June 1999 arXiv papers — page 15

A. L. Ferreira, M. A. Barroso

We show how to use the multiple histogram method to combine canonical ensemble Monte Carlo simulations made at different temperatures and densities. The method can be applied to study systems of particles with arbitrary interaction potential and to compute the thermodynamic properties over a range of temperatures and densities. The calculation of the Helmhol

D. Malzahn, A. Engel

We consider feed-forward neural networks with one hidden layer, tree architecture and a fixed hidden-to-output Boolean function. Focusing on the saturation limit of the storage problem the influence of replica symmetry breaking on the distribution of local fields at the hidden units is investigated. These field distributions determine the probability for fin

Dora M. Jezek, Marti Pi, Manuel Barranco

We have investigated the effect that dissipation may have on the cavitation process in normal liquid $^3$He. Our results indicate that a rather small dissipation decreases sizeably the quantum-to-thermal crossover temperature $T^*$ for cavitation in normal liquid $^3$He. This is a possible explanation why recent experiments have not yet found clear evidence

Leonid B. Litinskii

The set of the fixed points of the Hopfield type network is under investigation. The connection matrix of the network is constructed according to the Hebb rule from the set of memorized patterns which are treated as distorted copies of the standard-vector. It is found that the dependence of the set of the fixed points on the value of the distortion parameter

H. G. Ballesteros, L. A. Fernandez, V. Martin-Mayor, A. Munoz Sudupe

We have studied numerically the effect of quenched site dilution on a first order phase transition in three dimensions. We have simulated the site diluted three states Potts model studying in detail the second order region of its phase diagram. We have found that the $ν$ exponent is compatible with the one of the three dimensional diluted Ising model whereas

V. Eyert, K. -H. Hoeck, S. Horn, A. Loidl

We present results of all-electron electronic structure calculations for the recently discovered d electron heavy fermion compound LiV_2O_4. The augmented spherical wave calculations are based on density functional theory within the local density approximation. The electronic properties near the Fermi energy originate almost exclusively from V 3d t_{2g} stat

Y. Georgelin, T. Masson, J. -C. Wallet

We construct a family of holomorphic $β$-functions whose RG flow preserves the $Γ(2)$ modular symmetry and reproduces the observed stability of the Hall plateaus. The semi-circle law relating the longitudinal and Hall conductivities that has been observed experimentally is obtained from the integration of the RG equations for any permitted transition which c

J. Soubusta, R. Grill, P. Hlidek, M. Zvara

The effect of an external electric field F on the excitonic photoluminescence (PL) spectra of a symmetric coupled double quantum well (DQW) is investigated both theoretically and experimentally. We show that the variational method in a two-particle electron-hole wave function approximation gives a good agreement with measurements of PL on a narrow DQW in a w

Daijiro Yoshioka, Kentaro Nomura

Hall and diagonal resistances of bilayer fractional quantum Hall systems are discussed theoretically. The bilayers have electrodes attached separately to each layer. They are assumed to be coupled weakly by interlayer tunneling, while the interlayer Coulomb interaction is negligibly small. It is shown that source-drain voltage dependence of the resistances r

Matthieu Micoulaut, Gerardo G. Naumis

We give general topological rules which very accurately predict the chemical trends in glass transition temperature $T_g$ variation as a function of cross-linking. In multicomponent glasses, these chemical trends permit to distinguish homogeneous compositions (random network) from inhomogeneous ones (local phase separation). The stochastic origin of the Gibb

P. Ao, X. -M. Zhu

Using the random matrix theory we demonstrate explicitly the insensitivity of the transverse force on a moving vortex to non-intrinsic and non-magnetic impurities in a superconductor.

