Impulsive gravitational waves in general massive 3D gravity

Impulsive, non-diverging, Petrov-Segre type N gravitational wave solutions to a general massive three-dimensional gravity in the de Sitter, anti-de Sitter and flat Minkowski backgrounds are constructed in a unified manner by using the exterior algebra of differential forms.Comment: Published versio

On the universality of low-energy string model

The low-energy (bosonic "heterotic") string theory is interpreted as a universal limit of the Kaluza-Klein reduction when the dimension of an internal space goes to infinity. We show that such an approach is helpful in obtaining classical solutions of the string model. As a particular application, we obtain new exact static solutions for the two-dimensional effective string model. They turn out to be in agreement with the generalized no-hair conjecture, in complete analogy with the four and higher dimensional Einstein theory of gravity.Comment: 11 pages, LATEX, no figure

Hamilton-Jacobi Formulation of the Thermodynamics of Einstein-Born-Infeld-AdS Black Holes

A Hamilton-Jacobi formalism for thermodynamics was formulated by Rajeev [Ann. Phys. 323, 2265 (2008)] based on the contact structure of the odd dimensional thermodynamic phase space. This allows one to derive the equations of state of a family of substances by solving a Hamilton-Jacobi equation (HJE). In the same work it was applied to chargeless non-rotating black holes, and the use of Born-Infeld electromagnetism was proposed to apply it to charged black holes as well. This paper fulfills this suggestion by deriving the HJE for charged non-rotating black holes using Born-Infeld theory and a negative cosmological constant. The most general solution of this HJE is found. It is shown that there exists solutions which are distinct from the equations of state of the Einstein-Born-Infeld-AdS black hole. The meaning of these solutions is discussed.Comment: 5 pages, 2 figure

Dualisation of the Symmetric Space Sigma Model with Couplings

The first-order formulation of the G/K symmetric space sigma model of the scalar cosets of the supergravity theories is discussed when there is coupling of (m-1)-form matter fields. The Lie superalgebra which enables the dualized coset formulation is constructed for a general scalar coset G/K with matter coupling where G is a non-compact real form of a semi-simple Lie group and K is its maximal compact subgroup.Comment: 17 page