Probing a classically conformal B−L model with gravitational waves

Abstract

We study the cosmological history of the classical conformal B − L gauge extension of the standard model, in which the physical scales are generated via the Coleman-Weinberg-type symmetry breaking. Especially, we consider the thermal phase transition of the U(1)B−L symmetry in the early universe and resulting gravitational-wave production. Due to the classical conformal invariance, the phase transition tends to be a first-order one with ultra-supercooling, which enhances the strength of the produced gravitational waves. We show that, requiring (1) U(1)B−L is broken after the reheating, (2) the B −L gauge coupling does not blow up below the Planck scale, (3) the thermal phase transition completes in almost all the patches in the universe, the gravitational wave spectrum can be as large as ΩGW ∼ 10 −8 at the frequency f ∼ 0.01-1Hz for some model parameters, and a vast parameter region can be tested by future interferometer experiments such as eLISA, LISA, BBO and DECIGO.

Gravitational waves from hidden QCD phase transition

“…Consequently, because of the resonance condition m S 2m DM , the DM mass is bounded, too. Similarly, Λ H is bounded, because λ HS is bounded from above (24) and from below due to our parameter choice λ HS > 10 for each benchmark case is given in Table I. Under y 0.006 and (24), Cases A and B are located as close to the EW scale as possible and for C and D in an opposite way.…”

“…We require the perturbativity and stability condition (3) of the scalar potential for y 0.006 to be satisfied up to the Planck scale at the one-loop level. 2 We find that 0.13 λ H 0.14, 0 < λ HS < 0.12, 4λ 2 HS /λ H < λ S 0.23 (24) should be satisfied to meet the requirements. The inequality 0 < λ HS is our assumption (see (3)), and the interval of λ H is due to the observed Higgs mass.…”

“…However, if the SM is extended, observable GW signals associated with a symmetry breaking may be produced and tested in future experiments such as LISA [12,13] and DECIGO [14][15][16] as discussed in [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33].…”

Testing the Seesaw Mechanism and Leptogenesis with Gravitational Waves

“…Firstly, super-cooling increases the duration of the phase transition leading to larger bubbles whose collisions emit lower frequency gravitational waves and secondly in such a scenario the temperature the phase transition takes places is significantly lower than the breaking scale, T * v. In principle, if T * v/10 high frequency gravitational wave experiments are sensitive to the lower range of parameter space v ∼ 10 9 GeV. Some work has done in this direction [45,46], however, for a more generic probe of phase transitions from the seesaw scale, high-frequency gravitational wave detectors are required. Such a detector provides a unique tool to uncover physics at very early Universe, and hence should be pursued.…”

The Higgs of the Higgs and the diphoton channel

“…Both models give rise to an extended phase transition when the diphoton and the Higgs acquire vacuum expectation values. Such phase transition can be of first order, possibly giving gravitational wave signals [106] and the baryon asymmetry [107].…”