Speaker
Description
Effects of ultraviolet completions of gravity can be captured
in low-energy regimes by local higher curvature corrections. Such
description, however, is limited to yield strictly perturbative
corrections, due to unphysical Ostrogradsky instabilities induced by
higher derivatives in the correction terms. I will present a procedure
for expunging spurious degrees of freedom from effective theories of
gravity, and casting them as lower-derivative theories that capture all
the information about the corrections, but propagates only the massless
spin-2 graviton degree of freedom. Resulting reduced theories fall under
the category of Minimally modified gravity theories, that preserve
spatial diffeomorphisms, but modify temporal diffeomorphisms in a way
that preserves the constraint structure. Such theories are free from
Ostrogradsky instabilities, and can be used to study the ultraviolet
effects self-consistently.
