  Recent work has studied entanglement between the spin and momentum components
of a single spin-1/2 particle and showed that maximal entanglement is obtained
only when boosts approach the speed of light. Here we extend the boost scenario
to general geometries and show that, intriguingly, maximal entanglement can be
achieved with boosts less than the speed of light. Boosts approaching the speed
of light may even decrease entanglement. We also provide a geometric
explanation for this behavior.
