January 1996 arXiv papers — page 9

Laurent Baulieu, Martin Schaden

We reinterpret the Faddeev-Popov gauge-fixing procedure of Yang-Mills theories as the definition of a topological quantum field theory for gauge group elements depending on a background connection. This has the advantage of relating topological gauge-fixing ambiguities to the global breaking of a supersymmetry. The global zero modes of the Faddeev-Popov ghos

Benoit Tremblay, David Merritt

Bright elliptical galaxies have a markedly different distribution of Hubble types than faint ellipticals; the division occurs near M_B=-20 and bright ellipticals are rounder on average. The Hubble types of galaxies in both groups are narrowly clustered, around E1.5 in the case of the bright galaxies and around E3 for the fainter ones. The Hubble-type distrib

Henry P. Stapp

In quantum electrodynamics a classical part of the S-matrix is normally factored out in order to obtain a quantum remainder that can be treated perturbatively without the occurrence of infrared divergences. However, this separation, as usually performed, introduces spurious large-distance effects that produce an apparent breakdown of the important correspond

Sheldon Goldstein

This is a talk concerning the irrationality of prominent physicists with regard to the foundations of quantum mechanics, delivered at a conference on the irrationality of the postmodern attack on science by nonscientists.

G. A. Lalazissis, S. E. Massen

The effect of Short Range Correlations (SRC) on Ca isotopes is studied using a simple phenomenological model. Theoretical expressions for the charge (proton) form factors, densities and moments of Ca nuclei are derived. The role of SRC in reproducing the empirical data for the charge density differences is examined. Their influence on the depletion of the nu

J. L. Friar

It is shown how nucleon-nucleon potentials can be defined in N dimensions, using dimensional regularization to continue amplitudes. This provides an easy way to separate out contact ($δ$-function) terms arising from renormalization. An example is worked out several ways for the case of two scalar particles exchanged between nucleons, which involves a very si

J. L. Friar

Recent successes in {\it ab initio} calculations of light nuclei (A=2-6) will be reviewed and correlated with the dynamical consequences of chiral symmetry. The tractability of nuclear physics evinced by these results is evidence for that symmetry. The relative importance of three-nucleon forces, four-nucleon forces, multi-pion exchanges, and relativistic co

Zhen Cao, Yi Gao, Rudolph C. Hwa

Earlier study of quark-hadron phase transition in the Ginzberg-Landau theory is reexamined in the Ising model, so that spatial fluctuations during the transition can be taken into account. Although the dimension of the physical system is 2, as will be argued, both d=2 and d=4 Ising systems are studied, the latter being theoretically closer to the Ginzberg-La

Tomoyuki Maruyama, Koji Niita, Toshiki Maruyama, Satoshi Chiba

In order to investigate relativistic effects we compare the transverse flow calculated by using the four versions of the QMD approaches with that of the full covariant RQMD approach. From the comparison we conclude that the simplified RQMD (RQMD/S), which uses the common time coordinate to all particles, can be used instead of RQMD up to 6 GeV/u.

Daniel Cangemi, Gerald Dunne

We derive finite temperature expansions for relativistic fermion systems in the presence of background magnetic fields, and with nonzero chemical potential. We use the imaginary-time formalism for the finite temperature effects, the proper-time method for the background field effects, and zeta function regularization for developing the expansions. We emphasi

Stephen L. Adler

We extend the discussion of projective group representations in quaternionic Hilbert space which was given in our recent book. The associativity condition for quaternionic projective representations is formulated in terms of unitary operators and then analyzed in terms of their generator structure. The multi--centrality and centrality assumptions are also an

Stephan Elser, Alex C. Kalloniatis

We explore quantum electrodynamics in (1+1) dimensions at finite temperature using the method of Discretized Light-Cone Quantisation. The partition function, energy and specific heat are computed in the canonical ensemble using the spectrum of invariant masses computed with a standard DLCQ numerical routine. In particular, the specific heat exhibits a peak w

B. de Wit

We review characteristic features of N=2 supersymmetric vector multiplets and discuss symplectic reparametrizations and their relevance for monopoles and dyons. We close with an analysis of perturbative corrections to the low-energy effective action of N=2 heterotic superstring vacua.