Ioan Kosztin, Qijin Chen, Ying-Jer Kao, K. Levin

In this paper we study the BCS Bose Einstein condensation (BEC) crossover scenario within the superconducting state, using a T-matrix approach which yields the ground state proposed by Leggett. Here we extend this ground state analysis to finite temperatures T and interpret the resulting physics. We find two types of bosonic-like excitations of the system: l

Alexander I. Olemskoi

The theory of a flux steady-state (avalanche) formation is presented for the simplest model of a real sand pile within the framework of Lorenz approach. The stationary values of sand velocity and sand pile slope are derived as functions of controlling parameter (externally driven sandpile slope). The additive noises of above values are taken into account to

Fritz Haake, Hans-Juergen Sommers, Joachim Weber

We consider the spectral form factor of random unitary matrices as well as of Floquet matrices of kicked tops. For a typical matrix the time dependence of the form factor looks erratic; only after a local time average over a suitably large time window does a systematic time dependence become manifest. For matrices drawn from the circular unitary ensemble we

Mark Nelkin

This Resource Letter provides a guide to the literature on fully developed turbulence in fluids. It is restricted to mechanically driven turbulence in an incompressible fluid described by the Navier-Stokes equations of hydrodynamics, and places greatest emphasis on fundamental physical questions. Journal articles and books are cited for the following topics:

Awadhesh Prasad, Ramakrishna Ramaswamy

We study the probability densities of finite-time or \local Lyapunov exponents (LLEs) in low-dimensional chaotic systems. While the multifractal formalism describes how these densities behave in the asymptotic or long-time limit, there are significant finite-size corrections which are coordinate dependent. Depending on the nature of the dynamical state, the

Yoshihiro Hirata, Kazuhiro Nozaki, Tetsuro Konishi

We asymptotically compute the intersection angles between N-dimensional stable and unstable manifolds in 2N-dimensional symplectic mappings. There exist particular 1-dimensional stable and unstable sub-manifolds which experience exponentially small splitting of separatrix in our models. We show that the angle between the sub-manifolds is exponentially small

Gus Sinnis

Very-high-energy astronomy studies the Universe at energies between 30 GeV and 100 TeV. The past decade has seen enormous progress in this field. There are now at least seven known sources of VHE photons. By studying these objects in the VHE regime one can begin to understand the environments surrounding these objects, and how particle acceleration is realiz

Stuart Bowyer, Eric J. Korpela, Jerry Edelstein, Michael Lampton

We report on spectral observations of the night sky in the band around 900 angstroms where the emission line in the Sciama model of radiatively decaying massive neutrinos would be present. The data were obtained with a high resolution, high sensitivity spectrometer flown on the Spanish MINISAT satellite. The observed emission is far less intense than that ex

Juan Fabregat, J. Miguel Torrejon

We present a study of the abundance of Be stars in open clusters as a function of the cluster age, using whenever possible ages determined through Stromgren uvby photometry. For the first time in studies of this kind we have considered separately classical and Herbig Be stars. The main results can be summarized as follows: 1.- Clusters associated to emitting

C. Ian Short, Peter H. Hauschildt, E. Baron

We have used our PHOENIX multi-purpose model atmosphere code to calculate atmospheric models that represent novae in the optically thick wind phases of their outburst. We have improved the treatment of NLTE effects by expanding the number of elements that are included in the calculations from 15 to 19, and the number of ionization stages from 36 to 87. The c

A. M. Newsam, I. M. McHardy, L. Jones, K. Mason

At the faint end of the deepest X-ray surveys, a population of X-ray luminous galaxies is seen. In this paper, we present the results of a cross-correlation between the residual, unresolved X-ray photons in a very deep X-ray survey and the positions of faint galaxies, in order to examine the importance of these objects at even fainter flux levels. We measure

Davide Lazzati, Sergio Campana, Gabriele Ghisellini

We discuss how a powerful iron line emission can be produced if ~1-5 iron rich solar masses are concentrated in the close vicinity of the burst. Recombination, thermal and fluorescent reflection are discussed. We find that recombination suffers the high Compton temperature of the plasma while the other two scenarios are not mutually exclusive and could accou

Gabriele Ghisellini, Davide Lazzati, Sergio Campana

The discovery of a powerful and transient iron line feature in the X-ray afterglow spectra of gamma-ray bursts would be a major breakthrough for understanding the nature of their progenitors, strongly suggesting the presence of a large, iron rich, mass in the vicinity of the burst event. Model-independent limits to the size and the mass of the the iron line

Gerd Weigelt, Yuri Balega, Thomas Preibisch, Dieter Schertl

We present bispectrum speckle interferometry observations with the SAO 6 m telescope of the four brightest stars in the Orion Trapezium. Diffraction-limited images with an unprecedented resolution lambda/D of 57 mas and 76 mas were obtained in the H- and K-band, respectively. The The H and K images of Theta1 Ori C (the star responsible for the proplyds) show

