Anisotropic gravitational collapse and cosmic jets

Abstract

Consider a dynamic general relativistic spacetime in which the proper infinitesimal interval along one spatial coordinate direction decreases monotonically with time, while the corresponding intervals increase along other spatial directions. In a system undergoing such complete anisotropic collapse/expansion, we look for the formation of a cosmic double-jet configuration: free test particles in the ambient medium, relative to the collapsing system, gain energy from the gravitational field and asymptotically line up parallel and antiparallel to the direction of collapse such that their Lorentz factors approach infinity. A strong burst of electromagnetic radiation is expected to accompany this event if some of the free test particles carry electric charge. Previous work in this direction involved mainly Ricci-flat spacetimes; hence, we concentrate here on inhomogeneous perfect fluid spacetimes. We briefly explore the possible connection between these theoretical cosmic jets and astrophysical jets. We also discuss other general relativistic scenarios for the formation of cosmic jets.

Twisted gravitational waves in the presence of a cosmological constant

“…With respect to the static observers in these spacetimes, timelike geodesics exhibit the cosmic jet property, where the jet motion is parallel to the direction of motion of the plane wave [15,16]. However, the nonuniformity of the wave front in the case of nonplanar TGWs implies that the resulting cosmic jet direction is oblique with respect to the direction of wave propagation [16]. It is interesting to investigate this property for the case under consideration here.…”

“…[15] and further studied in Ref. [16]. A plane gravitational wave admits parallel null rays, so that the four principal null directions of the Weyl tensor coincide and are all parallel to the direction of propagation of the plane wave and hence perpendicular to the uniform wave front.…”

“…A plane gravitational wave admits parallel null rays, so that the four principal null directions of the Weyl tensor coincide and are all parallel to the direction of propagation of the plane wave and hence perpendicular to the uniform wave front. With respect to the static observers in these spacetimes, timelike geodesics exhibit the cosmic jet property, where the jet motion is parallel to the direction of motion of the plane wave [15,16]. However, the nonuniformity of the wave front in the case of nonplanar TGWs implies that the resulting cosmic jet direction is oblique with respect to the direction of wave propagation [16].…”

Vacuum gravitational fields with a null Killing vector

“…In recent years the "cosmic jet" property was intensively investigated: Test particles can gain (or lose) energy in time-dependent gravitational fields, e.g. plane waves [27,28]. It would be interesting to study this question also for the nonplanar waves presented in this article.…”

“…In deriving (42) starting from the definition equations (1), (2) we have made no further restricting assumptions, except of (m ,2 ) 2 + (m ,3 ) 2 = 0 (dropping this 4 The corresponding equation (28) in [20] is misprinted: instead of 4/3 read 2/3. The misprint was noted in [23].…”