## Structure formation in the universe

The formation of large scale structures in the universe is probabably *the* problem requiring solution in cosmology. I was fascinated by the purely theoretical question of developing a formalism to study statistical mechanics of gravitating systems - both (i) in the context of isolated Newtonian case as well as (ii) in an expanding universe.

You will find most of my results, views etc regarding (i) in the Physics Reports review I wrote in 1989 [ref 77 in my
list of publications] as well as in some of the papers, especially ref. 71.

I then started working on the statistical mechanics of gravitating systems in an expanding background and I believe I actually understand the physics at the level of power spectrum [see ref.101, 117,118]
(This is important since some people in this field use computers the way drunkard uses a lamppost - for support, not illumination.) The key
ideas are summarised in two pedagogical reviews:

(i) "* Aspects of gravitational clustering"*, in "Large Scale Structure Formation", Astrophysics and Space Science Library, volume 247, p.97 (Eds. R. Mansouri and R. Brandenberger, Kluwer 2000), [astro-ph/9911374].

(ii) * "Statistical Mechanics of gravitating systems in static and cosmological backgrounds",*Invited Contribution to `Dynamics and Thermodynamics of Systems with Long Range Interactions' Eds: T.Dauxois, S.Ruffo, E.Arimondo, M.Wilkens ;
Lecture Notes in Physics, Springer (2002), [astro-ph/0206131].

One still needs to set this up as a rigourous formalism, which is what I am working on nowadays.
More recently, I am trying to understand the issue of cosmological constant since observations seem to force us to take its existence seriously. My views are available in the recent reviews i wrote ref. 153,191,198.