Ryotaku Suzuki

We present an exact solution describing multirotating black holes in 4D Einstein-Maxwell-dilaton theory, which can be obtained from 5D Kaluza-Klein theory via dimensional reduction. The solution represents a multicentered configuration of rotating black holes carrying both electric and magnetic charges, with each black hole possessing a non-aligned angular momentum. This work generalizes our previous solution for black holes with aligned angular momenta to the more general case of nonaligned angular momenta. It includes, as special cases, the Majumdar-Papapetrou solution, the recent multicentered rotating black hole solutions of Teo and Wan, and our previous solution with unequal electric and magnetic charges. The resulting spacetimes are free of curvature singularities and closed timelike curves, both on and outside the horizons, provided that the magnitude of the spin angular momentum of each black hole remains below a certain upper bound. The absence of conical singularities has not been established for the general case with nonaligned angular momenta.

We present a new family of multicentered rotating black hole solutions in 5D vacuum Einstein gravity, providing explicit examples of cohomogeneity-three spacetimes. It is well known that, in the presence of two commuting Killing vector fields, the theory reduces to 3D gravity coupled to an S L ( 3 , R ) nonlinear sigma model with five scalar fields. We show that the scalar fields of the extremal Myers-Perry solution can be expressed in terms of two harmonic functions on 3D flat space, and that promoting these functions to include multiple sources yields explicit multicentered extremal Myers-Perry black holes located at arbitrary positions. Each center forms a smooth S 3 Killing horizon, provided that the rotation parameters satisfy | j i | < 1 / 2 . We further demonstrate that all curvature singularities are hidden behind the horizons and that no closed timelike curves arise on or outside the horizons. The solutions are asymptotically locally Minkowski in the sense that constant-time hypersurfaces are asymptotically locally Euclidean. As a concrete example, we consider a binary configuration, examine its rod structure, and demonstrate the absence of conical singularities between the two black holes, indicating that they are supported by an intermediate bubble region separating them.

We study the conditions under which nonsingular black hole solutions can exist in General relativity coupled to nonlinear electrodynamics, focusing on Lagrangians that depend on two electromagnetic invariants F and G . In particular, we derive a necessary criterion that the Lagrangian L ( F , G ) must satisfy for static, spherically symmetric dyonic black hole solutions to exist without curvature singularities. We demonstrate that this criterion is consistent with known no-go theorems for one-parameter Lagrangians L ( F ) , while allowing for new possibilities in two-parameter models. As an explicit example, we construct a simple Lagrangian that satisfies the criterion and supports a nonsingular dyonic configuration. We also present several additional models that satisfy the criterion, which may serve as possible candidates for supporting nonsingular dyonic solutions.

We construct an exact solution in four-dimensional Einstein-Maxwell-dilaton theory describing multicentered rotating black holes carrying both electric and magnetic charges obtained via dimensional reduction from five-dimensional Einstein gravity. This generalizes the Majumdar-Papapetrou solution to the rotating case and extends the recent multicentered rotating black hole solutions of Teo and Wan to configurations with unequal electric and magnetic charges. The resulting spacetimes are free of curvature singularities, conical defects, Dirac-Misner strings, and closed timelike curves, both on and outside the horizons, provided that the black holes have either aligned or antialigned spin orientations.

The topological censorship theorem suggests that higher-dimensional black holes can possess a domain of outer communication (DOC) of nontrivial topology. In this paper, we seek for a black hole coexisting with two bubbles adjacent to the horizon in five-dimensional minimal supergravity, under the assumptions of stationarity and biaxisymmetry. For simplicity, we also assume that the spacetime is symmetric under the exchange of the two axisymmetric Killing vectors. To find the solution, we combine the inverse scattering method and the Harrison transformation, and we present the conditions for the absence of conical, orbifold, and Dirac-Misner string singularities, respectively. As the result, we find that the black hole with topology of S 3 or S 2 × S 1 can be supported by two bubbles if we admit the conical singularities (deficits). Published by the American Physical Society 2025

We present a new non-BPS solution describing an asymptotically flat, stationary, biaxisymmetric capped black hole in the bosonic sector of five-dimensional minimal supergravity. This solution describes a spherical black hole, while the exterior region of the horizon exhibits a nontrivial topology of [ R 4 # C P 2 ] \ B 4 on a time slice. This solution extends our previously constructed three-parameter solution to a more general four-parameter solution. To derive this solution, we utilize a combination of the Ehlers and Harrison transformations and then impose appropriate boundary conditions on the solution’s parameters. It can be shown that the resultant solution is free from curvature, conical, Dirac-Misner string and orbifold singularities, as well as closed timelike curves on and outside the horizon. Characterized by four independent conserved charges—mass, two angular momenta, and electric charge—this solution reveals two distinct branches: a small bubble branch and a large bubble branch, distinguished by nonconserved local quantities such as magnetic flux or magnetic potential. This shows the nonuniqueness for spherical black holes, even among capped black holes. For equivalent sets of conserved charges, we find that the large/small bubble branch can have larger/smaller entropy than the Cvetič-Youm black hole.

We present a new exact solution for a general non-BPS black ring in the bosonic sector of five-dimensional minimal supergravity. This obtained solution carries four independent conserved charges: the mass, two angular momenta, an electric charge, and an additional dipole charge related to other charges. By employing the Ehlers-Harrison transformation, we derive this solution by transforming a five-dimensional vacuum solution into a charged solution in the theory. Previously, our work produced a vacuum doubly rotating black ring solution possessing a Dirac-Misner string singularity by using the Ehlers transformation. In this study, we use the singular black ring as the seed for the Harrison transformation. The resultant solution is regular, free from curvature singularities, conical singularities, orbifold singularities, Dirac-Misner string singularities, and closed timelike curves both on and outside the horizon. We show that within a specific parameter range, the black ring presents two branches for the same mass, two angular momenta and electric charge but these are distinguished by a dipole charge, which exhibits discontinuous nonuniqueness. Furthermore, this newly obtained black ring seamlessly connects to various physically significant solutions, such as the Pomeransky-Sen’kov black ring, the extremal black ring, the supersymmetric black ring, and the charged singly spinning black ring. Published by the American Physical Society 2024