November 1999 arXiv papers — page 23

Christopher Ronnewinkel, Claus O. Wilke, Thomas Martinetz

The influence of time-dependent fitnesses on the infinite population dynamics of simple genetic algorithms (without crossover) is analyzed. Based on general arguments, a schematic phase diagram is constructed that allows one to characterize the asymptotic states in dependence on the mutation rate and the time scale of changes. Furthermore, the notion of regu

Victoria E. Ceron, Jorge G. Hirsch

The double electron capture half-lives of 156Dy, 162Er and 168Yb are evaluated using the pseudo SU(3) model, which describes ground and excited bands as well as their B(E2) and B(M1) transition strengths in remarkable agreement with experiment. The best candidate for experimental detection is the decay 156Dy -> 156Gd, with tau{1/2} (0+{gs} --> 0+{gs}) = 2.74

R. Alkofer, S. Ahlig, C. Fischer, M. Oettel

Baryons are modeled as bound states of scalar or axialvector diquarks and a constituent quark which interact through quark exchange. This description results as an approximation to the relativistic Faddeev equation for three quarks. The corresponding effective Bethe-Salpeter equation is solved, and fully four-dimensional wave functions for both octet and dec

Valeri Dvoeglazov

It has long been claimed that the antisymmetric tensor field of the second rank is pure longitudinal after quantization. In my opinion, such a situation is quite unacceptable. I repeat the well-known procedure of the derivation of the set of Proca equations. It is shown that it can be written in various forms. Furthermore, on the basis of the Lagrangian form

G. Roepstorff, Ch. Vehns

Motivated by the supersymmetric version of Dirac's theory, chiral models in field theory, and the quest of a geometric fundament for the Standard Model, we describe an approach to the differential geometry of vector bundles on (semi)-Riemannian manifolds based on the concepts of superspaces, superalgebras, superconnections, and generalized Dirac operator

Eduardo Cattani, Alicia Dickenstein, Bernd Sturmfels

Multivariate hypergeometric functions associated with toric varieties were introduced by Gel'fand, Kapranov and Zelevinsky. Singularities of such functions are discriminants, that is, divisors projectively dual to torus orbit closures. We show that most of these potential denominators never appear in rational hypergeometric functions. We conjecture that

Tyler J. Jarvis, Takashi Kimura, Arkady Vaintrob

We review progress on the generalized Witten conjecture and some of its major ingredients. This conjecture states that certain intersection numbers on the moduli space of higher spin curves assemble into the logarithm of the tau function of a semiclassical limit of the r-th Gelfand-Dickey (or KdV_r) hierarchy. Additionally, we prove that tensor products of t

S. M. Natanzon

Let Y be a complex algebraic curve and let [Y]={X_1,...,X_n} be the set of all real algebraic curves X_i with complexification X_i(C)=Y, such that the real points X_i(R) divide X_i(C). We find all such families [Y]. According to Harnak theorem a number |X_i| of connected components of X_i(R) satifies by the inequality |X_i|<= g+1, where g is the genus of Y.

Peter G. Casazza, M. C. Lammers

In 1990, Daubechies proved a fundamental identity for Weyl-Heisenberg systems which is now called the Weyl-Heisenberg Frame Identity. WH-Frame Identity: If $g\in W(L^{\infty},L^{1})$, then for all continuous, compactly supported functions f we have: \[\sum_{m,n}|<f,E_{mb}T_{na}g>|^{2} = \frac{1}{b}\sum_{k}\int_{\Bbb R}\bar{f(t)}f(t-k/b)\sum_{n} g(t-na)\bar{g

Peter G. Casazza, M. C. Lammers

We provide a detailed development of a function valued inner product known as the bracket product and used effectively by de Boor, Devore, Ron and Shen to study translation invariant systems. We develop a version of the bracket product specifically geared to Weyl-Heisenberg frames. This bracket product has all the properties of a standard inner product inclu

A. Campillo, J. I. Farran, C. Munuera

In this paper we compute the order (or Feng-Rao) bound on the minimum distance of one-point algebraic geometry codes, when the Weierstrass semigroup at the point Q is an Arf semigroup. The results developed to that purpose also provide the dimension of the improved geometric Goppa codes related to those.