S. Esposito, G. Mangano, G. Miele, O. Pisanti

We report the results of a new accurate evaluation of light nuclei yields in primordial nucleosynthesis. All radiative effects, finite nucleon mass, thermal and plasma corrections are included in the proton to neutron conversion rates. The relic densities of He4, D and Li7 have been numerically obtained via a new updated version of the standard BBN code. In

Wing-Fai Thi, Ewine F. van Dishoeck, Geoffrey A. Blake, Gerd-Jan van Zadelhoff

We present the first detection of the low-lying pure rotational emission lines of H2 from circumstellar disks around T~Tauri stars, using the Short Wavelength Spectrometer on the Infrared Space Observatory. These lines provide a direct measure of the total amount of warm molecular gas in disks. The J=2->0 S(0) line at 28.218 mum and the J=3->1 S(1) line at 1

I. V. Moskalenko, A. W. Strong

We have made a calculation of the propagation of positrons from dark-matter particle annihilation in the Galactic halo for different models of the dark matter halo distribution using our 3D code. We show that the Green's functions are not very sensitive to the dark matter distribution for the same local dark matter energy density. We compare our predicti

A. W. Strong, I. V. Moskalenko, O. Reimer

Recent evidence for a large Galactic halo, based on cosmic-ray radioactive nuclei, implies a significant contribution from inverse Compton emission at high Galactic latitudes. We present predictions for the expected intensity distribution, and show that the EGRET gamma-ray latitude distribution is well reproduced from the plane to the poles. We show that the

A. W. Strong, I. V. Moskalenko

The cosmic-ray propagation code GALPROP has been generalized to include fragmentation networks of arbitrary complexity. The code can now provide an alternative to leaky-box calculations for full isotopic abundance calculations and has the advantage of including the spatial dimension which is essential for radioactive nuclei. Preliminary predictions for sub-F

Yoshinori Tutui, Yoshiaki Sofue

We have examined the trend between CO and HI linewidths by compiling the linewidths of 219 nearby galaxies. The trend is that the CO linewidths of fast rotating galaxies tend to be larger than the HI linewidths, and that the HI linewidths of slow rotating galaxies tend to be larger than the CO linewidths, whereas the intermediately rotating galaxies have alm

Cheongho Han, Mun-Suk Chun, Kyongae Chang

In this paper, we study the astrometric properties of gravitational microlensing events caused by binary lenses. By investigating the centroid shifts for various types of binary-lens events, we find that the deviations of the centroid shift trajectories from the elliptical ones of single-lens events are characterized by distortions, twistings, and big jumps.

Yoshiaki Sofue

We present high-accuracy rotation curves, which show a steep nuclear rise and high-velocity central rotation, followed by a broad maximum in the disk and flat part. We use the rotation curves to directly calculate the radial distribution of surface mass density, and obtain radial variations of the mass-to-luminosity ratio (M/L). The M/L ratio and, therefore,

Charles F. Gammie

The efficiency of thin disk accretion onto black holes depends on the inner boundary condition, specifically the torque applied to the disk at the last stable orbit. This is usually assumed to vanish. I estimate the torque on a magnetized disk using a steady magnetohydrodynamic inflow model originally developed by Takahashi et al., 1990. I find that the effi

Yoshiaki Sofue

The rotation curve of the Large Magellanic Cloud, which we have derived from high-resolution HI position-velocity diagrams observed by Kim et al (1998), shows a steep central rise and flat rotation with a gradual rise toward the edge. Using the rotation curve, we have calculated the distribution of surface mass density, and show that the LMC has a dark compa

Abhas Mitra

We have recently shown that at the Event Horizon of a Schwarzschild BH, the Kruskal derivative assumes a form du/dv = +,- f(r,t)/f(r,t) = +, - 1. Corespondingly, du^2 = dv^2, and the geodesic of a material particle becomes NULL at the EH. Physically this means that the free fall speed measured by the Kruskal observer V=1 at the EH. However, Tereno has diffic

Abhas Mitra

In a recent preprint (astro-ph/9905144) Tereno has tried to find the physical 3-velocity (V) at the Event Horizon of a Kruskal Black Hole. This has been done in the backdrop of the recent work by Mitra (astro-ph/9904162) where it was shown that the radial geodesic of material particle, unphysically, becomes null at the Event Horizon. Although Tereno stops sh

