Cosmic Strings, Inflation, and Gravity Waves

Abstract

We investigate the impact of Coleman-Weinberg inflation on the stochastic gravity wave background spectrum emitted by intermediate scale cosmic strings. The string network is partially inflated and re-enters the horizon at later times after the end of inflation, such that the short string loops are not produced. This leads to a significant modification of the gravity wave spectrum that we explore in detail. We find that Coleman-Weinberg inflation can help to satisfy the Parkes Pulsar Timing Array (PPTA) bound for dimensionless string tension values in the range $G\mu >1.1\times 10^{-10}$. We also identify the modified gravity wave spectra which, in the case of inflation, are compatible with the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) data. We then discuss the formation of monopoles and strings at the same breaking scale and the compatibility of the Monopole, Astrophysics and Cosmic Ray Observatory (MACRO) bound with the PPTA bound, and also with the NANOGrav data. Finally, an example of a realistic non-supersymmetric $E_6$ model incorporating successful Coleman-Weinberg inflation is presented in which monopoles and strings both survive inflation and are present at an observable level.

8 pages, Two columns, 12 figures, Version to appear in PRD

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• Primordial gravitational waves from NANOGrav: a broken power-law approach
• The NANOGrav 12.5-year data set: Search for Non-Einsteinian Polarization Modes in theGravitational-Wave Background
• Sneutrino Tribrid Inflation, Metastable Cosmic Strings and Gravitational Waves
• Gravitational Waves from Quasi-stable Strings
• $\mu$-hybrid Inflation, Gravitino Dark Matter and Stochastic Gravitational Wave Background from Cosmic Strings
• Monopoles, Strings and Gravitational Waves in Non-minimal Inflation
• A Predictive and Testable Unified Theory of Fermion Masses, Mixing and Leptogenesis
• Constraining the Cosmic Strings Gravitational Wave Spectra in No Scale Inflation with Viable Gravitino Dark matter and Non Thermal Leptogenesis
• Heavier $W$ boson, dark matter and gravitational waves from strings in an $SO(10)$ axion model
• Probing Minimal Grand Unification through Gravitational Waves, Proton Decay, and Fermion Masses
• Gravitational wave signal from primordial magnetic fields in the Pulsar Timing Array frequency band