Gravitational ultrarelativistic spin-orbit interaction and the weak equivalence principle

TL;DR

This paper demonstrates that in ultrarelativistic regimes, the gravitational spin-orbit interaction causes violations of the weak equivalence principle, challenging traditional assumptions about spinning test bodies in gravity.

Contribution

It reveals that the weak equivalence principle does not hold in the ultrarelativistic limit for spinning particles, based on analysis of Mathisson-Papapetrou equations.

Findings

Ultrarelativistic spin-orbit interaction violates the weak equivalence principle.

Deviation from geodesic motion is not due to tidal forces.

Traditional assumptions about spinning test bodies are incorrect in this regime.

Abstract

It is shown that the gravitational ultrarelativistic spin-orbit interaction violates the weak equivalence principle in the traditional sense. This fact is a direct consequence of the Mathisson-Papapetrou equations in the frame of reference comoving with a spinning test particle. The widely held assumption that the deviation of a spinning test body from a geodesic trajectory is caused by tidal forces is not correct