Higgs inflation in metric and Palatini formalisms: required suppression of higher dimensional operators

Abstract

© 2020 IOP Publishing Ltd and Sissa Medialab. We investigate the sensitivity of Higgs(-like) inflation to higher dimensional operators in the nonminimal couplings and in the potential, both in the metric and Palatini formalisms. We find that, while inflationary predictions are relatively stable against the higher dimensional operators around the attractor point in the metric formalism, they are extremely sensitive in the Palatini one: for the latter, inflationary predictions are spoiled by vertical bar xi(4)vertical bar greater than or similar to 10(-6) in the nonminimal couplings (xi(2)phi(2) + xi(4)phi(4) + ...) R, or by vertical bar lambda(6)vertical bar greater than or similar to 10(-16) in the Jordan-frame potential lambda(4)phi(4) + lambda(6)phi(6) + ... (both in Planck units). This extreme sensitivity results from the absence of attractor in the Palatini formalism. Our study underscores the challenge of realizing inflationary models with the nonminimal coupling in the Palatini formalism