4 research outputs found
Gravitational Instantons from Minimal Surfaces
Physical properties of gravitational instantons which are derivable from
minimal surfaces in 3-dimensional Euclidean space are examined using the
Newman-Penrose formalism for Euclidean signature. The gravitational instanton
that corresponds to the helicoid minimal surface is investigated in detail.
This is a metric of Bianchi Type , or E(2) which admits a hidden
symmetry due to the existence of a quadratic Killing tensor. It leads to a
complete separation of variables in the Hamilton-Jacobi equation for geodesics,
as well as in Laplace's equation for a massless scalar field. The scalar Green
function can be obtained in closed form which enables us to calculate the
vacuum fluctuations of a massless scalar field in the background of this
instanton.Comment: One figure available by fax upon request. Abstract missing in
original submission. Submitted to Classical and Quantum Gravit
Black brane solutions related to non-singular Kac-Moody algebras
A multidimensional gravitational model containing scalar fields and
antisymmetric forms is considered. The manifold is chosen in the form M = M_0 x
M_1 x ... x M_n, where M_i are Einstein spaces (i > 0). The sigma-model
approach and exact solutions with intersecting composite branes (e.g.,
solutions with harmonic functions and black brane ones) with intersection rules
related to non-singular Kac-Moody (KM) algebras (e.g. hyperbolic ones) are
considered. Some examples of black brane solutions are presented, e.g., those
corresponding to hyperbolic KM algebras: H_2(q,q) (q > 2), HA_2^(1) = A_2^{++}
and to the Lorentzian KM algebra P_{10}.Comment: 16 pages, Late