Kinetic Energy and Angular Momentum of Free Particles in the Gyratonic pp-Waves Space-times

TL;DR

This paper investigates how short bursts of gyratonic pp-waves influence free particles, showing that these gravitational waves can transfer energy and angular momentum, altering particles' kinetic energy and angular momentum after passage.

Contribution

It provides a numerical analysis of particle dynamics in gyratonic pp-waves, revealing energy and angular momentum transfer mechanisms not previously detailed.

Findings

Particles' kinetic energy changes after wave passage

Angular momentum per unit mass is affected by the waves

Energy and angular momentum transfer can increase or decrease

Abstract

Gyratonic pp-waves are exact solutions of Einstein's equations that represent non-linear gravitational waves endowed with angular momentum. We consider gyratonic pp-waves that travel in the $z$ direction and whose time dependence on the variable $u={1 \over \sqrt{2}}(z-t)$ is given by gaussians, so that the waves represent short bursts of gravitational radiation propagating in the $z$ direction. We evaluate numerically the geodesics and velocities of free particles in the space-time of these waves, and find that after the passage of the waves both the kinetic energy and the angular momentum per unit mass of the particles are changed. Therefore there is a transfer of energy and angular momentum between the gravitational field and the free particles, so that the final values of the energy and angular momentum of the free particles may be smaller or larger in magnitude than the initial values.