Extended-body effects in cosmological spacetimes

TL;DR

This paper investigates how extended bodies in cosmological spacetimes can change their physical properties like mass and spin through internal deformations, revealing effects absent in Newtonian physics.

Contribution

It demonstrates that extended test bodies can alter their inertial properties in cosmological backgrounds via internal deformations, highlighting non-Newtonian effects.

Findings

Bodies can change mass and spin through internal deformations.

Effects occur despite conserved momenta from symmetries.

Many effects have no Newtonian counterparts.

Abstract

We study the dynamics of extended test bodies in flat Friedmann-Robertson-Walker spacetimes. It is shown that such objects can usually alter their inertial mass, spin, and center-of-mass trajectory purely through the use of internal deformations. Many of these effects do not have Newtonian analogs, and exist despite the presence of conserved momenta associated with the translational and rotational symmetries of the background.