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We present the first experimental study of the ratio of cumulant to factorial moments of the charged-particle multiplicity distribution in high-energy particle interactions, using hadronic Z$^0$ decays collected by the SLD experiment at SLAC. We find that this ratio, as a function of the moment-rank $q$, decreases sharply to a negative minimum at $q=5$, which is followed by quasi-oscillations. These features are insensitive to experimental systematic effects and are in qualitative agreement with expectations from next-to-next-to-leading-order perturbative QCD., Comment: 13 pages, latex file, uuencoded eps figures

We investigate the evolution of globular clusters in the Galactic tidal field prior to core collapse. These multimass models incorporate mass loss by stellar evolution.

The fluorescence lifetime of acridine is measured as a function of temperature in three solvents. Whether the solvent is protic or aprotic, the same activation energy is extrapolated for energy dissipation. These results are inconsistent with a model used to describe electronic relaxation in acridine that depends solely on the energy gap between electronic states.

Gravitational, neutrino, and antineutrino radiation from stellar core collapse is analyzed by following the gravitational (Newtonian) collapse of rotating, 1.4 M/sub sun/ homogeneous ellipsoids initially in hydrostatic equilibrium at a density of 4 x 10/sup 9/g cm/sup -3/. The core is assumed to consist of neutrons, protons, and electrons in ..beta..-equilibrium with electron neutrinos and antineutrinos. The model is characterized by a temperature-dependent ''hard core'' nuclear equation of state, neutrino and antineutrino transport via a ''one-zone'' model atmosphere approximation, and a ''reflection shock'' algorithm which describes the initial rebound of the ''inner'' core following maximum compression. In the nonrotating, spherical limit the collapse is nearly adiabatic and the computed core parameters, the maximum neutrino luminosities, and the total radiated efficiencies are in reasonable agreement with the results of recent inhomogeneous, spherical hydrodynamical calculations by Arnett and by Wilson.Nonspherical gravitational collapse is analyzed, and the efficiencies of gravitational and neutrino radiation are computed as functions of the core angular momentum, J> Nonaxisymmetric deformations are also considered. It is found that for a wide range of angular momenta satisfying 5 x 10/sup 46/< or approx. =J< or approx. =3 x 10/sup 49/erg-s, eccentricities, gravitational radiation luminosities, and peak wave amplitudes increase dramaticallymore » after a few bounces whenever the ''inner'' core undergoes large-amplitude, homologous oscillations following the initial infall. Efficiencies can reach triangle-openE/sub GR//Mc/sup 2/approx.10/sup -4/-10/sup -2/ after a few oscillations in some cases. The implications of these results for stellar collapse occurring in nature are explored.« less

We numerically solve the plane-parallel, semi-infinite, static neutrino atmosphere problem. We assume that the atmosphere consists of free nucleons, electrons, positrons, and photons with electron neutrinos and antineutrinos flowing through this gas. We require that the atmosphere be in hydrostatic equilibrium and that energy flux and electron lepton number flux be conserved throughout the atmosphere. Neutrinos and antineutrinos are allowed to interact with the matter via beta emission-absorption processes, neutrino-nucleon and neutrino-electron scattering, and pair production-absorption by electron-positron pairs and plasmons. Atmospheres are completely specified by giving the values of the gravitational acceleration g, the energy flux ,F and the lepton number flux . We find that spectra are well approximated by Fermi distributions at large energies but deviate significantly at lower energies. For some values of the parameters F and N neutrinos and antineutrinos can carry energy in opposite directions at large depth due to chemical potential gradients. Other values of these two parameters can produce atmospheres dominated by relativistic particles (electron-positron pairs and photons). The dominant opacities are found to be neutrino-nucleon processes. We calculate the criterion for stability against convection and find that for values of F and N relevant to stellar collapse, convection will always occurmore » in at least part of the atmosphere.« less

A new, general relativistic, hydrodynamical computer code for spherical, stellar colapse to neutron stars and black holes is presented. The code is employed to construct spacetimes for the geometrodynamical evolution of spherical masses which are initially at rest and obey an adiabatic GAMMA-law equation of state. Collapse to a black hole can be followed accurately; the evolution outside the event horizon can be determined far into the future without having the integration terminate because of spacetime singularities inside.We use the code to address several fundamental points of principle regarding spherical, gravitational collapse and requiring a reliable, fully relativistic, numerical computation. We sample a variety of possible collapse and requiring a reliable, fully relativistic, numerical computation. We sample a variety of possible collapse scenarios, characterized by different masses, mass distributions, and equations of state, to examine stellar core collapse and its end fate. We distinguish three possible outcomes for adiabatic core collapse: homologous core, bounce, nonhomologous core bounce, and catastrophic collapse to a black hole. Even a very massive stellar core may undergo a nonhomologous bounce and only later collapse to a black hole on a secular time scale rather than a dynamical one. Accretion-driven neutron star collapse is also treatedmore » numerically. The implications of our findings for realistic core collapse believed to occur in nature are considered.« less

