62,085 research outputs found
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 . 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, , is
increased by a factor, , 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 , which corresponds to the region of the Lyman- 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
.Comment: 4 pages and 2 figure
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