September 1996 arXiv papers — page 11

R. D. Ball, A. De Roeck

We summarize recent developments in the understanding of nucleon structure. New data on F2, R and F2c, over a wide range of Q2 and x, are described. Conventional leading twist NLO perturbative QCD gives an excellent account of all the new data with Q2 above a GeV, leaving very little room for either higher twists or higher logarithms. We summarize the curren

B. C. Metsch, H. R. Petry

We present the results of a covariant constituent quark model, based on the Bethe-Salpeter equation, where confinement is implemented by a string like linear potential explaining the Regge trajectories. An instanton induced quark force explains not only the splitting and mixing of pseudoscalar mesons, but suggest that such effects are also present in the sca

Yoshitaka Kuno, Akihiro Maki, Yasuhiro Okada

A search for the lepton-flavor violating $\mu^{+}\rightarrow e^{+}\gamma$ decay using polarized muons is revisited in terms of suppression of the serious background arising from an accidental coincidence between a $e^{+}$ in the normal muon decay and a high energy photon in the radiative muon decay, $\mu^{+} \rightarrow e^{+} \nu \overline{\nu} \gamma$. It i

Alberto Giovannini, Sergio Lupia, Roberto Ugoccioni

We show that both the multiplicity distribution and the ratio of factorial cumulants over factorial moments for 2-jet events in e+e- annihilation at the Z^0 peak can be well reproduced by the weighted superposition of two negative binomial distributions, associated to the contribution of $b\bar b$ and light flavoured events respectively. The negative binomia

B. de Carlos, P. L. White

The MSSM with $R$-Parity violation allows flavour changing neutral currents through two mechanisms, directly through one loop diagrams, and indirectly through the generation of flavour violation in the sparticle sector. We discuss the use of these mechanisms for constraining $R$-Parity violation, and show that the indirect mechanism parametrised in terms of

Kuang-Ta Chao

Recent results on physics in the charm energy region are reviewed. (1) The new data and puzzles in exclusive hadronic decays of $J/ψ$ and $ψ'$ give new challenges to the theory of hadronic decays. (2) With the new observation for $ξ(2230)$ and $f_0(1500)$ in $J/ψ$ radiative decays and other experiments, the situation in searching for glueballs is encoura

Andrzej Czarnecki, Kirill Melnikov

We present an estimate of perturbative QCD corrections to the decay $Z \to Wu\bar d$. A simple approximate approach is described in detail. The difference of masses of $M_Z$ and $M_W$ is used as an expansion parameter. A complete analytical formula for a part of the corrections is also presented.

J. A. Gracey

Critical exponents are computed for a variety of twist-2 composite operators, which occur in polarized and unpolarized deep inelastic scattering, at leading order in the 1/N_f expansion. The resulting d-dimensional expressions, which depend on the moment of the operator, are in agreement with recent explicit two and three loop perturbative calculations. An i

P. Levai, J. Zimanyi

We introduce a kinetical description of the hadronization of semi-deconfined quark matter produced in heavy ion collisions. A minimal microscopic model is considered in which the produced quarks and anti-quarks are redistributed into hadrons according to the additive quark model. Assuming thermalized quark matter and hadron matter we determine the appropriat

Andrew O. Bazarko

A new measurement of $R_b$ with the ALEPH detector at LEP using five mutually exclusive hemisphere tags is presented. The preliminary result is $R_b = 0.2158 \pm 0.0009 (stat.) \pm 0.0011 (syst.)$.

J. Fuster, S. Cabrera, S. Marti i Garcia

Identified $b\overline{b}g$ and $q\overline{q}γ$ events from DELPHI are used to measure the ratio of the mean charged particle multiplicity distribution between gluon and quark jets. The dependence of this ratio with the jet energy is established using about three million Z$^0$ decays. Results from all other detectors are discussed and compared. A nice agree

V. Mukhanov, L. R. W. Abramo, R. Brandenberger

We derive the effective energy-momentum tensor for cosmological perturbations and prove its gauge-invariance. The result is applied to study the influence of perturbations on the behaviour of the Friedmann background in inflationary Universe scenarios. We found that the back reaction of cosmological perturbations on the background can become important alread

