36 research outputs found
Wightman function and vacuum fluctuations in higher dimensional brane models
Wightman function and vacuum expectation value of the field square are
evaluated for a massive scalar field with general curvature coupling parameter
subject to Robin boundary conditions on two codimension one parallel branes
located on -dimensional background spacetime
with a warped internal space . The general case of different Robin
coefficients on separate branes is considered. The application of the
generalized Abel-Plana formula for the series over zeros of combinations of
cylinder functions allows us to extract manifestly the part due to the bulk
without boundaries. Unlike to the purely AdS bulk, the vacuum expectation value
of the field square induced by a single brane, in addition to the distance from
the brane, depends also on the position of the brane in the bulk. The brane
induced part in this expectation value vanishes when the brane position tends
to the AdS horizon or AdS boundary. The asymptotic behavior of the vacuum
densities near the branes and at large distances is investigated. The
contribution of Kaluza-Klein modes along is discussed in various
limiting cases. As an example the case is considered,
corresponding to the bulk with one compactified dimension. An
application to the higher dimensional generalization of the Randall-Sundrum
brane model with arbitrary mass terms on the branes is discussed.Comment: 25 pages, 2 figures, discussion added, accepted for publication in
Phys.Rev.
Vacuum polarization by a global monopole with finite core
We investigate the effects of a -dimensional global monopole core on
the behavior of a quantum massive scalar field with general curvature coupling
parameter. In the general case of the spherically symmetric static core,
formulae are derived for the Wightman function, for the vacuum expectation
values of the field square and the energy-momentum tensor in the exterior
region. These expectation values are presented as the sum of point-like global
monopole part and the core induced one. The asymptotic behavior of the core
induced vacuum densities is investigated at large distances from the core, near
the core and for small values of the solid angle corresponding to strong
gravitational fields. In particular, in the latter case we show that the
behavior of the vacuum densities is drastically different for minimally and
non-minimally coupled fields. As an application of general results the
flower-pot model for the monopole's core is considered and the expectation
values inside the core are evaluated.Comment: 22 pages, 4 figures, misprint is corrected, discussion is added,
figures are change