Beecroft Institute for Particle Astrophysics and Cosmology

Abstract:

High resolution maps of the anisotropy of the microwave sky will yield invaluable clues as to the mechanisms involved in cosmic structure formation. One fundamental question they should answer is whether the fluctuations were Gaussian random noise, as predicted in inflationary models, or were nonGaussian as in theories based on symmetry breaking and cosmic defects. In the latter case there is the prospect of obtaining information regarding symmetry breaking at high energy scales, specifically the homotopy classes $\Pi_n$ of the vacuum manifold. In this paper we report on detailed calculations of the degree scale anisotropies predicted in the cosmic string, monopole texture and nontopological texture theories of structure formation, emphasising their distinct character from those predicted by inflation, and the bright prospects for experimental tests.

Abstract:

We have searched the Einstein Monitor Proportional Counter (MPC) data base for observations of clusters of galaxies. The MPC was a nonfocal plane instrument on board the Einstein Observatory and accumulated data during all pointed observations with the four focal plane instruments. By co-adding the MPC spectra obtained during all pointed observations of clusters with IPC count rates greater than 0.1 counts per second, we have obtained sufficient photon statistics to estimate the X-ray temperature of 84 clusters. Combining the MPC results with EXOSAT and Ginga results reported in the literature yields a combined sample of 104 clusters with known X-ray temperatures. This is approximately twice as large as any previously published sample. One of the best studied X-ray correlations between clusters is that between their X-ray luminosity and gas temperature. We show that the best-fit power-law relation for our combined cluster sample can be explained by the observed increase in the gas-to-stellar mass ratio between low- and high-temperature clusters. There have been several recent reports in the literature concerning the evolution of X-ray luminous clusters at fairly low redshifts. The statistical significance of any evolution in our combined X-ray sample has been examined and compared with the statistical properties of clusters culled from optical catalogs. We find that there is strong evidence for a decrease in the X-ray luminosity of optically rich clusters beyond z ≈ 0.06. This result is used to estimate the normalization of the primordial power spectrum of density fluctuations.

Abstract:

The inflationary cosmology is analyzed from the point of view of squeezed quantum states. As noted by Grishchuk and Sidorov, the amplification of quantum fluctuations into macroscopic perturbations which occurs during cosmic inflation is a process of quantum squeezing. We carefully develop the squeezed state formalism and derive the equations that govern the evolution of a gaussian initial state. We derive the power spectrum of density perturbations for a simple inflationary model and discuss its features. We conclude that the squeezed state formalism provides an interesting framework within which to study the amplification process, but,in disagreement with the claims of Grishchuk and Sidorov, that it does {\em not} provide us with any new physical results.