Winfried Bruns, Joseph Gubeladze

We investigate graded retracts of polytopal algebras (essentially the homogeneous rings of affine cones over projective toric varieties) as polytopal analogues of vector spaces. In many cases we show that these retracts are again polytopal algebras and that codimension 1 retractions factor through retractions preserving the semigroup structure. We expect tha

J. M. Maillet, V. Terras

A general method for solving the so-called quantum inverse scattering problem (namely the reconstruction of local quantum (field) operators in term of the quantum monodromy matrix satisfying a Yang-Baxter quadratic algebra governed by an R-matrix) for a large class of lattice quantum integrable models is given. The principal requirement being the initial con

Ashok Das, Gerald Dunne, J. Frenkel

We study the question of the Ward identity for &#34;large&#34; gauge invariance in 0+1 dimensional theories. We derive the relevant Ward identities for a single flavor fermion and a single flavor complex scalar field interacting with an Abelian gauge field. These identities are nonlinear. The Ward identity for any other complicated theory can be derived from

G W Gibbons

The Future Tube $T^+_n$ of n-dimensional Minkowski spacetime may be identified with the reduced phase space or &#34;space of motions&#34; of a particle moving in (n+1)-dimensional Anti-de-Sitter spacetime. Both are isomorphic to a bounded homogeneous domain in ${\bf C}^{n}$ whose Shilov boundary may be identified with $n$-dimensional conformally compactified

Paul Watts

Motivated by the form of the noncommutative *-product in a system of open strings and Dp-branes with constant nonzero Neveu-Schwarz 2-form, we define a deformed multiplication operation on a quasitriangular Hopf algebra in terms of its R-matrix, and comment on some of its properties. We show that the noncommutative string theory *-product is a particular exa

I. M. Krichever

The action-angle variables for N-particle Hamiltonian system with the Hamiltonian $H=\sum_{n=0}^{N-1} \ln sh^{-2}(p_n/2)+\ln(\wp(x_n-x_{n+1})- \wp(x_n+x_{n+1})), x_N=x_0,$ are constructed, and the system is solved in terms of the Riemann $θ$-functions. It is shown that this system describes pole dynamics of the elliptic solutions of 2D Toda lattice correspon

Tomomi Muto

We study brane configurations corresponding to D-branes on complex three-dimensional orbifolds ${\bf C}^3/Γ$ with $Γ=Δ(3n^2)$ and $Δ(6n^2)$, nonabelian finite subgroups of SU(3). We first construct a brane configuration for ${\bf C}^3/{\bf Z}_n \times {\bf Z}_n$ by using D3-branes and a web of (p,q) 5-branes of type IIB string theory. Brane configurations fo

G. J. Stephens

We study the formation of topological textures in a nonequilibrium phase transition of an overdamped classical O(3) model in 2+1 dimensions. The phase transition is triggered through an external, time-dependent effective mass, parameterized by quench timescale τ. When measured near the end of the transition the texture separation and the texture width scale

Harry J. Lipkin

The Constituent Quark Model has provided a remarkable description of the experimentally observed hadron spectrum but still has no firm theoretical basis. Attempts to provide a QCD justification discussed at Hadron99 include QCD Sum Rules, instantons, relativistic potential models and the lattice. Phenomenological analyses to clarify outstanding problems like

E. V. Shuryak

This is a short write-up of lectures at UK Theory Institute, Swansea UK, Sept.99; and XVII School ``QCD: Perturbative or Non-perturbative?&#39;&#39; Lisbon,Portugal, Oct.99. The covered topic include (i) discussion of the scales at which perturbative description should be changed by the non-perturbative one. A number of various examples are considered, leadi

M. Brhlik, G. J. Good, G. L. Kane

We revisit the results of recent electroweak baryogenesis calculations and include all allowed large CP-violating supersymmetric phases. If the phases are large, the resulting baryon asymmetry can be considerably larger than the observed value $n_B/s \sim 4 \times 10^{-11}$. Much of the asymmetry must therefore be washed out, and we argue that the upper boun

Victor T. Kim, Lev N. Lipatov, Grigorii B. Pivovarov

The next-to-leading order (NLO) corrections to the BFKL equation in the BLM optimal scale setting are briefly discussed. A striking feature of the BLM approach is rather weak Q^2-dependence of the Pomeron intercept, which might indicate an approximate conformal symmetry of the equation. An application of the NLO BFKL resummation for the virtual gamma-gamma t

