Challenging the Cosmological Constant

TL;DR

This paper proposes a dynamical dark energy model with a scalar field that interacts weakly with matter, potentially testable through astronomical observations and laboratory experiments, and predicts observable deviations from standard gravity and dark energy behavior.

Contribution

It introduces a chameleon-like scalar field model for dark energy with environmental dependence, linking cosmological acceleration to laboratory and astrophysical tests.

Findings

Potential for observable deviations in gravity in dilute environments

Dark energy equation of state w ≠ -1 possible

Sub-millimeter corrections to Newton's law near current limits

Abstract

We outline a dynamical dark energy scenario whose signatures may be simultaneously tested by astronomical observations and laboratory experiments. The dark energy is a field with slightly sub-gravitational couplings to matter, a logarithmic self-interaction potential with a scale tuned to $\sim 10^{-3} {\rm eV}$, as is usual in quintessence models, and an effective mass $m_\phi$ influenced by the environmental energy density. Its forces may be suppressed just below the current bounds by the chameleon-like mimicry, whereby only outer layers of mass distributions, of thickness $1/m_\phi$, give off appreciable long range forces. After inflation and reheating, the field is relativistic, and attains a Planckian expectation value before Hubble friction freezes it. This can make gravity in space slightly stronger than on Earth. During the matter era, interactions with nonrelativistic matter dig a minimum close to the Planck scale. However, due to its sub-gravitational matter couplings the field will linger away from this minimum until the matter energy density dips below $\sim 10^{-12} {\rm eV}^4$. Then it starts to roll to the minimum, driving a period of cosmic acceleration. Among the signatures of this scenario may be dark energy equation of state $w \ne -1$, stronger gravity in dilute mediums, that may influence BBN and appear as an excess of dark matter, and sub-millimeter corrections to Newton's law, close to the present laboratory limits.