Corrections to Bino Annihilation I: Sfermion Mixing

We consider corrections to bino annihilation due to sfermion mixing.Comment: 11 pages in LaTex plus 4 postscript figures (included), CfPA--93--th--21, UMN--TH--1205/9

Relic Abundances and the Boltzmann Equation

I discuss the validity of the quantum Boltzmann equation for the calculation of WIMP relic densities.Comment: 5 pages, no figures; talk given at Dark Matter 2000; an important reference is added in the revised versio

Thermal Abundances of Heavy Particles

Matsumoto and Yoshimura [hep-ph/9910393] have argued that there are loop corrections to the number density of heavy particles (in thermal equilibrium with a gas of light particles) that are not Boltzmann suppressed by a factor of e^(-M/T) at temperatures T well below the mass M of the heavy particle. We argue, however, that their definition of the number density does not correspond to a quantity that could be measured in a realistic experiment. We consider a model where the heavy particles carry a conserved U(1) charge, and the light particles do not. The fluctuations of the net charge in a given volume then provide a measure of the total number of heavy particles in that same volume. We show that these charge fluctuations are Boltzmann suppressed (to all orders in perturbation theory). Therefore, we argue, the number density of heavy particles is also Boltzmann suppressed.Comment: 9 pages, 1 figure; minor improvements in revised versio

Numerical determination of entanglement entropy for a sphere

We apply Srednicki's regularization to extract the logarithmic term in the entanglement entropy produced by tracing out a real, massless, scalar field inside a three dimensional sphere in 3+1 flat spacetime. We find numerically that the coefficient of the logarithm is -1/90 to 0.2 percent accuracy, in agreement with an existing analytical result

On the Role of Chaos in the AdS/CFT Connection

The question of how infalling matter in a pure state forms a Schwarzschild black hole that appears to be at non-zero temperature is discussed in the context of the AdS/CFT connection. It is argued that the phenomenon of self-thermalization in non-linear (chaotic) systems can be invoked to explain how the boundary theory, initially at zero temperature self thermalizes and acquires a finite temperature. Yang-Mills theory is known to be chaotic (classically) and the imaginary part of the gluon self-energy (damping rate of the gluon plasma) is expected to give the Lyapunov exponent. We explain how the imaginary part would arise in the corresponding supergravity calculation due to absorption at the horizon of the black hole.Comment: 18 pages. Latex file. Minor changes. Final version to appear in Modern Physics Letters