Nonuniqueness of capped black holes: Large and small bubbles

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 <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mo stretchy="false">[</a:mo><a:msup><a:mrow><a:mi mathvariant="double-struck">R</a:mi></a:mrow><a:mn>4</a:mn></a:msup><a:mo>#</a:mo><a:mi mathvariant="double-struck">C</a:mi><a:msup><a:mrow><a:mi mathvariant="double-struck">P</a:mi></a:mrow><a:mn>2</a:mn></a:msup><a:mo stretchy="false">]</a:mo><a:mo>\</a:mo><a:msup><a:mrow><a:mi mathvariant="double-struck">B</a:mi></a:mrow><a:mn>4</a:mn></a:msup></a:mrow></a:math> 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.