1,310 research outputs found
An Optical Approach to the Dynamical Casimir Effect
We recently proposed a new approach to analyze the parametric resonance in a
vibrating cavity based on the analysis of classical optical paths. This
approach is used to examine various models of cavities with moving walls. We
prove that our method is useful to extract easily basic physical outcome.Comment: 9 page
Laser photon merging in proton-laser collisions
The quantum electrodynamical vacuum polarization effects arising in the
collision of a high-energy proton beam and a strong, linearly polarized laser
field are investigated. The probability that laser photons merge into one
photon by interacting with the proton`s electromagnetic field is calculated
taking into account the laser field exactly. Asymptotics of the probability are
then derived according to different experimental setups suitable for detecting
perturbative and nonperturbative vacuum polarization effects. The
experimentally most feasible setup involves the use of a strong optical laser
field. It is shown that in this case measurements of the polarization of the
outgoing photon and and of its angular distribution provide promising tools to
detect these effects for the first time.Comment: 38 pages, 9 figure
Lamm, Valluri, Jentschura and Weniger comment on "A Convergent Series for the QED Effective Action" by Cho and Pak [Phys. Rev. Lett. vol. 86, pp. 1947-1950 (2001)]
Complete results were obtained by us in [Can. J. Phys. 71, 389 (1993)] for
convergent series representations of both the real and the imaginary part of
the QED effective action; these derivations were based on correct intermediate
steps. In this comment, we argue that the physical significance of the
"logarithmic correction term" found by Cho and Pak in [Phys. Rev. Lett. 86,
1947 (2001)] in comparison to the usual expression for the QED effective action
remains to be demonstrated. Further information on related subjects can be
found in Appendix A of hep-ph/0308223 and in hep-th/0210240.Comment: 1 page, RevTeX; only "meta-data" update
Quantum versus Classical Dynamics in a driven barrier: the role of kinematic effects
We study the dynamics of the classical and quantum mechanical scattering of a
wave packet from an oscillating barrier. Our main focus is on the dependence of
the transmission coefficient on the initial energy of the wave packet for a
wide range of oscillation frequencies. The behavior of the quantum transmission
coefficient is affected by tunneling phenomena, resonances and kinematic
effects emanating from the time dependence of the potential. We show that when
kinematic effects dominate (mainly in intermediate frequencies), classical
mechanics provides very good approximation of quantum results. Moreover, in the
frequency region of optimal agreement between classical and quantum
transmission coefficient, the transmission threshold, i.e. the energy above
which the transmission coefficient becomes larger than a specific small
threshold value, is found to exhibit a minimum. We also consider the form of
the transmitted wave packet and we find that for low values of the frequency
the incoming classical and quantum wave packet can be split into a train of
well separated coherent pulses, a phenomenon which can admit purely classical
kinematic interpretation
On the spectrum of S=1/2 XXX Heisenberg chain with elliptic exchange
It is found that the Hamiltonian of S=1/2 isotropic Heisenberg chain with
sites and elliptic non-nearest-neighbor exchange is diagonalized in each sector
of the Hilbert space with magnetization , , by means of
double quasiperiodic meromorphic solutions to the -particle quantum
Calogero-Moser problem on a line. The spectrum and highest-weight states are
determined by the solutions of the systems of transcendental equations of the
Bethe-ansatz type which arise as restrictions to particle pseudomomenta.Comment: 9 pages, Late
Comparison of QG-Induced Dispersion with Standard Physics Effects
One of the predictions of quantum gravity phenomenology is that, in
situations where Planck-scale physics and the notion of a quantum spacetime are
relevant, field propagation will be described by a modified set of laws.
Descriptions of the underlying mechanism differ from model to model, but a
general feature is that electromagnetic waves will have non-trivial dispersion
relations. A physical phenomenon that offers the possibility of experimentally
testing these ideas in the foreseeable future is the propagation of high-energy
gamma rays from GRB's at cosmological distances. With the observation of
non-standard dispersion relations within experimental reach, it is thus
important to find out whether there are competing effects that could either
mask or be mistaken for this one. In this letter, we consider possible effects
from standard physics, due to electromagnetic interactions, classical as well
as quantum, and coupling to classical geometry. Our results indicate that, for
currently observed gamma-ray energies and estimates of cosmological parameter
values, those effects are much smaller than the quantum gravity one if the
latter is first-order in the energy; some corrections are comparable in
magnitude with the second-order quantum gravity ones, but they have a very
different energy dependence.Comment: 8 pages; Version to be published in CQG as a letter; Includes some
new comments and references, but no changes in the result
Bound states in straight quantum waveguides with combined boundary conditions
We investigate the discrete spectrum of the Hamiltonian describing a quantum
particle living in the two-dimensional straight strip. We impose the combined
Dirichlet and Neumann boundary conditions on different parts of the boundary.
Several statements on the existence or the absence of the discrete spectrum are
proven for two models with combined boundary conditions. Examples of
eigenfunctions and eigenvalues are computed numerically.Comment: 24 pages, LaTeX 2e with 4 eps figure
Spectral Statistics in Chaotic Systems with Two Identical Connected Cells
Chaotic systems that decompose into two cells connected only by a narrow
channel exhibit characteristic deviations of their quantum spectral statistics
from the canonical random-matrix ensembles. The equilibration between the cells
introduces an additional classical time scale that is manifest also in the
spectral form factor. If the two cells are related by a spatial symmetry, the
spectrum shows doublets, reflected in the form factor as a positive peak around
the Heisenberg time. We combine a semiclassical analysis with an independent
random-matrix approach to the doublet splittings to obtain the form factor on
all time (energy) scales. Its only free parameter is the characteristic time of
exchange between the cells in units of the Heisenberg time.Comment: 37 pages, 15 figures, changed content, additional autho
QED One-loop Corrections to a Macroscopic Magnetic Dipole
We consider the field equations of a static magnetic field including one-loop
QED corrections, and calculate the corrections to the field of a magnetic
dipole.
PACS: 12.20.Ds, 97.60.Jd, 97.60.GbComment: 11 pages, 4 figures, to appear in Journal of Physics
Delocalization in the Anderson model due to a local measurement
We study a one-dimensional Anderson model in which one site interacts with a
detector monitoring the occupation of that site. We demonstrate that such an
interaction, no matter how weak, leads to total delocalization of the Anderson
model, and we discuss the experimental consequencesComment: 4 pages, additional explanations added, to appear in Phys. Rev. Let
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