Gravitational waves from conformal symmetry breaking

Abstract

We consider the electroweak phase transition in the conformal extension of the standard model known as SU(2)cSM. Apart from the standard model particles, this model contains an additional scalar and a gauge field that are both charged under the hidden SU(2) X . This model generically exhibits a very strong phase transition that proceeds after a large amount of supercooling. We estimate the gravitational wave spectrum produced in this model and show that its amplitude and frequency fall within the observational window of LISA. We also discuss potential pitfalls and relevant points of improvement required to attain reliable estimates of the gravitational wave production in this -as well as in more generalclass of models. In order to improve perturbativity during the early stages of transition that ends with bubble nucleation, we solve a thermal gap equation in the scalar sector inspired by the 2PI effective action formalism.

Gravitational waves from chiral phase transition in a conformally extended standard model

“…and ξ J is given in eq. (49). Although Ω sw is reduced by the reduction factor τ sw H and Ω turb is enhanced by (1 − τ sw H) and also by the identification κ turb = κ sw , the turbulence contribution Ω turb is about one order of magnitude smaller than Ω sw , because f turb /h n ∼ β/H ∼ 10 3 that is in the denominator of eq.…”

“…Since the minimum value of v − is c s for the detonations to be realized [69], we find that the minimum value of ξ w is just the Jouguet speed ξ J defined in eq. (49).…”

Strong supercooling as a consequence of renormalization group consistency

“…While the aforementioned fully consistent points are drawn in red, it different non-minimal realizations of classical scale invariance. For instance, in viable conformal models containing an extended gauge sector [12,14] strong supercooling can be circumvented by choosing O(10 −1 ) values for the extra gauge couplings. Unlike in the scalar case, this coupling is renormalized multiplicatively due to the protective gauge symmetry and therefore typically exhibits a more stable RG flow, so that sub-Planckian Landau poles can also be avoided for larger initial values of the gauge coupling at the TeV scale.…”

“…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.…”

Gravitational waves from scale-invariant vector dark matter model: probing below the neutrino-floor

“…Particularly, conformal DM models with Higgs portal are attractive because they can solve DM problem and at the same time can generate a strongly first order phase transition [8][9][10][11]. GWs due to first order phase transition have been studied within models where the scale-invariant symmetry is broken due to Coleman-Weinberg mechanism [12][13][14][15][16][17][18][19][20] or models with DM candidate [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39]. Conformal * a.mohamadnejad@ut.ac.ir symmetry also proposed as a possible solution for hierarchy problem [40].…”