1,706 research outputs found
Long-wavelength metric backreactions in slow-roll inflation
We examine the importance of second order corrections to linearized
cosmological perturbation theory in an inflationary background, taken to be a
spatially flat FRW spacetime. The full second order problem is solved in the
sense that we evaluate the effect of the superhorizon second order corrections
on the inhomogeneous and homogeneous modes of the linearized flucuations. These
second order corrections enter in the form of a {\it cumulative} contribution
from {\it all} of their Fourier modes. In order to quantify their physical
significance we study their effective equation of state by looking at the
perturbed energy density and isotropic pressure to second order. We define the
energy density (isotropic pressure) in terms of the (averaged) eigenvalues
associated with timelike (spacelike) eigenvectors of a total stress energy for
the metric and matter fluctuations. Our work suggests that that for many
parameters of slow-roll inflation, the second order contributions to these
energy density and pressures may dominate over the first order effects for the
case of super-Hubble evolution. These results hold in our choice of first and
second order coordinate conditions however we also argue that other
`reasonable` coordinate conditions do not alter the relative importance of the
second order terms. We find that these second order contributions approximately
take the form of a cosmological constant in this coordinate gauge, as found by
others using effective methods.Comment: Submitted to Phys. Rev.
Universal approach to gravitational thermal effects
A universal scheme for describing gravitational thermal effects is developed
as a generalization of Unruh effect. Quasi-Rindler (QR) coordinates are
constructed in an arbitrary curved space-time in such a way that the imaginary
QR time be periodical. The observer at rest in QR coordinates should experience
a thermal effect. Application to de Sitter space-time is considered.Comment: 8 pages, LATE
Trans-Planckian Tail in a Theory with a Cutoff
Trans-planckian frequencies can be mimicked outside a black-hole horizon as a
tail of an exponentially large amplitude wave that is mostly hidden behind the
horizon. The present proposal requires implementing a final state condition.
This condition involves only frequencies below the cutoff scale. It may be
interpreted as a condition on the singularity. Despite the introduction of the
cutoff, the Hawking radiation is restored for static observers. Freely falling
observers see empty space outside the horizon, but are "heated" as they cross
the horizon.Comment: 17 pages, RevTe
Increasing future gravitational-wave detectors sensitivity by means of amplitude filter cavities and quantum entanglement
The future laser interferometric gravitational-wave detectors sensitivity can
be improved using squeezed light. In particular, recently a scheme which uses
the optical field with frequency dependent squeeze factor, prepared by means of
a relatively short (~30 m) amplitude filter cavity, was proposed
\cite{Corbitt2004-3}. Here we consider an improved version of this scheme,
which allows to further reduce the quantum noise by exploiting the quantum
entanglement between the optical fields at the filter cavity two ports.Comment: 10 pages, 7 figure
First Order Corrections to the Unruh Effect
First order corrections to the Unruh effect are calculated from a model of an
accelerated particle detector of finite mass. We show that quantum smearing of
the trajectory and large recoil essentially do not modify the Unruh effect.
Nevertheless, we find corrections to the thermal distribution and to the Unruh
temperature. In a certain limit, when the distribution at equilibrium remains
exactly thermal, the corrected temperature is found to be , where is the Unruh temperature. We estimate the consequent
corrections to the Hawking temperature and the black hole entropy, and comment
on the relationship to the problem of trans-planckian frequencies.Comment: 23 pages, LaTe
Relativistic Quantum Measurements, Unruh effect and Black Holes
It is shown how the technique of restricted path integrals (RPI) or quantum
corridors (QC) may be applied for the analysis of relativistic measurements.
Then this technique is used to clarify the physical nature of thermal effects
as seen by an accelerated observer in Minkowski space-time (Unruh effect) and
by a far observer in the field of a black hole (Hawking effect). The physical
nature of the "thermal atmosphere" around the observer is analysed in three
cases: a) the Unruh effect, b) an eternal (Kruskal) black hole and c) a black
hole forming in the process of collapse. It is shown that thermal particles are
real only in the case (c). In the case (b) they cannot be distinguished from
real particles but they do not carry away mass of the black hole until some of
these particles are absorbed by the far observer. In the case (a) thermal
particles are virtual.Comment: 24 pages (Latex), 8 EPS figures The text was edited for the new
versio
Origin of the Thermal Radiation in a Solid-State Analog of a Black-Hole
An effective black-hole-like horizon occurs, for electromagnetic waves in
matter, at a surface of singular electric and magnetic permeabilities. In a
physical dispersive medium this horizon disappears for wave numbers with
. Nevertheless, it is shown that Hawking radiation is still emitted if
free field modes with are in their ground state.Comment: 13 Pages, 3 figures, Revtex with epsf macro
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