Arbab I. Arbab

We have studied the evolution of primordial black holes (PBHs) in a universe with a variable gravitational constant and bulk viscosity. We have found that the strength of gravity has changed appreciably in the early universe. The gravitational constant attained its greatest value at t=10^{-23} sec after the Big Bang. PBHs formed at the GUT and electroweak ep

Michael Duetsch, Bert Schroer

We show that the requirements of renormalizability and physical consistency imposed on perturbative interactions of massive vector mesons fix the theory essentially uniquely. In particular physical consistency demands the presence of at least one additional physical degree of freedom which was not part of the originally required physical particle content. In

Kaare Borchsenius

The quantized canonical space-time coordinates of a relativistic point particle are expressed in terms of the elements of a complex Clifford algebra which combines the complex properties of SL(2.C) and quantum mechanics. When the quantum measurement principle is adapted to the generating space of the Clifford algebra we find that the transition probabilities

Gabriel Lopes Cardoso, Bernard de Wit, Thomas Mohaupt

In four-dimensional N=2 compactifications of string theory or M-theory, modifications of the Bekenstein-Hawking area law for black hole entropy in the presence of higher-derivative interactions are crucial for finding agreement between the macroscopic entropy obtained from supergravity and subleading corrections to the microscopic entropy obtained via state

D. V. Anchishkin, A. M. Gavrilik, N. Z. Iorgov

We propose and develop to some extent a novel approach, which allows us to effectively describe, for relativistic heavy-ion collisions, the empirically observed deviation from unity of the intercept λ(i.e. the measured value corresponding to zero relative momentum {\bf p} of two registered identical pions or kaons) of the two-particle correlation function C(

D. Hardtke, S. A. Voloshin

The relationship between pion and kaon space-time freeze-out distributions and the HBT radius parameters in high-energy nucleus-nucleus collisions is investigated. We show that the HBT radius parameters in general do not reflect the R.M.S. deviations of the single particle production points. Instead, the HBT radius parameters are most closely related to the

A. Borowiec, M. Francaviglia, I. Volovich

An anti-Kaehlerian manifold is a complex manifold with an anti-Hermitian metric and a parallel almost complex structure. It is shown that a metric on such a manifold must be the real part of a holomorphic metric. It is proved that all odd Chern numbers of an anti-Kaehlerian manifold vanish and that complex parallelisable manifolds (in particular the factor s

Florin Ambro

An explanation to the boundness of minimal log discrepancies conjectured by V.V. Shokurov would be that the minimal log discrepancies of a variety in its closed points define a lower semi-continuous function. We check this lower semi-continuity behaviour for varieties of dimension at most 3 and for toric varieties of arbitrary dimension.

Morihiko Saito

We introduce the notion of mixed Hodge complex on an algebraic variety, improving Du Bois' filtered complex, and relate Deligne's theory of mixed Hodge structure with the theory of mixed Hodge module. This was supposed to be true, but is quite nontrivial, because the theory of mixed Hodge module does not work on a simplicial scheme. Some application

Norbert A'Campo

We deduce from a rooted tree in the disk a slalom divide and a slalom knot. A slalom knot is either the local link of a simple plane curve singularity of type A_2n, E_6, E_8 or a fibered hyperbolic knot with very special monodromy.

Bernard de Wit

Modifications of the area law are crucial in order to find agreement with microscopic entropy calculations based on string theory, when including contributions that are subleading for large charges. The deviations of the area law are in accord with Wald's proposal for the entropy based on a Noether charge. We discuss this for the case of four-dimensional

Marcos Alvarez, David I. Olive

A systematic treatment is given of the Dirac quantisation condition for electromagnetic fluxes through two-cycles on a four-manifold space-time which can be very complicated topologically, provided only that it is connected, compact, oriented and smooth. This is sufficient for the quantised Maxwell theory on it to satisfy electromagnetic duality properties.

H. B. Benaoum

A direct proof is given here which shows that instead of 6 complex numbers, the triangular mass matrix for each sector could just be expressed in terms of 5 by performing a specific weak basis transformation, leading therefore to a new textures for triangular mass matrices. Furthermore, starting with the set of 20 real parameters for both sectors, it can sho

Andrzej Borowiec

The Euler-Lagrange equations for some class of gravitational actions are calculated by means of Palatini principle. Polynomial structures with Einstein metrics appear among extremals of this variational problem.