B. Guberina, B. Melic, H. Stefancic

We extend the analysis of weak decays of heavy hadrons to the case of doubly charmed baryons, Ξ_{cc}^{++}, Ξ_{cc}^{+} and Ω_{cc}^{+}. Doubly charmed baryons are modeled as a heavy-light system containing a heavy cc-diquark and a light quark. Such a model leads to preasymptotic effects in semileptonic and nonleptonic decays which are essentially proportional

Wolfgang Ochs, Tokuzo Shimada

We derive the probability for rapidity gaps in a parton cascade and investigate the dual connection with hadronic final states. A good description of observations in e+e- annihilations is obtained by perturbative QCD calculations in MLLA using previously determined parameters (QCD scale Λand k_T-cut-off Q_0) and applying the parton hadron duality picture. Fu

A. V. Nefediev

The Hamiltonian approach is developed for QCD_2 in the limit of infinite number of colours N_C (&#39;t Hooft model). Bosonization of the theory is performed explicitly and the generalized Bogoliubov transformation for the composite boson operators is introduced and used to bring the Hamiltonian into diagonal form in the two-body sector. The resulting theory

Norbert Magnussen

This article reviews some recent developments in Astroparticle Physics. Due to the extension of the field only part of the results and developments can be covered. The status of the search for Dark Matter, some recent results on Cosmic Rays and Gamma Ray Astronomy and the status of Neutrino Astronomy are presented.

Alessandro Ballestrero

We review some recent results and open problems on four fermion physics at LEP2 and beyond

Artemiy Shoulgin

It is suggested the modification of traditional potential model, in which nontrivial structure of inside-hadron vacuum condensate is simulated by geometric properties of inside-hadron space. Confinement of quarks is ensured by closed effective (Riemannian) space. Interquark potential represents itself Coulomb&#39;s low in the effective space (Poisson equatio

J. Ranft

DPMJET samples hadron-hadron, hadron-nucleus, nucleus-nucleus and neutrino-nucleus interactions at high energies. The two-component Dual Parton Model is used with multiple soft chains and multiple minijets at each elementary interaction. Particle production is realized by the fragmentation of colorless parton-parton chains constructed from the quark content

David Atwood, Shaouly Bar-Shalom, Amarjit Soni

We consider the production of high invariant mass jet pairs at hadron colliders as a test for TeV scale gravitational effects. We find that this signal can probe effective Planck masses of about 10 TeV at the LHC with center of mass energy of 14 TeV and 1.5 TeV at the Tevatron with center of mass energy of 2 TeV. These results are compared to analogous scatt

Y. S. Kim

String models are designed to provide a covariant description of internal space-time structure of relativistic particles. The string is a limiting case of a series of massive beads like a pearl necklace. In the limit of infinite-number of zero-mass beads, it becomes a field-theoretic string. Another interesting limit is to keep only two pearls by eliminating

Thomas G. Rizzo

We discuss the physics of Kaluza-Klein excitations of the Standard Model gauge bosons that can be explored by a high energy muon collider in the era after the LHC and TeV Linear Collider. We demonstrate that the muon collider is a necessary ingredient in the unraveling the properties of such states and, perhaps, proving their existence. The possibility of ob

W. Krolikowski

A new lefthanded see-saw mechanism is constructed, implying both the smallness of active-neutrino masses and decoupling of heavy passive neutrinos, similarly to the situation in the case of conventional see-saw. But now, in place of the conventional righthanded neutrinos, the lefthanded sterile neutrinos play the role of heavy passive neutrinos, the righthan

Wolfgang Bock, Maarten F. L. Golterman, Ka Chun Leung, Yigal Shamir

We consider a lattice discretization of a covariantly gauge-fixed abelian gauge theory. The gauge fixing is part of the action defining the theory, and we study the phase diagram in detail. As there is no BRST symmetry on the lattice, counterterms are needed, and we construct those explicitly. We show that the proper adjustment of these counterterms drives t

Christoph Amelung

The status of measurements and interpretation of the proton structure function F2 is summarized. The measurements are subjected to DGLAP fits, from which the gluon density is extracted and a comparison to measurements of F2c is performed. The longitudinal structure function, FL, is extracted via an extrapolation of F2. At low Q2, the transition from virtual

Ulrich H. Gerlach

Rindler&#39;s acceleration-induced partitioning of spacetime leads to a nature-given interferometer. It accomodates quantum mechanical and wave mechanical processes in spacetime which in (Euclidean) optics correspond to wave processes in a ``Mach-Zehnder&#39;&#39; interferometer: amplitude splitting, reflection, and interference. These processes are describe

L. Herrera

We present a critical review of the relativistic rotation transformation of Trocheris and Takeno. A new transformation is proposed which is free from the drawbacks of the former. Some applications are presented.

