2,811 research outputs found
Detecting photon-photon scattering in vacuum at exawatt lasers
In a recent paper, we have shown that the QED nonlinear corrections imply a
phase correction to the linear evolution of crossing electromagnetic waves in
vacuum. Here, we provide a more complete analysis, including a full numerical
solution of the QED nonlinear wave equations for short-distance propagation in
a symmetric configuration. The excellent agreement of such a solution with the
result that we obtain using our perturbatively-motivated Variational Approach
is then used to justify an analytical approximation that can be applied in a
more general case. This allows us to find the most promising configuration for
the search of photon-photon scattering in optics experiments. In particular, we
show that our previous requirement of phase coherence between the two crossing
beams can be released. We then propose a very simple experiment that can be
performed at future exawatt laser facilities, such as ELI, by bombarding a low
power laser beam with the exawatt bump.Comment: 8 pages, 6 figure
Beam energy measurement at linear colliders using spin precession
Linear collider designs foresee some bends of about 5-10 mrad. The spin
precession angle of one TeV electrons on 10 mrad bend is 23.2 rad and it
changes proportional to the energy. Measurement of the spin direction using
Compton scattering of laser light on electrons before and after the bend allows
determining the beam energy with an accuracy about of 10^{-5}. In this paper
the principle of the method, the procedure of the measurement and possible
errors are discussed. Some remarks about importance of plasma focusing effects
in the method of beam energy measurement using Moller scattering are given.Comment: 7 pages, Latex, 4 figures(.eps). In v.3 corresponds to journal
publication. Talk at 26-th Advanced ICFA Beam Dynamic Workshop on
Nanometre-Size Colliding Beams (Nanobeam2002), Lausanne, Switzerland, Sept
2-6, 200
Combinatorics and formal geometry of the master equation
We give a general treatment of the master equation in homotopy algebras and
describe the operads and formal differential geometric objects governing the
corresponding algebraic structures. We show that the notion of Maurer-Cartan
twisting is encoded in certain automorphisms of these universal objects
A generalization of the Ginzburg-Landau theory to p-wave superconductors
We succeed to build up a straightforward theoretical model for spin-triplet
p-wave superconductors by introducing in Ginzburg-Landau theory a second order
parameter and a suitable interaction between the two mean fields.Comment: RevTeX, 4 pages, no figure
Dependence of the critical temperature on the Higgs field reparametrization
We show that, despite of the reparametrization symmetry of the Lagrangian
describing the interaction between a scalar field and gauge vector bosons, the
dynamics of the Higgs mechanism is really affected by the representation gauge
chosen for the Higgs field. Actually, we find that, varying the parametrization
for the two degrees of freedom of the complex scalar field, we obtain different
expressions for the Higgs mass: in its turn this entails different expressions
for the critical temperatures, ranging from zero to a maximum value, as well as
different expressions for other basic thermodynamical quantities.Comment: revtex, 12 pages, 2 eps figure
Electric field induced charge injection or exhaustion in organic thin film transistor
The conductivity of organic semiconductors is measured {\it in-situ} and
continuously with a bottom contact configuration, as a function of film
thickness at various gate voltages. The depletion layer thickness can be
directly determined as a shift of the threshold thickness at which electric
current began to flow. The {\it in-situ} and continuous measurement can also
determine qualitatively the accumulation layer thickness together with the
distribution function of injected carriers. The accumulation layer thickness is
a few mono layers, and it does not depend on gate voltages, rather depends on
the chemical species.Comment: 4 figures, to be published in Phys. Rev.
Positrons in Cosmic Rays from Dark Matter Annihilations for Uplifted Higgs Regions in MSSM
We point out that there are regions in the MSSM parameter space which
successfully provide a dark matter (DM) annihilation explanation for observed
positron excess (e.g. PAMELA), while still remaining in agreement with all
other data sets. Such regions (e.g. the uplifted Higgs region) can realize an
enhanced neutralino DM annihilation dominantly into leptons via a Breit-Wigner
resonance through the CP-odd Higgs channel. Such regions can give the proper
thermal relic DM abundance, and the DM annihilation products are compatible
with current antiproton and gamma ray observations. This scenario can succeed
without introducing any additional degrees of freedom beyond those already in
the MSSM.Comment: 11 pages, 9 figure
Sfermion Pair Production in Polarized and Unpolarized Collisions
We calculate total and differential cross sections for the production of
sfermion pairs in photon-photon collisions, including contributions from
resolved photons and arbitrary photon polarization. Sfermion production in
photon collisions depends only on the sfermion mass and charge. It is thus
independent of the details of the SUSY breaking mechanism, but highly sensitive
to the sfermion charge. We compare the total cross sections for bremsstrahlung,
beamstrahlung, and laser backscattering photons to those in
annihilation. We find that the total cross section at a polarized photon
collider is larger than the annihilation cross section up to the
kinematic limit of the photon collider.Comment: 19 pages, Latex, 18 (e)ps-figure
Quantum entanglement of spin-1 bosons with coupled ground states in optical lattices
We examine particle entanglement, characterized by pseudo-spin squeezing, of
spin-1 bosonic atoms with coupled ground states in a one-dimensional optical
lattice. Both the superfluid and Mott-insulator phases are investigated
separately for ferromagnetic and antiferromagnetic interactions. Mode
entanglement is also discussed in the Mott insulating phase. The role of a
small but nonzero angle between the polarization vectors of counter-propagating
lasers forming the optical lattice on quantum correlations is investigated as
well.Comment: 18 pages, 8 figures. To be published in Journal of Physics
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