Horatiu-Stefan Nastase

I try to argue that the only way out of the black hole information paradox is through a unified quantum field theory of gravity and other interactions. Superstring theory is especially interesting, since in a special limit, the classical picture of 't Hooft emerges.

Ernest Ma

The superstring-inspired E_6 model is reduced to the supersymmetric standard model extended by a specific U(1) factor. This choice allows for the existence of naturally light singlet neutrinos which also mix with the known three doublet neutrinos, thus making it possible to accommodate all present neutrino data. Other consequences of this model are also disc

A. V. Anisovich, H. Leutwyler

We demonstrate that the decay eta -> 3 pi represents a sensitive probe for the breaking of chiral symmetry by the quark masses. The transition amplitude is proportional to the mass ratio (m_d^2-m_u^2)/(m_s^2-m^2). The factor of proportionality is calculated by means of dispersion relations, using chiral perturbation theory to determine the subtraction consta

H. Leutwyler

Taken by itself, the interference with the etaprime appears to strongly affect the amplitude of the transition eta->3 pi. I point out that this effect is fictitious and also occurs in the mass spectrum of the pseudoscalars. Chiral symmetry implies that the same combination of effective coupling constants which determines the small deviations from the Gell-Ma

R. G. Roberts, G. G. Ross

We show how the operator product expansion evaluated in the approximation of ignoring gluons leads to the covariant formulation of the quark parton model. We discuss the connection with other formulations and show how the free quark model prediction, $g_2=0$, changes smoothly into the Wandzura-Wilczek (WW) relation for quark masses small relative to the nucl

C. E. M. Batista, M. Schiffer

In this paper we study the evolution of density perturbations in the framework of Phase Coupling Gravity theory at the very early universe. We show that these perturbation display an exponential-like behaviour.

Nils Andersson, Kostas D. Kokkotas, Bernard F. Schutz

The problem of relativistic stellar pulsations is studied in a somewhat ad hoc approximation that ignores all fluid motions. This {\em Inverse Cowling Approximation} (ICA) is motivated by two observations: 1) For highly damped ($w$-mode) oscillations the fluid plays very little role. 2) If the fluid motion is neglected the problem for polar oscillation modes

G. 't Hooft

By investigating the canonical commutation rules for gravitating quantized particles in a 2+1 dimensional world it is found that these particles live on a space-time lattice. The space-time lattice points can be characterized by three integers. Various representations are possible, the details depending on the topology chosen for energy-momentum space. We fi

M. Montesinos-Velasquez, T. Matos

In the present work we show that the Einstein equations on $M$ without cosmological constant and with perfect fluid as source, can be obtained from the field equations for vacuum with cosmological constant on the principal fibre bundle $P(\frac{1}{I} M,U(1))$, $M$ being the space-time and $I$ the radius of the internal space $U(1)$.

Macoto Kikuchi, Nobuyasu Ito, Yutaka Okabe

We review our recent studies on the dynamical correlations in MC simulations from the view point of the statistical dependence. Attentions are paid to the reduction of the statistical degrees of freedom for correlated data. Possible biases on several cumulants, such as the susceptibility and the Binder number due to finite MC length are discussed. A new meth

Chandan Dasgupta, Oriol T. Valls

Time scales associated with activated transitions between glassy metastable states of a free energy functional appropriate for a dense hard sphere system are calculated by using a new Monte Carlo method for the local density variables. We calculate the time the system,initially placed in a shallow glassy minimum of the free energy, spends in the neighborhood

Ping Ao, Staffan Grundberg, Jørgen Rammer

We present the results of studying the influence of different environmental states on the coherence of quantum processes. We choose to discuss a simple model which describe two electronic reservoirs connected through tunneling via a resonant state. The model could, e.g., serve as an idealization of inelastic resonant tunneling through a double barrier struct

Vijay Balasubramanian

The task of parametric model selection is cast in terms of a statistical mechanics on the space of probability distributions. Using the techniques of low-temperature expansions, we arrive at a systematic series for the Bayesian posterior probability of a model family that significantly extends known results in the literature. In particular, we arrive at a pr

Michael E. Bleich, Joshua E. S. Socolar

We suggest a spatially local feedback mechanism for stabilizing periodic orbits in spatially extended systems. Our method, which is based on a comparison between present and past states of the system, does not require the external generation of an ideal reference state and can suppress both absolute and convective instabilities. As an example, we analyze the

