  We propose a new method to account for quantum-gravitational effects in
cosmological and black hole spacetimes. At the core of our construction is the
"decoupling mechanism": when a physical infrared scale overcomes the effect of
the regulator implementing the Wilsonian integration of fluctuating modes, the
renormalization group flow of the scale-dependent effective action freezes out,
so that at the decoupling scale the latter approximates the standard quantum
effective action. Identifying the decoupling scale allows to access terms in
the effective action that were not part of the original truncation and thus to
study leading-order quantum corrections to field equations and their solutions.
Starting from the Einstein-Hilbert truncation, we exploit for the first time
the decoupling mechanism in quantum gravity to investigate the dynamics of
quantum-corrected black holes from formation to evaporation. Our findings are
in qualitative agreement with previous results in the context of
renormalization group improved black holes, but additionally feature novel
properties reminiscent of higher-derivative operators with specific non-local
form factors.