C. Stephen Hellberg, Efstratios Manousakis

We develop a general numerical method to study the zero temperature properties of strongly correlated electron models on large lattices. The technique, which resembles Green&#39;s Function Monte Carlo, projects the ground state component from a trial wave function with no approximations. We use this method to determine the phase diagram of the two-dimensiona

Peter Kleban

Crossing probabilities for critical 2-D percolation on large but finite lattices have been derived via boundary conformal field theory. These predictions agree very well with numerical results. However, their derivation is heuristic and there is evidence of additional symmetries in the problem. This contribution gives a preliminary examination some unusual m

Bruce Boghosian, Carson C. Chow, Terence Hwa

The large scale properties of spatiotemporal chaos in the 2d Kuramoto-Sivashinsky equation are studied using an explicit coarse graining scheme. A set of intermediate equations are obtained. They describe interactions between the small scale (e.g., cellular) structures and the hydrodynamic degrees of freedom. Possible forms of the effective large scale hydro

A. J. Wagner, C. E. Scott

In this letter we show that the late-time scaling state in spinodal decomposition is not unique. We performed lattice Boltzmann simulations of the phase-ordering of a 50%-50% binary mixture using as initial conditions for the phase-ordering both a symmetric morphology that was created by symmetric spinodal decomposition and a morphology of one phase disperse

Juan M. R. Parrondo

The relationship between entropy and information is reviewed, taking into account that information is stored in macroscopic degrees of freedom, such as the order parameter in a system exhibiting spontaneous symmetry breaking. It is shown that most problems of the relationship between entropy and information, embodied in a variety of Maxwell demons, are also

O Radulescu, P. D. Olmsted

We present analytic solutions for steady flow of the Johnson-Segalman (JS) model with a diffusion term in various geometries and under controlled strain rate conditions, using matched asymptotic expansions. The diffusion term represents a singular perturbation that lifts the continuous degeneracy of stable, banded, steady states present in the absence of dif

Rafael Salazar, Raul Toral

We present a new method devised to overcome the intrinsic difficulties associated to the numerical simulations of the Tsallis statistics. We use a standard Metropolis Monte Carlo algorithm at a fictitious temperature T&#39;, combined with a numerical integration method for the calculation of the entropy in order to evaluate the actual temperature T. We illus

F. Sciortino, W. Kob, P. Tartaglia

In this article we review the thermodynamics of liquids in the framework of the inherent structure formalism. We then present calculations of the distribution of the basins in the potential energy of a binary Lennard-Jones mixture as a function of temperature. The comparison between the numerical data and the theoretical formalism allows us to evaluate the d

G. T. Barkema, N. Mousseau

The continuous random network (CRN) model is an idealized model for perfectly coordinated amorphous semiconductors. The quality of a CRN can be assessed in terms of topological and configurational properties, including coordination, bond-angle distributions and deformation energy. Using a variation on the sillium approach proposed 14 years ago by Wooten, Win

Akinori Awazu

Size segregation of granular mixtures which are almost completely packed in a rotating drum is discussed with an effective simulation and a brief analysis. Instead of a 3D drum, we simulate 2D rotating thin box which is almost completely packed with granular mixtures. The phase inversion of radially segregated pattern which was found in a 3D experiment are q

Jan von Delft, Fabian Braun

Studies of pairing correlations in ultrasmall metallic grains have commonly been based on a simple reduced BCS-model describing the scattering of pairs of electrons between discrete energy levels that come in time-reversed pairs. This model has an exact solution, worked out by Richardson in the context of nuclear physics in the 1960s. Here we give a tutorial

K. Frikach, M. Poirier, M. Castonguay, K. D. Truong

In an ultrasonic experiment, we have investigated the temperature profile of the velocity of longitudinal elastic waves propagating along a direction perpendicular to the layers in the organic superconductors kappa-(BEDT-TTF)_2X, X = Cu(SCN)_2 and Cu[N(CN)_2]Br. Although a small decrease of the velocity is observed at the superconducting transition, the most

R. Chitra, G. Kotliar

We formulate the dynamical mean field theory directly in the continuum. For a given definition of the local Green&#39;s function, we show the existence of a unique functional, whose stationary point gives the physical local Green&#39;s function of the solid. We present the diagrammatic rules to calculate it perturbatively in the interaction. Inspired by the

