1,136,613 research outputs found
Angular distribution of positrons in coherent pair production in deformed crystals
We investigate the angular distribution of positrons in the coherent process
electronpositron pair creation process by high-energy photons in a periodically
deformed single crystal with a complex base. The formula for the corresponding
differential cross-section is derived for an arbitrary deformation field. The
case is considered in detail when the photon enters into the crystal at small
angles with respect to a crystallographic axis. The results of the numerical
calculations are presented for and diamond single crystals
and Moliere parameterization of the screened atomic potentials in the case of
the deformation field generated by the acoustic wave of S-type.Comment: 11 pages, 4 figures, figures and references adde
Approximate analytical results on the cavity dynamical Casimir effect in the presence of a two-level atom
We study analytically the photon generation from vacuum due to the Dynamical
Casimir effect in a cavity with a two-level atom, prepared initially in an
arbitrary pure state. Performing small unitary transformations we obtain closed
analytical expressions for the probability amplitudes and other important
quantities in the resonant/dispersive regimes.Comment: 5 pages, 2 figure
Dynamical Casimir Effect in two-atom cavity QED
We study analytically and numerically the dynamical Casimir effect in a
cavity containing two stationary 2-level atoms that interact with the resonance
field mode via the Tavis-Cummings Hamiltonian. We determine the modulation
frequencies for which the field and atomic excitations are generated and study
the corresponding dynamical behaviors in the absence of damping. It is shown
that the two-atom setup allows for monitoring of photon generation without
interrupting the growth, and different entangled states can be generated during
the process.Comment: 4+ pages, 2 figure
Influence of contacts on the microwave response of a two-dimensional electron stripe
Electromagnetic response of a finite-width two-dimensional electron stripe
with attached metallic side contacts is theoretically studied. It is shown that
contacts substantially influence the position, the linewidth, and the amplitude
of plasmon-polariton resonances in the stripe. In finite magnetic fields,
absorption of the wave with the inactive circular polarization (which is not
absorbed in an infinite system without contacts) may become larger than that of
the wave with the active polarization. The results are discussed in view of
recent microwave experiments in two-dimensional electron systems.Comment: 13 pages, incl. 9 figures, the paper has been substantially modified
and extended, new results have been added. Accepted for publication in Phys.
Rev.
Geodesic description of Heavy-Light Virasoro blocks
We continue to investigate the dual description of the Virasoro conformal
blocks arising in the framework of the classical limit of the AdS/CFT
correspondence. To give such an interpretation in previous studies, certain
restrictions were necessary. Our goal here is to consider more general
situation available through the worldline approximation to the dual AdS
gravity. Namely, we are interested in computing the spherical conformal blocks
without the previously imposed restrictions on the conformal dimensions of the
internal channels. The duality is realised as an equality of the so-called
heavy-light limit of the n-point conformal block and the action of n-2
particles propagating in some AdS-like background with either a conical
singularity or a BTZ black hole. We describe a procedure that allows relaxing
the constraint on the intermediate channels. To obtain an explicit expression
for the conformal block on the CFT side, we use a recently proposed recursion
procedure and find full agreement between the results of the boundary and bulk
computations.Comment: 13 pages, v3: refs added, typos remove
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