Spinning particles in scalar-tensor gravity

TL;DR

This paper introduces a new model for spinning particles in Brans-Dicke gravity, showing how their spin vectors behave along their trajectories when neglecting spin-curvature interactions.

Contribution

It develops a novel model of spinning particles in scalar-tensor gravity using a metric-compatible connection with torsion.

Findings

Spin vector is Fermi-parallel along the worldline.

Particle's worldline is an autoparallel of the connection.

Neglecting spin-curvature coupling simplifies spin behavior.

Abstract

We develop a new model of a spinning particle in Brans-Dicke spacetime using a metric-compatible connection with torsion. The particle's spin vector is shown to be Fermi-parallel (by the Levi-Civita connection) along its worldline (an autoparallel of the metric-compatible connection) when neglecting spin-curvature coupling.