S. Yukawa, M. Kikuchi

Density fluctuations in traffic current are studied by computer simulations using the deterministic coupled map lattice model on a closed single-lane circuit. By calculating a power spectral density of temporal density fluctuations at a local section, we find a power-law behavior, $\sim 1/f^{1.8}$, on the frequency $f$, in non-congested flow phase. The distr

Anatoly Malevanets, Agusti Careta, Raymond Kapral

The propagating chemical fronts found in cubic autocatalytic reaction-diffusion processes are studied. Simulations of the reaction-diffusion equation near to and far from the onset of the front instability are performed and the structure and dynamics of chemical fronts are studied. Qualitatively different front dynamics are observed in these two regimes. Clo

S. J. Lilly, O. Le Fevre, F. Hammer, David Crampton

The comoving luminosity density of the Universe is estimated from the CFRS faint galaxy sample in three wavebands (2800A, 4400A and 1 micron) over the redshift range 0 < z < 1. In all three wavebands, the comoving luminosity density increases markedly with redshift. For a (q_0 = 0.5, Omega = 1.0) cosmological model, the comoving luminosity density increases

Reuven Ramaty

Solar flare observations are used to demonstrate the new technique of abundance determination based on gamma ray line emission produced by accelerated particle bombardment. Some of the implications of similar gamma ray line emission observed from Orion, including the production of light elements by low energy cosmic rays, are reviewed. For such an origin for

Ph. Heraudeau, F. Simien, G. A. Mamon

We present $K&#39;$-band surface photometry of a sample of 31 inclined Sa-Scd galaxies, together with additional $J$- and $H$-band data for four of them. In this first paper of a series, profiles are presented, together with global and isophotal parameters. Our profiles are compared to similar $B$, $R$ and $I$ data collected from other sources. Three galaxie

David Schade, S. J. Lilly, O. Le Fevre, F. Hammer

The 143 galaxies with secure redshifts (median z = 0.62) from the 1415+52 field of the Canada-France Redshift Survey have been imaged at CFHT with median seeing of 0.67 arcseconds. Structural parameters have been derived by fitting multi-component models, and the results confirm two phenomena seen in a smaller sample of galaxies imaged with HST. First, 11% o

J. N. Hewitt, C. A. Katz, S. D. Barthelmy, W. H. Baumgartner

The Haystack 37-meter telescope was used in a pilot project in May 1995 to observe GRB error boxes at 23~GHz. Seven BATSE error boxes and two IPN arcs were scanned by driving the beam of the telescope rapidly across their area. For the BATSE error boxes, the radio observations took place two to eighteen days after the BATSE detection, and several boxes were

P. Magdziarz, A. A. Zdziarski

Analysis of broad-band X/$γ$-ray spectra of NGC~4151 from contemporaneous observations by {\it GRO}/OSSE, {\it ROSAT}, {\it Ginga} and {\it ASCA}, shows that the data are well modelled with an intrinsic spectrum due to thermal Comptonization. The X-ray spectral index changes from $α\sim$ 0.4 to 0.7, and temperature stays at about 50 keV. The X-ray spectrum v

Jos H. J. de Bruijne, Roeland P. van der Marel, P. Tim de Zeeuw

This paper presents two families of phase-space distribution functions (DFs) that generate scale-free spheroidal mass densities in scale-free spherical potentials. The `case I&#39; DFs are anisotropic generalizations of the flattened f(E,L_z) model, which they include as a special case. The `case II&#39; DFs generate flattened constant-anisotropy models, in

Shoichi Yamada

An implicit Lagrangian hydrodynamics code for general relativistic spherical collapse is presented. This scheme is based on an approximate linearized Riemann solver (Roe type scheme). This code is aimed especially at the calculation of the late phase of collapse-driven supernovae and the nascent neutron star, where there is a remarkable contrast between the

Jacco Th. van Loon, Albert A. Zijlstra, Valentin Bujarrabal, Lars-Ake Nyman

We report on the detection of SiO J=2--1 v=1 (86 GHz) maser emission from the red supergiant IRAS04553--6825 in the LMC. It has thereby become the first known source of SiO maser emission outside the Milky Way. We used the Swedish-ESO Submm Telescope at the European Southern Observatory at La Silla. With the help of good atmospheric conditions, the excellent

