  Twisted gravitational waves (TGWs) are nonplanar waves with twisted rays that
move along a fixed direction in space. We study further the physical
characteristics of a recent class of Ricci-flat solutions of general relativity
representing TGWs with wave fronts that have negative Gaussian curvature. In
particular, we investigate the influence of TGWs on the polarization of test
electromagnetic waves and on the motion of classical spinning test particles in
such radiation fields. To distinguish the polarization effects of twisted waves
from plane waves, we examine the theoretical possibility of existence of
spin-twist coupling and show that this interaction is generally consistent with
our results.
