February 1999 arXiv papers — page 14

K. H. Andersen, P. Muratore-Ginanneschi

We study a minimal shell model for the advection of a passive scalar by a Gaussian time correlated velocity field. The anomalous scaling properties of the white noise limit are studied analytically. The effect of the time correlations are investigated using perturbation theory around the white noise limit and non-perturbatively by numerical integration. The

Arvind Rajaraman, Moshe Rozali

We discuss the quantization of the Green-Schwarz string action on $AdS_5 \times S^5$. We construct consistent, globally well-defined, gauge fixing choices for kappa symmetry and worldsheet diffeomorphism invariance. We then proceed to quantize the theory in a perturbation series in the inverse radius of curvature, in a background field expansion. We discuss

John S Briggs, Jan M Rost

It is shown that the time-dependent equations (Schrödinger and Dirac) for a quantum system can be always derived from the time-independent equation for the larger object of the system interacting with its environment, in the limit that the dynamical variables of the environment can be treated semiclassically. The time which describes the quantum evolution is

V. M. Red'kov

Using the Weyl-Tetrode-Fock spinor formalism, the fermion triplet in the 't Hooft-Polyakov monopole field is examined all over again. Spherical solutions corresponding to the total conserved momentum J =l + S + T are constructed. The angular dependence is expressed in terms of the Wigner's functions. The radial system of 12 equations decomposes into

M. W. Jack, M. J. Collett, D. F. Walls

We present a non-Markovian quantum trajectory method for treating atoms radiating into a reservoir with a non-flat density of states. The results of an example numerical simulation of the case where the free space modes of the reservoir are altered by the presence of a cavity are presented and compared with those of an extended system approach.

A. Czirok, T. Vicsek

With the aim of understanding the emergence of collective motion from local interactions of organisms in a "noisy" environment, we study biologically inspired, inherently non-equilibrium models consisting of self-propelled particles. In these models particles interact with their neighbors by turning towards the local average direction of motion. In t

A. Czirok, K. Schlett, E. Madarasz, T. Vicsek

In vitro velocities of several cell types have been measured using computer controlled video microscopy, which allowed to record the cells' trajectories over several days. On the basis of our large data sets we show that the locomotion activity displays a universal exponential distribution. Thus, motion resulting from complex cellular processes can be we

A. Czirok, M. Vicsek, T. Vicsek

We study a model of flocking in order to describe the transitions during the collective motion of organisms in three dimensions (e.g., birds). In this model the particles representing the organisms are self-propelled, i.e., they move with the same absolute velocity. In addition, the particles locally interact by choosing at each time step the average directi

Jan M. L. Martin

Extensive ab initio calibration calculations combined with extrapolations towards the infinite-basis limit lead to a ground-state dissociation energy of Be_2, D_e=944 \pm 25 1/cm, substantially higher than the accepted experimental value, and confirming recent theoretical findings. Our best computed spectroscopic observables (expt. values in parameters) are

A. Z. Mekjian

A general expression is discussed for pion probability distributions coming from relativistic heavy ion collisions. The general expression contains as limits: 1) The disoriented chiral condensate (DCC), 2) the negative binomial distribution and Pearson type III distribution, 3) a binomial or Gaussian result, 4) and a Poisson distribution. This general expres

W. M. Alberico, A. De Pace, G. Garbarino, A. Ramos

We have made a new evaluation of the Lambda decay width in nuclear matter within the Propagator Method. Through the Local Density Approximation it is possible to obtain results in finite nuclei. We have also studied the dependence of the widths on the N-N and Lambda-N short range correlations. Using reasonable values for the parameters that control these cor

Daksh Lohiya, Annu Batra, Shobhit Mahajan, Amitabha Mukherjee

Primordial nucleosynthesis is a success story of the standard big bang (SBB) cosmology. We explore nucleosynthesis in possible models very different from SBB in which the cosmological scale factor increases linearly with time right through the period during which nucleosynthesis occurs till the present.It turns out that weak interactions remain in thermal eq

A. K. Pogrebkov

The set of integrable symmetries of the nonstationary Schrödinger equation is shown to admit a natural decomposition into subsets of mutually commuting symmetries. Hierarchies of time evolutions associated with each of these subsets ultimately lead to nonlinear (possibly, operator) equations of the Kadomtsev--Petviashvili I type or its higher analogues, thus

