arXiv subjects

Ze-Hua Wu

Publications and source records attributed to Ze-Hua Wu.

3 recordsLinked to original sources

arXiv2026

Exact Toda Black Holes of Rank-2 Lie Groups

We consider Einstein gravity coupled to two Maxwell fields and one dilatonic scalar, and construct spherically-symmetric and static black holes that are charged under both Maxwell fields in general $D$ dimensions. We find that for suitable dilaton couplings, the equations of motion can be cast into one-dimensional Toda equations of all rank-2 Lie groups. We devise a brute-force approach to obtain the most general but remarkably elegant solutions to the Toda equations. This allows us to construct exact black holes associated with all the rank-2 Lie groups. We study their thermodynamics and verify explicitly an earlier claim in the literature that all these thermodynamic quantities can be derived without having to solve for these black hole solutions.

hep-th↗

arXiv2024

Charging the Love numbers: Charged scalar response coefficients of Kerr-Newman black holes

We study the electrically-charged massless scalar response to the general Kerr-Newman black hole and obtain the exact (complex) response coefficients, whose real parts are the Love numbers. We find there is a curious discontinuity between the neutral and charged scalar. The Love numbers vanish for the neutral scalar, but are inversely proportional to the electric charge of the scalar in the small charge limit. We study the near-zone of the dynamical equation with non-vanishing frequency $ω$, and show that the system have an $SL(2,\mathbb{R})$ Love-like symmetry. The symmetry selects a special frequency $ω_{\rm cr}$, which vanishes in the neutral case, so that the real part of the response coefficient vanishes identically. We also generalize the results into higher dimensions to some extend.

gr-qc↗

arXiv2024

Superradiant Instability of Charged Extremal Black Holes in Einstein-Born-Infeld Gravity

We study charged scalar perturbations of charged extremal black holes in Einstein-Born-Infeld theory. Our numerical results indicate that these black holes all suffer from superradiant instability by the unstable quasi-bound states, regardless how small the coupling constant is. We therefore provide a new example that the superradiant stability of the Reissner-Nordström black hole is a fine-tuned result, as in the case when it is embedded in the STU supergravity model. The work is also motivated by the weak gravity conjecture since at the linear coupling constant level, the theory belongs to a subsect of four-derivative corrections in the effective field theory. Our results appear to support the notion that the black holes do decay when gravity is weaker by the correction, but the decaying halftime requires nonlinear effects and cannot be seen at the level of linear coupling constant. The full nonlinear effects also indicate that the black holes can decay even when gravity is stronger.

hep-th↗