Walter Dehnen, James Binney

The only way to map the Galaxy&#39;s gravitational potential $Φ({\bf x})$ and the distribution of matter that produces it is by modelling the dynamics of stars and gas. Observations of the kinematics of gas provide key information about gradients of $Φ$ within the plane, but little information about the structure of $Φ$ out of the plane. Traditional Galaxy m

A. Strominger, C. Vafa

The Bekenstein-Hawking area-entropy relation $S_{BH}=A/4$ is derived for a class of five-dimensional extremal black holes in string theory by counting the degeneracy of BPS soliton bound states.

Neil J. Cornish, David N. Spergel, Glenn D. Starkman

Yes, if the universe has compact topology. Inflation is currently the most elegant explanation of why the universe is old, large, nearly flat, homogeneous on large scales and structured on small scales. One of the weaknesses of the inflationary paradigm is the problem of initial conditions for inflation: the pre-inflationary universe must be somewhat old, so

P. M. Petropoulos, J. Rizos

In the context of a recently proposed method for computing exactly string loop corrections regularized in the infra-red, we determine and calculate the universal moduli-dependent part of the threshold corrections to the gauge couplings for the symmetric $Z_2\times Z_2$ orbifold model. We show that these corrections decrease the unification scale of the under

Jean-Loup Gervais

For the general operator product algebra coefficients derived by Cremmer Roussel Schnittger and the present author with (positive integer) screening numbers, the coupling constants determine the factors additional to the quantum group 6j symbols. They are given by path independent products over a two dimensional lattice in the zero mode space. It is shown th

F. J. Herranz, M. Santander

The general solution of the graded contraction equations for a $\zz_2^{\otimes N}$ grading of the real compact simple Lie algebra $so(N+1)$ is presented in an explicit way. It turns out to depend on $2^N-1$ independent real parameters. The structure of the general graded contractions is displayed for the low dimensional cases, and kinematical algebras are sh

Anthony Sudbery

A field theory with local transformations belonging to the quantum group SU_q(n) is defined on a classical spacetime, with gauge potentials belonging to a quantum Lie algebra. Gauge transformations are defined for the potentials which lead to the appropriate quantum-group transformations for field strengths and covariant derivatives, defined for all elements

Ofer Megged

A formulation for a non-trivial composition of two classical gauge structures is given: Two parent gauge structures of a common base space are synthesized so as to obtain a daughter structure which is fundamental by itself. The model is based on a pair of related connections that take their values in the product space of the corresponding Lie algebras. The c

N. Z. Akopov, G. G. Athanasiu, E. G. Floratos, G. K. Savvidy

We analyze the structure of the periodic trajectories of the matrix generator of pseudorandom numbers which has been proposed earlier. The structure of the periodic trajectories becomes more transparent when the rational sublattice coincides with the Galois field $GF[p]$. We are able to compute the period of the trajectories as a function of $p$ and the dime

H. Kleinert, A. M. Chervyakov

QCD strings are color-electric flux tubes between quarks with a finite thickness and thus a finite curvature stiffness. Contrary to an earlier rigid-string by Polyakov and Kleinert, and motivated by the properties of a magnetic flux tubes in type-II superconductors we put forward the hypothesis that QCD strings have a {\em negative\/ stiffness. We set up a n

Styliani Consta, Raymond Kapral

Proton transfer rates and mechanisms are studied in mesoscopic, liquid-state, molecular clusters. The proton transfer occurs in a proton-ion complex solvated by polar molecules comprising the cluster environment. The rates and mechanisms of the reaction are studied using both adiabatic and non-adiabatic molecular dynamics. For large molecular clusters, the p

Umesh A. Salian, S. N. Behera, V. S. Ramamurthy

We have performed classical molecular dynamics simulation of $Ar_{13}$ cluster to study the behavior of collective excitations. In the solid ``phase&#39;&#39; of the cluster, the collective oscillation of the monopole mode can be well fitted to a damped harmonic oscillator. The parameters of the equivalent damped harmonic oscillator-- the damping coefficient

