17,465 research outputs found
Exclusive Double Diffractive Events: Menu for LHC
Exclusive double diffractive events (EDDE) are considered in the framework of
the Regge-eikonal approach and perturbative calculations for "hard"
subprocesses. Total and differential cross-sections for processes are calculated.Comment: 18 pages, Latex 2.09, 6 postscript figures, references are adde
Bremsstrahlung radiation from the interaction of short laser pulses with dielectrics
An intense, short laser pulse incident on a transparent dielectric can excite
electrons from valence to the conduction band. As these electrons undergo
scattering, both from phonons and ions, they emit bremsstrahlung radiation.
Here we present a theory of bremsstrahlung emission appropriate for laser
pulse-dielectric interactions. Simulations of the interaction, incorporating
this theory, illustrate characteristics of the radiation (power, energy and
spectra) for arbitrary ratios of electron collision frequency to radiation
frequency. The conversion efficiency of laser pulse energy into bremsstrahlung
radiation depends strongly on both the intensity and duration of the pulse,
saturating at values of about 10e-5. Depending on whether the intensity is
above or below the damage threshold of the material, the emission can originate
either from the surface or the bulk of the dielectric respectively. The
bremsstrahlung emission may provide a broadband light source for diagnostics
Periodic variations in the colours of the classical T Tauri star RW Aur A
The classical T Tauri star RW Aur A is an irregular variable with a large
amplitude in all photometric bands. In an extended series of photometric data
we found small-amplitude periodic variations in the blue colours of the star,
with a period of 2.64 days. The period was relatively stable over several
years. The amplitude of the periodic signal is 0.21 mag in U-V, 0.07 mag in
B-V, and about 0.02 mag in V-R and V-I. No periodicity was found in the V
magnitude. The relevance of this photometric period to the recently discovered
periodicity in spectral features of the star is discussed, and the hypothesis
of a hot spot is critically considered.Comment: 5 pages, 8 figures, uses new aa.cls, accepted for publication in
Astronomy and Astrophysic
On aether terms in a space-time with a compact extra dimension
In this paper, for the CPT-even and CPT-odd extensions of the QED, we
explicitly obtain the aether-like corrections for the electromagnetic field in
the case when the space-time involves an extra compact spatial dimension
besides of usual four dimensions. Our methodology is based on an explicit
summation over the Kaluza-Klein tower of fields which is no more difficult than
the finite-temperature calculations. The quantum corrections turn out to be
large as the extra dimension is small. We demonstrate that in the CPT-even
case, the extra dimension manifests itself through a new scalar particle.Comment: 9 page
On the perturbative generation of the higher-derivative Lorentz-breaking terms
In this paper, we describe the perturbative generation of the
higher-derivative Lorentz-breaking terms for the gauge field, that is, the
Myers-Pospelov term and the higher-derivative Carroll-Field-Jackiw term. These
terms are explicitly calculated in the one-loop approximation and shown to be
finite and ambiguous.Comment: 12 pages, version accepted to PR
- …