Search

Abstract We study the stability of neutral electroweak vacua in two Higgs doublet models, and calculate the lifetime of these states when the parameters are such that they are false vacua. As the two Higgs doublet model is invariant under a sign change of both doublets, degenerate true vacua exist. It is shown that this degeneracy, despite the fact that each of these minima locally describes the same physics, can immensely affect their lifetime. We apply these calculations to the parameter space of the models which is allowed by recent LHC searches, and infer combinations of parameters which should be excluded on grounds of a tunneling time inferior to the age of the universe.

Abstract It has been recently shown that, contrary to an intuitive decoupling argument, the presence of new physics at very large energy scales (say around the Planck scale) can have a strong impact on the electroweak vacuum lifetime. In particular, the vacuum could be totally destabilized. This study was performed in a flat spacetime background, and it is important to extend the analysis to curved spacetime since these are Planckian-physics effects. It is generally expected that under these extreme conditions gravity should totally quench the formation of true vacuum bubbles, thus washing out the destabilizing effect of new physics. In this work we extend the analysis to curved spacetime and show that, although gravity pushes toward stabilization, the destabilizing effect of new physics is still (by far) the dominating one. In order to get model independent results, high energy new physics is parametrized in two different independent ways: as higher order operators in the Higgs field, or introducing new particles with very large masses. The destabilizing effect is observed in both cases, hinting at a general mechanism that does not depend on the parametrization details for new physics, thus maintaining the results obtained from the analysis performed in flat spacetime.

Assuming that the particle with mass ∼126  GeV discovered at LHC is the standard model Higgs boson, we find that the stability of the electroweak (EW) vacuum strongly depends on new physics interaction at the Planck scale MP, despite of the fact that they are higher-dimensional interactions, apparently suppressed by inverse powers of MP. In particular, for the present experimental values of the top and Higgs boson masses, if τ is the lifetime of the EW vacuum, new physics can turn τ from τ≫TU to τ≪TU, where TU is the age of the Universe, thus, weakening the conclusions of the so called metastability scenario.

The fluctuation-dissipation theorem (FDT) is very general and applies to a broad variety of different physical phenomena in condensed matter physics. With the help of the FDT and following the famous work of Caldeira and Leggett, we show that, whenever linear response theory applies, any generic bosonic or fermionic system at finite temperature T can be mapped onto a fictitious system of free-harmonic oscillators. To the best of our knowledge, this is the first time that such a mapping is explicitly worked out. This finding provides further theoretical support to the phenomenological harmonic oscillator models commonly used in condensed matter. Moreover, our result helps in clarifying an interpretation issue related to the presence and physical origin of the Bose-Einstein factor in the FDT.