Cosmology
	Very Early Universe
	Inflation
	Large Scale Structure

	Cosmology with extra dimensions
	Recent Talks

I am working to improve inflationary theory and to understand the origin of matter in the very early universe, as well as the growth of initial cosmological fluctuations in the universe. According to inflationary cosmology, all elementary particles which we see now have not been present at the moment of the Big Bang. Rather they were created by the at the very end of the stage of inflation in the process of preheating. This provides us with the new rich dynamics of the fields and particles in the very early universe.

The fundamental theory of the early universe is ultimately connected with the large scale structure of the present universe. Observationally, galaxies and clusters are not distributed at random but form a network of superclusters in the form of filaments and walls with voids in between. Numerical simulations of the hierarchical gravitational clustering also show a visually evident network of filaments. It turns out that the web of the filaments that defines the final state of large-scale galaxy distribution is actually present in the initial density inhomogeneities. The pattern of the web is defined largely by the peaks of the initial density fluctuations, with subsequent nonlinear evolution of the structure bringing the filamentary network into sharper relief.

If we look at the universe back in time, our understanding of how the matter and primordial gas evolved into galaxies and clusters of galaxies is necessarily mainly theoretical. Large-Scale structure in the distribution of galaxies is thought to have involved through gravitational instability from tiny density fluctuations in the gas of the largely homogeneous early universe. These primordial density fluctuations originated at the stage of inflation, the period about 13 billion years ago when our cosmos expanded extremely fast before being transformed into a homogeneous fireball of extremely hot elementary particles.

Selected Publications
"Reheating after Inflation", L. Kofman, A. Linde, and A. Starobinsky, Phys. Rev. Lett., 73, 3195-3198 (1994)
"How Filaments of Galaxies are Woven into the Cosmic Web", J. R. Bond, L. Kofman and D. Pogosyan, Nature, 380, 603-605 (1996)
"First-order nonthermal phase transition after Inflation", Khlebnikov, S., Kofman, L., Linde, A. and Tkachev, I., Phys. Rev. Lett., 81, 2012-2015 (1998)
"Cosmological Constant, COBE DMR Anisotropy, and Large Scale Clustering", Kofman, L., Gnedin, N., and Bachall, N., Astrophys. J. 413, 1-9 (1993)