10 research outputs found
Fermat's principle in quantum gravitational optics
Interactions incorporating the vacuum polarization effects in curved
backgrounds modify the null cone structure in such a way that the photon
trajectories would not be the space-time geodesics anymore. The gravitational
birefringence introduced as a direct consequence of these effects, will allow
shifts in the photon velocities leading to polarization dependent superluminal
propagation. Taking these effects into account we study Fermat's principle in
the context of the 1+3 (threading) formulation of the space-time decomposition.
We find an expression for the modified spacetime refractive index and show it
is proportional to the light cone correction to the first order. Consequences
of this modification on polarization sum rules and spatial light paths are
considered.Comment: 13 Pages, REVTex format, section on gravitomagnetic monopoles is
removed along with its references, new references adde
Quantum gravitational optics in the field of a gravitomagnetic monopole
Vacuum polarization in QED in a background gravitational field induces
interactions which {\it effectively} modify the classical picture of light rays
as the null geodesics of spacetime. After a short introduction on the main
aspects of the quantum gravitational optics, as a nontrivial example, we study
this effect in the background of NUT space characterizing the spacetime of a
spherical mass endowed with a gravitomagnetic monopole charge, the so called
NUT factor.Comment: 9 pages, title changed and the text abridged for publication in the
Journal of Physics: Conference serie
Quantum gravitational optics: the induced phase
The geometrical approximation of the extended Maxwell equation in curved
spacetime incorporating interactions induced by the vacuum polarization effects
is considered. Taking into account these QED interactions and employing the
analogy between eikonal equation in geometrical optics and Hamilton-Jacobi
equation for the particle motion, we study the phase structure of the modified
theory. There is a complicated, local induced phase which is believed to be
responsible for the modification of the classical picture of light ray. The
main features of QGO could be obtained through the study of this induced phase.
We discuss initial principles in conventional and modified geometrical optics
and compare the results.Comment: 10 pages, REVTex forma
Massive spinor fields in flat spacetimes with non-trivial topology
The vacuum expectation value of the stress-energy tensor is calculated for
spin massive fields in several multiply connected flat spacetimes.
We examine the physical effects of topology on manifolds such as , , , the Mobius strip and the Klein bottle.
We find that the spinor vacuum stress tensor has the opposite sign to, and
twice the magnitude of, the scalar tensor in orientable manifolds. Extending
the above considerations to the case of Misner spacetime, we calculate the
vacuum expectation value of spinor stress-energy tensor in this space and
discuss its implications for the chronology protection conjecture.Comment: 18 pages, Some of the equations in section VI as well as
typographical errors corrected, 5 figures, Revtex
Quantum gravitational optics: Effective Raychaudhuri equation
Vacuum polarization in QED in a background gravitational field induces
interactions which {\it effectively} modify the classical picture of light
rays, as the null geodesics of spacetime. These interactions violate the strong
equivalence principle and affect the propagation of light leading to
superluminal photon velocities. Taking into account the QED vacuum
polarization, we study the propagation of a bundle of rays in a background
gravitational field. To do so we consider the perturbative deformation of
Raychaudhuri equation through the influence of vacuum polarization on photon
propagation. We analyze the contribution of the above interactions to the
optical scalars namely, shear, vorticity and expansion using the Newman-Penrose
formalism.Comment: 17 pages, 1 figure, RevTex format, Replaced with the published
versio
Vacuum energy and the spacetime index of refraction: A new synthesis
In 1+3 (threading) formulation of general relativity spacetime behaves
analogous to a medium with a specific index of refraction with respect to the
light propagation. Accepting the reality of zero point energy, through the
equivalence principle, we elevate this analogy to the case of virtual photon
propagation in a quantum vacuum in a curved background spacetime. Employing
this new idea one could examine the response of vacuum energy to the presence
of a stationary gravitational field in its different quantum field theoretic
manifestations such as Casimir effect and Lamb shift. The results are given
explicitly for a Casimir apparatus in the weak field limit of a Kerr hole.Comment: 10 pages, RevTex, more typos corrected (combined with arXiv:1003.0614
published in PRD
Topology, Mass and Casimir energy
The vacuum expectation value of the stress energy tensor for a massive scalar
field with arbitrary coupling in flat spaces with non-trivial topology is
discussed. We calculate the Casimir energy in these spaces employing the
recently proposed {\it optical approach} based on closed classical paths. The
evaluation of the Casimir energy consists in an expansion in terms of the
lengths of these paths. We will show how different paths with corresponding
weight factors contribute in the calculation. The optical approach is also used
to find the mass and temperature dependence of the Casimir energy in a cavity
and it is shown that the massive fields cannot be neglected in high and low
temperature regimes. The same approach is applied to twisted as well as spinor
fields and the results are compared with those in the literature.Comment: 18 pages, 1 figure, RevTex format, Typos corrected and references
adde