Coherent Emission from Magnetars

It is proposed that magnetospheric currents above the surfaces of magnetars radiate coherent emission in analogy to pulsars. Scaling the magnetospheric parameters suggests that the coherent emission from magnetars would emerge in the infra-red or optical

On convergence of the ChPT HFF expansion for one loop contribution to meson production in NN collisions

We consider the application of heavy fermion formalism based chiral perturbation theory to meson production in nucleon-nucleon collisions. It is shown that for one loop contributions the heavy fermion formalism expansion corrections for the nucleon propagator produce infinite series of correction terms which are of the same momentum power order. This destroys the one-to-one correspondence between the perturbative and small momentum expansion and thus negates the application of any finite order heavy fermion formalism chiral perturbation theory to the $NN\to NN \pi$ reactions.Comment: 13 pages, 3figure

Effective Chiral Theory for Pseudoscalar and Vector Mesons

We consider the vector meson mixing scheme and mass splitting within the framework of an extended $U(3)_L\bigotimes U(3)_R$ chiral effective field theory based on the hidden local symmetry approach where, the pseudoscalar and vector meson nonets play the role of dynamic variables. Unlike other variants of this model, we show that the diagonalization of the vector meson mass matrix and the assumption that its eigenvalues are identical with the physical meson masses, determines the mixing scheme as well as the model free parameters. We show that VMD can be derived from our lagrangian and that for electromagnetic processes at low momenta the VMD model is a good first approximation. The model reproduces nicely the radii of the charged pions and kaons.Comment: 12 pages, 1 figur

Collisionless electrons in a thin high Mach number shock: dependence on angle and </b><b><i>b</i></b>

International audienceIt is widely believed that electron dynamics in the shock front is essentially collisionless and determined by the quasistationary magnetic and electric fields in the shock. In thick shocks the electron motion is adiabatic: the magnetic moment is conserved throughout the shock and v2^ ? B. In very thin shocks with large cross-shock potential (the last feature is typical for shocks with strong electron heating), electrons may become demagnetized (the magnetic moment is no longer conserved) and their motion may become nonadiabatic. We consider the case of substantial demagnetization in the shock profile with the small-scale internal structure. The dependence of electron dynamics and downstream distributions on the angle between the shock normal and upstream magnetic field and on the upstream electron temperature is analyzed. We show that demagnetization becomes significantly stronger with the increase of obliquity (decrease of the angle) which is related to the more substantial influence of the inhomogeneous parallel electric field. We also show that the demagnetization is stronger for lower upstream electron temperatures and becomes less noticeable for higher temperatures, in agreement with observations. We also show that demagnetization results, in general, in non-gyrotropic down-stream distributions