Echoes of Inflationary First-Order Phase Transitions in the CMB

Abstract

Cosmological phase transitions (CPTs), such as the Grand Unified Theory (GUT) and the electroweak (EW) ones, play a significant role in both particle physics and cosmology. In this letter, we propose to probe the first-order CPTs, by detecting gravitational waves (GWs) which are generated during the phase transitions through the cosmic microwave background (CMB). If happened around the inflation era, the first-order CPTs may yield low-frequency GWs due to bubble dynamics, leaving imprints on the CMB. In contrast to the nearly scale-invariant primordial GWs caused by vacuum fluctuation, these bubble-generated GWs are scale dependent and have non-trivial B-mode spectra. If decoupled from inflaton, the EWPT during inflation may serve as a probe for the one after reheating where the baryon asymmetry could be generated via EW baryogenesis (EWBG). The CMB thus provides a potential way to test the feasibility of the EWBG, complementary to the collider measurements of Higgs potential and the direct detection of GWs generated during EWPT.

5+6 pages, 4 figures. V2 changed title, added one figure about constraints of Planck2015+BICEP2/Keck data, added references and removed appendix. Accepted by PLB

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• The Gravitational-Wave Physics II: Progress
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• Gravitational Waves from an Inflation Triggered First-Order Phase Transition
• Gravitational-wave signatures from reheating
• Phase-transition sound of inflation at gravitational waves detectors
• Gravitational Waves from Incomplete Inflationary Phase Transitions
• Gravitational Waves of GUT Phase Transition during Inflation
• Traces of a Heavy Field in Gravitational Waves
• Crescendo Beyond the Horizon: More Gravitational Waves from Domain Walls Bounded by Inflated Cosmic Strings
• Ghost Free Theory in Unitary Gauge: A New Candidate
• Curvature perturbations from vacuum transition during inflation
• Simulating first-order phase transition during inflation