Cristian Stelea

Nuttier (A)dS black holes in higher dimensions

We construct new solutions of the vacuum Einstein field equations with cosmological constant. These solutions describe spacetimes with non-trivial topology, which are asymptotically dS, AdS or flat. For a negative cosmological constant these solutions are NUT charged generalizations of the topological black-hole solutions in higher dimensions. We also point out the existence of such NUT charged spacetimes in odd dimensions and explicitly construct such spaces in five and seven dimensions. The existence of such spacetimes with non-trivial topology is closely related to the existence of the cosmological constant. Finally, we discuss the global structure of such solutions and possible applications in string theory.

New multiply nutty spacetimes

Abstract We construct new solutions of the vacuum Einstein field equations with multiple NUT parameters, with and without cosmological constant. These solutions describe spacetimes with non-trivial topology that are asymptotically dS, AdS or flat. We also find the multiple nut parameter extension of the inhomogeneous Einstein metrics on complex line bundles found recently by Lu, Page and Pope. We also provide a more general form of the Eguchi–Hanson solitons found by Clarkson and Mann. We discuss the global structure of such solutions and possible applications in string theory.

On the gravitational energy of the Kaluza–Klein monopole

Abstract We use local counterterm prescriptions for asymptotically flat space to compute the action and conserved quantities in five-dimensional Kaluza–Klein theories. As an application of these prescriptions we compute the mass of the Kaluza–Klein magnetic monopole. We find consistent results with previous approaches that employ a background subtraction.

Thermodynamics of Newman-Unti-Tamburino charged spaces

We discuss and compare the results of two main methods used recently to describe the thermodynamics of Taub-NUT solutions in a deSitter background. In the first approach (C-approach), one deals with an analytically continued version of metric while in the second approach (R-approach), the discussion is carried out using the unmodified metric with Lorentzian signature. No analytic continuation is performed on the coordinates and/or the parameters that appear in the metric. We find that the results of both these approaches are completely equivalent modulo analytic continuation and we provide the exact prescription that relates the results in both methods. Extending these results to the AdS/flat cases yields a physical interpretation of the thermodynamics of NUT-charged spacetimes in the Lorentzian sector.

On squashed black holes in Godel universes

We investigate five-dimensional rotating and charged black holes with squashed horizons in Goedel universes. The general solution was recently derived by applying a squashing transformation on the general nonextremal charged and rotating black hole in the Goedel universe found by Wu. We give a discussion of the squashed geometry and also consider its lift to ten dimensions and discuss the T-dual geometry. Finally, using the counterterms method we compute its conserved charges and explore its thermodynamics.

Features of gravity–Yang-Mills hierarchies in d dimensions

Higher-dimensional, direct analogues of the usual d=4 Einstein-Yang-Mills (EYM) systems are studied. They feature single members of both the gravitational and the Yang-Mills hierarchies in d=4p-dimensional spacetimes, both consisting of 2p-form curvature terms only. This enables us to probe the effects of higher order gravitational terms, which in the presence of the usual Einstein term would be masked. Regular and black hole solutions are constructed in 2p+2{<=}d{<=}4p, in which dimensions the total mass-energy is finite, generalizing the familiar Bartnik-McKinnon solutions in EYM theory for p=1. In d=4p, this similarity is complete. In the special case of d=2p+1, just beyond the finite energy range of d, exact solutions in closed form are found. Finally, d=2p+1 purely gravitational systems, whose solutions generalize the static d=3 BTZ solutions, are discussed.

New Taub-NUT-Reissner-Nordström spaces in higher dimensions

Abstract We construct new charged solutions of the Einstein–Maxwell field equations with cosmological constant. These solutions describe the nut-charged generalisation of the higher-dimensional Reissner–Nordstrom spacetimes. For a negative cosmological constant these solutions are the charged generalizations of the topological nut-charged black hole solutions in higher dimensions. Finally, we discuss the global structure of such solutions and possible applications.

Cosmological monopoles and non-Abelian black holes

Abstract We discuss magnetic monopole solutions of the Einstein–Yang–Mills–Higgs equations with a positive cosmological constant. These configurations approach asymptotically the de Sitter spacetime background and exist only for a nonzero Higgs potential. We find that the total mass of the solutions within the cosmological horizon is finite. However, their mass evaluated by using the surface counterterm method outside the cosmological horizon at early/late time infinity generically diverges. Magnetic monopole solutions with finite mass and non-integer charge exist however in a truncation of the theory with a vanishing Higgs field. Both solutions with a regular origin and cosmological black holes are studied, special attention being paid to the computation of the global charges.

Charged squashed black holes with negative cosmological constant in odd dimensions

Abstract We construct numerically new electrically charged solutions of the Einstein–Maxwell equations with negative cosmological constant in general odd dimensions d = 2 n + 3 ⩾ 5 . They correspond to higher-dimensional generalizations of the squashed black hole solutions, which were known so far only in five dimensions. We explore numerically the general properties of such classical solutions and, using a counterterm prescription, we compute their conserved charges and discuss their thermodynamics.

Charged black holes on the Taub-Bolt instanton

We construct a new exact solution of the Einstein-Maxwell-Dilaton field equations in five dimensions, which describes a system of two general charged and static black holes sitting at the two turning points of the Taub-bolt instanton. We show that in this case the conical singularities can be completely eliminated and the black hole system remains in static equilibrium. We show how to recover some of the known solutions in particular cases and also obtain as a new solution the extremal double-black hole solution on the Taub-bolt instanton. Finally, we compute the conserved charges and investigate some of the thermodynamic properties of this system.