D. A. Garanin, E. M. Chudnovsky, R. Schilling

We consider a large spin \bf S in the magnetic field parallel to the uniaxial crystal field, interacting with N >> 1 nuclear spins \bf I_i via Hamiltonian \cal H = -DS_z^2 - H_zS_z+ A{\bf S}\cdot \sum_{i=1}^N {\bf I}_i with A << D, at temperature T. Tunneling splittings and the selection rules for the resonant values of H_z are obtained perturbatively. The q

Yue Yu

We derive a microscopic model describing the low-lying edge excitations in the fractional quantum Hall liquid with $ν=\frac{ν^*} {\tildeϕν^*+1}$. For $ν^*>0$, it is found that the composite fermion model reduces to an SU$(ν^*)$ Calogero-Sutherland model in a dimension reduction, whereas it is not exact soluble for $ν^*<0$. However, the ground states in both

Yue Yu, Zhaobin Su

We calculate the conductivity associated with the anomalous propagation of a surface acoustic wave above a two-dimensional electron gas at $ν=1/2$. Murthy-Shankar&#39;s middle representation is adopted and a contribution to the response functions beyond the random phase approximation has been taken into account. We give a phenomenological fit for the effecti

Theo M. Nieuwenhuizen

A model system with fast and slow processes is introduced. After integrating out the fast ones, the considered dynamics of the slow variables is exactly solvable. In statics the system undergoes a Kauzmann transition to a glassy state. The relaxation time obeys a generalized Vogel-Fulcher-Tammann-Hesse law. The aging dynamics on the approach to and below the

M. C. Gordillo, J. Boronat, J. Casulleras

We report results of diffusion Monte Carlo calculations for both $^4$He absorbed in a narrow single walled carbon nanotube (R = 3.42 Å) and strictly one dimensional $^4$He. Inside the tube, the binding energy of liquid $^4$He is approximately three times larger than on planar graphite. At low linear densities, $^4$He in a nanotube is an experimental realizat

Yupeng Wang

An integrable Kondo lattice model, which describes a strongly correlated electron host interacting with a spin-1/2 lattice, is proposed. It is found that with the variations of the Kondo coupling J, the hole concentration n_h and the magnetic field H, the system may fall into a variety of phases. The phase boundaries of the ground state are determined exactl

Yupeng Wang

We study a two-leg spin-1/2 ladder with isotropic exchanges and biquadratic interactions in the basic plaquettes. It is shown that for the extremely frustrated case, the system exhibits a self-organized phase separation. In some parameter regions, the singlet rungs form a Wigner-like lattice in the triplet-rung host. There are three types of elementary excit

Weiqun Peng, Paul M. Goldbart

The vulcanization transition - the crosslink-density-controlled equilibrium phase transition from the liquid to the amorphous solid state - is explored analytically from a renormalization group perspective. The analysis centers on a minimal model that accounts for both the thermal motion of the constituents and the quenched random constraints imposed on thei

Sukyoung YI, T. M. Brown, S. Heap, I. Hubeny

The recent spectral analysis of LBDS 53W091 by Spinrad and his collaborators has suggested that this red galaxy at z=1.55 is at least 3.5 Gyr old. This imposes an important constraint on cosmology, suggesting that this galaxy formed at z > 6.5, assuming recent estimates of cosmological parameters. We have performed chi^2 tests to the continuum of this galaxy

Daniel D. Kelson, Garth D. Illingworth, Pieter G. van Dokkum, Marijn Franx

Using HST imaging of CL1358+62 (z=0.33) structural parameters are derived for 53 cluster members. We fit integrated r^{1/4}-laws to the integrated S.B. profiles, and fit two-dimensional r^{1/4}-law model galaxies to the images directly. The results from the two methods agree very well, with an rms scatter of 13% in r_e. The half-light radii range from 1 to 2

S. J. Warren, P. C. Hewett, C. B. Foltz

The longstanding question of the extent to which the quasar population is affected by dust extinction, within host galaxies or galaxies along the line of sight, remains open. More generally, the spectral energy distributions of quasars vary significantly and flux-limited samples defined at different wavelengths include different quasars. Surveys employing fl

