Seminarium "Teoria cząstek elementarnych i kosmologia"

According to the current experimental data, the SM Higgs vacuum appears to be metastable due to the development of a second, lower ground state in the Higgs potential. Since vacuum decay would induce nucleation of the true vacuum bubbles, with catastrophic consequences for our false-vacuum Universe, we are motivated to study possible stabilising mechanisms in the early Universe. In our current investigation, we study the experimentally motivated metastability of the electroweak vacuum in the context of inflation, with a particular emphasis on the observationally favoured model of Starobinsky inflation. The focus of our work has been to calculate the probability of the false vacuum to decay during the period of inflation, and use it to constrain the parameter $\xi$ that couples the Higgs field with space-time curvature. Following the motivation and techniques from our first study [arXiv:2011.037633], we wish to obtain similar constraints on the Higgs-curvature coupling $\xi$, while treating Starobinsky inflation more rigorously. Thus, we embed the SM into the modified gravity scenario $R + R^2$, that introduces Starobinsky inflation naturally, with significant repercussions for the effective Higgs potential in the form of additional negative terms that destabilize the vacuum. Our results dictate stronger lower $\xi$-bounds that are very sensitive to the final moments of inflation when bubble nucleation is most prominent [arXiv:2207.00696].