# Spectral distortions in CMB by the bulk Comptonization due to Zeldovich pancakes

## TL;DR

This paper investigates how large-scale structures like Zeldovich pancakes could distort the Cosmic Microwave Background spectrum through bulk Comptonization, providing formulas to estimate these spectral changes.

## Contribution

It introduces approximate formulas for the CMB spectrum after bulk Comptonization by Zeldovich pancakes, highlighting differences from thermal Comptonization effects.

## Key findings

- Formulas for the CMB spectrum after bulk Comptonization are derived.
- Spectral differences between thermal and bulk Comptonization are estimated.
- Potential observational signatures of large-scale structure formation on CMB spectrum are discussed.

## Abstract

If the large scale structure of the Universe was created, even partially, via Zeldovich pancakes, than the fluctuations of the CMB radiation should be formed due to bulk comptonization of black body spectrum on the contracting pancake. Approximate formulas for the CMB energy spectrum after bulk comptonization are obtained. The difference between comptonized energy spectra of the CMB due to thermal and bulk comptonization may be estimated by comparison of the plots for the spectra in these two cases.