B. Scott Gaudi, Andrew Gould

In order to understand the nature of the lenses that generate microlensing events, one would like to measure their mass, distance, and velocity. Unfortunately, current microlensing experiments measure only one parameter of the events, the characteristic timescale, which is a combination of the underlying physical parameters. Other methods are required to ext

Paolo Aschieri, Leonardo Castellani

A bicovariant calculus on the twisted inhomogeneous multiparametric $q$-groups of the $B_n,C_n,D_n$ type, and on the corresponding quantum planes, is found by means of a projection from the bicovariant calculus on $B_{n+1}$, $C_{n+1}$, $D_{n+1}$. In particular we obtain the bicovariant calculus on a dilatation-free $q$-Poincaré group $ISO_q (3,1)$, and on th

Dennis Bonatsos, C. Daskaloyannis, P. Kolokotronis, D. Lenis

The polynomial deformations of the Witten extensions of the U(su(2)) and U(osp(1,2)) algebras are three generator algebras with normal ordering, admitting a two generator subalgebra. The modules and the representations of these algebras are based on the construction of Verma modules, which are quotient modules, generated by ideals of the original algebra. Th

U. van Kolck, J. L. Friar, T. Goldman

Phenomenological Lagrangians and dimensional power counting are used to assess isospin violation in the nucleon-nucleon force. The $πNN$ coupling constants (including the Goldberger-Treiman discrepancy), charge-symmetry breaking, and meson-mixing models are examined. A one-loop analysis of the isospin-violating $πNN$ coupling constants is performed using chi

Akira Ono, Hisashi Horiuchi

On the basis of the antisymmetrized molecular dynamics (AMD) of wave packets for the quantum system, a novel model (called AMD-V) is constructed by the stochastic incorporation of the diffusion and the deformation of wave packets which is calculated by Vlasov equation without any restriction on the one-body distribution. In other words, the stochastic branch

Tomoyuki Maruyama

We define the Dirac-Fock current to hold the current conservation in the momentum-dependent Dirac fields, and discuss its effect on the magnetic-moment in the nuclear matter. It is shown that the Dirac-Fock current can largely reduce the magnetic-moment even in the isovector case, whose value has been too big due to the small effective mass in the usual rela

M. J. Duff, R. Minasian, Edward Witten

We re-examine the question of heterotic - heterotic string duality in six dimensions and argue that the $E_8\times E_8$ heterotic string, compactified on $K3$ with equal instanton numbers in the two $E_8$&#39;s, has a self-duality that inverts the coupling, dualizes the antisymmetric tensor, acts non-trivially on the hypermultiplets, and exchanges gauge fiel

E. Ramos, J. Roca

We show how to obtain all covariant field equations for massless particles of arbitrary integer, or half-integer, helicity in four dimensions from the quantization of the rigid particle, whose action is given by the integrated extrinsic curvature of its worldline, {\ie} $S=α\int ds κ$. This geometrical particle system possesses one extra gauge invariance bes

Y. M. Cho, D. Maison

We present a new type of spherically symmetric monopole and dyon solutions with the magnetic charge $ 4π/e$ in the standard Weinberg-Salam model. The monopole (and dyon) could be interpreted as a non-trivial hybrid between the abelian Dirac monopole and non-abelian &#39;t Hooft-Polyakov monopole (with an electric charge). We discuss the possible physical imp

H. Leutwyler

The corrections to the current algebra mass formulae for the pseudoscalar mesons are analyzed by means of a simultaneous exansion in powers of the light quark masses and powers of 1/N. A set of mass formulae is derived, including an inequality, which leads to bounds for ratios of quark masses.

G. Gounaris, J. -L. Kneur, D. Zeppenfeld, Z. Ajaltouni

We present the results obtained by the &#34;Triple Gauge Couplings&#34; working group during the LEP2 Workshop (1994-1995). The report concentrates on the measurement of $WWγ$ and $WWZ$ couplings in $e^-e^+\to W^-W^+$ or, more generally, four-fermion production at LEP2. In addition the detection of new interactions in the bosonic sector via other production

S. Rigolin

We derive the low-energy electroweak effective lagrangian for the case of additional heavy, unmixed, sequential fermions. Present LEP1 data still allow for the presence of a new quark and/or lepton doublet with masses greater than $M_Z/2$, provided that these multiplets are sufficiently degenerate. Keeping in mind this constraint, we analyse the virtual effe

