23,702 research outputs found
Allowed charge transfers between coherent conductors driven by a time-dependent scatterer
We derive constraints on the statistics of the charge transfer between two
conductors in the model of arbitrary time-dependent instant scattering of
non-interacting fermions at zero temperature. The constraints are formulated in
terms of analytic properties of the generating function: its zeroes must lie on
the negative real axis. This result generalizes existing studies for scattering
by a time-independent scatterer under time-dependent bias voltage.Comment: 5 pages, no figures, corrected misprints and minor changes in version
Hard exclusive production of a vector meson
The processes of a light neutral vector meson, V=\rho^0, \omega, \phi,
electroproduction and a heavy quarkonium, V=J/\Psi, \Upsilon, photoproduction
are studied in the framework of QCD factorization. We derive a complete set of
hard-scattering amplitudes which describe these processes at next-to-leading
order (NLO).Comment: 3 pages, prepared for Diffraction 2004, International Workshop on
Diffraction in High-Energy Physics, Cala Gonone, Sardinia, Italy, September
18 - 23, 200
Factorization of quantum charge transport for non-interacting fermions
We show that the statistics of the charge transfer of non-interacting
fermions through a two-lead contact is generalized binomial, at any temperature
and for any form of the scattering matrix: an arbitrary charge-transfer process
can be decomposed into independent single-particle events. This result
generalizes previous studies of adiabatic pumping at zero temperature and of
transport induced by bias voltage.Comment: 13 pages, 3 figures, typos corrected, references adde
On the Coulomb corrections to the total cross section of the interaction of the atom with ordinary atoms at high energy
The size of atom in the low lying states is considerably smaller
than the radius of atomic screening. Due to that we can neglect this screening
calculating the contribution of multi-photon exchanges. We obtain the analytic
formula for Coulomb corrections which works with a very good accuracy for the
ground state of atom.Comment: 9 pages, LATEX with 1 Postscript figur
Resonant acousto-optics in the terahertz range: TO-phonon polaritons driven by an ultrasonic wave
The resonant acousto-optic effect is studied both analytically and
numerically in the terahertz range where the transverse-optical (TO) phonons
play the role of a mediator which strongly couples the ultrasound and light
fields. A propagating acoustic wave interacts with the TO phonons via
anharmonic channels and opens band gaps in the TO-phonon polariton energy
dispersion that results in pronounced Bragg scattering and reflection of the
incoming light. The separation in frequency of different Bragg replicas, which
is at the heart of acousto-optics, allows us to study the resonant
acousto-optic effect in the most simple and efficient geometry of collinear
propagation of electromagnetic and ultrasonic waves. The acoustically induced
energy gaps, Bragg reflection spectra, and the spatial distribution of the
electric field and polarization are calculated for CuCl parameters, in a wide
range of frequencies and intensities of the pumping acoustic wave. Our results
show drastic changes in terahertz spectra of semiconductor crystals that opens
the way for efficient and accessible manipulation of their infrared properties,
by tuning the parameters of the acoustic wave.Comment: 20 pages, 14 figure
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