Violation of the action-reaction principle in an asymmetrically excited system

TL;DR

This paper demonstrates that in an asymmetrically excited two-atom system, the action-reaction principle is violated due to electromagnetic vacuum momentum transfer, leading to directional spontaneous emission.

Contribution

It provides a quantitative prediction of action-reaction violation in excited atom systems and links it to electromagnetic vacuum momentum transfer.

Findings

Action-reaction principle is violated in excited atom interactions.

Vacuum momentum results from asymmetric virtual photon interference.

Directional spontaneous emission releases the transferred momentum.

Abstract

Violation of the action-reaction principle is shown to occur in the van der Waals interaction between two atoms, one of which is excited. It is accompanied by the transfer of linear momentum to the electromagnetic vacuum. The vacuum momentum results from the asymmetric interference of the virtual photons scattered off each atom along the interatomic direction, which is in itself a manifestation of the optical theorem. This momentum, of equal strength and opposite direction to the momentum gained by the two-atom system, is ultimately released through directional spontaneous emission. A quantitative prediction of this phenomenon is made in a two-alkali atom system. It is conjectured that action-reaction violation takes place in any asymmetrically excited system.