Hideki Asada, Masaru Shibata

We present a formalism to obtain equilibrium configurations of uniformly rotating fluid in the second post-Newtonian approximation of general relativity. In our formalism, we need to solve 29 Poisson equations, but their source terms decrease rapidly enough at the external region of the matter(i.e., at worst $O(r^{-4})$). Hence these Poisson equations can be

Sergei E. Esipov, Thorsten Poeschel

The kinetic energy distribution function satisfying the Boltzmann equation is studied analytically and numerically for a system of inelastic hard spheres in the case of binary collisions. Analytically, this function is shown to have a similarity form in the simple cases of uniform or steady-state flows. This determines the region of validity of hydrodynamic

D. N. Sheng, Z. Y. Weng

The disappearance of integer quantum Hall effect (IQHE) at strong disorder and weak magnetic field is studied in a lattice model. A generic sequence by which the IQHE plateaus disappear is revealed: higher IQHE plateaus always vanish earlier than lower ones, and extended levels between those plateaus do not float up in energy but keep merging together after

Andrei Manolescu, Rolf R. Gerhardts

We calculate the magnetoconductivity tensor of a 2D electron gas in a 1D periodic potential and quantising magnetic fields. We study the internal structure of the Shubnikov-de Haas peaks and analyse recent experimental results. The electron-electron interaction is accounted for within a screened Hartree-Fock approximation (HFA), which describes both compress

T. Portengen, Th. Ostreich, L. J. Sham

We present a theory of the linear and nonlinear optical characteristics of the insulating phase of the Falicov-Kimball model within the self-consistent mean-field approximation. The Coulomb attraction between the itinerant d-electrons and the localized f-holes gives rise to a built-in coherence between the d and f-states, which breaks the inversion symmetry

F. Gebhard, K. Bott, M. Scheidler, P. Thomas

In this last of three articles on the optical absorption of electrons in a half-filled Peierls-distorted chain we address the dimerized extended Hubbard model in the limit of a large on-site interaction $U$. When the Hubbard interaction is large both compared to the band width $W$ and the nearest neighbor interaction $V$ the charge dynamics is properly descr

F. Gebhard, K. Bott, M. Scheidler, P. Thomas

In this second of three articles on the optical absorption of electrons in a half-filled Peierls-distorted chain we present exact results for strongly correlated tight-binding electrons. In the limit of a strong on-site interaction $U$ we map the Hubbard model onto the Harris-Lange model which can be solved exactly in one dimension in terms of spinless fermi

F. Gebhard, K. Bott, M. Scheidler, P. Thomas

In this first of three articles on the optical absorption of electrons in half-filled Peierls-distorted chains we present analytical results for non-interacting tight-binding electrons. We carefully derive explicit expressions for the current operator, the dipole transition matrix elements, and the optical absorption for electrons with a cosine dispersion re

Pierre-Antoine Rey, Michel Droz

We study a class of reaction-diffusion model extrapolating continuously between the pure coagulation-diffusion case ($A+A\to A$) and the pure annihilation-diffusion one ($A+A\to\emptyset$) with particles input ($\emptyset\to A$) at a rate $J$. For dimension $d\leq 2$, the dynamics strongly depends on the fluctuations while, for $d >2$, the behaviour is mean-

E. Balkovsky, G. Falkovich, I. Kolokolov, V. Lebedev

We consider the tails of probability density function (PDF) for the velocity that satisfies Burgers equation driven by a Gaussian large-scale force. The saddle-point approximation is employed in the path integral so that the calculation of the PDF tails boils down to finding the special field-force configuration (instanton) that realizes the extremum of prob

N. D. Whelan

We discuss the symmetry decomposition of the average density of states for the two dimensional potential $V=x^2y^2$ and its three dimensional generalisation $V=x^2y^2+y^2z^2+z^2x^2$. In both problems, the energetically accessible phase space is non-compact due to the existence of infinite channels along the axes. It is known that in two dimensions the phase

Wayne Hu, Martin White

By decomposing the damping tail of CMB anisotropies into a series of transfer functions representing individual physical effects, we provide ingredients that will aid in the reconstruction of the cosmological model from small-scale CMB anisotropy data. We accurately calibrate the model-independent effects of diffusion and reionization damping which provide p

P. Ruiz-Lapuente, R. Canal, A. Burkert

A review of type Ia supernovae (SNe Ia) statistics as expected from the different scenarios and explosion models so far suggested is presented.

