Chameleon Dark Energy and Atom Interferometry

TL;DR

This paper introduces a new numerical relaxation method for calculating chameleon scalar field forces in atom interferometry experiments, improving accuracy and generality over previous approximations, and helps refine constraints on chameleon theories.

Contribution

The authors develop a versatile numerical relaxation scheme to compute chameleon forces without assuming spherical symmetry, enhancing theoretical predictions for atom interferometry tests.

Findings

The new method agrees within 20% of previous analytical approximations.

Constraints on chameleon field parameters are confirmed, with minor adjustments due to chamber size.

The technique is adaptable for future experiments with higher precision.

Abstract

Atom interferometry experiments are searching for evidence of chameleon scalar fields with ever-increasing precision. As experiments become more precise, so too must theoretical predictions. Previous work has made numerous approximations to simplify the calculation, which in general requires solving a 3-dimensional nonlinear partial differential equation (PDE). In this paper, we introduce a new technique for calculating the chameleonic force, using a numerical relaxation scheme on a uniform grid. This technique is more general than previous work, which assumed spherical symmetry to reduce the PDE to a 1-dimensional ordinary differential equation (ODE). We examine the effects of approximations made in previous efforts on this subject, and calculate the chameleonic force in a set-up that closely mimics the recent experiment of Hamilton et al. Specifically, we simulate the vacuum chamber as a cylinder with dimensions matching those of the experiment, taking into account the backreaction of the source mass, its offset from the center, and the effects of the chamber walls. Remarkably, the acceleration on a test atomic particle is found to differ by only 20% from the approximate analytical treatment. These results allow us to place rigorous constraints on the parameter space of chameleon field theories, although ultimately the constraint we find is the same as the one we reported in Hamilton et al. because we had slightly underestimated the size of the vacuum chamber. This new computational technique will continue to be useful as experiments become even more precise, and will also be a valuable tool in optimizing future searches for chameleon fields and related theories.