Electroweak symmetry breaking in the inverse seesaw mechanism

We investigate the stability of Higgs potential in inverse seesaw models. We derive the full two-loop RGEs of the relevant parameters, such as the quartic Higgs self-coupling, taking thresholds into account. We find that for relatively large Yukawa couplings the Higgs quartic self-coupling goes negative well below the Standard Model instability scale ∼ 1010 GeV. We show, however, that the “dynamical” inverse seesaw with spontaneous lepton number violation can lead to a completely consistent and stable Higgs vacuum up to the Planck scale.

Nucleon and dinucleon decays to leptonic final states in a left-right symmetric model with large extra dimensions

We consider baryon-number-violating nucleon and dinucleon decays to leptonic final states in the context of a left-right symmetric (LRS) model with large extra dimensions. Specifically, we study (a) nucleon to trilepton decays with $$\varDelta B=-1$$ Δ B = - 1 and $$\varDelta L=-3$$ Δ L = - 3 , and (b) dinucleon to dilepton decays with $$\varDelta B=-2$$ Δ B = - 2 and $$\varDelta L=-2$$ Δ L = - 2 . In the LRS model, $$B-L$$ B - L is gauged and is spontaneously broken by a Higgs vacuum expectation value $$v_R$$ v R , which characterizes the scale at which processes violating $$B-L$$ B - L occur. We show that together with the lower bound on $$v_R$$ v R from experimental limits on n-$${\bar{n}}$$ n ¯ oscillations, constraints from searches for other nucleon decay modes imply sufficient suppression of these nucleon to trilepton and dinucleon to dilepton decay modes in this model to agree with experimental bounds.

On catalyzed vacuum decay around a radiating black hole and the crisis of the electroweak vacuum

False vacuum decay is a key feature in quantum field theories and exhibits a distinct signature in the early Universe cosmology. It has recently been suggested that the false vacuum decay is catalyzed by a black hole (BH), which might cause the catastrophe of the Standard Model Higgs vacuum if primordial BHs are formed in the early Universe. We investigate vacuum phase transition of a scalar field around a radiating BH with taking into account the effect of Hawking radiation. We find that the vacuum decay rate slightly decreases in the presence of the thermal effect since the scalar potential is stabilized near the horizon. However, the stabilization effect becomes weak at the points sufficiently far from the horizon. Consequently, we find that the decay rate is not significantly changed unless the effective coupling constant of the scalar field to the radiation is extremely large. This implies that the change of the potential from the Hawking radiation does not help prevent the Standard Model Higgs vacuum decay catalyzed by a BH.

Higgs inflation, vacuum stability, and leptogenesis

We consider the introduction of a complex scalar field carrying a global lepton number charge to the Standard Model and the Higgs inflation framework. The conditions are investigated under which this model can simultaneously ensure Higgs vacuum stability up to the Planck scale, successful inflation, non-thermal Leptogenesis via the pendulum mechanism, and light neutrino masses. These can be simultaneously achieved when the scalar lepton is minimally coupled to gravity, that is, when standard Higgs inflation and reheating proceed without the interference of the additional scalar degrees of freedom. If the scalar lepton also has a non-minimal coupling to gravity, a multi-field inflation scenario is induced, with interesting interplay between the successful inflation constraints and those from vacuum stability and Leptogenesis. The parameter region that can simultaneously achieve the above goals is explored.

COSMOLOGICAL CONSTANT, PLANCK MASS, HUBBLE MASS AND AXION: A RELATION THROUGH HIGHER-ORDER LOOPS COLEMAN-WEINBERG POTENTIAL WITH WEINBERG/LANDAU GAUGE

In this communication, a conformal coupling gravity is discussed in the presence of a complex Coleman-Weinberg potential which is generated from the contributions from 1st, 2nd and all higher order loops. A relation between the cosmological constant, the Hubble mass and the Higgs vacuum energy is obtained in particular when Weinberg/Landau gauge is used. Moreover, it was observed that the removal of the logarithmic mass boosts the scalar mass from Hubble mass of order 10⁻³³eV to 2.47× 10⁻³eV which is comparable to the mass of non-baryonic Cold Dark Matter or axion based on recent observations and which constitutes about 84% of all matter in the Universe.