Luis J. Boya, Mark S. Byrd

We deduce the periodicity 8 for the type of $Pin$ and $Spin$ representations of the orthogonal groups $O(n)$ from simple combinatorial properties of the finite Clifford groups generated by the gamma matrices. We also include the case of arbitrary signature $O(p,q)$. The changes in the type of representation can be seen as a rotation in the complex plane. The

Peng Lu

We show the existence of special Lagrangian tori on one family of Borcea-Voisin threefolds. We also construct a family of special Lagrangian submanifolds on the total space of the canonical line bundle of projective spaces.

A. I. Molev

A weight basis for each finite-dimensional irreducible representation of the orthogonal Lie algebra o(2n) is constructed. The basis vectors are parametrized by the D-type Gelfand--Tsetlin patterns. Explicit formulas for the matrix elements of generators of o(2n) in this basis are given. The construction is based on the representation theory of the Yangians a

JM Figueroa-O'Farrill

We present details of a geometric method to associate a Lie superalgebra with a large class of bosonic supergravity vacua of the type AdS x X, corresponding to elementary branes in M-theory and type II string theory.

C. D. Fosco, E. Fradkin, A. Lopez

We study some dynamical properties of a Dirac field in 2+1 dimensions with spacetime dependent domain wall defects. We show that the Callan and Harvey mechanism applies even to the case of defects of arbitrary shape, and in a general state of motion. The resulting chiral zero modes are localized on the worldsheet of the defect, an embedded curved two dimensi

Gerald V. Dunne, Theodore M. Hall

We give an explicit demonstration that the derivative expansion of the QED effective action is a divergent but Borel summable asymptotic series, for a particular inhomogeneous background magnetic field. A duality transformation B\to iE gives a non-Borel-summable perturbative series for a time dependent background electric field, and Borel dispersion relation

Sze-Shiang Feng, Zi-Xiang Wang, Xi-Jun Qiu

The N=1 self-dual supergravity has SL(2.C) symmetry. This symmetry results in SU(2) charges as the angular-momentum. As in the non-supersymmetric self-dual gravity, the currents are also of their potentials and are therefore identically conserved. The charges are generally invariant and gauge covariant under local SU(2) transforms approaching to be rigid at

Yu. P. Rybakov, A. M. Tarabay, I. G. Chugunov

A regular method is suggested for constructing vortex-like solutions with cylindrical symmetry in the Skyrme-Einstein chiral model. The method is based on the expansion of metric and field functions in power series with respect to the two small parameters entering the model. The length mass density of the vortex is estimated.

Jiro Sakamoto, Yasuaki Fukuoka

We study a massive Thirring-like model in 2-dimensional space-time, which contains fermions with arbitrary number (N) of different species. This model is an extension of that of a previous paper, where we have considered two-species case. By this extension we expect that we can expose more general structures of this kind of model. We obtain the equivalent bo

Abilio De Freitas, Sebastián Salamó

A simple algebraic technique is developed to obtain deformed energy spectra for the Pöschl-Teller potentials.

Gerard 't Hooft

Absolute confinement of its color charges is a natural property of gauge theories such as quantum chromodynamics. On the one hand, it can be attributed to the existence of color-magnetic monopoles, a topological feature of the theory, but one can also maintain that all non-Abelian gauge theories confine. It is illustrated how ``confinement'' works in

Gerard 't Hooft

This is an account of the author's recollections of the turbulent days preceding the establishment of the Standard Model as an accurate description of all known elementary particles and forces.

Riccardo D'Auria, Pietro Fre'

In these lectures we explain the concept of supergravity p-branes and BPS black holes. Introducing an audience of general relativists to all the necessary geometry related with extended supergravity (special geometry, symplectic embeddings and the like) we describe the general properties of N=2 black holes, the structure of central charges in extended superg

Arjun Berera

A quantum field theory warm inflation model is presented that solves the cosmological horizon/flatness problems. An interpretation of the model is given from supersymmetry and superstring theory.

