5,749 research outputs found
Electromagnetic energy-momentum and forces in matter
We discuss the electromagnetic energy-momentum distribution and the
mechanical forces of the electromagnetic field in material media. There is a
long-standing controversy on these notions. The Minkowski and the Abraham
energy-momentum tensors are the most well-known ones. We propose a solution of
this problem which appears to be natural and self-consistent from both a
theoretical and an experimental point of view.Comment: Revtex, 17 pages, 1 eps figur
Black Holes in Two Dimensions
Models of black holes in (1+1)-dimensions provide a theoretical laboratory
for the study of semi-classical effects of realistic black holes in Einstein's
theory. Important examples of two-dimensional models are given by string theory
motivated dilaton gravity, by ordinary general relativity in the case of
spherical symmetry, and by {\em Poincar\'e gauge gravity} in two spacetime
dimensions. In this paper, we present an introductory overview of the exact
solutions of two-dimensional classical Poincar\'e gauge gravity (PGG). A
general method is described with the help of which the gravitational field
equations are solved for an arbitrary Lagrangian. The specific choice of a
torsion-related coframe plays a central role in this approach. Complete
integrability of the general PGG model is demonstrated in vacuum, and the
structure of the black hole type solutions of the quadratic models with and
without matter is analyzed in detail. Finally, the integrability of the general
dilaton gravity model is established by recasting it into an effective PGG
model.Comment: Latex2e, 28 pages, with 5 postscript figure
- …