Propagation of Partially Coherent Photons in an Ultra-Intense Radiation Gas

The scattering of photons off photons at the one-loop level is investigated. We give a short review of the weak field limit, as given by the first order term in the series expansion of the Heisenberg-Euler Lagrangian. The dispersion relation for a photon in a radiation gas is presented. Based on this, a wave kinetic equation and a set of fluid equations is formulated. These equations describe the interaction between a partially coherent electromagnetic pulse and an intense radiation gas. The implications of the results are discussed.Comment: 10 pages, 1 figure, revtex

Radiation dominated particle and plasma dynamics

We consider the general problem of charged particle motion in a strong electromagnetic field of arbitrary configuration and find a universal behaviour: for sufficiently high field strengths, the radiation losses lead to a general tendency of the charge to move along the direction that locally yields zero lateral acceleration. The relativistic motion along such a direction results in no radiation losses, according to both classical and quantum descriptions of radiation reaction. We show that such a radiation-free direction (RFD) exists at each point of an arbitrary electromagnetic field, while the time-scale of approaching this direction decreases with the increase of field strength. Thus, in the case of a sufficiently strong electromagnetic field, at each point of space, the charges mainly move and form currents along local RFD, while the deviation of their motion from RFD can be calculated in order to account for their incoherent emission. This forms a general description of particle, and therefore plasma, dynamics in strong electromagnetic fields, the latter can be generated by state-of-the-art lasers or in astrophysical environments

Scalar Perturbations in Two-Temperature Cosmological Plasmas

We study the properties of density perturbations of a two-component plasma with a temperature difference on a homogeneous and isotropic background. For this purpose we extend the general relativistic gauge invariant covariant (GIC) perturbation theory to include a multi-fluid with a particular equations of state (ideal gas) and imperfect fluid terms due to the relative energy flux between the two species. We derive closed sets of GIC vector and subsequently scalar evolution equations. We then investigate solutions in different regimes of interest. In particular, we study long wavelength and arbitrary wavelength Langmuir and ion-acoustic perturbations. The harmonic oscillations are superposed on a Jeans type instability. We find a generalised Jeans criterion for collapse in a two-temperature plasma, which states that the species with the largest sound velocity determines the Jeans wavelength. Furthermore, we find that within the limit for gravitational collapse, initial perturbations in either the total density or charge density lead to a growth in the initial temperature difference. These results are relevant for the basic understanding of the evolution of inhomogeneities in cosmological models.Comment: 9 pages. Accepted for publication in MNRAS, 5 April 2006 (submitted 20 Januari 2006

Rotating matter in general relativity -- stationary state I

Stationary rotating matter configurations in general relativity are considered. A formalism for general stationary space times is developed. Axisymmetric systems are discussed by the use of a nonholonomic and nonrigid frame in the three-space of the time-like Killing trajectories. Two symmetric and trace-free tensors are constructed. They characterize a class of matter states in which both the interior Schwarzschild and the Kerr solution are contained. Consistency relations for this class of perfect fluids are derived. Incompressible fluids characterized by these tensors are investigated, and one differentially rotating solution is found.Comment: 25 pages, REVTe

Nonlinear resonant wave interaction in vacuum

The basic equations governing propagation of electromagnetic and gravitational waves in vacuum are nonlinear. As a consequence photon-photon interaction as well as photon-graviton interaction can take place without a medium. However, resonant interaction between less than four waves cannot occur in vacuum, unless the interaction takes place in a bounded region, such as a cavity or a waveguide. Recent results concerning resonant wave interaction in bounded vacuum regions are reviewed and extended.Comment: 8 pages, 1 figure; Talk given at ITCPP03, Santorini, Greece (2003