David Dooling, Kyungsik Kang, Sin Kyu Kang

In light of recent experimental results, we present updated bounds on the lightest Higgs boson mass in the Standard Model (SM) and in the Minimal Supersymmetric extension of the Standard Model (MSSM). The vacuum stability lower bound on the SM Higgs boson mass lies above the MSSM lightest Higgs boson mass upper bound for a large amount of SUSY parameter spac

M. N. Chernodub, F. V. Gubarev, E. -M. Ilgenfritz, A. Schiller

Embedded defects proposed long ago (Z-vortices and Nambu monopoles) have been successfully searched for in 3D equilibrium lattice studies within the standard model near the electroweak phase transition and the crossover (which follows it for realistic Higgs mass). Gauge independent lattice-vortex operators are proposed. Vortex condensation (percolation) is f

Smaragda Lola, Graham G. Ross

Motivated by the Super-Kamiokande data, we revisit models with U(1) symmetries and discuss the origin of neutrino masses and mixings in such theories. We show that, in models with just three light neutrinos and a hierarchy of neutrino masses, large (2-3) mixing fixes the lepton doublet U(1) charges and is thus related to the structure of the charged lepton m

M. Laine

We review the motivation for, lattice results on, and some implications of, external magnetic fields present at the time of the cosmological electroweak phase transition.

C. E. Carlson, J. Hanlon, K. E. Lassila

In this paper, we do three things in the study of deuteron break-up by high energy neutrino beams. (1) We present previously unpublished data on neutrino induced backward protons from deuteron targets; (2) we calculate the contributions from both the two-nucleon (2N) and six-quark (6q) deuteron components, which depend upon the overall normalization of the p

V. N. Gribov

This is the second of the two last papers by V. N. Gribov concluding his 20 year long study of the problem of quark confinement in QCD. In this paper the analytic structure of quark and gluon Green's functions is investigated in the framework of the theory of confinement based on the phenomenon of supercritical binding of light quarks. The problem of uni

L. Ya. Glozman

It is shown that the principal pattern in baryon spectroscopy, which is associated with the flavor-spin dependent hyperfine interaction, is due to the spontaneous breaking of chiral symmetry in QCD and thus cannot be addressed by chiral perturbation theory, which is based on the explicit chiral symmetry breaking.

A. M. Cooper-Sarkar, A. Bodek, K. Long, E. Rizvi

High Q^2 NC and CC cross-sections as measured at HERA can give information on two distinct areas of current interest. Firstly, supposing that all the electroweak parameters are well known, these cross-sections may be used to give information on parton distributions at high x and high Q^2. Secondly, supposing that parton distributions are well known, after ev

Taizo Muta, Mao-Zhi Yang

The QCD anomaly coupling of $η'-g-g$ is treated as the axial vector current triangle anomaly. By assuming the divergent axial vector coupling of the $η'$ meson with the quark line in the triangle diagram, we calculate the QCD anomaly of $η'-g-g$ as well as the QED anomaly of $η'-γ-γ$ with only one common parameter $κ_{η'}$. We obtain cons

Susan Morrison, Simon Hands

We identify the Goldstone modes appropriate to the low and high density phases of SU(2) lattice gauge theory with staggered fermions. We present hybrid Monte Carlo simulation results for susceptibilities on a 6^4 lattice at beta=1.5, m=0.05. We specify how to implement a diquark source term in a lattice simulation and present first measurements of the lattic

Simon Hands, Susan Morrison

We discuss general aspects of the possibility of Bose condensation of diquark pairs in systems of dense matter. Lattice field theory simulations are presented for model four-fermion theories which are expected to manifest the phenomenon, and results from measurements of both diquark two-point and one-point functions presented. Whilst initial results are prom

Jane Nachtman, David Saltzberg, Matthew Worcester

We propose a like-sign dilepton search for chargino-neutralino production in p-pbar collisions at sqrt(s) = 1.8 TeV, which complements the previously published trilepton search by the CDF detector using Fermilab Run I data. Monte Carlo predictions for the signal and background efficiencies indicate a significant increase in sensitivity to chargino-neutralino

Thomas W. Baumgarte, Scott A. Hughes, Stuart L. Shapiro

We include matter sources in Einstein's field equations and show that our recently proposed 3+1 evolution scheme can stably evolve strong-field solutions. We insert in our code known matter solutions, namely the Oppenheimer-Volkoff solution for a static star and the Oppenheimer-Snyder solution for homogeneous dust sphere collapse to a black hole, and evo