M. A. Pahre, S. G. Djorgovski, J. Bechtold, R. Elston

We report the detection, both in line and continuum emission, of a galaxy responsible for a damped Ly-alpha absorption (DLA) system at z=3.15 projected 2.3 arcsec from QSO 2233+131. The star formation rate implied by both the Ly-alpha and restframe far-UV continuum is approximately 7 M_sun / yr. The galaxy also shows no sign of an active nucleus and has blue

Tom Theuns, S. J. Warren

We have identified ten candidate intergalactic planetary nebulae in the Fornax galaxy cluster. These objects were found during observations in 1992 and 1993 in three fields chosen well away from any Fornax galaxy at 15 arcmin, 30 arcmin, and 45 arcmin from the centre of Fornax. We used the usual method of blinking images taken in a narrow OIII filter, with i

A. Naim, K. U. Ratnatunga, R. E. Griffiths

The advent of the Hubble Space Telescope (HST) has provided images of galaxies at moderate and high redshifts and changed the scope of galaxy morphologies considerably. It is evident that the Hubble Sequence requires modifications in order to incorporate all the various morphologies one encounters at such redshifts. We investigate and compare different appro

A. Amatuni

Nonlinear dynamics of the one-dimensional ultrarelativistic bunch of electrons,moving in cold plasma,is considered in multiple scales perturbative approach. A square root of the inverse Lorentz factor of the bunch electrons is taken as a small parameter. Bunch electrons momenta is changed in the first approximation.In the underdense plasma and for the model

S. W. Sides, R. A. Ramos, P. A. Rikvold, M. A. Novotny

Experimental, analytical, and numerical results suggest that the mechanism by which a uniaxial single-domain ferromagnet switches after sudden field reversal depends on the field magnitude and the system size. Here we report new results on how these distinct decay mechanisms influence hysteresis in a two-dimensional nearest-neighbor kinetic Ising model. We p

K. Moriarty, J. Machta, R. Greenlaw

A parallel algorithm for ``diffusion-limited aggregation'' (DLA) is described and analyzed from the perspective of computational complexity. The dynamic exponent z of the algorithm is defined with respect to the probabilistic parallel random-access machine (PRAM) model of parallel computation according to $T \sim L^{z}$, where L is the cluster size,

N. Armesto, C. Pajares, C. A. Salgado, Yu. M. Shabelski

We calculate the A-dependence of open charm and beauty as well as Drell-Yan pair production cross sections on nuclear targets taking into account the difference of quark and gluon distributions in free and bound nucleons. The results are presented for both proton-nucleus and nucleus-nucleus collisions. For the case of heavy flavour production at comparativel

S. Moretti, R. Munoz-Tapia, K. Odagiri

Heavy flavour tagging provides a broad range of possibilities in testing QCD features at LEP. We present here a study of 4jets events at LEP I where the so-called light gluinos could be directly produced. We show that microvertex techniques offer a unique chance to exploit simple kinematical distributions in order to optimise the signal coming from gluino pr

Keith A. Olive

The current of status of big bang nucleosynthesis is reviewed and the concordance between theory and observation is examined in detail. It is argued that when using the observational data on he4 and li7, the two isotopes whose abundances are least affected by chemical and stellar evolution, both are completely consistent with BBN theory. In addition, these i

Manuel Drees

There is plenty of evidence that most matter in the Universe is dark (non-luminous). Particle physics offers several possible explanations. In this talk I focus on cold dark matter; the most promising candidates are then axions and the lightest supersymetric particle. I briefly summarize estimates of the present relic density of these particles, and describe

Alan Chodos, Andras Kaiser

We study an integral representation for the zeta function of the one-loop effective potential for a minimally coupled massive scalar field in D-dimensional de Sitter spacetime. By deforming the contour of integration we present it in a form suitable for letting the de Sitter radius tend to infinity, and we demonstrate explicitly for the case D=2 that the qua

H. Heiselberg, A. P. Vischer

Many--particle correlations due to Bose-Einstein interference are studied in ultrarelativistic heavy--ion collisions. We calculate the higher order correlation functions from the 2--particle correlation function by assuming that the source is emitting particles incoherently. In particular parametrizations of and relations between longitudinal, sidewards, out

