Hawking Radiation and Ultraviolet Regulators

Polchinski has argued that the prediction of Hawking radiation must be independent of the details of unknown high-energy physics because the calculation may be performed using `nice slices', for which the adiabatic theorem may be used. If this is so, then any calculation using a manifestly covariant --- and so slice-independent --- ultraviolet regularization must reproduce the standard Hawking result. We investigate the dependence of the Hawking radiation on such a short-distance regulator by calculating it using a Pauli--Villars regularization scheme. We find that the regulator scale, $\Lambda$, only contributes to the Hawking flux by an amount that is exponentially small in the large variable {\Lambda}/{T_\ssh} \gg 1, where T_\ssh is the Hawking temperature; in agreement with Polchinski's arguments. We also solve a technical puzzle concerning the relation between the short-distance singularities of the propagator and the Hawking effect.Comment: Tex, 11 pages, no figures, new references adde

Solar Fluctuations and the MSW Effect

This talk summarizes the results of recent calculations of how fluctuations within the solar medium can influence resonant neutrino oscillations within the sun. Although initial calculations pointed to helioseismic waves as possibly producing detectable effects, recent more careful calculations show this not to be true. Those features of fluctuations which maximize their influence on neutrino propagation are identified, and are likely to have implications for supernovae and the early universe.Comment: 10 pages, LaTeX, talk given at the Erice School on Neutrinos in Astro, Particle and Nuclear Physic

Effective Actions, Boundaries and Precision Calculations of Casimir Energies

We perform the matching required to compute the leading effective boundary contribution to the QED lagrangian in the presence of a conducting surface, once the electron is integrated out. Our result resolves a confusion in the literature concerning the interpretation of the leading such correction to the Casimir energy. It also provides a useful theoretical laboratory for brane-world calculations in which kinetic terms are generated on the brane, since a lot is known about QED near boundaries.Comment: 5 pages. revtex; Added paragraphs describing finite-conductivity effects and effects due to curvatur

Massive-Scalar Effective Actions on Anti-de Sitter Spacetime

Closed forms are derived for the effective actions for free, massive spinless fields in anti-de Sitter spacetimes in arbitrary dimensions. The results have simple expressions in terms of elementary functions (for odd dimensions) or multiple Gamma functions (for even dimensions). We use these to argue against the quantum validity of a recently-proposed duality relating such theories with differing masses and cosmological constants.Comment: 23 pages, plain TeX, one figur

Supersymmetric Large Extra Dimensions and the Cosmological Constant: An Update

This article critically reviews the proposal for addressing the cosmological constant problem within the framework of supersymmetric large extra dimensions (SLED), as recently proposed in hep-th/0304256. After a brief restatement of the cosmological constant problem, a short summary of the proposed mechanism is given. The emphasis is on the perspective of the low-energy effective theory in order to see how it addresses the problem of why low-energy particles like the electron do not contribute too large a vacuum energy. This is followed by a discussion of the main objections, which are grouped into the following five topics: (1) Weinberg's No-Go Theorem. (2) Are hidden tunings of the theory required, and a problem? (3) Why should the mechanism not rule out earlier epochs of inflation? (4) How big are quantum effects, and which are the most dangerous? (5) Can the mechanism be consistent with cosmological constraints? It is argued that there are plausible reasons why the mechanism can thread the potential objections, but that a definitive proof that it does depends on addressing well-defined technical points. These points include identifying what fixes the size of the extra dimensions, checking how topological obstructions renormalize and performing specific calculations of quantum corrections. More detailed studies of these issues, which are well reach within our present understanding of extra-dimensional theories, are currently underway. As such, the jury remains out concerning the proposal, although the prospects for acquittal still seem good.Comment: 21 pages; an extended version of the contribution to the proceedings of SUSY 2003, University of Arizona, Tucson AZ, June 2003, which has also been updated to include developments since the conference. (v2 includes some updated references and corrects a minor error in the bulk loop section