Yu. S. Grishkan, E. G. Vertogradova

The variant of quasiclassical (half-quantum) theory of gravity in strong gravitational field is presented. The exact solution of the problem of the renormalized energy-momentum tensor calculation is performed in terms of non-local operator-signed function. The procedure of quasilocalization is proposed, which leads to the equations of non-equilibrium thermod

Brien C. Nolan

Examples of space-times are given which contain scalar curvature singularities whereat the metric tensor is regular and continuous, but which are gravitationally strong. Thus the argument that such singularities are necessarily weak is incomplete; in particular the question of the gravitational strength of the null Cauchy horizon singularity which occurs in

Naomi Dushay, James C. French, Carl Lagoze

We describe an architecture and investigate the characteristics of distributed searching in federated digital libraries. We introduce the notion of a query mediator as a digital library service responsible for selecting among available search engines, routing queries to those search engines, and aggregating results. We examine operational data from the NCSTR

Wei Ding, Gary Marchionini, Dagobert Soergel

Three types of video surrogates - visual (keyframes), verbal (keywords/phrases), and combination of the two - were designed and studied in a qualitative investigation of user cognitive processes. The results favor the combined surrogates in which verbal information and images reinforce each other, lead to better comprehension, and may actually require less p

Yong Lin, Jian Xu, Ee-Peng Lim, Wee-Keong Ng

A query routing broker is a software agent that determines from a large set of accessing information sources the ones most relevant to a user's information need. As the number of information sources on the Internet increases dramatically, future users will have to rely on query routing brokers to decide a small number of information sources to query with

Michael J. Hu, Ye Jian

MPEG is undertaking a new initiative to standardize content description of audio and video data/documents. When it is finalized in 2001, MPEG-7 is expected to provide standardized description schemes for concise and unambiguous content description of data/documents of complex media types. Meanwhile, other meta-data or description schemes, such as Dublin Core

Maxim Vavilov, Vinay Ambegaokar

We discuss the influence of the electromagnetic environment and the electron-electron interaction on the weak localization correction to the conductivity of a disordered metal. The theory of this phenomenon for sufficiently high temperature, where the quantum nature of the interaction of electrons with the electromagnetic field can be disregarded, has been u

Uwe Grimm, Michael Baake

A while ago, Luck (J. Stat. Phys. 72 (1993) 417) investigated the critical behaviour of one-dimensional Ising quantum chains with couplings constants modulated according to general non-periodic sequences. In this short note, we take a closer look at the case where the sequences are obtained from (two-letter) substitution rules and at the consequences of Luck

Z. Y. Weng

It is natural for a Mott antiferromagnetism in RVB description to become a superconductor in doped metallic regime. But the issue of superconducting transition temperature is highly nontrivial, as the AF fluctuations in the form of RVB pair-breaking are crucial in determining the phase coherence of the superconductivity. Underestimated AF fluctuations in a f

Leonid B. Litinskii

It turned out that the set of the fixed points is not necessarily the same as the set of the local minima of the energy functional. It depends on the diagonal elements of the connection matrix. The simple method which allows to cut off fictitious fixed points with high energies was found out. Especially the method is effective if the connection matrix is the

A. G. Mal'shukov, V. V. Shlyapin, K. A. Chao

Taking into account the spin precession caused by the spin-orbit splitting of the conduction band in semiconductor quantum wells, we have calculated the Fourier spectra of conductance and state-density correlators in a 2D ring, in order to investigate the structure of the main peak corresponding to Aharonov-Bohm oscillations. In narrow rings the peak structu

Marisol Ripoll, Pep Español, Matthieu H. Ernst

We study by means of numerical simulations the model of dissipative particle dynamics with energy conservation for the simple case of thermal conduction. It is shown that the model displays correct equilibrium fluctuations and reproduces Fourier law. The connection between "mesoscopic coarse graining" and "resolution" is clarified.

