Gravitational waves and dark radiation from dark phase transition: Connecting NANOGrav pulsar timing data and hubble tension

Spectra of stochastic gravitational waves (GW) generated in cosmological first-order phase transitions are computed within strongly correlated theories with a dual holographic description. The theories are mostly used as models of dark sectors. In particular, we consider the so-called Witten-Sakai-Sugimoto model, a SU(N) gauge theory coupled to different matter fields in both the fundamental and the adjoint representations. The model has a well-known top-down holographic dual description which allows us to perform reliable calculations in the strongly coupled regime. We consider the GW spectra from bubble collisions and sound waves arising from two different kinds of first-order phase transitions: a confinement/deconfinement one and a chiral symmetry breaking/restoration one. Depending on the model parameters, we find that the GW spectra may fall within the sensibility region of ground-based and space-based interferometers, as well as of Pulsar Timing Arrays. In the latter case, the signal could be compatible with the recent potential observation by NANOGrav. When the two phase transitions happen at different critical temperatures, characteristic spectra with double frequency peaks show up. Moreover, in this case we explicitly show how to correct the redshift factors appearing in the formulae for the GW power spectra to account for the fact that adiabatic expansion from the first transition to the present times cannot be assumed anymore.

Section: Jhep04(2021)094mentioning

confidence: 93%

Dark holograms and gravitational waves

Bigazzi

Caddeo

Cotrone

et al. 2021

“…[56], where it was found that missing O(g 4 ) terms, revealed through renormalisation scale dependence, give potentially the largest source of error for one-loop computations. 11 The amplitude of the gravitational wave spectrum depends very sensitively on the thermodynamic parameters, and these in turn have relatively large uncertainties. Although the theoretical arguments in ref.…”

Section: The Consequences For Gravitational Wave Predictionsmentioning

confidence: 99%

“…[2][3][4]), which may be visible by planned gravitational wave experiments such as LISA [5], DECIGO [6], BBO [7] and Taiji [8]. In fact recent evidence for a possible stochastic background of gravitational waves by the NANOGrav experiment [9] has been interpreted as the gravitational wave signal of a first-order phase transition [10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

On the perturbative expansion at high temperature and implications for cosmological phase transitions

Gould

Tenkanen

2021

We revisit the perturbative expansion at high temperature and investigate its convergence by inspecting the renormalisation scale dependence of the effective potential. Although at zero temperature the renormalisation group improved effective potential is scale independent at one-loop, we show how this breaks down at high temperature, due to the misalignment of loop and coupling expansions. Following this, we show how one can recover renormalisation scale independence at high temperature, and that it requires computations at two-loop order. We demonstrate how this resolves some of the huge theoretical uncertainties in the gravitational wave signal of first-order phase transitions, though uncertainties remain stemming from the computation of the bubble nucleation rate.

“…Thus, the dark QCD in the present model may also have the first-order phase transition, although the dark pion mass induced by the U(1) D gauge interaction could also affect the order of the phase transition. Once the dark QCD undergoes the first order transition at the GeV range, the gravitational waves generated at the transition could be observed by the pulsar timing array experiments (see, e.g., [52,53]).…”

Section: Phenomenology and Cosmology Of N F = 3 Modelmentioning

confidence: 99%

Oscillating composite asymmetric dark matter

Ibe

Kobayashi

Nagai

et al. 2020

The asymmetric dark matter (ADM) scenario can solve the coincidence problem between the baryon and the dark matter (DM) abundance when the DM mass is of O(1) GeV. In the ADM scenarios, composite dark matter is particularly motivated, as it can naturally provide the DM mass in the O(1) GeV range and a large annihilation cross section simultaneously. In this paper, we discuss the indirect detection constraints on the composite ADM model. The portal operators connecting the B − L asymmetries in the dark and the Standard Model(SM) sectors are assumed to be generated in association with the seesaw mechanism. In this model, composite dark matter inevitably obtains a tiny Majorana mass which induces a pair-annihilation of ADM at late times.We show that the model can be efficiently tested by the searches for gamma-ray from the dwarf spheroidal galaxies. *