26,131 research outputs found
Radiation from a moving planar dipole layer: patch potentials vs dynamical Casimir effect
We study the classical electromagnetic radiation due to the presence of a
dipole layer on a plane that performs a bounded motion along its normal
direction, to the first non-trivial order in the amplitude of that motion. We
show that the total emitted power may be written in terms of the dipole layer
autocorrelation function. We then apply the general expression for the emitted
power to cases where the dipole layer models the presence of patch potentials,
comparing the magnitude of the emitted radiation with that coming from the
quantum vacuum in the presence of a moving perfect conductor (dynamical Casimir
effect).Comment: 5 pages, no figure
Ultraviolet cutoffs for quantum fields in cosmological spacetimes
We analyze critically the renormalization of quantum fields in cosmological
spacetimes, using non covariant ultraviolet cutoffs. We compute explicitly the
counterterms necessary to renormalize the semiclassical Einstein equations,
using comoving and physical ultraviolet cutoffs. In the first case, the
divergences renormalize bare conserved fluids, while in the second case it is
necessary to break the covariance of the bare theory. We point out that, in
general, the renormalized equations differ from those obtained with covariant
methods, even after absorbing the infinities and choosing the renormalized
parameters to force the consistency of the renormalized theory. We repeat the
analysis for the evolution equation for the mean value of an interacting scalar
fieldComment: 19 pages. Minor changes. References adde
On the renormalization procedure for quantum fields with modified dispersion relation in curved spacetimes
We review our recent results on the renormalization procedure for a free
quantum scalar field with modified dispersion relations in curved spacetimes.
For dispersion relations containing up to powers of the spatial momentum,
the subtraction necessary to renormalize depends
on . We first describe our previous analysis for spatially flat
Friedman-Robertson-Walker and Bianchi type I metrics. Then we present a new
power counting analysis for general background metrics in the weak field
approximation.Comment: Talk given at the 7th Alexander Friedmann International Seminar on
Gravitation and Cosmology, Joao Pessoa, Brazil, July 200
Practice of physical activity, prosocial behavior and self-concept in adolescents: connections in school contexts
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