1,618 research outputs found
Squeezing and photon distribution in a vibrating cavity
We obtain explicit analytical expressions for the quadrature variances and
the photon distribution functions of the electromagnetic field modes excited
from vacuum or thermal states due to the non-stationary Casimir effect in an
ideal one-dimensional Fabry--Perot cavity with vibrating walls, provided the
frequency of vibrations is close to a multiple frequency of the fundamental
unperturbed electromagnetic mode.Comment: 20 pages, LaTex2e, iopart document class, 2 ps figures, accepted for
publication in J. Phys.
A modified Schwinger's formula for the Casimir effect
After briefly reviewing how the (proper-time) Schwinger's formula works for
computing the Casimir energy in the case of "scalar electrodynamics" where the
boundary conditions are dictated by two perfectly conducting parallel plates
with separation "a" in the Z-axis, we propose a slightly modification in the
previous approach based on an analytical continuation method. As we will see,
for the case at hand our formula does not need the use of Poisson summation to
get a (renormalized) finite result.Comment: 6 pages, DFTUZ/93/14 (a short version will appear in the Letters in
Math. Phys.
Quantum Fluctuations of a Coulomb Potential as a Source of Flicker Noise
The power spectrum of quantum fluctuations of the electromagnetic field
produced by an elementary particle is determined. It is found that in a wide
range of practically important frequencies the power spectrum of fluctuations
exhibits an inverse frequency dependence. The magnitude of fluctuations
produced by a conducting sample is shown to have a Gaussian distribution around
its mean value, and its dependence on the sample geometry is determined. In
particular, it is demonstrated that for geometrically similar samples the power
spectrum is inversely proportional to the sample volume. It is argued also that
the magnitude of fluctuations induced by external electric field is
proportional to the field strength squared. A comparison with experimental data
on flicker noise measurements in continuous metal films is made.Comment: 11 pages, substantially corrected and extende
Two-Loop Bethe Logarithms for non-S Levels
Two-loop Bethe logarithms are calculated for excited P and D states in
hydrogenlike systems, and estimates are presented for all states with higher
angular momenta. These results complete our knowledge of the P and D energy
levels in hydrogen at the order of alpha^8 m_e c^2, where m_e is the electron
mass and c is the speed of light, and scale as Z^6, where Z is the nuclear
charge number. Our analytic and numerical calculations are consistent with the
complete absence of logarithmic terms of order (alpha/pi)^2 (Z alpha)^6 ln[(Z
alpha)^(-2)] m_e c^2 for D states and all states with higher angular momenta.
For higher excited P and D states, a number of poles from lower-lying levels
have to subtracted in the numerical evaluation. We find that, surprisingly, the
corrections of the "squared decay-rate type" are the numerically dominant
contributions in the order (alpha/pi)^2 (Z alpha)^6 m_e c^2 for states with
large angular momenta, and provide an estimate of the entire B_60-coefficient
for Rydberg states with high angular momentum quantum numbers. Our results
reach the predictive limits of the quantum electrodynamic theory of the Lamb
shift.Comment: 14 pages, RevTe
Schwinger, Pegg and Barnett approaches and a relationship between angular and Cartesian quantum descriptions II: Phase Spaces
Following the discussion -- in state space language -- presented in a
preceding paper, we work on the passage from the phase space description of a
degree of freedom described by a finite number of states (without classical
counterpart) to one described by an infinite (and continuously labeled) number
of states. With that it is possible to relate an original Schwinger idea to the
Pegg and Barnett approach to the phase problem. In phase space language, this
discussion shows that one can obtain the Weyl-Wigner formalism, for both
Cartesian {\em and} angular coordinates, as limiting elements of the discrete
phase space formalism.Comment: Subm. to J. Phys A: Math and Gen. 7 pages, sequel of quant-ph/0108031
(which is to appear on J.Phys A: Math and Gen
Sensitivity to new physics: a_e vs. a_mu
At present it is generally believed that ``new physics'' effects contribute
to leptonic anomalous magnetic moment, a_l, via quantum loops only and they are
proportional to the squared lepton mass, (m_l)^2. An alternative mechanism for
a contribution by new physics is proposed. It occurs at the tree level and
exhibits a linear rather than quadratic dependence on m_l. This leads to a much
larger sensitivity of a_e to the new physics than was expected so far.Comment: 4 pages, 2 figure
Scalar Casimir Energies of Tetrahedra
New results for scalar Casimir self-energies arising from interior modes are
presented for the three integrable tetrahedral cavities. Since the eigenmodes
are all known, the energies can be directly evaluated by mode summation, with a
point-splitting regulator, which amounts to evaluation of the cylinder kernel.
The correct Weyl divergences, depending on the volume, surface area, and the
corners, are obtained, which is strong evidence that the counting of modes is
correct. Because there is no curvature, the finite part of the quantum energy
may be unambiguously extracted. Dirichlet and Neumann boundary conditions are
considered and systematic behavior of the energy in terms of geometric
invariants is explored.Comment: Talk given at QFEXT 1
Quantum radiation in a plane cavity with moving mirrors
We consider the electromagnetic vacuum field inside a perfect plane cavity
with moving mirrors, in the nonrelativistic approximation. We show that low
frequency photons are generated in pairs that satisfy simple properties
associated to the plane geometry. We calculate the photon generation rates for
each polarization as functions of the mechanical frequency by two independent
methods: on one hand from the analysis of the boundary conditions for moving
mirrors and with the aid of Green functions; and on the other hand by an
effective Hamiltonian approach. The angular and frequency spectra are discrete,
and emission rates for each allowed angular direction are obtained. We discuss
the dependence of the generation rates on the cavity length and show that the
effect is enhanced for short cavity lengths. We also compute the dissipative
force on the moving mirrors and show that it is related to the total radiated
energy as predicted by energy conservation.Comment: 17 pages, 1 figure, published in Physical Review
Schwinger's Method for the Massive Casimir Effect
We apply to the massive scalar field a method recently proposed by Schwinger
to calculate the Casimir effect. The method is applied with two different
regularization schemes: the Schwinger original one by means of Poisson formula
and another one by means of analytical continuation.Comment: plain TeX, 6 pages, DFTUZ-93-2
Quark-antiquark pair production in space-time dependent fields
Fermion-antifermion pair-production in the presence of classical fields is
described based on the retarded and advanced fermion propagators. They are
obtained by solving the equation of motion for the Dirac Green's functions with
the respective boundary conditions to all orders in the field. Subsequently,
various approximation schemes fit for different field configurations are
explained. This includes longitudinally boost-invariant forms. Those occur
frequently in the description of ultrarelativistic heavy-ion collisions in the
semiclassical limit. As a next step, the gauge invariance of the expression for
the expectation value of the number of produced fermion-antifermion pairs as a
functional of said propagators is investigated in detail. Finally, the
calculations are carried out for a longitudinally boost-invariant model-field,
taking care of the last issue, especially.Comment: 32 pages, 8 figures, revised versio
- …