Lev Kofman

Research Summary

[ Cosmology, Early Universe and General Relativity ]

Lev Kofman works on the theory of inflation, with the aim to understand the origin of matter in the very early universe and the growth of initial cosmological fluctuations. Kofman also is interested in higher dimensional formulations of superstring and M-theory and phenomenological braneworlds models, which might be tied to observations of the cosmic microwave background and large scale structure.

Research Projects:
(September 2002 - August 2003)

Thermodynamical aspects of quasi-de Sitter geometry

Lev Kofman and Andrei Frolov considered thermodynamical aspects of the quasi-de Sitter geometry of the inflationary universe. They calculated the energy flux of the slowly rolling background scalar field through the quasi-de Sitter apparent horizon and set it equal to the change of the entropy (1/4 of the area) multiplied by the temperature, dE=TdS. Remarkably, this thermodynamic law reproduces the Friedmann equation for the rolling scalar field. Next they added inflaton fluctuations which generate scalar metric perturbations. Metric perturbations result in a variation of the area entropy. Again, the equation dE=TdS with fluctuations reproduces the linearized Einstein equations. In this picture, as long as the Einstein equations hold, holography does not put limits on the quantum field theory during inflation. Due to the accumulating metric perturbations, the horizon area during inflation randomly wiggles with dispersion increasing with time. They discussed this in connection with the stochastic description of inflation.

Numerical Studies of Braneworld Dynamics

Working with Johannes Martin, Andrei Frolov, Gary Felder, and Marco Peloso of CITA, Kofman developed a program for calculating the time evolution of a braneworld system. It is the first numerical code to treat the fully non-linear dynamics of the braneworlds.

Dynamics of the rolling tachyon

Kofman studied the dynamics of the rolling tachyon which forms after the antibrane annihilation. This is a vital part in the string theory of cosmology inflation.

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