Black Hole Persistence in Scalar Tensor Theories

@misc{yildirim2026black,
  title = {{Black Hole Persistence in Scalar Tensor Theories}},
  author = {Balkar Yildirim and Alan Albert Coley},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2607.02409},
  eprint = {2607.02409},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2607.02409},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - Black Hole Persistence in Scalar Tensor Theories
AU  - Balkar Yildirim
AU  - Alan Albert Coley
PY  - 2026
DA  - 2026/09/20
PB  - arXiv
DO  - 10.48550/arxiv.2607.02409
UR  - https://arxiv.org/abs/2607.02409
AB  - We construct a perturbative scalar-tensor solution describing a central inhomogeneity embedded in an evolving cosmological background, with the aim of studying black hole persistence through a nonsingular bounce. Scalar-tensor gravity provides a natural framework for realizing bouncing cosmologies, while the inclusion of a localized inhomogeneity makes the field equations substantially more difficult to solve. We therefore adopt a perturbative scheme, with perturbative parameter ε, in which the leading-order equations are solved by a spatially flat bouncing FLRW spacetime sourced by a radiation perfect fluid. At next order, a central inhomogeneity is introduced through a generalized McVittie geometry, with the perturbations encoded in the corresponding first-order metric and scalar-field functions. We first allow an anisotropic fluid with radial and tangential pressures, whose diagonal components solve the diagonal field equations. The field equations are solved as a series expansion up to 𝒪(η^4) near the bounce at η=0. The resulting perfect fluid solution contains three arbitrary functions which are constrained by requiring the spacetime to asymptote to FLRW as r→∞. With suitable initial conditions preserving the parabolic structure of the bounce, the integration constant d_0 emerges as the true perturbative parameter: all perturbations vanish as d_0→0. Finally, we find a small evolving horizon, r_h∼ d_0, which we interpret as the horizon of the central inhomogeneity. Its persistence through the bounce supports the interpretation of a black hole surviving the cosmological transition, and its evolution is not symmetric about η=0.
ER  -