The 2023 Shanghai Symposium on Particle Physics and Cosmology: Phase Transitions, Gravitational Waves, and Colliders (SPCS 2023)

Have pulsar timing array methods detected a cosmological phase transition?

24 Sept 2023, 09:00

30m

Tsung-Dao Lee Institute/S5F-S500 - Lecture Hall (Tsung-Dao Lee Institute)

Sunday 1

Speaker

Prof. Antonino Marciano (Fudan University and INFN Frascati)

Description

We show [1] that the recent detection of a gravitational wave (GW) background reported by various pulsar timing array (PTA) collaborations including NANOGrav-15yr, PPTA, EPTA, and CPTA can be explained in terms of first order phase transitions (FOPTs) from dark sector models (DSM). Specifically, we explore a model for first order phase transitions that involves the majoron, a Nambu-Goldstone boson that is emerging from the spontaneous symmetry breaking of a U(1)L or U(1)B−L symmetry. We show how the predicted GW power spectrum, with a realistic choice of the FOPT parameters, is consistent with 1-σ deviations from the estimated parameters of the background detected by the PTA collaborations.

[1] A. Addazi, Y.F. Cai, A. Marciano and L. Visinelli, [arXiv:2306.17205 [astro-ph.CO]].