S. D. Bass, A. W. Thomas

We suggest that the Standard Model may undergo a supercritical transition near the Landau scale, where the U(1) gauge boson couples to the left and right handed states of any given fermion with different charges. This scenario naturally gives rise to three generations of fermion, corresponding to the three critical scales for the right-right, right-left and

Marco A. Diaz, Steve F. King

In the framework of a particular supergravity model which provides a natural solution to the $μ$--problem we show how the discovery of a chargino at LEP2 and the measurement of its mass and production cross--section, together with the measurement of the mass of the lightest neutralino, would determine the entire Higgs and SUSY spectrum. We give detailed pred

M. Kachelriess

We question the use of stable asymptotic scattering states in QED of strong magnetic fields. To correctly describe excited Landau states and photons above the pair creation threshold the asymptotic fields are chosen as generalized Licht fields. In this way the off-shell behavior of unstable particles is automatically taken into account, and the resonant dive

W. Kerler, C. Rebbi, A. Weber

We show that, independently of the boundary conditions, the two phases of the 4-dimensional compact U(1) lattice gauge theory can be characterized by the presence or absence of an ``infinite&#39;&#39; current network, with an appropriate definition of ``infinite&#39;&#39; for the various types of boundary conditions imposed on the finite lattice. The probabi

M. Montesinos-Velasquez

In this work we find the Killing vector fields of the riemannian submanifolds of the thermodynamic phase space of an ideal gas and show that the isometry group corresponding to them is homomorphic to the euclidean group $E(2)$. We also give the embedding of these submanifolds in the euclidean space $(R^{3},\ delta)$.

Henri Waelbroeck, Jose A. Zapata

We show that &#39;t Hooft&#39;s representation of (2+1)-dimensional gravity in terms of flat polygonal tiles is closely related to a gauge-fixed version of the covariant Hamiltonian lattice theory. &#39;t Hooft&#39;s gauge is remarkable in that it leads to a Hamiltonian which is a linear sum of vertex Hamiltonians, each of which is defined modulo $2 π$. A cy

Steven R. Brandt, Edward Seidel

In this paper we study a new family of black hole initial data sets corresponding to distorted ``Kerr&#39;&#39; black holes with moderate rotation parameters, and distorted Schwarzschild black holes with even- and odd-parity radiation. These data sets build on the earlier rotating black holes of Bowen and York and the distorted Brill wave plus black hole dat

Richard H. Price, Jorge Pullin

We present analytic expressions that approximate the behavior of the spacetime of a collapsing spherically symmetric scalar field in the critical regime first discovered by Choptuik. We find that the critical region of spacetime can usefully be divided into a ``quiescent&#39;&#39; region and an ``oscillatory&#39;&#39; region, and a moving ``transition edge&#

Roberto De Pietri, L. Lusanna, Massimo Pauri

The possible external couplings of an extended non-relativistic classical system are characterized by gauging its maximal dynamical symmetry group at the center-of-mass. The Galilean one-time and two-times harmonic oscillators are exploited as models. The following remarkable results are then obtained: 1) a peculiar form of interaction of the system as a who

Barbara Drossel, Mehran Kardar

We study analytically and numerically the winding of a flux line around a columnar defect. Reflecting and absorbing boundary conditions apply to marginal or repulsive defects, respectively. In both cases, the winding angle distribution decays exponentially for large angles, with a decay constant depending only on the boundary condition, but not on microscopi

Igor Vilfan

Step patterns on vicinal $(2\times1)$ reconstructed surfaces of noble metals Au(110) and Pt(110), miscut towards the (100) orientation, are investigated. The free energy of the reconstructed surface with a network of crossing opposite steps is calculated in the strong chirality regime when the steps cannot make overhangs. It is explained why the steps are no

Kazuhiro Sano

We investigate a t-J ladder model by numerical diagonalization method. By calculating correlation functions and assuming the Luttinger liquid relation, we obtained a possible phase diagram of the ground state as a function of J/t and electron density $n$. We also found that behavior of correlation functions seems to consist with the prediction of Luttinger l

Julio Gonzalo, Teresa Solias

We present a metagrammatical formalism, {\em generic rules}, to give a default interpretation to grammar rules. Our formalism introduces a process of {\em dynamic binding} interfacing the level of pure grammatical knowledge representation and the parsing level. We present an approach to non-constituent coordination within categorial grammars, and reformulate