Venkatesh Gopal, Sushil Mujumdar, Hema Ramachandran, A. K. Sood

We study by means of experiments and Monte Carlo simulations, the scattering of light in random media, to determine the distance upto which photons travel along almost undeviated paths within a scattering medium, and are therefore capable of casting a shadow of an opaque inclusion embedded within the medium. Such photons are isolated by polarisation discrimi

A. A. Tsvetkov, D. Dulic, D. van der Marel, A. Damascelli

We present grazing incidence reflectivity measurements in the far infrared region at temperatures above and below Tc for a series of thallium (Tl2Ba2CuO6, Tl2Ba2CaCu2O8) and bismuth (Bi2Sr2CuO6, Bi2Sr2CaCu2O8, and Bi(2-x)Pb(x)Sr2CaCu2O8) based cuprate superconductors. From the spectra, which are dominated by the c-axis phonons, longitudinal frequencies (LO)

M. B. Hastings

The large N infinite range spin glass is considered, in particular the number of spin components k needed to form the ground state and the sample-to-sample fluctuations in the Lagrange multiplier field on each site. The physical significance of k for the correlation functions is discussed. The difference between the large N and spherical spin glass is emphas

N. Bulut

The effects of dilute Zn impurities on the uniform magnetic susceptibility are calculated in the normal metallic state for a model of the spin fluctuations of the layered cuprates. It is shown that scatterings from extended impurity potentials can lead to a coupling of the q~(pi,pi) and the q~0 components of the magnetic susceptibility chi(q). Within the pre

G. Baskaran

Jahn-Teller theorem, proposed in 1937, predicts a distortional instability for a molecule that has symmetry based degenerate electronic states. In 1939 Krishnan emphasized the importance of this theorem for the arrangement of water molecules around the transition metal or rare earth ions in aqueous solutions and hydrated saltes, in a short and interesting pa

G. Baskaran

In this talk I will briefly review our present theoretical understanding of some of the important issues in the high Tc cuprates. In view of its success, at a qualitative level and some times quantitative level, the theory initiated by Anderson and developed further by him and collaborators will be discussed. Many issues that still challenges us will be poin

M. R. Panzera, G. Tagliaferri, L. Pasinetti, E. Antonello

We use the ROSAT public data archive to study the X-ray emission of a sample of supposedly single A0-F6 spectral type stars from the Bright Star Catalogue. We detected X-ray emission from 19 A and 33 F-type stars. However, our results are not sufficient to associate with certainty the X-ray emission to the A-type stars themselves, since the usual argument th

J. A. Templon, C. E. Vellidis, R. E. J. Florizone, A. J. Sarty

We present a direct calculation of the cross section for the reaction 3He(e,e'p) including the radiation tail originating from bremsstrahlung processes. This calculation is compared to measured cross sections. The calculation is carried out from within a Monte Carlo simulation program so that acceptance-averaging effects, along with a subset of possible ener

HongSheng Zhao

We propose an observational test that can break the degeneracy of two main classes of microlensing models to the Magellanic Clouds: (a) the lenses are located in the Galactic halo, and (b) the lenses are located in the LMC disk. The source stars in the latter (self-lensing) models tend to be at the far side or behind the LMC disk, thus experience more redden

D. Pripstein, C. N. Brown, T. A. Carey, Y. C. Chen

Results of a search for the three neutral charm decays, D0 -> mu e, D0 -> mu mu, and D0 -> e e, are presented. This study was based on data collected in Experiment 789 at the Fermi National Accelerator Laboratory using 800 GeV/c proton-Au and proton-Be interactions. No evidence is found for any of the decays. Upper limits on the branching ratios, at the 90%

Adonai S. Sant'Anna, Alexandre M. S. Santos

Quasi-set theory provides us a mathematical background for dealing with collections of indistinguishable elementary particles. In this paper, we show how to obtain the usual statistics (Maxwell-Boltzmann, Bose-Einstein, and Fermi-Dirac) into the scope of quasi-set theory. We also show that, in order to derive Maxwell-Boltzmann statistics, it is not necessary

