arXiv subjects

Shoupan Liu

Publications and source records attributed to Shoupan Liu.

4 recordsLinked to original sources

arXiv2026

Quasi-equilibrium tidal folds of white dwarfs around rotating black holes in shift-symmetric Einstein--scalar--Gauss--Bonnet gravity

We examine how the geometry of rotating black holes in linear, shift-symmetric Einstein--scalar--Gauss--Bonnet (EsGB) gravity changes the limiting tidal equilibria of white dwarfs (WDs). The relativistic tidal field is obtained from numerical EsGB backgrounds in a parallel-transported frame and coupled to a compressible affine model. Comparisons with Kerr black holes matched in Arnowitt--Deser--Misner (ADM) mass and angular momentum show a positive shift in the orbital frequency at the tidal fold. At fixed spin the relative correction follows an approximately quadratic dependence on the EsGB coupling, consistent with the leading response of the metric to the scalar field. Over the sampled backgrounds, the relative correction reaches order $10^{-3}$. Black hole rotation also changes the relation between the tidal fold and the innermost stable circular orbit (ISCO): the sampled prograde folds remain outside the ISCO, while retrograde folds move inside it at higher spins. Orbital orientation therefore controls whether tidal equilibrium is lost before the orbital stability limit is reached. For the stellar and black hole masses considered here, the characteristic gravitational wave (GW) frequencies fall in the millihertz band relevant to planned space based interferometers. Future GW observations capable of resolving deviations from Kerr predictions could constrain the EsGB coupling.

gr-qc↗

arXiv2025

Wiggling boundary and corner edge modes in JT gravity with defects

We study the gravitational edge modes (GrEMs) and gauge edge modes (GaEMs) in Jackiw-Teitelboim (JT) gravity on a wiggling boundary. The wiggling effect manifests as a series of spacetime topological and bulk constraints for both conical and wormhole defect solutions. For the conical defect solution, we employ the generalized Fefferman-Graham (F-G) gauge to extend the boundary action, allowing for non-constant temperature and horizon position. We find that the infrared behavior of this boundary action is determined by the local dynamics of the temperature and horizon. For the wormhole defect solution, the boundary action can, in special cases, be described by a field with variable mass subject to a constant external force. We classify this corner system as a first-class constrained system influenced by field decomposition, confirming that the physical degrees of freedom are determined by constraints from the wiggling boundary information. We find that GrEMs and GaEMs can be linked at the corners by imposing additional constraints. Additionally, we show that the ``parallelogram'' composed of corner variables exhibits discreteness under a unitary representation. Finally, we explore that information from extrinsic vectors can be packaged into the GaEMs via a Maurer-Cartan form, revealing the boundary degrees of freedom as two copies of the $\mathfrak{sl}(2,\mathbb{R})$ algebra. By separating pure gauge transformations, we identify the gluing condition for gauge invariance and the corresponding integrable charges.

hep-th↗

arXiv2025

Non-linearly scalarized supermassive black holes

In this study, we investigate a nonlinear mechanism driving the formation of scalarized rotating black holes within a scalar-Gauss-Bonnet gravity framework that includes an additional squared Gauss-Bonnet term. With the specific coupling function, Kerr metric is a solution to this modified gravity. In linear level Kerr black holes are stable against the scalar perturbation, while nonlinearly they suffer the so-called ``nonlinear scalarization" and are unstable. By employing a pseudo-spectral method, we derive the spectrum of nonlinearly scalarized rotating black hole solutions, revealing multiple scalarized branches. Our analysis demonstrates that both the black hole's spin and the additional squared Gauss-Bonnet term significantly influence the existence and properties of these solutions. Furthermore, we explore the thermodynamic properties of nonlinearly scalarized rotating black holes, and find that the scalarized black holes are entropically favored over Kerr black holes of the same mass and spin across a wide range of parameters.

gr-qc↗

arXiv2025

Rotating scalarized supermassive black holes

In this study, we investigate rotating black hole solutions within a scalar Gauss-Bonnet gravity framework that incorporates a squared Gauss-Bonnet term. By employing a quadratic exponential coupling function between the scalar field and the Gauss-Bonnet invariant, we derive both the standard General Relativity solutions and novel scalarized black hole configurations. Utilizing a pseudo spectral method to solve the coupled field equations, we examine how black hole spin and coupling constants influence the existence and properties of these solutions. Our findings reveal that both the rotation of the black hole and the squared coupling term effectively constrain the parameter space available for scalarization. Moreover, we demonstrate that, over a wide range of parameters, scalarized black holes exhibit higher entropy than Kerr black holes of equivalent mass and spin, indicating that they are thermodynamically favored. These results significantly expand the phase space of black holes in modified gravity theories.

gr-qc↗