Gravitational radiation from the head-on collision of two identical compact stars is calculated using a two-dimensional, time-dependent, Newtonian hydrodynamical code. The star fluid is treated in an adiabatic approximation, and all relativistic effects are ignored. Gravitational radiation is computed as a small perturbation using linearized theory. The efficiency with which collisions generate radiation, ..delta..E/M, is typically < or approx. =0.1% for colliding 1.4 M/sub sun/ neutron stars. The efficiency is a steeply increasing function of the degree of central compaction M/R. These results indicate that neutron star collisions might be the most copious emitters of gravitational radiation among promising astrophysical sources. However, there may be no likely astrophysical events that generate radiation with order unity efficiency. Our calculations are compared with previous one-dimensional studies (Shapiro 1980) and serve as a useful limit in which to compare future fully relativistic treatments.

Gravitational radiation from the nonspherical collapse of a rotating stellar core is calculated using homogeneous ellipsoids. The adiabatic, ''hot'' equation of state for dense matter due to Lamb et al. is employed, together with a realistic hydrodynamical dissipation algorithm. It is found that the large amplitude, homologous density oscillations are effectively damped after the first few core bounces. However, small amplitude (deltarho/rho<

The burst of gravitational radiation emitted during the initial collapse and rebound of a homogeneous ellipsoid with internal pressure is analyzed numerically. a configuration of mass 1.4 M/sub sun/ is assumed to collapse aspherically from rest at an initial density of 10/sup 1/0 g cm/sup -/3. The deviations from spherical symmetry arise from rotation and internal magnetic fields; deviations from axisymmetry are also considered. By following the collapse along two distinct low-entropy adiabats (''hot'' and ''cold'' collapse) on free-fall time scales, we estimate the maximum amount of gravitational radiation liberated during the initial implosion of a compact stellar core. We calculate the total gravitational (quadrupole) radiation energy loss, the radiation spectra, and the wave forms for several collapse sequences, parametrized by their initial deviations from spherical symmetry. A minimum estimate of the total neutrino losses during this initial collapse phase is also provided.

The thermal evolution of a hot, dense medium, cooling via neutrino and photon emission, is analyzed. The medium is assumed to be a plane-parallel, semi-infinite atmosphere in hydrostatic equilibrium and initially isothermal. The thermal history of the neutrino photosphere is governed by a nonlinear diffusion equation. At late times the solution of this equation acquires a self-similar form. Since the photon opacity everywhere exceeds the neutrino opacity, the photon flux is significantly below the neutrino flux and can be treated as a small perturbation. The temperature profile, together with the neturino and photon fluxes, are obtained as functions of depth and time by a combination of numerical and analytic calculations. Key results are summarized by a convenient set of compact, closed-form similarity formulae. These are employed to examine the cooling of a young neutron star during the first approx.15 s of its lifetime, when the star is hot, optically thick to photons and neutrinos, and quasi-static out to the neutrino photosphere.

This is the second of a series of papers on the numerical solution of Einstein's equations for the dynamical evolution of a collisionless gas of particles in general relativity. This paper deals mainly with applications to sphericcal star clusters. Previous studies were restricted to static equilibria and linear perturbations. We bring together the tools of numerical relativity and N-body particle simulation to follow the full nonlinear evolution of such dynamical systems.

We investigate the effect of neutrino Comptonization, by which energy is exchanged between a hot, dense nucleon gas and a neutrino gas via Compton scattering, on the final spectrum of the neutrinos. We derive the diffusion equation which governs Comptonization, and integrate it to get energy exchange rates. We use the rates and other reasonable assumptions to develop rough criteria by which it is possible to determine whether or not Comptonization will be important in a gas of given temperature and density. We construct a crude model transport equation which accounts for several of the processes that cause energy exchange between neutrinos and the gas and calculate spectra. We conclude that Comptonization can have a marked effect on neutrino spectra whenever our rough criteria are satisfied. When applied to conditions likely to occur during stellar core collapse, we find that COmptonization will be important for densities in excess of 10/sup 13/ g cm/sup -3/ and temperatures in a wide range about 10/sup 11/ K in a free nucleon gas. A dominance of high-A nuclei, however, will make Comptonization less important than electron scattering, typicallly, due to the larger number of electrons per baryon Y/sub e/ necessary to cancel the chargemore » of the protons found in the nuclei.« less

Spatial variations in cosmic He abundance attributed to primordial temperature fluctuations at early epochs in Friedmann universe