Gravitational waves from fundamental axion dynamics

Abstract

A totally asymptotically free QCD axion model, where all couplings flow to zero in the infinite energy limit, was recently formulated. A very interesting feature of this fundamental theory is the ability to predict some low-energy observables, like the masses of the extra fermions and scalars. Here we find and investigate a region of the parameter space where the Peccei-Quinn (PQ) symmetry is broken quantum mechanically through the Coleman-Weinberg mechanism. This results in an even more predictive framework: the axion sector features only two independent parameters (the PQ symmetry breaking scale and the QCD gauge coupling). In particular, we show that the PQ phase transition is strongly first order and can produce gravitational waves within the reach of future detectors. The predictivity of the model leads to a rigid dependence of the phase transition (like its duration and the nucleation temperature) and the gravitational wave spectrum on the PQ symmetry breaking scale and the QCD gauge coupling.

Gravitational waves from an axion-dark photon system: A lattice study

“…3 Dark photons of this type can appear in UV complete axion models [15]. GW probes of axion models have also been explored in the context of phase transitions [16][17][18][19][20] and inflation/preheating [21][22][23][24][25].…”

Prospects of gravitational waves in the minimal left-right symmetric model

“…The condition of the strong FOPT in the new physics beyond the SM can be more easily realized when the Higgs sector includes more scalars [52]. For example, there are works on a singlet extension of the SM [53][54][55][56] or more than one singlet extension [57][58][59][60], two-Higgs-doublet models (2HDMs) [61][62][63][64] or other doublet extensions [65,66], models with triplet extension [67], SUSY models [68][69][70][71], composite models [72][73][74] and walking technicolor models [75][76][77], twin Higgs models [78], Pati-Salam model [79,80], the left-right SU(4) model [81,82] motived by the B physics anomalies, Gorgi-Machacek model [83], axion or axion-like particle models [84][85][86], extra dimensional models [87], models with charged singlet [88], seesaw models [89], models with hidden sectors [90][91][92] and dark matter (DM) models [93][94]…”

Vacuum bubble collisions: From microphysics to gravitational waves

“…Such a circumstance appears fine-tuned in Higgs transitions within minimal electroweak extensions, due both to the relatively small supercooling necessary for percolation to complete in allowed regions of parameter space [12][13][14][15][16][17][18] and also the relatively large friction caused by the Higgs field's interactions with Standard Model particles [19][20][21][22][23]. On the other hand, in dark sectors with relatively few degrees of freedom [24][25][26][27], in nearconformal extensions of the Standard Model [28][29][30], and in certain QCD axion models [31], a large degree of supercooling is more feasible.…”