A Potential Black Hole Mimicker From Non-Minimal Coupling
Abstract
We present a class of horizonless, regular ultra-compact objects arising in a theory of gravity that allows curvature-fluid coupling. The non-minimal interaction between fluid variables and the Ricci scalar generates a vacuum-like equation of state in the interior, while the exterior remains exactly Schwarzschild. The two spacetimes are glued through a thin shell at the junction. The interior metric is non-singular, the shell acquires a stiff-matter equation of state, and near-horizon compactness allows the configuration to mimic black-hole phenomenology without an event horizon. For radii in the astrophysically motivated range $5−−7$ km, imposed as an external input rather than predicted by the theory, the model's mass-compactness relation maps this radius window onto a mass window of $1.4−2.1 M_\odot$ for a suitable choice of the curvature-fluid coupling coefficient. We carry out a detailed stability analysis of the shell in the frozen-bulk approximation, identify the compactness window in which the interior is everywhere regular and the shell is stable, and quantify the accuracy of the frozen-bulk approximation through an explicit adiabaticity parameter. We then develop the surface thermodynamics of the shell assuming a first order phase transition-like origin of the ultra-compact object. This idea then gives rise to shell temperature and radiation, the shell temperature scaling TΣ∝ M−1/2 turns out to be a falsifiable predictions of the model.
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BibTeX
@misc{debnath2026potential,
title = {{A Potential Black Hole Mimicker From Non-Minimal Coupling}},
author = {Debanjan Debnath and Rikpratik Sengupta and Kaushik Bhattacharya},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2606.19291},
eprint = {2606.19291},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.19291},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - A Potential Black Hole Mimicker From Non-Minimal Coupling
AU - Debanjan Debnath
AU - Rikpratik Sengupta
AU - Kaushik Bhattacharya
PY - 2026
DA - 2026/09/27
PB - arXiv
DO - 10.48550/arxiv.2606.19291
UR - https://arxiv.org/abs/2606.19291
AB - We present a class of horizonless, regular ultra-compact objects arising in a theory of gravity that allows curvature-fluid coupling. The non-minimal interaction between fluid variables and the Ricci scalar generates a vacuum-like equation of state in the interior, while the exterior remains exactly Schwarzschild. The two spacetimes are glued through a thin shell at the junction. The interior metric is non-singular, the shell acquires a stiff-matter equation of state, and near-horizon compactness allows the configuration to mimic black-hole phenomenology without an event horizon. For radii in the astrophysically motivated range $5−−7$ km, imposed as an external input rather than predicted by the theory, the model's mass-compactness relation maps this radius window onto a mass window of $1.4−2.1 M_\odot$ for a suitable choice of the curvature-fluid coupling coefficient. We carry out a detailed stability analysis of the shell in the frozen-bulk approximation, identify the compactness window in which the interior is everywhere regular and the shell is stable, and quantify the accuracy of the frozen-bulk approximation through an explicit adiabaticity parameter. We then develop the surface thermodynamics of the shell assuming a first order phase transition-like origin of the ultra-compact object. This idea then gives rise to shell temperature and radiation, the shell temperature scaling T_Σ∝ M^−1/2 turns out to be a falsifiable predictions of the model.
ER -