Youngman Kim, Hyun Kyu Lee

We calculate perturbatively the effect of density on hadronic properties using the chiral quark model implemented by the QCD trace anomaly to see the possibility of constructing Lorentz invariant Lagrangian at finite density. We calculate the density dependent masses of the constituent quark, the scalar field and the pion in one-loop order using the techniqu

H. Heiselberg, A. P. Vischer

Bose-Einstein correlations in relativistic heavy ion collisions are very different for opaque sources than fortransparent ones. The Bose-Einstein radius parameters measured in two-particle correlation functions depend sensitively on the mean free path of the particles. In particular we find that the outward radius for an opaque source is smaller than the sid

M. R. Douglas, S. Katz, C. Vafa

Small instantons of exceptional groups arise geometrically by a collapsing del Pezzo surface in a CY. We use this to explain the physics of a 4-brane probe in Type I' compactification to 9 dimensions.

Ronald E. Cohen

Total energies, electronic structure, surface energies, polarization, potentials and charge densities were studied for slabs of BaTiO_3 using the Linearized Augmented Plane Wave (LAPW) method. The depolarization field inhibits ferroelectricity in the slabs, and the macroscopic field set up across a ferroelectric slab is sufficient to cause electronic states

David R. Morrison, Nathan Seiberg

We study five-dimensional supersymmetric field theories with one-dimensional Coulomb branch. We extend a previous analysis which led to non-trivial fixed points with $E_n$ symmetry ($E_8$, $E_7$, $E_6$, $E_5=Spin(10)$, $E_4=SU(5)$, $E_3=SU(3)\times SU(2)$, $E_2=SU(2)\times U(1)$ and $E_1=SU(2)$) by finding two new theories: $\tilde E_1$ with $U(1)$ symmetry

Takanori Sugihara, Masanobu Yahiro

The three-dimensional real scalar model, in which the $Z_2$ symmetry spontaneously breaks, is renormalized in a nonperturbative manner based on the Tamm-Dancoff truncation of the Fock space. A critical line is calculated by diagonalizing the Hamiltonian regularized with basis functions. The marginal ($ϕ^6$) coupling dependence of the critical line is weak. I

Takahiro Masuda, Hisao Suzuki

We show how to obtain the explicite form of the low energy quantum effective action for $N=2$ supersymmetric Yang-Mills theory in the weak coupling region from the underlying hyperelliptic Riemann surface. This is achieved by evaluating the integral representation of the fields explicitly. We calculate the leading instanton corrections for the group $SU(\nc)

Takahiro Masuda, Hisao Suzuki

We derive a simple formula for the periods associated with the low energy effective action of $N=2$ supersymmetric $SU(2)$ Yang-Mills theory with massive $N_f\le 3$ hypermultiplets. This is given by evaluating explicitly the integral associated to the elliptic curve using various identities of hypergeometric functions. Following this formalism, we can calcul

M. Boiti, J. Leon, F. Pempinelli

The explicit analytical expression of the Nonlinear Fourier Transform (NFT) of a finite set of data is provided. Then a simple recursion relation for the NFT is constructed as a function of the spectral parameter. These tools provide a complete characterization of the nonlinear coherent structures (solitons, breathers, ...) present in numerical or experiment

Chang Soo Park, Soo-Young Lee, Jae-Rok Kahng, Sahng-Kyoon Yoo

We investigate the effect of anharmonicity on the WKB approximation in a double well potential. By incorporating the anharmonic perturbation into the WKB energy splitting formula we show that the WKB approximation can be greatly improved in the region over which the tunneling is appreciable. We also observe that the usual WKB results can be obtained from our

M. Irac-Astaud

We define a three-parameter deformation of the Weyl-Heisenberg algebra that generalizes the q-oscillator algebra. By a purely algebraical procedure, we set up on this quantum space two differential calculi that are shown to be invariant on the same quantum group, extended to a ten-generator Hopf-star-algebra. We prove that, when the values of the parameters

Andrei Goryachev, Raymond Kapral

The spatiotemporal structure of reactive media supporting a solitary spiral wave is studied for systems where the local reaction law exhibits a period-doubling cascade to chaos. This structure is considerably more complex than that of simple period-1 oscillatory media. As one moves from the core of the spiral wave the local dynamics takes the form of perturb

