Early Universe Relics:
Inflation and Reheating

Very recently I became interested in issues of gravitational and matter field instabilities during preheating after inflation. Together with Karsten Jedamzik from the Early Universe Gang at the Max Planck Institut für Astrophysik, Garching bei München I started to study these phenomena consistently by trying to take backreaction into account. This is important in order to reliably describe the resonance phenomena, and especially their termination and thus the resulting field and metric fluctuations. Our goal is to determine observational consequences and in turn constrain models of inflation.

preheating in a simple model The figure on the left shows first results for the evolution of the matter field fluctuations and the metric perturbations, for the simple case of a massive inflaton with quadratic coupling to another scalar field. From these calculations, presented in detail in this paper, we conclude that, contrary to some other claims in the literature, metric perturbations at least on scales relevant for structure formation, are not strongly modified during preheating and certainly do not grow non-linear.

We began to investigate preheating in the context of more general inflaton and matter field potentials. To this end a numerical code should be developed which takes into account as many nonlinear effects during preheating and reheating as possible. Preliminary results seem to indicate that significant increase of large scale metric fluctuations is possible in certain cases but typically requires considerable fine tuning of parameters. In the farther future this numerical tool should probably also be extended to fermions, gauge bosons, gravitinos etc.

Processes during reheating after inflation may also be important for the creation of superheavy particles and/or topological defects at the end of inflation which today may constitute non-thermal dark matter and whose decay may contribute to the ultrahigh energy cosmic ray flux.


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