### [0707.0121] Generation of primordial cosmological density i

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**July 10 2007**I found this paper quite interesting. The author has shown that energy density correlations which are weakly suppressed (with the two point correlation falling as [tex]r^{-4}[/tex] for [tex]r\to\infty[/tex]) at the last scattering epoch, can lead to a scale invariant power spectrum at large scales [tex]k\to0[/tex]. Further he constructs a toy mechanism using standard (non-inflationary) physics that can generate such correlations.

The paper is quite readable and uses very simple arguments. I have one observation though. Some work done by Tarun Souradeep and coworkers (astro-ph/0312174, astro-ph/0611352) has shown that the primordial power spectrum estimated directly from the CMB angular power spectrum, in fact has several features which include a sharp infrared cutoff at roughly the horizon scale. I wonder whether arguments such as those presented in Oaknin's paper will be sufficient to explain such features. (Of course it is not yet clear whether inflationary models can explain such features either.)

Any comments?

Aseem

The paper is quite readable and uses very simple arguments. I have one observation though. Some work done by Tarun Souradeep and coworkers (astro-ph/0312174, astro-ph/0611352) has shown that the primordial power spectrum estimated directly from the CMB angular power spectrum, in fact has several features which include a sharp infrared cutoff at roughly the horizon scale. I wonder whether arguments such as those presented in Oaknin's paper will be sufficient to explain such features. (Of course it is not yet clear whether inflationary models can explain such features either.)

Any comments?

Aseem