Dr Kin-ya Oda (left, Osaka university) and Dr Masatoshi Yamada (right, Kyoto university).

It has been revealed that we are living on the edge of vacuum instability by the discovery of Higgs particle at the Large Hadron Collider since 2012. The determination of Higgs mass finally provides the last-missed parameter, the Higgs self coupling, to be 0.12 in the Standard Model of particle physics after nearly half century of its foundation. This value completes the initial conditions for a set of differential equations, called renormalization group (RG) equations, which govern how particles interact at very high energy scales. It turns out that the self coupling can vanish or even become negative at the Planck scale, where the quantum gravity effects become significant. We note for later reference that the Yukawa coupling between the Higgs and top quark plays a crucial role to reduce the Higgs self coupling in its RG evolution. The Higgs potential is about to become Continue reading →