Ignas Snellen, Richard Schilizzi

In this paper we discuss the early phase of radio source evolution as represented by Gigahertz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) radio sources. Correlations between their spectral peak and angular size strongly suggest that the spectral turnovers are caused by synchrotron self absorption, and indicate that young radio sources evolve in a

Matthew G. Baring

One of the principal results obtained by the EGRET experiment aboard the Compton Gamma-Ray Observatory (CGRO) was the detection of several Gamma-ray bursts (GRBs) above 100 MeV. The broad-band spectra obtained for these bursts gave no indication of any high energy spectral attenuation that might preclude detection of bursts by ground-based Cerenkov telescope

Ofer Lahav

We review observational tests for the homogeneity of the Universe on large scales. Redshift and peculiar velocity surveys, radio sources, the X-Ray Background, the Lyman-alpha forest and the Cosmic Microwave Background are used to set constraints on inhomogeneous models and in particular on fractal-like models. Assuming the Cosmological Principle and the FRW

Yu. A. Golubkov, M. Yu. Khlopov

The all-sky survey in high-energy gamma rays (E > 30 MeV) carried out by the Energetic Gamma Ray Experiment Telescope (EGRET) aboard the Compton Gamma-Ray Observatory provides a unique opportunity to examine in detail the diffuse gamma-ray emission. The observed diffuse emission has a Galactic component arising from cosmic-ray interactions with the local int

Y. Dabrowski, M. J. Hall, I. L. Sawicki, A. N. Lasenby

A new method arising from a gauge-theoretic approach to general relativity is applied to the formation of clusters in an expanding universe. The three cosmological models (Omega_0=1, Omega_Lambda=0), (Omega_0=0.3, Omega_Lambda=0.7), (Omega_0=0.3, Omega_Lambda=0) are considered, which extends our previous application (Lasenby et al. 1999 -&#34;http://xxx.soto

D. M. Worrall

X-ray emission traces the gaseous environments of radio sources. The medium must be present for jet confinement, but what are its influence on jet fuelling, dynamics, propagation, and disruption? The observational situation is both complicated and enriched by radio sources being multi-component X-ray emitters, with several possible regions of non-thermal emi

M. Gliozzi, W. Brinkmann, S. A. Laurent-Muehleisen, L. O. Takalo

We present the results of three ROSAT HRI observations of AGN expected to reside in clusters of galaxies. Although the exposures were truncated by the premature end of the ROSAT mission, valuable information could be achieved which greatly improved upon the previous PSPC results. For RGB 1745+398 we could separate the cluster emission from that of the BL Lac

G. Nelemans, T. M. Tauris, E. P. J. van den Heuvel

Both the recently observed high runaway velocities of Cyg X-1 (~50 km/s) and X-ray Nova Sco 1994 (> ~100 km/s) and the relatively low radial velocities of the black hole X-ray binaries with low mass donor stars, can be explained by symmetric mass ejection in the supernovae (SNe) which formed the black holes in these systems. Assuming symmetric mass ejection

B. Rothberg, W. Saunders, R. B. Tully, P. L. Witchalls

The relationship between galaxy luminosities and rotation rates is studied with total luminosities in the K&#39; band. Extinction problems are essentially eliminated at this band centered at 2.1 micron. A template luminosity-linewidth relation is derived based on 65 galaxies drawn from two magnitude-limited cluster samples. The zero-point is determined using

R. Brent Tully, M. J. Pierce

The correlation between the luminosities and rotation velocities of galaxies can be used to estimate distances to late-type galaxies. It is an appropriate moment to re-evaluate this method given the great deal of new information available. The major improvements described here include: (a) the template relations can now be defined by large, complete samples,

David Elbaz

We present the results of the extragalactic surveys performed at 15 and 175 microns using the ISOCAM and ISOPHOT instruments on-board the Infrared Space Observatory (ISO). The number counts at both wavelengths present a strong evolution. The preliminary study of the individual galaxies responsible for this evolution suggest that more star formation was hidde

S. Ridgway, T. Heckman, D. Calzetti, M. Lehnert

We will present the results of a NICMOS H-band imaging survey of a small sample of z ~ 2 to 3 radio-quiet quasars. We have resolved extension in at least 4 of 5 objects and find evidence for a wide range in the morphologies and magnitudes of these hosts. The host galaxy luminosities range from sub-L* to about 4 L*, with most of the hosts having luminosities

