Higgs-Inflaton Mixing and Vacuum Stability
  The quartic and trilinear Higgs field couplings to an additional real scalar
are renormalizable, gauge and Lorentz invariant. Thus, on general grounds, one
expects such couplings between the Higgs and an inflaton in quantum field
theory. In particular, the (often omitted) trilinear coupling is motivated by
the need for reheating the Universe after inflation, whereby the inflaton
decays into the Standard Model (SM) particles. Such a coupling necessarily
leads to the Higgs-inflaton mixing, which could stabilize the electroweak
vacuum by increasing the Higgs self-coupling. We find that the inflationary
constraints on the trilinear coupling are weak such that the Higgs-inflaton
mixing up to order one is allowed, making it accessible to colliders. This
entails an exciting possibility of a direct inflaton search at the LHC.
