586 research outputs found
Euclidean spinor Green's functions in the spacetime of a straight cosmic string
We determine generally the spinor Green's function and the twisted spinor
Green's function in an Euclidean space with a conical-type line singularity. In
particular, in the neighbourhood of the point source, we expree them as a sum
of the usual Euclidean spinor Green's functin and a regular term. In four
dimensions, we use these determinations to calculate the vacuum energy density
and the twisted one for a massless spinor field in the spacetime of a straight
cosmic string. In the Minkowski spacetime, we determine explicitly the vacuum
energy density for a massive twisted spinor field.Comment: 20 pages, latex, no figure
Electrostatics in a Schwarzschild black hole pierced by a cosmic string
We explicitly determine the expression of the electrostatic potential
generated by a point charge at rest in the Schwarzschild black hole pierced by
a cosmic string. We can then calculate the electrostatic self-energy. From
this, we find again the upper entropy bound for a charged object by employing
thermodynamics of the black hole.Comment: Latex, 8 pages, 1 figure in late
Black holes in which the electrostatic or scalar equation is solvable in closed form
We show that the method used in the Schwarzschild black hole for finding the
elementary solution of the electrostatic equation in closed form cannot extend
in higher dimensions. By contrast, we prove the existence of static,
spherically symmetric geometries with a non-degenerated horizon in which the
static scalar equation can be solved in closed form. We give the explicit
results in 6 dimensions. We determine moreover the expressions of the
electrostatic potential and of the static scalar field for a point source in
the extremal Reissner-Nordstrom black holes in higher dimensions.Comment: 20 pages, no figur
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