Gravitational waves from first-order phase transitions: LIGO as a window to unexplored seesaw scales

Abstract

Within a recently proposed classically conformal model, in which the generation of neutrino masses is linked to spontaneous scale symmetry breaking, we investigate the associated phase transition and find it to be of strong first order with a substantial amount of supercooling. Carefully taking into account the vacuum energy of the meta-stable minimum, we demonstrate that a significant fraction of the model's parameter space can be excluded simply because the phase transition cannot complete. We argue this to be a powerful consistency check applicable to general theories based on classical scale invariance. Finally, we show that all remaining parameter points predict a sizable gravitational wave signal, so that the model can be fully tested by future gravitational wave observatories. In particular, most of the parameter space can already be probed by the upcoming LIGO science run starting in early 2019.

Strong supercooling as a consequence of renormalization group consistency

“…while that of the Goldstone bosons matches Π φ (T ) from Eq. (13). Thermal mass-squares for r and the Goldstone bosons are simply calculated as the sum of field-dependent tree-level mass-squares and the respective thermal part Π.…”

“…Refs. [8,13]. This type of transition is known to proceed via the nucleation of bubbles containing the true ground state, which subsequently grow inside an expanding Universe that is still in the metastable phase.…”

“…One such approach is built around models based on classical scale invariance [1][2][3][4][5][6][7], in which the Lagrangian contains exclusively dimensionless parameters and where all mass scales arise by dimensional transmutation. Apart from their connection to the hierarchy problem, classically scale-invariant theories recently received some attention because of the role they could play in facilitating strongly supercooled phase transitions with various interesting implications for the physics of the early Universe and the detection of gravitational waves [8][9][10][11][12][13][14][15]. In the present paper we will investigate the interplay between the aforementioned two crucial features of scaleinvariant models more closely.…”

“…Alternatively, the electroweak scale can be radiatively generated from quantum fluctuations of heavy right-handed neutrinos [18][19][20][21][22], which simultaneously produce light active neutrino masses via the type-I seesaw mechanism [23][24][25][26]. Interestingly, both methods of scale transmission are anticipated to be testable by gravitational wave detectors [8,13]. In this work, we will concentrate on the minimal portal model [27,28], which can additionally be probed at colliders.…”

Gravitational waves from phase transition in minimal SUSY U(1)B−L model

“…Recent work on gravitational waves from the breaking of a new visible U(1) gauge group that occurs separately from electroweak symmetry breaking includes [14,15,16,17,18].…”