C. J. Benesh, T. Goldman

Using a quark model, we study the effect of charge symmetry breaking on the valence quark distributions of the nucleon. The effect due to quark mass differences and the Coulomb interaction of the electrically charged quarks is calculated and, in contrast to recent claims, found to be small. In addition, we investigate the effect of charge symmetry breaking i

M. Kirchbach, L. Tiator, S. Neumeier, S. Kamalov

We show that the contact couplings of neutral pseudoscalar and axial mesons to the nucleon are proportional to $Δs$, the fraction of nucleon spin carried by the strange quark sea, and thus are strongly suppressed relative to the couplings of charged mesons to the nucleon. On the other side, recent high accuracy data on $η$ photoproduction at threshold reveal

F. Ruiz Ruiz, P. van Nieuwenhuizen

We prove that three-dimensional $N=1$ supersymmetric Yang-Mills-Chern-Simons theory is finite to all loop orders. In general this leaves open the possibility that different regularization methods lead to different finite effective actions. We show that in this model dimensional regularization and regularization by dimensional reduction yield the same effecti

M. Porrati

We review the "no-go" theorems that severely constrain the breaking of N=2 supersymmetry to N=1 (both in rigid supersymmetry and supergravity), and we exhibit some models that evade them.

M. Bonini, G. Marchesini

We show that it is possible to formulate a gauge theory starting from a local action at the ultraviolet (UV) momentum cutoff which is BRS invariant. One has to require that fields in the UV action and the fields in the effective action are not the same but related by a local field transformation. The few relevant parameters involved in this transformation (s

P. Mejean, F. A. Smirnov

We construct the form factors of the trace of energy-momentum tensor for the massless model described by $SU(2)$ principal chiral field model with WZNW tern on level 1. We explain how this construction can be generalized to a class of integrable massless models including the flow from tricritical to critical Ising model.

Estia Eichten, Kenneth Lane

This is the second of two reports cataloging the principal signatures of electroweak and flavor dynamics at $\pbarp$ and $pp$ colliders. Here, we complete our overview of technicolor with a discussion of signatures specific to topcolor-assisted technicolor. We also review signatures of flavor dynamics associated with quark and lepton substructure. These occu

Estia Eichten, Kenneth Lane

This is the first of two reports cataloging the principal signatures of electroweak and flavor dynamics at $\pbarp$ and $pp$ colliders. Here, we discuss some of the signatures of dynamical elecroweak and flavor symmetry breaking. The framework for dynamical symmetry breaking we assume is technicolor, with a walking coupling $α_{TC}$, and extended technicolor

N. Brambilla, A. Vairo

The $Q \bar{Q}$ semirelativistic interaction in QCD can be expressed in terms of the Wilson loop and its functional derivatives. In this framework we discuss the complete (velocity and spin dependent) $1/m^2$ potential in the stochastic vacuum model and in the dual theory.

H. Navelet, R. Peschanski, Ch. Royon, L. Schoeffel

We show that, provided that the non-perturbative input is regular at the right of the $ω=0$ singularity of the dominant DGLAP anomalous dimension, the rise of $F_2$ at small $x,$ experimentally measured by the averaged observable $λ= <(\partial ln F_2)/(\partial ln 1/x)>,$ is input-independent in the perturbative $Q^2$ regime at small $x$. $(\partial ln xF)/

A. Patrascioiu, E. Seiler

There is a growing body of evidence that the running of $α_s$ predicted by perturbation (PT) theory is not correctly describing the accelerator experiments at the highest energies. A natural explanation is provided by the authors&#39; 1992 proposal that in fact the true running predicted by the nonperturbatively defined lattice QCD is different, leading to a

M. Kirchbach, A. Wirzba

Two-point functions related to the pion weak decay constant $f_π$ are calculated from the generating functional of chiral perturbation theory in the mean field approximation and the heavy-baryon limit. The aim is to demonstrate that Lorentz invariance is violated in the presence of background matter. This fact manifests itself in the splitting of both $f_π$

J. P. Bowes, R. Foot, R. R. Volkas

In gauge theories like the standard model, the electric charges of the fermions can be heavily constrained from the classical structure of the theory and from the cancellation of anomalies. There is however mounting evidence suggesting that these anomaly constraints are not as well motivated as the classical constraints. In light of this we discuss possible