Michael Isenberg, D. Q. Lamb, John C. L. Wang

There is mounting evidence that, if gamma-ray bursters are Galactic in origin, they are located in a Galactic corona at distances greater than 100 kpc. This has created a need to explore new models of cyclotron line formation. In most previous calculations the line-forming region was modeled as a static slab of plasma, optically thin to continuum scattering,

David L. Band

To investigate the repeater content of gamma ray burst samples I develop two models where sources burst at a constant average rate. I find that the sky coverage affects the number of repeaters in a sample predominantly through the detector livetime, and that the number of bursts in the sample is the primary parameter. Thus the repeater content of burst sampl

Byung-Il Jun, Michael L. Norman

Young supernova remnants such as Tycho generally exhibit a bright circular clumpy shell in both radio and X-ray emission. For several young remnants, various arguments suggest that the magnetic field is larger than can be explained by compression of a few $μG$ ambient magnetic field by the shock wave. Radio polarization studies reveal a net radial orientatio

Bennett Link, Richard Epstein

We study the temporal asymmetry of over 600 bursts from the BATSE 3B catalog, encompassing a 200-fold range in peak flux. By comparing the rates of rise and fall of the flux near the highest burst peak, we find that about two-thirds of the bursts exhibit a preferred asymmetry in the sense that the flux rises more rapidly than it falls, confirming the conclus

Brian D. Fields, Michel Casse, Elisabeth Vangioni-Flam, Ken&#39;ichi Nomoto

The fastest ejecta of supernova explosions propagate as a precursor to the main supernova shock wave, and can be quite energetic. The spectrum of such fast ejecta is estimated based on recent analytic and numerical supernova models, and found to be a power law having a cutoff at an energy of order 10 MeV/nucl, the precise value of which depends on the supern

G. Burbidge, F. Hoyle, P. Schneider

It is pointed out that there are now known four very close pairs of QSOs with separations < 5 arcsec and very different redshifts. Several estimates of the probability that they are accidental configurations range between 10^{-7} and 3.5 x 10^{-3}. We conclude either that this is further evidence that QSOs have significant non-cosmological redshift component

J. F. Poyatos, R. Walser, J. I. Cirac, P. Zoller

A method for the experimental reconstruction of the quantum state of motion for a single trapped ion is proposed. It is based on the measurement of the ground state population of the trap after a sudden change of the trapping potential. In particular, we show how the Q function and the quadrature distribution can be measured directly. In an example we demons

X. Y. Pham, M. Gourdin

Strictly within the standard electro-weak interaction, CP violation in the flavour conserving process $η\rightarrow π+ π$ could originate from the mixing of the $η$ meson with the virtual scalar Higgs boson $ H^{0}$ via $W$ and top quark exchange. The parity-violation carried by weak gauge bosons makes the mixing possible by quantum effect at two-loop level.

T. A. Brun, J. J. Halliwell

In the context of the decoherent histories approach to the quantum mechanics of closed systems, Gell-Mann and Hartle have argued that the variables typically characterizing the quasiclassical domain of a large complex system are the integrals over small volumes of locally conserved densities -- hydrodynamic variables. The aim of this paper is to exhibit some

Nicole Mestrano

Soit $X$ une hypersurface lisse de degré $δ\geq 4$ dans $\pp ^3$ telle que $Pic(X)=Z$. On désigne par $M_X(c_2)$ l&#39;espace de modules des fibrés vectoriels sur $X$ de classes de Chern $c_1 = 0$ et $c_2$, semi-stables par rapport au diviseur hyperplan. Nous contribuons ici à la recherche de différentes composantes irréductibles pour $c_2$ petit. On prouve

Frank Sottile

We present a new geometric proof of Pieri&#39;s formula, exhibiting an explicit chain of rational equivalences from a suitable sum of distinct Schubert varieties to the intersection of a Schubert variety with a special Schubert variety. The geometry of these rational equivalences indicate a link to a combinatorial proof of Pieri&#39;s formula using Schensted

L. Vaidman

A brief review of the attempts to define ``elements of reality&#39;&#39; in the framework of quantum theory is presented. It is noted that most definitions of elements of reality have in common the feature to be a definite outcome of some measurement. Elements of reality are extended to pre- and post-selected systems and to measurements which fulfill certain

Abhee K. Dutt-Mazumder, Triptesh De, Binayak Dutta-Roy, Anirban Kundu

The running of the $ρ\bar N N$ couplings in presence of nuclear matter is studied, and the relevant $β$-functions are shown to be different for $ρ^0$ and $ρ^+$, when the nuclear medium is asymmetric.

