2,153 research outputs found
Phenomenology of the polarized cross-sections of the rho meson leptoproduction at high energy
We present a model for the polarized cross-sections of the hard diffractive
leptoproduction of rho meson in the high energy limit. Our model is based on
the light-cone collinear factorization of the virtual photon to rho meson
impact factor when using the impact factor representation of the helicity
amplitudes of the rho meson leptoproduction. This gauge invariant treatment
when expressed in impact parameter space, leads to the factorization on one
hand of the color dipole scattering amplitude and on the other hand of the
distribution amplitudes of the rho meson up to twist 2 and 3. We show that the
results of this approach are in good agreement with HERA data for virtualities
above ~5 GeV^2.Comment: 6 pages, 3 figures, proceedings of Photon 2013, May 20 - 24 2013,
Paris, Franc
Charging of DMSP/F6 spacecraft in aurora on 10 January 1983
Spacecraft charging has been widely observed in geosynchronous orbit on the ATS-5 and ATS-6 pair and on the SCATHA spacecraft. An adequate theory for explaining the observations exist. Neither the data or theory can be exported to low polar orbit and its drastically different environment. Evidence of charging on the DMSP F6 spacecraft is presented. A simple model is set up explaining the observations. Two independent instruments on the spacecraft showed charging to a moderate (44 volts) negative potential. The selection spectrometer showed a flux of 2 billion electrons per sq. cm. sec. ster. peaked at 9.5 keV. This was marginally sufficient to overcome the flux of cold ambient ions. Charging calculations are presented showing where simplications are justified and where serious uncertainties exist. More serious charging is predicted for the Shuttle in polar orbit
Pseudo-Riemannian geodesic foliations by circles
We investigate under which assumptions an orientable pseudo-Riemannian
geodesic foliations by circles is generated by an -action. We construct
examples showing that, contrary to the Riemannian case, it is not always true.
However, we prove that such an action always exists when the foliation does not
contain lightlike leaves, i.e. a pseudo-Riemannian Wadsley's Theorem. As an
application, we show that every Lorentzian surface all of whose
spacelike/timelike geodesics are closed, is finitely covered by .
It follows that every Lorentzian surface contains a non-closed geodesic.Comment: 14 page
Pattern formation by kicked solitons in the two-dimensionnal Ginzburg-Landau medium with a transverse grating
We consider the kick-induced mobility of two-dimensional (2D) fundamental
dissipative solitons in models of lasing media based on the 2D complex
Ginzburg-Landau (CGL) equation including a spatially periodic potential
(transverse grating). The depinning threshold is identified by means of
systematic simulations, and described by means of an analytical approximation,
depending on the orientation of the kick. Various pattern-formation scenarios
are found above the threshold. Most typically, the soliton, hopping between
potential cells, leaves arrayed patterns of different sizes in its wake. In the
laser cavity, this effect may be used as a mechanism for selective pattern
formation controlled by the tilt of the seed beam. Freely moving solitons
feature two distinct values of the established velocity. Elastic and inelastic
collisions between free solitons and pinned arrayed patterns are studied too.Comment: 15 pages, 20 figures (with 41 sub-figures
Nonlinear stability of the Taub-NUT soliton in 6+1 dimensions
Using mixed numerical and analytical methods we give evidence that the 6+1
dimensional Taub-NUT soliton is asymptotically nonlinearly stable against small
perturbations preserving biaxial Bianchi IX symmetry. We also show that for
sufficiently strong perturbations the soliton collapses to a warped black hole.
Since this black hole solution is not known in closed form, for completeness of
the exposition we prove its existence and determine its properties. In
particular, the mass of the black hole is computed.Comment: 19 pages, 5 figure
Building patterns by traveling vortices and dipoles in periodic dissipative media
We analyze pattern-formation scenarios in the two-dimensional (2D) complex
Ginzburg-Landau (CGL) equation with the cubic-quintic (CQ) nonlinearity and a
cellular potential. The equation models laser cavities with built-in gratings,
which are used to stabilize 2D patterns. The pattern-building process is
initiated by kicking a localized compound mode, in the form of a dipole,
quadrupole, or vortex which is composed of four local peaks. The hopping motion
of the kicked mode through the cellular structure leads to the generation of
various extended patterns pinned by the structure. In the ring-shaped system,
the persisting freely moving dipole hits the stationary pattern from the
opposite side, giving rise to several dynamical regimes, with the pinned
multi-soliton chain playing the role of the Newton's cradle (NC)
New string vacua from twistor spaces
We find a new family of AdS_4 vacua in IIA string theory. The internal space
is topologically either the complex projective space CP^3 or the "flag
manifold" SU(3)/(U(1)xU(1)), but the metric is in general neither Einstein nor
Kaehler. All known moduli are stabilized by fluxes, without using quantum
effects or orientifold planes. The analysis is completely ten--dimensional and
does not rely on assumptions about Kaluza--Klein reduction.Comment: 19 pages. v3: published version, further minor correction
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