Peculiar velocities in dynamic spacetimes

TL;DR

This paper explores how peculiar velocities of particles behave in dynamic spacetimes, identifying two scenarios—collapse and wave—each leading to jet formations with increasing Lorentz factors, and examines their potential connection to cosmic jets.

Contribution

It introduces a second wave scenario for jet formation in dynamic spacetimes, expanding understanding beyond the previously studied collapse scenario.

Findings

Collapse scenario leads to double-jet patterns with infinite Lorentz factor.

Wave scenario results in single-jet patterns with infinite Lorentz factor.

Examines the potential link between the two jet formation mechanisms.

Abstract

We investigate the asymptotic behavior of peculiar velocities in certain physically significant time-dependent gravitational fields. Previous studies of the motion of free test particles have focused on the \emph{collapse scenario}, according to which a double-jet pattern with Lorentz factor $\gamma \to \infty$ develops asymptotically along the direction of complete gravitational collapse. In the present work, we identify a second \emph{wave scenario}, in which a single-jet pattern with Lorentz factor $\gamma \to \infty$ develops asymptotically along the direction of wave propagation. The possibility of a connection between the two scenarios for the formation of cosmic jets is critically examined.