Updated constraints on the primordial power spectrum at sub-Mpc scales

TL;DR

This paper derives new constraints on the primordial power spectrum at small scales using ultracompact minihalo formation, providing bounds independent of dark matter annihilation assumptions.

Contribution

It introduces a novel method to constrain small-scale primordial fluctuations through ultracompact minihalo formation, avoiding reliance on dark matter annihilation.

Findings

Constraints of $ ext{P}_ ext{R}(k) extless 5 imes 10^{-6}$ over a broad scale range

Constraints do not depend on dark matter annihilation assumptions

Provides the most stringent limits on small-scale primordial power spectrum to date

Abstract

The primordial power spectrum of matter density perturbations contains highly valuable information about new fundamental physics, in particular cosmological inflation, but is only very weakly constrained observationally for small cosmological scales $k\gtrsim 3\,{\rm Mpc}^{-1}$. We derive novel constraints, $\mathcal{P}_\mathcal{R}(k)\lesssim 5\cdot10^{-6}$ over a large range of such scales, from the formation of ultracompact minihalos in the early universe. Unlike most existing constraints of this type, our results do not rest on the assumption that dark matter can annihilate into ordinary matter.