Cosmic Archaeology with Gravitational Waves from Cosmic Strings

TL;DR

This paper explores how gravitational wave observations from cosmic strings can reveal the universe's energy composition and history before primordial nucleosynthesis, offering a new window into early cosmology.

Contribution

It demonstrates that gravitational wave detectors can measure signals from cosmic strings, enabling probing of the universe's energy content at very early times beyond current cosmological tests.

Findings

Gravitational waves from cosmic strings can be detected by LIGO and LISA.

The frequency spectrum of these waves encodes the universe's energy history.

This method allows probing epochs before nucleosynthesis.

Abstract

Cosmic strings are generic cosmological predictions of many extensions of the Standard Model of particle physics, such as a $U(1)^\prime$ symmetry breaking phase transition in the early universe or remnants of superstring theory. Unlike other topological defects, cosmic strings can reach a scaling regime that maintains a small fixed fraction of the total energy density of the universe from a very early epoch until today. If present, they will oscillate and generate gravitational waves with a frequency spectrum that imprints the dominant sources of total cosmic energy density throughout the history of the universe. We demonstrate that current and future gravitational wave detectors, such as LIGO and LISA, could be capable of measuring the frequency spectrum of gravitational waves from cosmic strings and discerning the energy composition of the universe at times well before primordial nucleosynthesis and the cosmic microwave background where standard cosmology has yet to be tested. This work establishes a benchmark case that gravitational waves may provide an unprecedented, powerful tool for probing the evolutionary history of the very early universe.