Cosmic strings and primordial black holes

TL;DR

This paper explores the interactions between cosmic strings and primordial black holes, revealing their impact on network formation, gravitational wave emission, and potential observational signatures in the universe.

Contribution

It demonstrates how cosmic strings and PBHs interact, forming networks and nets, influencing black hole mergers, and affecting dark matter and galaxy formation theories.

Findings

Black-hole-string networks form at PBH and string interaction.

Oscillating nets emit gravitational waves leading to PBH mergers.

Strings can influence PBH distribution and observable astrophysical phenomena.

Abstract

Cosmic strings and primordial black holes (PBHs) commonly and naturally form in many scenarios describing the early universe. Here we show that if both cosmic strings and PBHs are present, their interaction leads to a range of interesting consequences. At the time of their formation, the PBHs get attached to the strings and influence their evolution, leading to the formation of black-hole-string networks and commonly to the suppression of loop production in a range of redshifts. Subsequently, reconnections within the network give rise to small nets made of several black holes and connecting strings. The number of black holes in the network as well as the stability of the nets depend on the topological properties of the strings. The nets oscillate and shrink exponentially due to the emission of gravitational waves. This leads to potentially observable string-driven mergers of PBHs. The strings can keep PBHs from galactic halos, making the current bounds on PBHs not generally applicable. Alternatively, heavy PBHs can drag low-tension strings into the centers of galaxies. The superconducting strings can appear as radio filaments pointing towards supermassive black holes.