G. Salis, T. Heinzel, K. Ensslin, O. J. Homan

A tunable quantum point contact with modes occupied in both transverse directions is studied by magnetotransport experiments. We use conductance quantization of the one-dimensional subbands as a tool to determine the mode spectrum. A magnetic field applied along the direction of the current flow couples the modes. This can be described by an extension of the

J. Perez-Conde, A. K. Bhattacharjee

We present a symmetry-based calculation of the electronic structure of a compound semiconductor quantum dot (QD) in the sp^3s* tight-binding model including the spin-orbit interaction. The Hamiltonian matrix is diagonalized exactly for CdTe QD sizes up to 60 Å. The surface dangling bonds are passivated by hydrogen through a careful analysis of the density of

Gregory C. Psaltakis

In the context of an effective model for doped antiferromagnets, whereby the charge carriers are treated as hard-core bosons, we demonstrate that the ground state energy close to half-filling is an even periodic function of the external magnetic flux threading the square lattice in an Aharonov-Bohm geometry. The period is equal to the flux quantum $Φ_{0}=2π\

G. Santoro, S. Sorella, L. Guidoni, A. Parola

We consider an exchange model describing two isotropic spin-1/2 Heisenberg antiferromagnets coupled by a quartic term on the square lattice. The model is relevant for systems with orbital degeneracy and strong electron-vibron coupling in the large Hubbard repulsion limit, and is known to show a spin-Peierls-like dimerization in one dimension. In two dimensio

Feng Sze-Shiang, Zhu Dong-Pei

It is noticed that the excellent proof of the connection of magnetic flux quantization and off-diagonal long range order (ODLRO) presented recently by Nieh, Su and Zhao suffers from an imperfection, namely, the f-factors in the case of finite translation do not satisfy $f(a)f(b)=f(a+b)$, which was employed in the proof. A corrected proof is proposed to remed

H. J. Schulz, B. S. Shastry

We present a many chain generalization of a recent work of ours, wherein an arbitrary number of fermionic chains are coupled via a Gauge interaction. Central to this construction is the role of an antisymmetric tensor which enters the couplings and helps define a pseudo-unitary transformation, that maps the models on to ``free fermi'' models with twi

Y. Jiang, P. J. Swart, A. Saxena, M. Asipauskas

Foams have unique rheological properties that range from solid-like to fluid-like. We study two-dimensional non-coarsening foams of different disorder under shear in a Monte Carlo simulation, using a driven large-Q Potts model. We find that the dynamics of topological rearrangements depend sensitively on the structural disorder.

P. B. Blakie, R. J. Ballagh, C. W. Gardiner

A condensate with two internal states coupled by external electromagnetic radiation, is described by coupled Gross Pitaevskii equations, whose eigenstates are analogous to the dressed states of quantum optics. We solve for these eigenstates numerically in the case of one spatial dimension, and explore their properties as a function of system parameters. In c

Achim Feldmeier, Isaac Shlosman

We analyze the dynamics of 2-D stationary, line-driven winds from accretion disks in cataclysmic variable stars. The driving force is that of line radiation pressure, in the formalism developed by Castor, Abbott & Klein for O stars. Our main assumption is that wind helical streamlines lie on straight cones. We find that the Euler equation for the disk wind h

Achim Feldmeier, Isaac Shlosman, Peter Vitello

We analyze the dynamics of 2D stationary line-driven winds from accretion disks in cataclysmic variables (CVs), by generalizing the Castor, Abbott and Klein theory. In paper 1, we have solved the wind Euler equation, derived its two eigenvalues, and addressed the solution topology and wind geometry. Here, we focus on mass loss and velocity laws. We find that

S. Boissier, N. Prantzos

The chemical and spectro-photometric evolution of spiral galaxies is investigated with detailed models, making use of up-to-date ingredients (like metallicity dependent stellar properties) and a prescription for the star formation rate (SFR) justified both empirically and theoretically. As a first application, the model is used to describe the evolution of t

L. Simard, D. C. Koo, S. M. Faber, V. L. Sarajedini

As part of the Deep Extragalactic Evolutionary Probe (DEEP) survey, a sample of 190 field galaxies (I_{814} <= 23.5) in the ``Groth Survey Strip&#39;&#39; has been used to analyze the magnitude-size relation over the range 0.1 < z < 1.1. The survey is statistically complete to this magnitude limit. All galaxies have photometric structural parameters, includi