Yi-Xin Chen

A framework for a quantum information theory is introduced that is based on the measure of quantum information associated with probability distribution predicted by quantum measuring of state. The entanglement between states of measured system and "pointer" states of measuring apparatus, which is generated by dynamical process of quantum measurement,

Hasan R. Karadayi, Meltem Gungormez

We show that permutation weights, which are previously introduced for finite Lie algebras, can be appropriately defined also for affine Lie algebras. This allows us to classify all the weights of an affine Weyl orbit explicitly. Let $Λ$ be a dominant weight of an affine Lie algebra $ G_N^{(r)} $ for r=1,2,3. At each and every order M of weight depths, the se

Noam D. Elkies

In an earlier paper (math.NT/9906019) we showed that any integral unimodular lattice L of rank n which is not isometric with Z^n has a characteristic vector of norm at most n-8. [A "characteristic vector" of L is a vector w in L such that 2|(v,w-v) for all v in L; it is known that the characteristic vectors all have norm congruent to n mod 8 and comp

C. Viazminsky

The relations between solutions of the three types of totally linear partial differential equations of first order are presented. The approach is based on factorization of a non-homogeneous first order differential operator to products consisting of a scalar function, a homogeneous first order differential operator and the reciprocal of the scalar function.

Allen Hatcher

We consider collections of disjoint simple closed curves in a compact orientable surface which decompose the surface into pairs of pants. The isotopy classes of such curve systems form the vertices of a 2-complex, whose edges correspond to certain simple moves in which only one curve changes, and whose 2-cells correspond to certain elementary cycles of simpl

David P. Blecher

We give a solution, via operator spaces, of an old problem in the Morita equivalence of C*-algebras. Namely, we show that C*-algebras are strongly Morita equivalent in the sense of Rieffel if and only if their categories of left operator modules are isomorphic via completely contractive functors. Moreover, any such functor is completely isometrically isomorp

David P. Blecher

We continue our study of the general theory of possibly nonselfadjoint algebras of operators on a Hilbert space, and modules over such algebras, developing a little more technology to connect `nonselfadjoint operator algebra' with the C$^*-$algebraic framework. More particularly, we make use of the universal, or maximal, C$^*-$algebra generated by an ope

David P. Blecher

We show that two operator algebras are strongly Morita equivalent (in the sense of Blecher, Muhly and Paulsen) if and only if their categories of operator modules are equivalent via completely contractive functors. Moreover, any such functor is completely isometrically isomorphic to the Haagerup tensor product (= interior tensor product) with a strong Morita

Andrew E. Chubykalo, Rolando A. Flores, Juan A. Pérez

Ambiguity is shown in the context of the differential calculus of several variables and with the help of the language of category theory, a way to solve it in its most general form is offered. It is also shown that this new definition is related to other well-known definitions in the literature.

A. A. Bytsenko, L. Vanzo, S. Zerbini

The invariant integration method for Chern-Simons theory defined on the compact hyperbolic manifold Γ\H^3 is verified in the semiclassical approximation. The semiclassical limit for the partition function is presented. We discuss briefly L^2 - analytic torsion and the eta invariant of Atiyah-Patodi-Singer for compact hyperbolic 3-manifolds.

S. A. Bulgadaev

The Berezinsky-Kosterlitz-Thouless (BKT) type phase transitions in two-dimensional systems with internal abelian continuous symmetries are investigated. The necessary conditions for they can take place are: 1) conformal invariance of the kinetic part of the model action, 2) vacuum manifold must be degenerated with abelian discrete homotopy group pi_1. Then t

C. G. Lester, D. J. Summers

We introduce a variable useful for measuring masses of particles pair produced at hadron colliders, where each particle decays to one particle that is directly observable and another particle whose existence can only be inferred from missing transverse momenta. This variable is closely related to the transverse mass variable commonly used for measuring the $

De-Hai Zhang

A new idea of the cosmological constant is proposed in this paper. Due to the horizon is limited, the quantum fluctuation of the inflaton field is not zero, a nonzero vacuum energy is remained as a residual inflationary energy of an unusual potential, however the true stable vacuum energy is zero fortunately. A unified model of the cosmological constant and

