# Dispersion Interactions between Neutral Atoms and the Quantum Electrodynamical Vacuum

## TL;DR

This review explores the fundamental nature of dispersion interactions between neutral atoms, emphasizing their connection to quantum vacuum fluctuations, and discusses recent advances including effects of acceleration and boundaries.

## Contribution

It provides a comprehensive overview of dispersion interactions, linking them to vacuum fluctuations, and introduces models that clarify their physical origin and computational evaluation, especially in complex scenarios.

## Key findings

- Dispersion interactions are deeply connected to vacuum fluctuations and energy.
- Models based on vacuum field energy densities elucidate the physical origin.
- Recent results relate atomic motion and acceleration to dispersion forces.

## Abstract

Dispersion interactions are long-range interactions between neutral ground-state atoms or molecules, or polarizable bodies in general, due to their common interaction with the quantum electromagnetic field. They arise from the exchange of virtual photons between the atoms, and, in the case of three or more atoms, are not additive. In this review, after having introduced the relevant coupling schemes and effective Hamiltonians, as well as properties of the vacuum fluctuations, we~outline the main properties of dispersion interactions, both in the nonretarded (van der Waals) and retarded (Casimir--Polder) regime. We then discuss their deep relation with the existence of the vacuum fluctuations of the electromagnetic field and vacuum energy. We describe some transparent physical models of two- and three-body dispersion interactions, based on dressed vacuum field energy densities and spatial field correlations, which stress their deep connection with vacuum fluctuations and vacuum energy. These models give a clear insight of the physical origin of dispersion interactions, and also provide useful computational tools for their evaluation. We show that this aspect is particularly relevant in more complicated situations, for example when macroscopic boundaries are present. We also review recent results on dispersion interactions for atoms moving with noninertial motions and the strict relation with the Unruh effect, and on resonance interactions between entangled identical atoms in uniformly accelerated motion.