Significant modifications of Lamb shift at small centripetal accelerations

TL;DR

This paper explores how the Lamb shift of atoms is affected by small centripetal accelerations, revealing anisotropic and polarization-dependent modifications that can be significant even at very low accelerations.

Contribution

It demonstrates that circular motion can cause notable modifications to the Lamb shift at small accelerations, with effects depending on atomic polarization and rotation speed.

Findings

Noninertial effects depend on atomic polarization direction.

Rotation can significantly alter the Lamb shift at small accelerations.

Anisotropic and polarization-dependent level shifts are observed.

Abstract

We investigate the Lamb shift of centripetally accelerated atoms coupled to electromagnetic vacuum fluctuations. Focusing on a very small orbital radius (so that the tangential speed remains nonrelativistic and the proper centripetal acceleration can be extremely small), we show that the resulting level shift is intrinsically anisotropic and depends sensitively on the atomic polarization direction. For atoms polarizable along the rotation axis, the leading noninertial contribution enters only at second order in the orbital radius and can slightly decrease or increase the energy-level spacing, depending on the angular-velocity regime. In contrast, for atoms polarizable perpendicular to the rotation axis, the noninertial contribution appears already at the leading order in the radius and always increases the energy-level spacing. Remarkably, when the angular velocity greatly exceeds the transition frequency, the rotation-induced correction can become comparable in magnitude to the inertial Lamb shift, indicating that circular motion can significantly modify the Lamb shift even in the regime of very small centripetal accelerations.