@article{oai:nagoya.repo.nii.ac.jp:02001531, author = {Nojiri, Shin’ichi and Odintsov, Sergei D. and Faraoni, Valerio}, issue = {4}, journal = {Physical Review D}, month = {Feb}, note = {We construct models of Einstein and f(R) gravity with two scalar fields, which admit analytical solutions describing time-varying dynamical black holes. Their thermodynamics is investigated in the adiabatic approximation. In addition to the Misner-Sharp-Hernandez quasilocal mass, we provide time-dependent thermodynamical quantities, including the Hawking temperature, Helmholtz free energy, entropy, and thermodynamical energy. The latter does not always coincide with the Misner-Sharp-Hernandez mass at the horizon, although they coincide in the static limit. For Schwarzschild-type (i.e., gttgrr=−1) black holes in Einstein gravity, one of the two scalars is always a ghost with negative kinetic energy. We show that this ghost can be avoided in f(R) gravity.}, title = {Searching for dynamical black holes in various theories of gravity}, volume = {103}, year = {2021} }