Speaker
Description
We construct and classify asymptotically flat, static, and spherically symmetric hairy black hole solutions in $U(1)$ gauge-invariant scalar-vector-tensor (SVT) theories [1] carrying both electric and magnetic charges. Extending previous analyses beyond the second-order SVT interaction [2], we include the third- and fourth-order SVT interactions in dyonic backgrounds [3]. We show that the fourth-order SVT interaction generically gives rise to higher-derivative terms in the field equations and derive the condition required to eliminate them, thereby ensuring that the field equations remain second order.
We classify the obtained solutions based on their symmetry properties: shift-symmetric couplings yield secondary hair governed by the Noether current, whereas $\phi$-dependent interactions generate primary hair. Crucially, our analysis reveals that the magnetic charge plays a key role in activating specific interaction sectors such as the third-order SVT interaction $\tilde{f}_3$, which does not appear in the field equations in purely electric configurations. We also clarify the behavior of the solutions in the vanishing monopole limit ($P\to0$). Depending on the interaction sector and the solution branch, the solutions either continuously reduce to the Reissner-Nordstr\"om solution or retain nontrivial scalar hair in the purely electric limit. The scalar field exhibits interaction-dependent asymptotic falloff rates, which may lead to distinct phenomenology. For the branches admitting global solutions, we connect the near-horizon and asymptotic solutions through numerical integration and confirm that the fields remain finite and smooth throughout the exterior region.
[1] L. Heisenberg, JCAP 10 (2018), 054, arXiv:1801.01523 [gr-qc].
[2] K. Taniguchi, S. Takagishi, and R. Kase, Phys. Rev. D 110, 044006 (2024), arXiv:2403.17484 [gr-qc].
[3] M. Kitagawa, N. Tsukamoto, and R. Kase, arXiv:2603.04884 [gr-qc].