Atom-interferometry constraints on dark energy (1502.03888v3)

Abstract: If dark energy --- which drives the accelerated expansion of the universe --- consists of a light scalar field, it might be detectable as a "fifth force" between normal-matter objects, in potential conflict with precision tests of gravity. Chameleon fields and other theories with screening mechanisms, however, can evade these tests by suppressing the forces in regions of high density, such as the laboratory. Using a cesium matter-wave interferometer near a spherical mass in an ultra-high vacuum chamber, we reduce the screening mechanism by probing the field with individual atoms rather than bulk matter. Thus, we constrain a wide class of dark energy theories, including a range of chameleon and other theories that reproduce the observed cosmic acceleration.

• The paper presents a novel atom interferometry experiment that precisely constrains chameleon dark energy fields using cesium atoms in ultra-high vacuum.
• It employs a cesium-133 matter-wave interferometer to measure accelerations below 5.5 μm/s, expanding the exclusion region for scalar field theories.
• The experimental setup simulates low-density cosmic conditions, providing robust, photon-independent constraints on dark energy models.

Atom-Interferometry Constraints on Dark Energy

The paper "Atom-Interferometry Constraints on Dark Energy" presents a novel approach using atom interferometry to probe theories of dark energy, specifically those involving chameleon fields and other theories with screening mechanisms. This research primarily addresses the challenge of detecting light scalar fields posited as candidates for dark energy, which might manifest as a "fifth force" detectable by precision experiments but typically remain hidden due to screening effects in high-density environments.

The experimental framework leverages a cesium matter-wave interferometer in an ultra-high vacuum chamber to reduce screening by probing the field with atoms rather than bulk matter. This is achieved through meticulous experimentation involving a cesium-133 atom interferometer, set up to measure forces between the atoms and a spherical aluminum mass. Such a setup is designed to mimic low-density cosmic conditions within a controlled laboratory environment, thereby liberating the chameleon field to become long-ranged and measurable.

Key experimental results show that the acceleration of atoms, attributed to chameleon interactions, is constrained to be below 5.5 μm/s at a 95% confidence level. This finding translates to specific constraints in the parameter space of chameleon and other scalar field theories. The exclusion regions in the parameter space defined by mass parameters Λ and M, indicated in their analysis, rule out a wide class of chameleon theories capable of replicating observed cosmic acceleration, up to certain theoretical thresholds. These precise measurements place significant bounds on M, particularly below the reduced Planck mass, and show exclusion levels that surpass those established by previous neutron-based gravitational experiments.

Several strong points emerge from this investigation:

1. Improved Measurement Techniques: The use of atom interferometry allows for precision detection of the chameleon field by minimizing the screening effect, which often obscures scalar field coupling to matter in typical high-density, bulk experiments.
2. Robust Constraints: The results presented circumvent reliance on photon coupling, which enhances the robustness of the constraints on chameleon fields. This extends current bounds on scalar field theories without depending on additional coupling assumptions.
3. Practical and Theoretical Implications: Practically, this research demonstrates the capability of atom interferometry to test theoretical postulates about dark energy within a controlled environment. Theoretically, it reinforces the viability of scalar fields as dark energy candidates by providing empirical limits on their properties.

In conclusion, the advancements laid out in this paper contribute significantly to cosmological research by refining our understanding of dark energy and the potential scalar fields that could reside within the underlying framework of the universe's expansion. The innovative use of atom interferometry presents a promising avenue for future explorations of fundamental physics, essentially enhancing experimental techniques to uncover additional properties of dark energy fields. With continued development, this research could lead to further breakthroughs in understanding the fundamental processes governing the evolution of the cosmos.