A. Pompili, F. Selleri

A very general local realistic theory of single $B^{0}_{d}$ mesons and of correlated $B^{0}_{d}\bar{B^{0}_{d}}$ pairs is formulated. If these pairs are produced in the $Υ(4S)$ decay, the local realistic asymmetry for observing pairs with like and unlike flavour at different proper times remarkably differs from the quantum mechanical prediction. Asymmetric B-

Dieter Brill

Vacuum Einstein theory in three spacetime dimensions is locally trivial, but admits many solutions that are globally different, particularly if there is a negative cosmological constant. The classical theory of such locally "anti-de Sitter" spaces is treated in an elementary way, using visualizable models. Among the objects discussed are black holes,

Anatoly A. Svidzinsky, Alexander L. Fetter

Based on an analytic solution of the Gross-Pitaevskii equation in the large-condensate (Thomas-Fermi) limit we determine the structure of a stationary vortex in a Bose-Einstein condensate in a nonaxisymmetric rotating trap. The condensate velocity field has cylindrical symmetry only near the vortex core and becomes intrinsically anisotropic near the condensa

N. I. Lebovka, M. I. Bazhal, E. I. Vorobiev

We consider the simplified dielectric breakage model used for simulation of the kinetics of cellular material breakage under the pulsed electric field (PEF) treatment. The model is based on an effective media approximation, which includes equations with the same morphology parameters as in percolation theory. The probability of a whole cell breakage by the p

O. M. Bulashenko, J. M. Rubi, V. A. Kochelap

A general formula for current noise in a two-terminal ballistic nondegenerate conductor under the action of long-range Coulomb correlations has been derived. The noise reduction factor (in respect to the uncorrelated value) is obtained for biases ranging from thermal to shot noise limits, and it is related to spatial variations in transport characteristics.

G. Grabecki, J. Wrobel, T. Dietl, K. Byczuk

Conductance of submicron constrictions of PbTe:Bi was studied up to 8T and between 4.2K and 50mK. The structures were fabricated by electron beam lithography and chemical etching of high--electron mobility films grown by MBE on BaF_2. In the moderately strong magnetic fields perpendicular to the current, B>1T, the conductance shows accurate quantization in t

K. Saito, S. Miyashita, H. De Raedt

We discuss the effect of the thermal environment on the low-temperature response of the magnetization of uniaxial magnets to a time-dependent applied magnetic field. At sufficiently low temperatures the staircase magnetization curves observed in molecular magnets such as Mn_{12} and Fe_8 display little temperature dependence. However the changes of the magne

S. Jha, P. Garnavich, R. Kirshner, P. Challis

We present optical and near-infrared photometry and spectroscopy of the type Ia SN 1998bu in the Leo I Group galaxy M96 (NGC 3368). The data set consists of 356 photometric measurements and 29 spectra of SN 1998bu between UT 1998 May 11 and July 15. The well-sampled light curve indicates the supernova reached maximum light in B on UT 1998 May 19.3 (JD 245095

Bruce G. Elmegreen

A recent model for the stellar initial mass function (IMF), in which the stellar masses are randomly sampled down to the thermal Jeans mass from hierarchically structured pre-stellar clouds, predicts that regions of ultra-cold CO gas, such as those recently found in nearby galaxies by Allen and collaborators, should make an abundance of Brown Dwarfs with rel

Bruce G. Elmegreen

Observations of the stellar initial mass function are reviewed. The flattening at low mass is evidence for a characteristic mass in star formation, which could be the minimum stellar mass for the onset of deuterium burning or the thermal Jeans mass. Variations in the mass of the flattened part are important for understanding star formation; e.g., starburst g

B. Elmegreen

The thermal and chemical phases of the cool component of interstellar gas are discussed. Variations with galactocentric radius and from galaxy to galaxy are mostly the result of changes in the ambient interstellar pressure and radiation field. Interstellar structure that is hierarchical or fractal in the cloudy parts and has large and connected empty regions

Daniel Thomas, Guinevere Kauffmann

In models of galaxy formation in a hierarchical Universe, elliptical galaxies form through the merging of smaller disk systems. These models yield a number of testable predictions if reliable techniques for determining the relative ages and compositions of the stellar populations of different galaxies can be found: 1) ellipticals in low-density environments

