Speaker
Description
Constructing exact solutions describing compact objects embedded in dynamical cosmological environments remains a major challenge in General Relativity, with most known results restricted to highly symmetric settings. In this talk, we present new exact solutions and solution-generating techniques that extend the analytical description of dynamical black holes in cosmological backgrounds.
First, we introduce a novel method for the self-interacting Einstein–scalar system that generates non-stationary, axisymmetric geometries. Using this approach, we obtain the first exact solution describing a dynamical axisymmetric black (or white) hole embedded in an expanding or contracting cosmology. Its dynamical trapping horizons are characterized using the mean curvature vector, which generalizes the Kodama vector beyond spherical symmetry and allows a foliation-independent identification of trapped and untrapped regions.
We then construct a new exact solution of the Einstein–scalar–Maxwell system describing a dynamical black hole interacting with a time-dependent external electromagnetic field. The configuration is obtained by dressing a Schwarzschild black hole with a radially and temporally varying scalar field within the Fonarev framework, producing a time-dependent generalization of the Fisher–Janis–Newman–Winicour solution. An external electromagnetic field is subsequently generated through a Lie point symmetry extending the Harrison transformation to dynamical settings. The resulting spacetime features a dynamical horizon, an axisymmetric electromagnetic field, and asymptotics combining Friedmann–Lemaître–Robertson–Walker and Levi–Civita geometries.
We analyze the geometric and physical properties of these solutions, including their horizon structure and asymptotic behavior. Notably, time dependence can cloak curvature singularities that would otherwise be naked in stationary limits. These results provide new analytical tools to explore dynamical compact objects in cosmology, with potential applications to primordial black holes.