Y. Iwasaki, K. Kanaya, S. Kaya, T. Yoshie

The finite temperature transition of QCD with two degenerate light quarks is studied on the lattice with a renormalization group improved gauge action and the Wilson quark action. We have made simulations on an $8^3\times 4$ lattice near the chiral transition point. It is shown that the chiral condensate which is the order parameter of chiral symmetry satisf

Paul R. Anderson

It is shown that if a generalized definition of gauge invariance is used, gauge invariant effective stress-energy tensors for gravitational waves and other gravitational perturbations can be defined in a much larger variety of circumstances than has previously been possible. In particular it is no longer necessary to average the stress-energy tensor over a r

Reinaldo Gleiser, Oscar Nicasio, Richard Price, Jorge Pullin

We study the head-on collision of two equal-mass momentarily stationary black holes, using black hole perturbation theory up to second order. Compared to first-order results, this significantly improves agreement with numerically computed waveforms and energy. Much more important, second-order results correctly indicate the range of validity of perturbation

S. Monni, M. Cadoni

A two-dimensional (2D) dilaton gravity model, whose static solutions have the same features of the Reissner-Nordstrom solutions, is obtained from the dimensional reduction of a four-dimensional (4D) string effective action invariant under S-duality transformations. The black hole solutions of the 2D model and their relationship with those of the 4D theory ar

D. Scialom

We discuss the coupled Einstein-Klein-Gordon equations for a complex scalar field with and without a quartic self-interaction in a zero curvature Friedman-Lema\^ıtre Universe. The complex scalar field, as well as the metric, is decomposed in a homogeneous, isotropic part (the background) and in first order gauge invariant scalar perturbation terms. The backg

Luis A. Nunes Amaral, Joachim Krug

We introduce two models for the action of impurities in epitaxial growth. In the first, the interaction between the diffusing adatoms and the impurities is ``barrier&#39;&#39;-like and, in the second, it is ``trap&#39;&#39;-like. For the barrier model, we find a symmetry breaking effect that leads to an overall down-hill current. As expected, such a current

Deniz Ertas, Yacov Kantor

We report further findings on the size distribution of the largest neutral segments in a sequence of N randomly charged monomers [D. Ertas and Y. Kantor, Phys. Rev. E53, 846 (1996); cond-mat/9507005]. Upon mapping to one--dimensional random walks (RWs), this corresponds to finding the probability distribution for the size L of the largest segment that return

K. K. Ng, F. C. Zhang, V. I. Anisimov, T. M. Rice

Recent dramatic changes in the optical properties of LaH_{2+x} and YH_{2+x} films discovered by Huiberts et al. suggest their electronic structure is described best by a local model. Electron correlation is important in H^- -centers and in explaining the transparent insulating behavior of LaH_3. The metal-insulator transition at $x\sim 0.8$ takes place in a

Jiri Maly, K. Levin, D. Z. Liu

We extend previous work on pre-formed pair models of superconductivity to incorporate Coulomb correlation effects. For neutral systems, these models have provided a useful scheme which interpolates between BCS and Bose Einstein condensation with increasing coupling and thereby describes some aspects of pseudo-gap phenomena. However, charge fluctuations (via

A. Jagannathan, H. J. Schulz

We consider the Hubbard model for electrons in a two-dimensional quasiperiodic tiling using the Hartree--Fock approximation. Numerical solutions are obtained for the first three square approximants of the perfect octagonal tiling. At half-filling, the magnetic state is antiferromagnetic. We calculate the distributions of local magnetizations and their depend

E. Kanzieper, V. Freilikher

A one-parameter random matrix model is proposed for describing the statistics of the local amplitudes and phases of electron eigenfunctions in a mesoscopic quantum dot in an arbitrary magnetic field. Comparison of the statistics obtained with recent results derived from first principles within the framework of supersymmetry technique allows to identify a tra

Diane J. Litman

Cue phrases may be used in a discourse sense to explicitly signal discourse structure, but also in a sentential sense to convey semantic rather than structural information. Correctly classifying cue phrases as discourse or sentential is critical in natural language processing systems that exploit discourse structure, e.g., for performing tasks such as anapho

B. Jönsson, C. Peterson, B. Söderberg

A variational approach, based on a discrete representation of the chain, is used to calculate free energy and conformational properties in polyelectrolytes. The true bond and Coulomb potentials are approximated by a trial isotropic harmonic energy containing force constants between {\em all}monomer-pairs as variational parameters. By a judicious choice of re

