extruded into different profiles. The selection of raw materials is discussed. Two techniques to add wavelength shifting dopants to polystyrene pellets and to extrude plastic scintil

L. Lapikas, J. Wessling, R. B. Wiringa

Experimental momentum distributions for the transitions to the ground state and first excited state of 6He have been measured via the reaction 7Li(e,e&#39;p)6He, in the missing momentum range from -70 to 260 MeV/c. They are compared to theoretical distributions calculated with mean-field wave functions and with variational Monte Carlo (VMC) wave functions wh

Aaron Robertson

We present a recursive algorithm for finding good lower bounds for the classical Ramsey numbers. Using notions from this algorithm we then give some results for generalized Schur numbers, which we call Issai numbers.

A. Rivero

A problem from Democritus is used to illustrate the building, and use, of infinitesimal covectors from its regularized, finite, counterpart.

Ruy Exel

We show that every Fell bundle B over a locally compact group G is &#34;proper&#34; in a sense recently introduced by Ng. Combining our results with those of Ng we show that if B satisfies the &#34;approximation property&#34; then it is amenable in the sense that the full and reduced cross-sectional C*-algebras coincide.

John Quigg, Nandor Sieben

Groupoid actions on C*-bundles and inverse semigroup actions on C*-algebras are closely related when the groupoid is r-discrete.

A. A. Akhmetshin, I. M. Krichever, Y. S. Volvovski

An exact formula for the solutions to the WDVV equation in terms of horizontal sections of the corresponding flat connection is found.

Fabio Scardigli

We review versions of the Generalized Uncertainty Principle (GUP) obtained in string theory and in gedanken experiments carried out in Quantum Gravity. We show how a GUP can be derived from a measure gedanken experiment involving micro-black holes at the Planck scale of spacetime. The model uses only Heisenberg principle and Schwarzschild radius and it is in

Ian G. Moss, Noriko Shiiki

It has been assumed that it is possible to approximate the interactions of quantized BPS solitons by quantising a dynamical system induced on a moduli space of soliton parameters. General properties of the reduction of quantum systems by a Born-Oppenheimer approximation are described here and applied to sigma models and their moduli spaces in order to learn

Jens Erler

We summarize the status of the Standard Model with special emphasis on the extraction of the Higgs boson mass using Bayesian inference.

Ambreesh K. Gupta, Naba K. Mondal, Sreerup Raychaudhuri

We use the invariant mass distribution of Drell-Yan dileptons as measured by the CDF and D0 Collaborations at the Fermilab Tevatron and make a careful analysis to constrain Kaluza-Klein models with large extra dimensions. The combined data from both collaborations lead to a conservative lower bound on the string scale M_S of about 1 TeV at 95% confidence lev

Dilip Kumar Ghosh, Rohini M. Godbole, Sreerup Raychaudhuri

We investigate the production of charginos and neutralinos at a 500 GeV e^+e^- collider (NLC) and study their decays to the lightest neutralino, which then decays into multi-fermion final states through couplings which do not conserve R-parity. These couplings are assumed to affect only the decay of the lightest neutralino. Detailed analyses of the possible

Xiao-Jun Bi, Yuan-Ben Dai

We calculate the CP-violating effects in the top quark semi-leptonic three body decays induced by the supersymmetric CP-odd phase of the top squark trilinear soft breaking term $\arg(A_t)$. The light top squark mass is assumed to be close to the top quark mass $m_{\tilde{t}}\sim m_t$. The CP-conserving phase is provided by the $χ^+$ and $χ^0$ cut. We find th

N. O. Agasian

The gluon fields screening in the stochastic vacuum of gluodynamics is studied. The effective action is derived for the instanton interacting with nonperturbative fields. Quantum nonperturbative effects are shown to affect greatly the shape of instanton. The power asymptotics x^2 of the classical &#34;instanton&#39;s profile function&#34; at large distances

M. Ruiz-Altaba, J. L. Lucio, M. Napsuciale

Chiral Ward identities lead to consistent accounting for the sigma&#39;s width in the linear sigma model&#39;s Feynman rules. Reanalysis of pion scattering data at threshold imply a mass for the sigma of 600+ 200 - 100 MeV.

N. N. Achasov

It is presented a critical consideration of all unusual properties of the scalar $a_0(980)$ and $f_0(980)$-mesons in the four-quark, two-quark and molecular models. The arguments are adduced that the four-quark model is more preferable. It is discussed the complex of experiments that could finally resolve this issue.

Lochlain O&#39;Raifeartaigh, Norbert Straumann

One of the major developments of twentieth century physics has been the gradual recognition that a common feature of the known fundamental interactions is their gauge structure. In this article the authors review the early history of gauge theory, from Einstein&#39;s theory of gravitation to the appearance of non-abelian gauge theories in the fifties. The au

Andrew W Halley

Measurements of b and c quark asymmetries using data collected at LEP 1 are described. The relative merits of each of the individual techniques used is emphasised as is the most profitable way of combining them. Effects of radiative corrections are discussed, together with the impact of these measurements on global electroweak fits used to estimate the expec

John T. Whelan

I describe the current status of a collaboration with J.D. Romano, R.H. Price, and W. Krivan to model the geometry of and gravitational radiation emitted by a binary system of compact objects in the regime where non-perturbative gravitational effects exist, but the rate of inspiral is still small relative to the orbital frequency. The method of looking for a

