String Necklaces and Primordial Black Holes from Type IIB Strings

TL;DR

This paper explores cosmic string loops in type IIB string theory, showing their potential to form primordial black holes early on and dark matter relics later, with implications for cosmological observations.

Contribution

It introduces a model of cosmic string loops with windings in type IIB strings, highlighting their role in primordial black hole formation and dark matter production, differing from previous field theory models.

Findings

Primordial black holes form in a small early-time window.

Dark matter relics emerge at late times in the scaling regime.

Experimental data constrains string theory parameters.

Abstract

We consider a model of static cosmic string loops in type IIB string theory, where the strings wrap cycles within the internal space. The strings are not topologically stabilised, however the presence of a lifting potential traps the windings giving rise to kinky cycloops. We find that PBH formation occurs at early times in a small window, whilst at late times we observe the formation of dark matter relics in the scaling regime. This is in stark contrast to previous predictions based on field theoretic models. We also consider the PBH contribution to the mass density of the universe, and use the experimental data to impose bounds on the string theory parameters.