Alessandro Torcini, Stefano Lepri

Propagation of initially localized perturbations is investigated in chaotic coupled map lattices with long-range couplings decaying as a power of the distance. The initial perturbation propagates exponentially fast along the lattice, with a rate given by the ratio of the maximal Lyapunov exponent and the power of the coupling. A complementary description in

Fridolin Weber, Norman K. Glendenning

After giving an overview of the history and idea of neutron stars, I shall introduce, in part one of my lectures, a representative collection of models for the equation of state of superdense neutron star matter, which account for various physical possibilities concerning the unknown behavior of such matter. Part two of my lectures deal with the construction

Bohdan Paczynski

This is a personal review of various issues related to massive photometric and astrometric searches. A complete inventory of variable stars down to almost any magnitude limit will improve our understanding of the stellar evolution and the galactic structure. A search for detached eclipsing binaries will improve the distance scale, the value of the Hubble con

Jeffrey P. Gardner, Neal Katz, Lars Hernquist, David H. Weinberg

Lyman limit and damped Lyman-alpha absorption systems probe the distribution of collapsed, cold gas at high redshift. Numerical simulations that incorporate gravity and gas dynamics can predict the abundance of such absorbers in cosmological models. We develop a semi-analytical method to correct the numerical predictions for the contribution of unresolved lo

P. Höflich, A. Khokhlov, J. C. Wheeler, M. Hamuy

We compare the observed correlations between the maximum brightness, postmaximum decline rate and color at maximum light of Type Ia supernovae (SN Ia) with model predictions. The observations are based on a total of 40 SN Ia with 29 SN of the Calan Tololo Supernova Search and 11 local SN which cover a range of 2 mag in the absolute visual brightness. The obs

E. M. Puchnarewicz, K. O. Mason, F. J. Carrera

We present optical and X-ray spectra of a radio-quiet X-ray selected AGN, RX J1042+1212 ($z$=0.271). The Halpha and Hbeta emission lines are very broad (with full widths at half maximum of ~10000 km s-1) and have double-peaked profiles. Such features are rarely observed in AGN in general but are even more unusual in radio-quiet objects. The analysis of the R

Philippe Jetzer

One of the most important problems in astrophysics concerns the nature of the dark matter in galactic halos, whose presence is implied mainly by the observed flat rotation curves in spiral galaxies. Due to the Pauli exclusion principle it can be shown that neutrinos cannot be a major constituent of the halo dark matter. As far as cold dark matter is concerne

F. Weber, Ch. Schaab, M. K. Weigel, N. K. Glendenning

This paper gives an overview of the properties of all possible equilibrium sequences of compact strange-matter stars with nuclear crusts, which range from strange stars to strange dwarfs. In contrast to their non-strange counterparts, --neutron stars and white dwarfs--, their properties are determined by two (rather than one) parameters, the central star den

James Binney, Ortwin Gerhard, David Spergel

The light distribution in the inner few kiloparsecs of the Milky Way is recovered non-parametrically from a dust-corrected near-infrared COBE/DIRBE surface brightness map of the inner Galaxy. The best fits to the photometry are obtained when the Sun is assumed to lie $\sim14\pm4\pc$ below the plane. The recovered density distributions clearly show an elongat

D. Cline, B. Norum, R. Rossmanith

In this paper the possibility of obtaining polarized beams in a high energy muon collider is discusssed

M. Fujisaki, M. Okuda, Y. Tago, T. Hashimoto

The finite temperature transition of QCD can be seen as a change in the structure of the hadrons and as a symmetry breaking transition -- a change in the structure of the vacuum. These phenomena are observed differently and carry complementary information. We aim at a correlated analysis involving hadronic correlators and the vacuum structure including field

Jinwu Ye

We analyze in detail all the possible fixed points of the effective Hamiltonian of a non-magnetic impurity hopping between two sites in a metal obtained by Moustakas and Fisher(MF). We find a line of non-fermi liquid fixed points which continuously interpolates between the 2-channel Kondo fixed point(2CK) and the one channel, two impurity Kondo (2IK) fixed p