N. I. Shakura, M. E. Prokhorov, K. A. Postnov, N. A. Ketsaris

A strong X-ray illumination of the optical star atmosphere in Her X-1, asymmetric because of a partial shadowing by the tilted twisted accretion disk around central neutron star, leads to the formation of matter flows coming out of the orbital plane and crossing the line of sight before entering the disk. We suggest that the absorption of X-ray emission by t

Sylvie Vauclair

While theoretical computations of the lithium abundances in Pop II stars predict variations from star to star, the most recent observations confirm the existence of a &#34;lithium plateau&#34; with no abundance dispersion. This apparent paradox has to be faced and a solution has to be found before deriving the primordial lithium abundance. In any case lithiu

Ilse M. van Bemmel, Peter D. Barthel, Thijs de Graauw

In order to test the unification scheme for double-lobed radio sources, the far-infrared properties of matched samples of radio-galaxies and radio-loud quasars were studied using ISOPHOT. The quasar data were complemented with nearly simultaneous submillimeter and centimeter radio data. The results show that quasars are generally brighter than radio-galaxies

C. Pichon, F. Bernardeau

A fundamental hypothesis for the interpretation of the measured large-scale line-of-sight peculiar velocities of galaxies is that the large-scale cosmic flows are irrotational. In order to assess the validity of this assumption, we estimate, within the frame of the gravitational instability scenario, the amount of vorticity generated after the first shell cr

B. Guiderdoni, F. R. Bouchet, J. Devriendt, E. Hivon

Our view on the deep universe has been so far biased towards optically bright galaxies. Now, the measurement of the Cosmic Infrared Background in FIRAS and DIRBE residuals, and the observations of FIR/submm sources by the ISOPHOT and SCUBA instruments begin unveiling the ``optically dark side&#39;&#39; of galaxy formation. Though the origin of dust heating i

Christos Siopis

Schwarzschild models of a Plummer sphere were constructed and compared with analytical results to test the robustness of Schwarzschild&#39;s method and its efficiency in probing the degeneracy of the solution space. The method was then used to construct and study the nonuniqueness of triaxial equilibria with central density cusps, for which no analytical sol

P. Kahabka, X. -D. Li

We report observations of SMC X-1 in three new high-intensity states with ROSAT HRI in December 1995, May 1997, and March 1998 in which pulsations with a period of 0.70769+/-0.00006 sec, 0.70706+/-0.00001 sec, and 0.706707+/-0.00001 sec respectively were detected. Combining the pulse periods from observations with ROSAT PSPC in high-intensity states in Octob

Cyriel Wagemans, Gert Goeminne, Jan Wagemans, Ronald Bieber

The energy dependent 37Ar(n,p)37Cl and 37Ar(n,alpha)34S reaction cross sections were determined for the first time in an experimental effort involving three large facilities: the cyclotron of the UCL (Louvain-la-Neuve, Belgium) where implanted 37Ar samples were produced; the high flux reactor of the ILL (Grenoble, France) where thermal (n,p), (n,alpha_0) and

S. Nasiri, V. Rezania

We introduce a phenomenological investigation of the evolution and large scale distribution of quasars using a modified version of the Field and Colgate gravitational contraction model for proto-galaxies. By studying the distribution of about 7000 quasars in 5 luminosity classes, it seems that, such a model is capable of solving the energy problem and discus

S. Biswas, B. Modak, A. Shaw

The complex time WKB (CWKB) approximation has been an effective technique to understand particle production in curved as well as in flat spacetime. Earlier we obtained the standard results on particle production in time dependent gauge in various curved spacetime. In the present work we generalize the technique of CWKB to the equivalent problems in space dep

J. M. Diego, E. Martinez-Gonzalez, J. L. Sanz, S. Mollerach

We present an alternative method to analyse cosmic microwave background (CMB) maps. We base our analysis on the study of the partition function. This function is used to examine the CMB maps making use of the different information embedded at different scales and moments. Using the partition function in a likelihood analysis in two dimensions (Q_rms,n), we f

V. G. Gurzadyan

The information theory approach is suggested to the Cosmic Microwave Background (CMB) problem for negatively curved homogeneous and isotropic Universe. Namely, the Kolmogorov complexity of anisotropy of spots in CMB sky maps is proposed as a new descriptor for revealing crucial cosmological information, particularly on the curvature of the Universe. Such pro

Sungsoo S. Kim, Myeong-Gu Park, Hyung Mok Lee

A star can be tidally disrupted around a massive black hole. It has been known that the debris forms a precessing stream, which may collide with itself. The stream collision is a key process determining the subsequent evolution of the stellar debris: if the orbital energy is efficiently dissipated, the debris will eventually form a circular disk (or torus).

