NANOGrav results and dark first order phase transitions

Abstract

We show 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.must be included in the Lagrangian.

Scalar Induced Gravitational Waves Review

“…It is important to note that the induced GWs are not the only explanations of the NANOGrav results. For example, among many others, possible candidates are cosmic strings [328][329][330][331] and first order phase transitions [332][333][334][335][336][337][338][339]. Within the next decades, we expect to have more information from PTA experiments.…”

Gravitational waves in models with multicritical-point principle

“…The differences in the predictions of m h φ and θ from the previous analysis solely originate from the numerical factor 0.28 in Eq. (12). The current maximally critical model tends to predict a slightly larger mass of h φ compared with the previous one.…”

“…Gravitational Wave (GW) astronomy [1,2,3] is one of the most fascinating research fields because it allows us to explore the physics of the early universe, complementary to the cosmic microwave background (CMB) observations. Gravitational waves from compact binaries [4,5,6] and stochastic background [7,8,9,10,11,12] allow us to test new physics models as well as gravity theories. In particular, stochastic GWs originating from first-order phase transitions (FOPTs) [13,14,15,16] have received much attention in recent years, as many new physics models predict them in the early Universe, contrary to the pure Standard Model (SM), which shows a crossover electroweak (EW) transition [17,18].…”

Generating enhanced primordial GWs during inflation with intermittent violation of NEC and diminishment of GW propagating speed

“…Recently, evidence for a commonspectrum process, which might be interpreted as a stochastic GW background (see e.g. [3][4][5][6][7][8][9][10][11][12][13] for related studies, see also [14][15][16]), was reported by the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) collaboration in their 12.5-year dataset [17] and also reported later by the Parkes Pulsar Timing Array (PPTA) collaboration [18].…”