Superluminal Effects Research Articles

Dispersionless, highly superluminal propagation in a medium with a gain doublet

In the region between two lines of a doublet of an inverted medium, there exists a point of zero group-velocity dispersion, where highly superluminal effects may be observable without significant gain, loss, distortion, or broadening. The results of this group-velocity analysis hold for sufficiently narrow-band, analytic pulses, and do not constitute a violation of causality, although the group, ``signal,'' and energy velocities as defined by Sommerfeld and Brillouin may all exceed c or even become negative. No sharp disturbance in the pulse (a real signal) could propagate faster than light, but the scheme offers an unusual noiseless amplification scheme for the leading edge of a pulse, both at the classical and at the single-photon level.

Einstein-Rosen metrics generated by the inverse scattering transform

The most general Einstein-Rosen solutions obtainable by the inverse scattering transform, using the Levi-Civita metric as seed are analyzed. They can be classified as a family of evolving metrics without a clear physical interpretation and a family representing gravitational waves absorbed and radiated by a massive cylinder. The physical interpretation is based on a perturbative analysis, which shows that the solition waves have a peculiar superluminal effect, on the evaluation of the optical scalars and on Thorne's C energy.

A New Geometry for Superluminal Motions

In the context of superluminal motions, the statistical difficulties intrinsic to the canonical jet geometry are alleviated if the relativistic flows occur on a plane screen, orthogonal to the source axis. The strongest superluminal effects should be detected when the source lies in the plane of the sky, rather than pointing at the observer. The polarization properties, the simplest deviations from the basic geometry, and the connection with other non-thermal phenomena are also indicated.

Non-radial ejection in 3C345

The radio source 3C345 is associated with a 16th magnitude quasar with z = 0.595 (ref. 1). At radio wavelengths it has six major components. From largest to smallest these are: a low brightness halo2; a 3 kpc curved jet3; three steep-spectrum components (C1, C2, and C3) which define a curved jet4,5; and a compact component D which is self-absorbed at frequencies up to at least 10 GHz. Components C2 and C3 show proper motion relative to D at an apparent superluminal speed. We present VLBI observations at 10.7 GHz which show that a new radio component C4 has appeared and is moving along a non-radial path. This behaviour is consistent with the hypothesis that bending causes the jet curvature. We interpret our observations in light of the relativistic beam model6 as this is currently the most attractive explanation for both the superluminal effect and the weak X-ray emission4.

The dynamics of relativistic plasmoids and rapidly varying radio sources

Variability and superluminal expansion of compact radio sources are investigated in terms of a theoretical model for the dynamics of radio sources involving relativistic motion of ram-pressure confined plasmoids (defined to be aggregates of magnetized plasma and relativistic particles). It is shown that relativistic spherical blast waves are subject to fragmentation leading to the formation of a number of discrete, relativistic plasmoids. It is shown that the initial temperature of the thermal component of the plasma fragments is likely to be on the order of 10/sup 12/ K. At this temperture the electrons in the plasma are relativistic, although the proton thermal velocity is nonrelativistic. As a result, the Faraday depolarization of such plasmoids is negligible, in agreement with observations of compact sources. Because of relativistic beaming, the plasmoids whose trajectories lie closest to the observer's line of sight are preferentially seen, causing the sources to exhibit variability and superluminal expansion effects which are also consistent with observations of rapidly varying radio sources.