A Uniqueness theorem for black holes with Kaluza-Klein asymptotic in 5D Einstein-Maxwell gravity

In the present paper we prove a uniqueness theorem for stationary multi black hole configurations with Kaluza-Klein asymptotic in a certain sector of 5D Einstein-Maxwell gravity. We show that such multi black hole configurations are uniquely specified by the interval structure, angular momenta of the horizons, magnetic charges and the magnetic flux. A straightforward generalization of the uniqueness theorem for 5D Einstein-Maxwell-dilaton gravity is also given.Comment: 14 pages, v2 comments and references adde

Uniqueness of the static spacetimes with a photon sphere in Einstein-scalar field theory

In the present paper we prove a uniqueness theorem for the static and asymptotically flat solutions to the Einstein-scalar field equations which possess a photon sphere. We show that such solutions are uniquely specified by their mass $M$ and scalar charge $q$ and that they are isometric to the Janis-Newman-Winicour solution with the same mass and scalar charge subject to the inequality $\frac{q^2}{M^2}<3$.Comment: 13 page

Exact static solutions in Einstein-Maxwell-Dilaton gravity with arbitrary dilaton coupling parameter

We present solution generating methods which allow to construct exact static solutions to the equations of four-dimensional Einstein-Maxwell-Dilaton gravity starting with arbitrary static solutions to the pure vacuum Einstein equations, Einstein-dilaton or Einstein-Maxwell equations.Comment: 6 pages, latex; V2 references added, some formulas generalized; A short version of the talk given at the $4^{th}$ General Conference of the Balkan Physical Union, Veliko Turnovo, Bulgaria, 22-25 August, 2000. Part of the present work (4 pages) was published in Bulg.J.Phys. 27N3 (2000) 58-6

Dilaton black holes with squashed horizons and their thermodynamics

New charged solutions describing black holes with squashed horizons in 5D dilaton gravity are presented. The black hole spacetimes are asymptotically locally flat and have a spacial infinity $R\times S^1\hookrightarrow S^2$. The solutions are analyzed and their thermodynamics is discussed by using the counterterm method.Comment: 12 pages,LaTex; v2 references added; v3 typos corrected; PR

Geodesically complete nondiagonal inhomogeneous cosmological solutions in dilatonic gravity with a stiff perfect fluid

New nondiagonal $G_{2}$ inhomogeneous cosmological solutions are presented in a wide range of scalar-tensor theories with a stiff perfect fluid as a matter source. The solutions have no big-bang singularity or any other curvature singularities. The dilaton field and the fluid energy density are everywhere regular, too. The geodesic completeness of the solutions is investigated.Comment: 11 pages, Revtex; v2 improvements, references and acknowledgments added; v3 comments, references and acknowledgments added, Phys. Rev. D in pres

Generating dyonic solutions in 5D Einstein-dilaton gravity with antisymmetric forms and dyonic black rings

We consider 5-dimensional Einstein-dilaton gravity with antisymmetric forms. Assuming staticity and a restriction on the dilaton coupling parameters, we derive 4-dimensional sigma-model with a target space $SL(2,R)/SO(1,1)\times SL(2,R)/SO(1,1)$. On this basis, using the symmetries of the target space, we develop a solution generating technique and employ it to construct new asymptotically flat and non-flat dyonic black rings solutions. The solutions are analyzed and the basic physical quantities are calculated.Comment: 14 pages, LaTeX; v2 references and comments added, typos corrected; v3 title changed, comments and references added; PR

Asymptotically and non-asymptotically flat static black rings in charged dilaton gravity

We systematically derive the asymptotically flat five dimensional black rings in EMd gravity by using the sigma model structure of the dimensionally reduced field equations. New non-asymptotically flat EMd black ring solutions in five dimensions are also constructed and their physical properties are analyzed.Comment: LaTex, 10 pages; v2 some typos corrected, some cosmetic changes,a reference adde

Rotating dyonic dipole black rings: exact solutions and thermodynamics

New rotating dyonic dipole black ring solutions are derived in 5D Einstein-dilaton gravity with antisymmetric forms. The black rings are analyzed and their thermodynamics is discussed. New dyonic black string solutions are also presented.Comment: LaTeX, 21 pages;v2 references added, some typos corrected;v3 refferences adde

Exact dark energy star solutions

Adopting the phantom (ghost) scalar field description of dark energy, we construct a general class of exact interior solutions describing mixed relativistic stars containing both ordinary matter and dark energy in different proportions. The exterior solution that continuously matches the interior solutions is found. Exact solutions describing extremal configuration with zero ordinary matter pressure are also constructed.Comment: 8 pages, LaTex; v2 comments and references added, typos correcte

Cold scalar-tensor black holes coupled to a massless scalar field

New four-dimensional black hole solutions of Brans-Dicke equations with a negative constant $\omega$, coupled to a massless scalar field, are presented. The temperature of these black holes is zero and the horizon area is infinite. An astrophysical application is also discussed.Comment: 4 pages, latex; v2 a reference and comment adde