Ph. Ghosez, X. Gonze, J. -P. Michenaud

Using first-principles calculations, the phonon frequencies at the $Γ$ point and the dielectric tensor are determined and analysed for the cubic and rhombohedral phases of BaTiO$_{3}$. The dipole-dipole interaction is then separated à la Cochran from the remaining short-range forces, in order to investigate their respective influence on lattice dynamics. Thi

R. Gianvittorio, I. Martin, A. Restuccia

A supersymmetric gauge invariant action is constructed over any 4-dimensional Riemannian manifold describing Witten&#39;s theory of 4-monopoles. The topological supersymmetric algebra closes off-shell. The multiplets include the auxiliary fields and the Wess-Zumino fields in an unusual way, arising naturally from BRST gauge fixing. A new canonical approach o

Oleg Andreev

A new formulation of $c\leq 1$ matter coupled to 2D gravity is proposed. This model, being closely analogous to one in the Polyakov light-cone gauge, possesses well defined global properties which allow to calculate correlation functions. As an example, the three point correlation functions of discrete states are found.

A. Krajewska, A. Ushveridze, Z. Walczak

It is demonstrated that quasi-exactly solvable models of quantum mechanics admit an interesting duality transformation which changes the form of their potentials and inverts the sign of all the exactly calculable energy levels. This transformation helps one to reveal some new features of quasi-exactly solvable models and associated orthogonal polynomials.

Christoph Adam

For the exactly solvable Schwinger model one interesting question is how to infer the exact solution from perturbation theory. We give a systematic procedure of deriving the exact solution from Feynman diagrams of arbitrary order for arbitrary $n$-point functions. As a byproduct, from perturbation theory we derive exact integral equations that the $n$-point

Christoph Adam

We use (fermion) mass perturbation theory for the massive Schwinger model to compute the boson-boson bound state mass in lowest order. For small fermion mass the lowest possible Fock state turns out to give the main contribution and leads to a second order result for the bound state mass.

C. A. Savoy

Recent work on flavour changing neutral current effects in supersymmetric models is reviewed. The emphasis is put on new issues related to solutions to the flavour problem through new symmetries: GUTs, horizontal symmetries, modular invariances.

F. Boudjema, B. Mele et al

We present the results obtained by the Standard Model Process group in the CERN Workshop &#34;Physics at LEP2&#34; (1994/95).

Kurt Langfeld, Hugo Reinhardt

The restoration of chiral symmetry at finite density and/or temperature is investigated in a wide class of one-gluon exchange models in the instantaneous approximation. If the effective quark interaction is less divergent than $1/k^2$ for small momentum transfer $k$, we obtain Gaussian critical exponents for the chiral phase transitions at finite temperature

Kaoru Hagiwara

The most important hint of physics beyond the Standard Model (SM) from the 1995 precision electroweak data is that the most precisely measured quantities, the total, leptonic and hadronic decay widths of the $Z$ and the effective weak mixing angle, $\sin^2θ_W$, measured at LEP and SLC, and the quark-lepton universality of the weak charged currents measured a

Beat Frischmuth, Beat Ammon, Matthias Troyer

The temperature dependence of the uniform susceptibility and the ground state energy of antiferromagnetic Heisenberg ladders with up to 6 legs has been calculated, using the Monte Carlo loop algorithm. The susceptibilities of even-leg-ladders show spin gaps while these of odd-leg-ladders remain finite in the zero temperature limit. For small ratios of intra-

C. W. J. Beenakker, J. C. J. Paasschens, P. W. Brouwer

A theory is presented (and supported by numerical simulations) for phase-coherent reflection of light by a disordered medium which either absorbs or amplifies radiation. The distribution of reflection eigenvalues is shown to be the Laguerre ensemble of random-matrix theory. The statistical fluctuations of the albedo (the ratio of reflected and incident power