Saturation effects in exclusive rhoT, rhoL meson electroproduction

We use recent results for the gamma*L -> rhoL and gamma*T -> rhoT impact factors, computed in the impact parameter representation within the collinear factorization scheme, to get predictions for the polarized cross-sections sigmaT and sigmaL of the diffractive leptoproduction of the rho meson at high energy. In this approach the helicity amplitude is a convolution of the scattering amplitude of a color dipole with a target, together with the virtual gamma wave function and with the first moments of the rho meson wave function (in the transverse momentum space), given by the distribution amplitudes up to twist 3 for the gamma*T -> rhoT impact factor and up to twist 2 for the gamma*L -> rhoL impact factor. Combining these results with recent dipole models fitted to DIS data, which include saturation effects, we show that the predictions are in good agreement with HERA data for photon virtuality (Q**2) larger than typically 5 GeV**2, without free parameters and with a weak dependence on the choice of the factorization scale, i.e. the shape of the DAs, for both longitudinally and transversely polarized rho meson. For lower values of Q**2, the inclusion of saturation effects is not enough to provide a good description of HERA data. We believe that it is a signal of a need for higher twist contributions in the rho meson DAs. We also analyze the radial distributions of dipoles between the initial gamma* and the final rho meson states.Comment: 49 pages, 20 figure

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

A model for high energy rho meson leptoproduction based on collinear factorization and dipole models

We present a phenomenological model for the helicity amplitudes T11 and T00 of the rho meson exclusive diffractive leptoproduction in the forward limit. This model leads to a very good description of the polarized cross-sections sigmaT and sigmaL when compared to HERA data. This model is based on the impact factor representation of the helicity amplitudes. The gamma* -> rho impact factor is computed within the light-cone collinear factorization scheme, the impact parameter space representation allowing to factorize out the dipole-target amplitude. Finally our description combines a model for the dipole-target amplitude that includes the saturation effects with the results for the impact factor where the twist 2 and twist 3 distribution amplitudes of the rho meson are involved.Comment: 5 pages, 3 figures, to appear in the proceedings of XXI International Workshop on Deep-Inelastic Scattering and Related Subject - DIS 2013, 22-26 April 2013, Marseille, Franc

High energy rho meson leptoproduction

We investigate the longitudinal and transverse polarized cross-sections of the leptoproduction of the rho meson in the high energy limit. Our model is based on the computation of the impact factor gamma*(lambda_gamma) -> rho(lambda_rho) using the twist expansion in the forward limit and expressed in the impact parameter space. This treatment involves in the final stage the twist 2 and twist 3 distribution amplitudes (DAs) of the rho meson and the dipole scattering amplitude. Taking models that exist for the DAs and for the dipole cross-section, we get a phenomenological model for the helicity amplitudes, we compare our predictions with HERA data and get a fairly good description for large enough virtualities of the photon.Comment: 6 pages, 3 figures, proceedings of the International Workshop on Low X Physics, May 30 - June 4 2013, Rehovot and Eilat, Israe

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 $S^1$-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 $S^1\times \R$. 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