Wave Modes in the Magnetospheres of Pulsars and Magnetars

We study the wave propagation modes in the relativistic streaming pair plasma of the magnetospheres of pulsars and magnetars, focusing on the effect of vacuum polarization. We show that the combined plasma and vacuum polarization effects give rise to a vacuum resonance, where ``avoided mode crossing'' occurs between the extraordinary mode and the (superluminous) ordinary mode. When a photon propagates from the vacuum-polarization-dominated region at small radii to the plasma-dominated region at large radii, its polarization state may undergo significant change across the vacuum resonance. We map out the parameter regimes (e.g., field strength, plasma density and Lorentz factor) under which the vacuum resonance occurs and examine how wave propagation is affected by the resonance. Some possible applications of our results are discussed, including high-frequency radio emission from pulsars and possibly magnetars, and optical/IR emission from neutron star surfaces and inner magnetospheres.Comment: 19 pages, 10 figures. Accepted by MNRA

Influence of Plasma Collective Effects on Cosmological Evolution

It is well-known that the universe was in a plasma state both before decoupling and after reionization. However, the conventional wisdom has been that the plasma effects are largely Debye-shielded and can thus be safely ignored when considering large scale evolutions. Recently we showed that large scale structure formation in the universe may actually be suppressed by the plasma collective effect. Indeed, observational data indicate that the conventional theoretical formula tends to overestimate the matter power spectrum at scales $k>1h{\rm Mpc}^{-1}$. In this paper, we further develop our theory through a more thorough and general derivation of the Maxwell-Einstein-Boltzmann equation. In addition to baryon density perturbation post reionization, we apply this general formulation to investigate the possible plasma effect on CMB anisotropy. As expected, while the plasma effect does render an observable effect to the former, its impact on the latter is totally negligible.Comment: 8 pages, no figur

Plasma Suppression of Large Scale Structure Formation in the Universe

We point out that during the reionization epoch of the cosmic history, the plasma collective effect among the ordinary matter would suppress the large scale structure formation. The imperfect Debye shielding at finite temperature would induce a residual long-range electrostatic potential which, working together with the baryon thermal pressure, would counter the gravitational collapse. As a result the effective Jean's length, $\tilde{\lambda}_J$, is increased by a factor, $\tilde{\lambda}_J/\lambda_J=\sqrt{8/5}$, relative to the conventional one. For scales smaller than the effective Jean's scale the plasma would oscillate at the ion-acoustic frequency. The modes that would be influenced by this effect depend on the starting time and the initial temperature of reionization, but roughly lie in the range $0.5 h{\rm Mpc}^{-1}< k$, which corresponds to the region of the Lyman-$\alpha$ forest from the inter-galactic medium. We predict that in the linear regime of density-contrast growth, the plasma suppression of the matter power spectrum would approach $1-(\Omega_{dm}/\Omega_m)^2\sim 1-(5/6)^2\sim 30$.Comment: 4 pages and 2 figure