Distinguishing de Sitter universe from thermal Minkowski spacetime by Casimir-Polder-like force

TL;DR

This paper shows that a static atom in de Sitter space experiences a position-dependent energy shift leading to a Casimir-Polder-like force, which can distinguish it from thermal Minkowski spacetime where no such force occurs.

Contribution

It introduces a method to differentiate de Sitter universe from thermal Minkowski spacetime using atom-field interactions and Casimir-Polder-like forces.

Findings

Static atom in de Sitter space experiences a position-dependent energy shift.

No Casimir-Polder-like force occurs for inertial atoms in thermal Minkowski spacetime.

The force can serve as an indicator to distinguish the two spacetimes.

Abstract

We demonstrate that the static ground state atom, which interacts with a conformally coupled massless scalar field in the de Sitter invariant vacuum, can obtain a position-dependent energy-level shift and this shift could cause a Casimir-Polder-like force on it. Interestingly no such force arises on the inertial atom bathed in a thermal radiation in the Minkowski universe. Thus, although the energy-level shifts of the static atom for these two cases are structurally the same, whether the energy-level shift causes the Casimir-Polder-like force, in principle, could be as an indicator to distinguish de Sitter universe from the thermal Minkowski spacetime.