F. PIRON

The Very High Energy (VHE) gamma-ray emission of the closest BL Lacertae objects Markarian 501 and Markarian 421 has been observed by the CAT telescope in 1997 and 1998. In 1997 Mrk 501 exhibited a remarkable series of flares, with a VHE emission peaking above 250 GeV. The source showed correlated emissions in the X-ray and VHE gamma-ray bands, together with

Ariyeh H. Maller, Luc Simard, Puragra Guhathakurta, Jens Hjorth

The degeneracy between the disk and the dark matter contribution to galaxy rotation curves remains an important uncertainty in our understanding of disk galaxies. Here we discuss a new method for breaking this degeneracy using gravitational lensing by spiral galaxies, and apply this method to the spiral lens B1600+434 as an example. The combined image and le

A. Y. Potekhin

Practical expressions are derived for evaluation of electrical and thermal conductivities and thermopower of degenerate electrons in the outer envelopes of neutron stars with magnetic fields. All tensor components of the kinetic coefficients are calculated (those related to conduction along and across magnetic field and to the Hall currents). The kinetic coe

Mirjam Cvetic, Michael Plumacher, Jing Wang

We address the implementation of non-Abelian Wilson lines in D=4 N=1 Type IIB orientifold constructions. We present an explicit three-family example with the gauge group (U(4)xU(2)xSU(2)xSU(2))^2x(U(6)xSp(4))^2 and give the particle spectrum and the trilinear superpotential. Emphasizing the new subtleties associated with the introduction of non-Abelian Wilso

L. M. Nieto, H. C. Rosu, M. Santander

An old result of A.F. Stevenson [Phys. Rev.} 59, 842 (1941)] concerning the Kepler-Coulomb quantum problem on the three-dimensional (3D) hypersphere is considered from the perspective of the radial Schrödinger equations on 3D spaces of any (either positive, zero or negative) constant curvature. Further to Stevenson, we show in detail how to get the hypergeom

G. Tavares-Velasco, J. J. Toscano

We analyze the effects of a doubly charged vector bilepton as well as exotic quarks with charge 5/3 e and -4/3 e on light by light scattering. We consider mass values in the range 0.3--1 TeV, which would be reached at the planned future linear colliders. It is found that such exotic particles, especially the doubly charged vector bilepton, give raise to rema

Xi Lin, Hongkai Zhang, Andrew M. Rappe

An algorithm is proposed to optimize quantum Monte Carlo (QMC) wave functions based on New ton&#39;s method and analytical computation of the first and second derivatives of the variati onal energy. This direct application of the variational principle yields significantly low er energy than variance minimization methods when applied to the same trial wave fu

N. Boccara, H. Fukś

We derive the critical behavior of a CA traffic flow model using an order parameter breaking the symmetry of the jam-free phase. Random braking appears to be the symmetry-breaking field conjugate to the order parameter. For $v_{\max}=2$, we determine the values of the critical exponents $β$, $γ$ and $δ$ using an order-3 cluster approximation and computer sim

E. V. Bezuglyi, A. L. Gaiduk, V. D. Fil, W. L. Johnson

The superconducting energy gap and the parameter of the intensity of electron scattering at two-level systems in amorphous ZrTiCuNiBe are determined from the results of measurements of sound attenuation. The mechanism of adiabatic renormalization of the amplitude of coherent tunneling is used for a quantitative description of the peculiarities of sound absor

Luis A. Anchordoqui

A detailed simulation of air showers produced by dust grains has been performed by means of the {\sc aires} Monte Carlo code with the aim of comparing with experimental data. Our analysis indicates that extensive dust grain air showers must yet be regarded as highly speculative but they cannot be completely ruled out.

E. Dudas, J. Mourad

We consider, in a string theory framework, physical processes of phenomenological interest in models with a low string scale. The amplitudes we study involve tree-level virtual gravitational exchange, divergent in a field-theoretical treatment, and massive gravitons emission, which are the main signatures of this class of models. First, we discuss the regula

Bárbara Pichardo, Enrique Vázquez-Semadeni, Adriana Gazol, Thierry Passot

We study the effects of projection of three-dimensional (3D) data onto the plane of the sky by means of numerical simulations of turbulence in the interstellar medium including the magnetic field, parameterized cooling and diffuse and stellar heating, self-gravity and rotation. We compare the physical-space density and velocity distributions with their repre

Ruth Gregory

We consider an exotic `compactification&#39; of spacetime in which there are two infinite extra dimensions, using a global string instead of a domain wall. By having a negative cosmological constant we prove the existence of a nonsingular static solution using a dynamical systems argument. A nonsingular solution also exists in the absence of a cosmological c

