The cosmological Higgstory of the vacuum instability
http://arxiv.org/abs/1505.04825
The Standard Model Higgs potential becomes unstable at large field values. After clarifying the issue of gauge dependence of the effective potential, we study the cosmological evolution of the Higgs field in presence of this instability throughout inflation, reheating and the present epoch. We conclude that anti-de Sitter patches in which the Higgs field lies at its true vacuum are lethal for our universe. From this result, we derive upper bounds on the Hubble constant during inflation, which depend on the reheating temperature and on the Higgs coupling to the scalar curvature or to the inflaton. Finally we study how a speculative link between Higgs meta-stability and consistence of quantum gravity leads to a sharp prediction for the Higgs and top masses, which is consistent with measured values.
Why should we care about the top quark Yukawa coupling?
http://arxiv.org/abs/1411.1923
In the cosmological context, for the Standard Model to be valid up to the scale of inflation, the top quark Yukawa coupling yt should not exceed the critical value ycritt, coinciding with good precision (about 0.02%) with the requirement of the stability of the electroweak vacuum. So, the exact measurements of yt may give an insight on the possible existence and the energy scale of new physics above 100 GeV, which is extremely sensitive to yt. We overview the most recent theoretical computations of ycritt and the experimental measurements of yt. Within the theoretical and experimental uncertainties in yt the required scale of new physics varies from 107 GeV to the Planck scale, urging for precise determination of the top quark Yukawa coupling.