F. Aharonian

We present the results on the TeV gamma emission from Mkn 501 in 1997 obtained with the standalone Cherenkov telescopes CT1 and CT2 (threshold > 1.2 and > 1.0 resp.) of the HEGRA collaboration. The CT1 lightcurve has the most complete coverage of all TeV observations of Mkn 501 in 1997 due to the additional observations made under the presence of moonlight.

Hector Aceves, Jaime Perea

The projected (PME) and virial mass estimator (VME) are revisited and tested using an N-body equilibrium system. It is found that the PME can overestimate the mass by approx 40% if a cluster is sampled only about its effective radius, Re. The exact value of this error depends on the mass profile of the cluster. The VME can yield errors of approx 20% if we ar

K. Agashe, N. G. Deshpande

It has been proposed recently that the scale of quantum gravity (``the string scale&#39;&#39;) can be $M_S \sim$ few TeV with $n \geq 2$ extra dimensions of size $R \stackrel{<}{\sim}$ mm so that, at distances greater than $R$, Newtonian gravity with $M_{Pl} \sim 10^{18}$ GeV is reproduced if $M_{Pl}^2 \sim R^n M_S^{n+2}$. Exchange of virtual gravitons in th

Vijay Balasubramanian, Steven B. Giddings, Albion Lawrence

The AdS/CFT conjecture relates quantum gravity on Anti-de Sitter (AdS) space to a conformal field theory (CFT) defined on the spacetime boundary. We interpret the CFT in terms of natural analogues of the bulk S-matrix. Our first approach finds the bulk S-matrix as a limit of scattering from an AdS bubble immersed in a space admitting asymptotic states. Next,

Antal Jevicki, Sanjaye Ramgoolam

The exclusion principle of Maldacena and Strominger is seen to follow from deformed Heisenberg algebras associated with the chiral rings of S_N orbifold CFTs. These deformed algebras are related to quantum groups at roots of unity, and are interpreted as algebras of space-time field creation and annihilation operators. We also propose, as space-time origin o

S. A. Abel, J. L. F. Barbon, I. I. Kogan, E. Rabinovici

We discuss the thermal properties of string gases propagating in various D-brane backgrounds in the weak-coupling limit, and at temperatures close to the Hagedorn temperature. We determine, in the canonical ensemble, whether the Hagedorn temperature is limiting or non-limiting. This depends on the dimensionality of the D-brane, and the size of the compact di

Anupam Mazumdar, Luis E. Mendes

We study the preheating scenario in Generalized Einstein Theories, considering a class of such theories which are conformally equivalent to those of an extra field with a modified potential in the Einstein frame. Resonant creation of bosons from oscillating inflaton has been studied before in the context of general relativity taking also into account the eff

A. Cowie, L. F. Cohen, M. W. Denhoff

We have measured the power dependent microwave properties of a weak link in a YBa2Cu3O7 thin film formed by writing a line of damage using a focused ion beam. The measurement was made using a parallel plate resonator at 5.5 GHz with the weak link written across the width of one of the plates. The ion induced damage was characterized using a TRIM computer sim

V. Yu. Yushankhai, R. Hayn

The magnetic anisotropy af a rectangular Cu-O-Cu bond is investigated in second order of the spin-orbit interaction. Such a bond is characteristic for cuprates having edge sharing CuO_2 chains, and exists also in the Cu_3O_4 plane or in ladder compounds. For a ferromagnetic coupling between the copper spins an easy axis is found perpendicular to the copper o

D. A. Kirzhnits, A. A. Shatskiy

The value of excess charge in the kernel of massive body (and the opposite in sign excess charge at the surface) caused by the influence of gravitational forces is determined.