Ronald Stark, Floris F. S. van der Tak, Ewine F. van Dishoeck

We report the detection of the 1_{10}-1_{11} ground state transition of ortho-H_2D^+ at 372.421 GHz in emission from the young stellar object NGC 1333 IRAS 4A. Detailed excitation models with a power-law temperature and density structure yield a beam-averaged H_2D^+ abundance of 3 x 10^{-12} with an uncertainty of a factor of two. The line was not detected t

H. K. Lee, R. A. M. J. Wijers, G. E. Brown

We investigate the possibility that gamma-ray bursts are powered by a central engine consisting of a black hole with an external magnetic field anchored in a surrounding disk or torus. The energy source is then the rotation of the black hole, and it is extracted electromagnetically via a Poynting flux, a mechanism first proposed by Blandford and Znajek (1997

Alon E. Faraggi, Keith A. Olive, Maxim Pospelov

Realistic superstring models generically give rise to exotic matter states, which arise due to the ``Wilson-line'' breaking of the non-Abelian unifying gauge symmetry. Often such states are protected by a gauge or local discrete symmetry and therefore may be stable or meta-stable. We study the possibility of a flux of high energy neutrinos coming fro

D. Elazzar Kaplan, Graham D. Kribs

The phenomenology of a new economical SUSY model that utilizes dynamical SUSY breaking and gauge-mediation (GM) for the generation of the sparticle spectrum and the hierarchy of fermion masses is discussed. Similarities between the communication of SUSY breaking through a messenger sector, and the generation of flavor using the Froggatt-Nielsen (FN) mechanis

Zahid Zakir

A new treatment of the gravitational energy on the basis of 4-index gravitational equations is reviewed. The gravitational energy for the Schwarzschild field is considered.

J. -P. Blaizot, E. Iancu, A. Rebhan

Self-consistent approximations in terms of fully dressed propagators provide a simple expression for the entropy of an ultrarelativistic plasma, which isolates the contribution of the elementary excitations as a leading contribution. Further approximations, whose validity is checked on a soluble model involving a scalar field, allow us to calculate the entro

B. G. Piner, S. C. Unwin, A. E. Wehrle, P. G. Edwards

We present thirty VLBI images of the TeV blazar Markarian 421 (1101+384) at fifteen epochs spanning the time range from 1994 to 1997, and at six different frequencies from 2.3 to 43 GHz. The imaged observations include a high-resolution 5 GHz VLBI Space Observatory Programme (VSOP) observation with the HALCA satellite on 1997 November 14; full-track VLBA obs

Barbara Coluzzi, Giorgio Parisi, Paolo Verrocchio

We use the results derived in the framework of the replica approach to study the liquid-glass thermodynamic transition. The main results are rederived without using replicas and applied to the study of the Lennard-Jones binary mixture introduced by Kob and Andersen. We find that there is a phase transition due to the entropy crisis. We compute both analytica

S. Natschlaeger, J. Alberich, N. Barberan, J. Bausells

A previous two-step hydrodynamic model calculation of angle-resolved photoemission has been improved by modeling the surface with a soft analytic function. The same ground-state potential is used to screen the photon field and to calculate the electronic wave functions. The implemented code can be used for arbitrary ground state densities along the perpendic

J. Dukelsky, G. Sierra

We study the properties of ultrasmall metallic grains with sizes in the range of 20 up to 400 electrons. Using a particle-hole version of the DMRG method we compute condensation energies, spectroscopic gaps, pairing parameters and particle-hole probabilities of the ground state wave function. The results presented in this paper confirm that the bulk supercon

Anastasios C. Petkou, George Siopsis

We discuss the free-energy density of bosonic and fermionic theories possessing strongly coupled critical points in D=3. We construct a stationary renormalization group trajectory which interpolates between the free massless theory of N scalars and a class of interacting theories including both bosons and fermions. At a special point of this trajectory the f

S. Yazadjiev

Recently in boson star models in framework of Brans-Dicke theory, three possible definitions of mass have been identified, all identical in general relativity, but different in scalar-tensor theories of gravity.It has been conjectured that it's the tensor mass which peaks, as a function of the central density, at the same location where the particle numb

Takeshi Sato

We propose a (generalized) ``mass formula'' for a fundamental string described as a BPS solution of a D-brane's worldvolume. The mass formula is obtained by using the Hamiltonian density on the worldvolume, based on transformation properties required for it. Its validity is confirmed by investigating the cases of point charge solutions of D-brane