Alessandro Strumia

A right-handed stop not much heavier or even lighter than the Z boson has today desirable phenomenological consequences. We study how it can result within the usual radiative scenario of electroweak symmetry breaking. A restriction on the gaugino mass parameters, M_2 < 0.3 m_10, arises if soft terms satisfy relations suggested by unification theories. Moreov

Cong-feng Qiao, Feng Yuan, Kuang-Ta Chao

The direct production rates of $D$-wave charmonia in the decays of $Z^0$ is evaluated. The color-octet production processes $Z^0\rightarrow ^3D_J(c\bar c) q\bar q$ are shown to have distinctively large branching ratios, the same order of magnitude as that of $J/\psi$ prodution, as compared with other $D$-wave charmonium production mechanisms. This may sugges

Bao-An Li, Che Ming Ko

Within the framework of a relativistic transport model (ART) for heavy-ion collisions at AGS energies, we examine the effects of kaon dispersion relation on the transverse flow of kaons and their transverse momentum and azimuthal angle distributions. We find that the transverse flow is the most sensitive observable for studying the kaon dispersion relation i

G. Amelino-Camelia, L. Hua

The general structure of the partition function of an anyon gas is discussed, especially in relation to statements made in Phys. Rev. Lett. 68 (1992) 1621 and Phys. Rev. Lett. 69( 1992) 2877.

G. Amelino-Camelia

The ultraviolet structure of the Calogero-Sutherland models is examined, and, in particular, semions result to have special properties. An analogy with ultraviolet structures known in anyon quantum mechanics is drawn, and it is used to suggest possible physical consequences of the observed semionic properties.

Holger Ewen, Kristin Foerger, Stefan Theisen

We explicitly determine the instanton corrections to the prepotential for N=2 supersymmetric SU(3) Yang-Mills theory with massless hypermultiplets in the weak coupling regions $u\to\infty$ and $v\to\infty$. We construct the Picard-Fuchs equations for $N_f<6$ and calculate the monodromies using Picard-Lefschetz theorem for $N_f=2,4$. For all $N_f<6$ the insta

H. C. Eggers, B. Buschbeck, P. Lipa

We have measured second- and third-order cumulants in UA1 data ($\bar pp$ collisions at 630 GeV/c). Rather than quoting numerical values for source parameters, we have used these in three checks to test the ``quantum statistics&#39;&#39; theory for consistency over these cumulants. In the process, we have found a method for folding theoretical correlation fu

S. M. H. Wong

We investigate the thermalization and the chemical equilibration of a parton plasma created from Au+Au collision at LHC and RHIC energies starting from the early moment when the particle momentum distributions in the central region become for the first time isotropic due to longitudinal cooling. Using the relaxation time approximation for the collision terms

K. Sridhar

The production of the ${}^1P_1$ charmonium state, $h_c$, at large-$p_T$ at the Tevatron is considered. The colour-octet contributions to this state are found to be dominant and give a reasonably large rate for the production of $h_c$. This should make it feasible to look for this resonance in the $J/ψ+π$ decay channel. This production rate is a prediction of

Y. Alhassid, C. H. Lewenkopf

Analytical expressions for the width and conductance peak distributions of irregularly shaped quantum dots in the Coulomb blockade regime are presented in the limits of conserved and broken time-reversal symmetry. The results are obtained using random matrix theory and are valid in general for any number of non-equivalent and correlated channels, assuming th

N. Read, E. Rezayi

The quasihole states of several paired states, the Pfaffian, Haldane-Rezayi, and 331 states, which under certain conditions may describe electrons at filling factor $ν=1/2$ or 5/2, are studied, analytically and numerically, in the spherical geometry, for the Hamiltonians for which the ground states are known exactly. We also find all the ground states (witho

J. M. G. Vilar, A. Pérez-Madrid, J. M. Rubí

We show that the dipole, a system usually proposed to model relaxation phenomena, exhibits a maximum in the signal-to-noise ratio at a non-zero noise level, thus indicating the appearance of stochastic resonance. The phenomenon occurs in two different situations, i.e. when the minimum of the potential of the dipole remains fixed in time and when it switches

J. M. G. Vilar, J. M. Rubí

We present a class of systems for which the signal-to-noise ratio always increases when increasing the noise and diverges at infinite noise level. This new phenomenon is a direct consequence of the existence of a scaling law for the signal-to-noise ratio and implies the appearance of stochastic resonance in some monostable systems. We outline applications of