Leptogenesis and dark matter through relativistic bubble walls with observable gravitational waves

Abstract

We study a scenario where both dark matter and heavy right handed neutrino (RHN) responsible for leptogenesis acquire masses by crossing the relativistic bubble walls formed as a result of a TeV scale supercooled first order phase transition (FOPT). While this leads to a large out-of-equilibrium abundance of right handed neutrino inside the bubble sufficient to produce the required lepton asymmetry, the dark matter being lighter can still remain in equilibrium with its relic being set by subsequent thermal freeze-out. A classical conformal symmetry ensures the origin of mass via FOPT induced by a singlet scalar while also ensuring supercooling leading to enhanced gravitational wave amplitude within the sensitivity of the LISA experiment. A minimal scenario with three RHN, one inert scalar doublet and one singlet scalar as additional fields beyond the standard model is sufficient to realize this possibility which also favours inert RHN dark matter over inert scalar doublet.

Criterion for ultra-fast bubble walls: the impact of hydrodynamic obstruction

“…All the above-mentioned processes depend crucially on the regime of the bubble wall expansion, making the terminal velocity ξ w a key parameter. In recent years, ultrarelativistic bubble walls (bubbles expanding with a Lorentz factor γ w ≡ 1/ 1 − ξ 2 w ≫ 1) have been used for phenomenological studies on baryogenesis [40][41][42][43][44][45] and dark matter production [46][47][48][49][50]. For the application of ultrarelativistic bubble walls, it is extremely important to determine whether the bubble wall can enter into the ultrarelativistic regime or not [51].…”

Impact of high-scale Seesaw and Leptogenesis on inflationary tensor perturbations as detectable gravitational waves

“…Therefore, it is necessary, although very challenging to find newer and complementary tests of such heavy neutrino seesaw physics and consequently the leptogenesis mechanism. Recently it has been proposed to complement these indirect tests with the observations of GWs of primordial origin such as that from cosmic strings [84], domain walls [85] and other topological defects [86] or from nucleating and colliding vacuum bubbles [87,88], graviton bremsstrahlung [89] and primordial black holes [90,91]. These previous studies on GW [35,84,86,[92][93][94][95][96][97][98] focused on the stochastic GW background from the dynamics of the scalar field, whose vacuum expectation value is responsible for the RHN mass, whereas (when it comes to leptogenesis) we only extend the SM by adding nothing more than three RHNs with hard mass terms.…”