1,141 research outputs found
Radiation Reaction fields for an accelerated dipole for scalar and electromagnetic radiation
The radiation reaction fields are calculated for an accelerated changing
dipole in scalar and electromagnetic radiation fields. The acceleration
reaction is shown to alter the damping of a time varying dipole in the EM case,
but not the scalar case. In the EM case, the dipole radiation reaction field
can exert a force on an accelerated monopole charge associated with the
accelerated dipole. The radiation reaction of an accelerated charge does not
exert a torque on an accelerated magnetic dipole, but an accelerated dipole
does exert a force on the charge. The technique used is that originally
developed by Penrose for non-singular fields and extended by the author for an
accelerated monopole charge.Comment: 11 page
Influence Functionals and the Accelerating Detector
The influence functional is derived for a massive scalar field in the ground
state, coupled to a uniformly accelerating DeWitt monopole detector in
dimensional Minkowski space. This confirms the local nature of the Unruh
effect, and provides an exact solution to the problem of the accelerating
detector without invoking a non-standard quantization. A directional detector
is presented which is efficiently decohered by the scalar field vacuum, and
which illustrates an important difference between the quantum mechanics of
inertial and non-inertial frames. From the results of these calculations, some
comments are made regarding the possibility of establishing a quantum
equivalence principle, so that the Hawking effect might be derived from the
Unruh effect.Comment: 32 page
Quantum field and uniformly accelerated oscillator
We present an exact treatment of the influences on a quantum scalar field in
its Minkowski vacuum state induced by coupling of the field to a uniformly
accelerated harmonic oscillator. We show that there are no radiation from the
oscillator in the point of view of a uniformly accelerating observer. On the
other hand, there are radiations in the point of view of an inertial observer.
It is shown that Einstein-Podolsky-Rosen (EPR) like correlations of Rindler
particles in Minkowski vacuum states are modified by a phase factor in front of
the momentum-symmetric Rindler operators. The exact quantization of a
time-dependent oscillator coupled to a massless scalar field was given.Comment: 28 pages, LaTe
Quantum radiation by electrons in lasers and the Unruh effect
In addition to the Larmor radiation known from classical electrodynamics,
electrons in a laser field may emit pairs of entangled photons -- which is a
pure quantum effect. We investigate this quantum effect and discuss why it is
suppressed in comparison with the classical Larmor radiation (which is just
Thomson backscattering of the laser photons). Further, we provide an intuitive
explanation of this process (in a simplified setting) in terms of the Unruh
effect.Comment: 4 pages, 3 figure
Lattice Black Holes
We study the Hawking process on lattices falling into static black holes. The
motivation is to understand how the outgoing modes and Hawking radiation can
arise in a setting with a strict short distance cutoff in the free-fall frame.
We employ two-dimensional free scalar field theory. For a falling lattice with
a discrete time-translation symmetry we use analytical methods to establish
that, for Killing frequency and surface gravity satisfying
in lattice units, the continuum Hawking spectrum
is recovered. The low frequency outgoing modes arise from exotic ingoing modes
with large proper wavevectors that "refract" off the horizon. In this model
with time translation symmetry the proper lattice spacing goes to zero at
spatial infinity. We also consider instead falling lattices whose proper
lattice spacing is constant at infinity and therefore grows with time at any
finite radius. This violation of time translation symmetry is visible only at
wavelengths comparable to the lattice spacing, and it is responsible for
transmuting ingoing high Killing frequency modes into low frequency outgoing
modes.Comment: 26 pages, LaTeX, 2 figures included with psfig. Several improvements
in the presentation. One figure added. Final version to appear in Phys.Rev.
Hawking Radiation as Tunneling
We present a short and direct derivation of Hawking radiation as a tunneling
process, based on particles in a dynamical geometry. The imaginary part of the
action for the classically forbidden process is related to the Boltzmann factor
for emission at the Hawking temperature. Because the derivation respects
conservation laws, the exact spectrum is not precisely thermal. We compare and
contrast the problem of spontaneous emission of charged particles from a
charged conductor.Comment: LaTeX, 10 pages; v2. journal version, added section on relation of
black hole radiation to electric charge emission from a charged conducting
sphere; v3. restored cut referenc
Fluctuation-dissipation theorem and the Unruh effect of scalar and Dirac fields
We present a simple and systematic method to calculate the Rindler noise,
which is relevant to the analysis of the Unruh effect, by using the
fluctuation-dissipative theorem. To do this, we calculate the dissipative
coefficient explicitly from the equations of motion of the detector and the
field. This method gives not only the correct answer but also a hint as to the
origin of the apparent statistics inversion effect. Moreover, this method is
generalized to the Dirac field, by using the fermionic fluctuation-dissipation
theorem. We can thus confirm that the fermionic fluctuation-dissipation theorem
is working properly.Comment: 26 page
Optimal configurations of filter cavity in future gravitational-wave detectors
Sensitivity of future laser interferometric gravitational-wave detectors can
be improved using squeezed light with frequency-dependent squeeze angle and/or
amplitude, which can be created using additional so-called filter cavities.
Here we compare performances of several variants of this scheme, proposed
during last years, assuming the case of a single relatively short (tens of
meters) filter cavity suitable for implementation already during the life cycle
of the second generation detectors, like Advanced LIGO. Using numerical
optimization, we show that the phase filtering scheme proposed by Kimble et al
[Phys.Rev.D 65, 022002 (2001)] looks as the best candidate for this scenario.Comment: 17 pages, 5 figure
Rotational quantum friction in superfluids: Radiation from object rotating in superfluid vacuum
We discuss the friction experienced by the body rotating in superfluid liquid
at T=0. The effect is analogous to the amplification of electromagnetic
radiation and spontaneous emission by the body or black hole rotating in
quantum vacuum, first discussed by Zel'dovich and Starobinsky. The friction is
caused by the interaction of the part of the liquid, which is rigidly connected
with the rotating body and thus represents the comoving detector, with the
"Minkowski" vacuum outside the body. The emission process is the quantum
tunneling of quasiparticles from the detector to the ergoregion, where the
energy of quasiparticles is negative in the rotating frame. This quantum
rotational friction caused by the emission of quasiparticles is estimated for
phonons and rotons in superfluid 4He and for Bogoliubov fermions in superfluid
3He.Comment: RevTex file, 4 pages, 1 figur
Probing optomechanical correlations between two optical beams down to the quantum level
Quantum effects of radiation pressure are expected to limit the sensitivity
of second-generation gravitational-wave interferometers. Though ubiquitous,
such effects are so weak that they haven't been experimentally demonstrated
yet. Using a high-finesse optical cavity and a classical intensity noise, we
have demonstrated radiation-pressure induced correlations between two optical
beams sent into the same moving mirror cavity. Our scheme can be extended down
to the quantum level and has applications both in high-sensitivity measurements
and in quantum optics
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