Stationary axisymmetric solutions of three-dimensional Einstein gravity

Einstein theory in three space-time dimensions is studied in the stationary, rotationally symmetric regime. Explicit interior solutions for various types of matter sources are found and their properties discussed.     

Thin-shell wormholes from charged black holes in generalized dilaton-axion gravity

This paper discusses a new type of thin-shell wormhole constructed by applying the cut-and-paste technique to two copies of a charged black hole in generalized dilaton-axion gravity, which was inspired by low-energy string theory. After analyzing various aspects of this thin-shell wormhole, we discuss its stability to linearized spherically symmetric perturbations.     

Stationary,spherically symmetric solutions of Jordan's unified theory of gravity and electromagnetism

All stationary, spherically symmetric solutions of Jordan's unified theory of gravity and electromagnetism are constructed. Conditions for the solutions are given to represent black holes with nonvanishing mass, electric and magnetic charge.     

Self-dual solutions to euclidean gravity

Recent work on Euclidean self-dual gravitational fields is reviewed. We discuss various solutions to the Einstein equations and treat asymptotically locally Euclidean self-dual metrics in detail. These latter solutions have vanishing classical action and nontrivial topological invariants, and so may play a role in quantum gravity resembling that of the Yang-Mills instantons.     

Covariant formulation of BPS black holes and the scalar weak gravity conjecture

We find through a systematic analysis that all but 29,223 of the 473.8 million 4D reflexive polytopes found by Kreuzer and Skarke have a 2D reflexive subpolytope. Such a subpolytope is generally associated with the presence of an elliptic or genus one fibration in the corresponding birational equivalence class of Calabi-Yau threefolds. This extends the growing body of evidence that most Calabi-Yau threefolds have an elliptically fibered phase.     

Stationary states in a quantum gravity model

A model theory for quantized gravity is discussed where only selected degrees of freedom are quantized. The concept of stationary states is introduced. It is shown that the Planck length arises as a lower bound to the space-time length scale in a natural way.     

Stationary cosmological Bianchi II solutions

Stationary cosmological solutions for the Bianchi metric II are derived. In the models, use is made of a scalar field with a vacuum-averaged energy-momentum tensor, a cosmological constant, and ideal co-moving or not co-moving liquids as sources of gravitations.     

Selection criteria for two-parameter solutions to scalar-tensor gravity

We investigate the generic properties of static, spherically symmetric, asymptotically flat solutions to the field equations describing gravity minimally coupled to a nonlinear self-gravitating real scalar field. Five corollaries and a theorem on selection criteria for two- and one-parametric solutions are proven and conditions for obtaining particle-like solutions, black holes or naked singularities are derived. A series of exact solutions in closed forms including different black holes, naked singularities and particle-like solutions, all of which obey the weak energy condition at spatial infinity, are provided. Two further corollaries elaborate on the behavior of solutions at spatial infinity, critical mass, mass density, pressure and energy conditions.     

4D gravity on a BPS brane in 5D AdS-Minkowski space

We calculate small correction terms to gravitational potential near an asymmetric BPS brane embedded in a 5D AdS-Minkowski space in the context of supergravity. The normalizable wave functions of gravity fluctuations around the brane describe only massive modes. We compute such wave functions analytically in the thin wall limit. We estimate the correction to gravitational potential for small and long distances, and show that there is an intermediate range of distances in which we can identify 4D gravity on the brane below a crossover scale. The 4D gravity is metastable and for distances much larger than the crossover scale the 5D gravity is recovered.     

Stationary solutions in three-dimensional general relativity

All the stationary solutions of the three-dimensional vacuum Einstein equations are obtained. These include a class of multicenter solutions representing systems of massive and spinning point particles. The geodesic motion of a test particle in the one-particle metric is discussed. A class of geodesics contain finite intervals where the particle moves back in coordinate time, without violation of causality.     

Stationary solutions in five-dimensional general relativity

Asymptotically Minkowskian stationary axisymmetric solutions of the five-dimensional Einstein equations are generated from particular classes of stationary axisymmetric solutions of the four-dimensional Einstein-Maxwell equations. First, the five-dimensional electrostatic and magnetostatic solutions are generated from the four-dimensional electrostatic solutions and a harmonic scalar field. Then, a new class of five-dimensional nonstatic solutions are generated from the four-dimensional class =+1. As an example, a three-parameter family of regular asymptotically flat rotating solutions is constructed. These solutions can be interpreted, after dimensional reduction to four dimensions, as extended elementary particles with mass, spin, electric charge, and magnetic dipole moment.     

Rediscussion of charged dilaton-axion black hole entropy

We rediscuss the entropy of a charged dilaton-axion black hole for both the asymptotically flat and non-flat cases by using the thin film brick-wall model. This improved method avoids some drawbacks in the original brick-wall method such as the small mass approximation, neglecting the logarithm term, and taking the term L ³ as the contribution of the vacuum surrounding the black hole. The entropy we obtain turns out to be proportional to the horizon area of the black hole, conforming to the Bekenstein-Hawking area-entropy formula for black holes.