Jesus M. Mira, Enrico Nardi, Diego A. Restrepo

A non anomalous horizontal $U(1)_H$ gauge symmetry can be responsible for the fermion mass hierarchies of the minimal supersymmetric standard model. Imposing the consistency conditions for the absence of gauge anomalies yields the following results: i) unification of leptons and down-type quarks Yukawa couplings is allowed at most for two generations. ii) Th

G. X. Peng, H. C. Chiang, J. J. Yang, L. Li

The previous treatments for strange quark matter in the quark mass-density-dependent model have unreasonable vacuum limits. We provide a method to obtain the quark mass parametrizations and give a self-consistent thermodynamic treatment which includes the MIT bag model as an extreme. In this treatment, strange quark matter in bulk still has the possibility o

Ansar Fayyazuddin, Maxim Zabzine

We sketch the main steps of old covariant quantization of bosonic open strings in a constant $B$ field background. We comment on its space-time symmetries and the induced effective metric. The low-energy spectrum is evaluated and the appearance of a new non-commutative gauge symmetry is addressed.

Pierre-Henri Chavanis, Clément Sire

This paper is devoted to a statistical analysis of the fluctuations of velocity and acceleration produced by a random distribution of point vortices in two-dimensional turbulence. We show that the velocity probability density function (p.d.f.) behaves in a manner which is intermediate between Gaussian and Lévy laws while the distribution of accelerations is

N. Mebarki, A. Taleb, H. Aissaoui, N. Belaloui

Successive toro\&#34;ıdal compactifications of a closed bosonic string are studied and some Lie groups solutions are derived.

Suman Kumar Banik, Jyotipratim Ray Chaudhuri, Deb Shankar Ray

The Kramers&#39; theory of activated processes is generalized for nonequilibrium open one-dimensional systems. We consider both the internal noise due to thermal bath and the external noise which are stationary, Gaussian and are characterized by arbitrary decaying correlation functions. We stress the role of a nonequilibrium stationary state distribution for

M. Chaichian, S. S. Masood, C. Montonen, A. Perez Martinez

We study the thermodynamics of degenerate electron and charged vector boson gases in very intense magnetic fields. In degenerate conditions of the electron gas, the pressure transverse to the magnetic field $B$ may vanish, leading to a transverse collapse. For W-bosons an instability arises because the magnetization diverges at the critical field B_c = M_W^2

Yu-feng Liu, Wu-jun Huo, Jinyan Zeng

It was shown that the Runge-Lenz vector for a hydrogen atom is equivalent to the raising and lowering operators derived from the factorization of radial Schrödinger equation. Similar situation exists for an isotropic harmonic oscillator. It seems that there may exist intimate relation between the closeness of classical orbits and the factorization of radial

Sergei Gukov

In this paper we study several issues related to the generation of superpotential induced by background Ramond-Ramond fluxes in compactification of Type IIA string theory on Calabi-Yau four-folds. Identifying BPS solitons with D-branes wrapped over calibrated submanifolds in a Calabi-Yau space, we propose a general formula for the superpotential and justify

Etsuro Date, Shi-shyr Roan

We study the Onsager algebra from the ideal theoretic point of view. A complete classification of closed ideals and the structure of quotient algebras are obtained. We also discuss the solvable algebra aspect of the Onsager algebra through the use of formal Lie algebras.

J. S. Bagla

We describe the TreePM method for carrying out large N-Body simulations to study formation and evolution of the large scale structure in the Universe. This method is a combination of Barnes and Hut tree code and Particle-Mesh code. It combines the automatic inclusion of periodic boundary conditions of PM simulations with the high resolution of tree codes. Th

Angel Ballesteros, Francisco J. Herranz

A family of completely integrable nonlinear deformations of systems of N harmonic oscillators are constructed from the non-standard quantum deformation of the sl(2,R) algebra. Explicit expressions for all the associated integrals of motion are given, and the long-range nature of the interactions introduced by the deformation is shown to be linked to the unde

Cicogna G

We consider dynamical systems depending on one or more real parameters, and assuming that, for some ``critical&#39;&#39; value of the parameters, the eigenvalues of the linear part are resonant, we discuss the existence -- under suitable hypotheses -- of a general class of bifurcating solutions in correspondence to this resonance. These bifurcating solutions