Characteristic Scales of Initial Density and Velocity Fields

TL;DR

This paper calculates the characteristic length and mass scales of initial density and velocity fields, linking them to observed structures in the universe across different redshifts.

Contribution

It provides a theoretical framework for understanding how initial fluctuation scales determine the sizes and masses of cosmic structures observed today.

Findings

Initial density and velocity fields' scales match observed galaxy and halo sizes.

The length and mass scales serve as fossil imprints of early universe conditions.

Theoretical calculations explain the origin of large-scale cosmic structures.

Abstract

For the initial fields of the density contrast and peculiar velocity, we theoretically calculate the differential and integral length scales, i.e., statistical measures that respectively characterize the small- and large-scale fluctuations of a random field. These length scales and the associated mass scales explain the length and mass scales observed for (1) halos of young galaxies at z > 5, (2) halos of galaxies at z = 0, and (3) the largest structures in the galaxy distribution at z = 0. We thereby discuss that such observed scales are fossil imprints of the characteristic scales of the initial fields.