Inflationary Perturbations: The Cosmological Schwinger Effect
Abstract
This pedagogical review aims at presenting the fundamental aspects of the theory of inflationary cosmological perturbations of quantummechanical origin. The analogy with the wellknown Schwinger effect is discussed in detail and a systematic comparison of the two physical phenomena is carried out. In particular, it is demonstrated that the two underlying formalisms differ only up to an irrelevant canonical transformation. Hence, the basic physical mechanisms at play are similar in both cases and can be reduced to the quantization of a parametric oscillator leading to particle creation due to the interaction with a classical source: pair production in vacuum is therefore equivalent to the appearance of a growing mode for the cosmological fluctuations. The only difference lies in the nature of the source: an electric field in the case of the Schwinger effect and the gravitational field in the case of inflationary perturbations. Although, in the laboratory, it is notoriously diffcult to produce an electric field such that pairs extracted from the vacuum can be detected, the gravitational field in the early universe can be strong enough to lead to observable effects that ultimately reveal themselves as temperature fluctuations in the cosmic microwave background. Finally, the question of how quantum cosmological perturbations can be considered as classical is discussed at the end of this chapter.
 Publication:

Lecture Notes in Physics, Berlin Springer Verlag
 Pub Date:
 2007
 DOI:
 10.1007/9783540743538_6
 arXiv:
 arXiv:0704.3540
 Bibcode:
 2007LNP...738..193M
 Keywords:

 High Energy Physics  Theory;
 Astrophysics;
 General Relativity and Quantum Cosmology;
 High Energy Physics  Phenomenology
 EPrint:
 49 pages, 6 figures, to appear in a LNP volume "Inflationary Cosmology"