P. Monaco, G. Efstathiou

We present and test a new method for the reconstruction of cosmological initial conditions from a full-sky galaxy catalogue. This method, called ZTRACE, is based on a self-consistent solution of the growing mode of gravitational instabilities according to the Zel&#39;dovich approximation and higher order in Lagrangian perturbation theory. Given the evolved r

Ulrich Heinz, Barbara V. Jacak

Two-particle momentum correlations between pairs of identical particles produced in relativistic heavy-ion reactions can be analyzed to extract the space-time structure of the collision fireball. We review recent progress in the application of this method, based on newly developed theoretical tools and new high-quality data from heavy-ion collision experimen

R. Rapp, C. Gale

Using effective meson Lagrangians we study the interaction of rho mesons in a hot baryon-free system. Various mesonic resonances in direct $s$-channel reactions are investigated employing standard self-energy techniques, including new reactions that have up to now not been considered in a self-consistent approach at finite temperature. The importance of subt

C. R. Hagen

Calculations of the Casimir energy for spherical geometries which are based on integrations of the stress tensor are critically examined. It is shown that despite their apparent agreement with numerical results obtained from mode summation methods, they contain a number of serious errors. Specifically, these include (1) an improper application of the stress

P. van Loock, Samuel L. Braunstein, H. J. Kimble

Quantum teleportation of an unknown broadband electromagnetic field is investigated. The continuous-variable teleportation protocol by Braunstein and Kimble [Phys. Rev. Lett. {\bf 80}, 869 (1998)] for teleporting the quantum state of a single mode of the electromagnetic field is generalized for the case of a multimode field with finite bandwith. We discuss c

B. Normand, Jordan Kyriakidis, Daniel Loss

We present a theoretical analysis of the properties of low-dimensional quantum antiferromagnets in applied magnetic fields. In a nonlinear sigma model description, we use a spin stiffness analysis, a 1/N expansion, and a renormalization group approach to describe the broken-symmetry regimes of finite magnetization, and, in cases of most interest, a low-field

Rodolfo Bonifacio

We propose a novel approach to intrinsic decoherence without adding new assumptions to standard Quantum Mechanics. We generalize the Liouville equation just by requiring the dynamical semigroup property of time evolution and dropping the unitarity requirement. With no approximations and specific statistical assumptions we find a generalized Liouville equatio

M. Copelli, M. Bouten, C. Van den Broeck, B. Van Rompaey

We show that the center of mass of Ising vectors that obey some simple constraints, is again an Ising vector.

I. Antoniadis, B. Pioline

We study large dimensions and low string scale in four-dimensional compactifications of type II theories of closed strings at weak coupling. We find that the fundamental string scale, together with all compact dimensions, can be at the TeV, while the smallness of the string coupling accounts for the weakness of gravitational interactions. This is in contrast

J. Suzuki

We prove one of conjectures, raised by Dorey and Tateo in the connection among the spectral determinant of anharmonic oscillator and vacuum eigenvalues of transfer matrices in field theory and statistical mechanics. The exact sequence of $U_q(\hat{sl}_2)$ plays a fundamental role in the proof.

Renato A. Dupke, Raymond E. White

Analysis of spatially resolved ASCA spectra of the intracluster gas in Abell 496 confirms there are mild metal abundance enhancements near the center, as previously found by White et al. (1994) in a joint analysis of Ginga LAC and Einstein SSS spectra. Simultaneous analysis of spectra from all ASCA instruments (SIS + GIS) shows that the iron abundance is 0.3

B. M. Caradoc-Davies, R. J. Ballagh, K. Burnett

Simulations of a rotationally stirred condensate show that a regime of simple behaviour occurs in which a single vortex cycles in and out of the condensate. We present a simple quantitative model of this behaviour, which accurately describes the full vortex dynamics, including a critical angular speed of stirring for vortex formation. A method for experiment

B. G. Sidharth

In recent papers it was shown that stochastic processes in the universe as a whole lead to discrete space time at Compton scales as also non-relativistic Quantum Mechanics. In this paper, we deduce the Dirac equation and thence a unified formulation of quarks and leptons. In the process several puzzling empirical results and coincidences are shown to be a co