N. Stergioulas, J. A. Font, K. D. Kokkotas

We present first results of the non-linear evolution of rotating relativistic stars obtained with an axisymmetric relativistic hydrodynamics code in a fixed spacetime. As initial data we use stationary axisymmetric and perturbed configurations. We find that, in order to prevent (numerical) angular momentum loss at the surface layers of the star a high-resolu

Marc Barthelemy, S. V. Buldyrev, S. Havlin, H. E. Stanley

We study the backbone connecting two given sites of a two-dimensional lattice separated by an arbitrary distance $r$ in a system of size $L$. We find a scaling form for the average backbone mass: $<M_B>\sim L^{d_B}G(r/L)$, where $G$ can be well approximated by a power law for $0\le x\le 1$: $G(x)\sim x^ψ$ with $ψ=0.37\pm 0.02$. This result implies that $<M_B

S. B. Rutkevich

We calculate perturbatively the tunneling decay rate $Γ$ of the metastable phase in the quantum d=1 Ising model in a skew magnetic field near the coexistence line $0<h_{x}<1, h_{z}\to -0$ at T=0. It is shown that $Γ$ oscillates in the magnetic field $h_{z}$ due to discreteness of the excitation energy spectrum. After mapping of the obtained results onto the

Tohru Okamoto, Kunio Hosoya, Shinji Kawaji, Atsuo Yagi

We have investigated correlation between spin polarization and magnetotransport in a high mobility silicon inversion layer which shows the metal-insulator transition. Increase in the resistivity in a parallel magnetic field reaches saturation at the critical field for the full polarization evaluated from an analysis of low-field Shubnikov-de Haas oscillation

I. V. Ponomarev, V. V. Flambaum, A. L. Efros

The exchange interaction between electrons located at different randomly distributed impurities is studied for small density of impurities. The singlet-triplet splitting 2J(R) is calculated for two Coulomb centers at a distance R. Interpolated formulas are found which work for all distances R from zero to infinity. The data from atomic physics are used for t

Bibhas Bhattacharyya, Shreekantha Sil

We have studied the Hubbard model with bond-charge interaction on a triangular lattice for a half-filled band. At the point of particle-hole symmetry the model could be analyzed in detail in two opposite regimes of the parameter space. Using a real space renormalization group we calculate the ground state energy and the local moment over the whole parameter

Rajesh Kasturirangan

Small-world architectures may be implicated in a range of phenomena from disease propagation to networks of neurons in the cerebral cortex. While most of the recent attention on small-world networks has focussed on the effect of introducing disorder/randomness into a regular network, we show that that the fundamental mechanism behind the small-world phenomen

P. A. Rikvold, G. Korniss, C. J. White, M. A. Novotny

We briefly introduce hysteresis in spatially extended systems and the dynamic phase transition observed as the frequency of the oscillating field increases beyond a critical value. Hysteresis and the decay of metastable phases are closely related phenomena, and a dynamic phase transition can occur only for field amplitudes, temperatures, and system sizes at

G. E. Volovik

We discuss topological properties of the ground state of spatially homogeneous ensemble of fermions. There are several classes of topologically different fermionic vacua; in each case the momentum space topology of the vacuum determines the low-energy (infrared) properties of the fermionic energy spectrum. Among them there is a class of the gapless systems w

Nobuko Fuchikami

A discrete stochastic process involving random amplification with additive noise is studied analytically. If the non-negative random amplification factor $b$ is such that $<b^β>=1$ where $β$ is any positive non-integer, then the steady state probability density function for the process will have power law tails of the form $p(x) \sim 1/x^{β+1}$. This is a ge

Hakeem M. Oluseyi, A. B. C. Walker, II, David I. Santiago

In the present work we undertake a study of the quasi-static loop model and the observational consequences of the various solutions found. We obtain the most general solutions consistent with certain initial conditions. Great care is exercised in choosing these conditions to be physically plausible (motivated by observations). We show that the assumptions of

S. T. Staggs, J. O. Gundersen, S. E. Church

A handful of new experiments aimed at measuring the as-yet-undetected polarization of the cosmic background radiation are described, with somewhat more detail given for three experiments with which the authors are are associated.

B. G. Sidharth

On the basis of a recent cosmological model, the puzzle of galactic rotational velocities at their edges is explained without invoking dark matter. A rationale for the existence of structures like galaxies and superclusters is also obtained.

B. G. Sidharth

In this brief note, we would like to point out that large-scale structures like galaxies and superclusters would arise quite naturally in the universe.

H. Matsumoto, T. G. Tsuru

An X-ray spectrum of the famous starburst galaxy M82 consists of three components: soft, medium, and hard components (Tsuru et al. 1997). The spectrum of the hard component, which is spatially unresolved, is well represented by an absorbed thermal bremsstrahlung, or an absorbed power-law model. However the origin of the hard component was unclear. Thus, we m

Alexander K. Konopelko, John G. Kirk, Floyd W. Stecker, Apostolos Mastichiadis

The recent HEGRA observations of the blazar Mkn 501 show strong curvature in the very high energy gamma-ray spectrum. Applying the gamma-ray opacity derived from an empirically based model of the intergalactic infrared background radiation field (IIRF), to these observations, we find that the intrinsic spectrum of this source is consistent with a power-law:

B. W. Stappers, B. M. Gaensler, S. Johnston

Using the Australia Telescope Compact Array (ATCA) we have imaged the fields around five promising pulsar candidates to search for radio pulsar wind nebulae (PWNe). We have used the ATCA in its pulsar gating mode; this enables an image to be formed containing only off-pulse visibilities, thereby dramatically improving the sensitivity to any underlying PWN. D