Gravitational waves from cosmic superstrings and gauge strings

Abstract

We perform a phenomenological comparison of the gravitational wave (GW) spectrum expected from cosmic gauge string networks and superstring networks comprised of multiple string types. We show how violations of scaling behavior and the evolution of the number of relativistic degrees of freedom in the early Universe affect the GW spectrum. We derive simple analytical expressions for the GW spectrum from superstrings and gauge strings that are valid for all frequencies relevant to pulsar timing arrays (PTAs) and laser interferometers. We analyze the latest data from PTAs and show that superstring networks are consistent with 32 nHz data from NANOGrav, but are excluded by 3.2 nHz data at $3\sigma$ unless the string coupling $g_s<0.2$ or the strings evolve in only about 10% of the volume of the higher-dimensional space. We also point out that while gauge string networks are excluded by NANOGrav-15 data at $3\sigma$, they are completely compatible with EPTA and PPTA data. Finally, we study correlations between GW signals at PTAs and laser interferometers.

29 pages, 12 figures, 2 tables. Version to appear in JHEP

References in corpus (1)

• Stochastic gravitational wave background from smoothed cosmic string loops

Cited by in corpus (4)

• Revised bounds on local cosmic strings from NANOGrav observations
• Cosmic superstrings in large volume compactifications: PTAs, LISA and time-varying tension
• Primordial black holes and magnetic fields in conformal neutrino mass models
• Imprints of an early matter-dominated era arising from dark matter dilution mechanism on cosmic string dynamics and gravitational wave signatures