[Paper Review] Evading Equivalence Principle Violations, Astrophysical and Cosmological Constraints in Scalar Field Theories with a Strong Coupling to Matter

David F. Mota, Douglas J. Shaw|arXiv (Cornell University)|Aug 7, 2006

Quantum Electrodynamics and Casimir Effect22 citations

TL;DR

This paper proposes that scalar fields with strong couplings to matter—despite violating the equivalence principle—can remain consistent with terrestrial, astrophysical, and cosmological constraints due to non-linear self-interactions. These light, strongly coupled scalar fields may drive both early and late-time cosmic acceleration and be detectable in future experiments.

ABSTRACT

We show that, as a result of non-linear self-interactions, it is feasible, at least in light of the bounds coming from terrestrial tests of gravity and those constraints imposed by the physics of compact objects, big-bang nucleosynthesis and measurements of the cosmic microwave background, for there to exist, in our Universe, one or more scalar fields that couple to matter much more strongly than gravity does. Not only are these scalar fields very strongly coupled to matter, but they are also light over cosmological scales and could be responsible for the late and early time acceleration of the universe. These fields could also be detected by a number of future experiments provided they are properly designed to do so. These results open up an altogether new window, which might lead to a completely different view of the role played by light scalar fields in particle physics and cosmology.

Motivation & Objective

• To investigate whether scalar fields with strong couplings to matter can remain consistent with current experimental and cosmological constraints.
• To explore the viability of such scalar fields in explaining cosmic acceleration at both early and late times.
• To assess the detectability of these fields through future experiments.
• To examine the role of non-linear self-interactions in shielding the theory from observational bounds.
• To re-evaluate the potential cosmological and particle physics significance of light scalar fields with strong matter couplings.

Proposed method

• Analyzing scalar field theories with non-linear self-interactions to suppress observable deviations from general relativity.
• Applying constraints from terrestrial gravity tests, big-bang nucleosynthesis, and cosmic microwave background measurements.
• Evaluating the behavior of scalar fields in compact object environments to assess equivalence principle violations.
• Using cosmological models to assess the fields' role in driving early and late-time acceleration.
• Assessing detectability via future experimental designs sensitive to strong scalar couplings.

Experimental results

Research questions

• RQ1 Can scalar fields with strong couplings to matter evade constraints from terrestrial gravity experiments?
• RQ2 How do non-linear self-interactions prevent observable violations of the equivalence principle?
• RQ3 What cosmological roles can such strongly coupled scalar fields play in early and late-time acceleration?
• RQ4 Are there viable parameter regimes for these fields that satisfy nucleosynthesis and CMB observations?
• RQ5 What experimental designs could detect these scalar fields in the future?

Key findings

• Non-linear self-interactions allow scalar fields with strong matter couplings to remain consistent with terrestrial gravity tests.
• These scalar fields can be light over cosmological scales, enabling them to contribute to cosmic acceleration.
• The fields may drive both early and late-time acceleration of the universe, offering a unified mechanism.
• Constraints from big-bang nucleosynthesis and the cosmic microwave background do not rule out such scalar fields.
• Future experiments, if properly designed, could detect these scalar fields.
• The results open a new avenue for understanding the role of light scalar fields in particle physics and cosmology.