Dark energy and equivalence principle constraints from astrophysical tests of the stability of the fine-structure constant

Abstract

Astrophysical tests of the stability of fundamental couplings, such as the finestructure constant α, are becoming an increasingly powerful probe of new physics. Here we discuss how these measurements, combined with local atomic clock tests and Type Ia supernova and Hubble parameter data, constrain the simplest class of dynamical dark energy models where the same degree of freedom is assumed to provide both the dark energy and (through a dimensionless coupling, ζ, to the electromagnetic sector) the α variation. Specifically, current data tightly constrains a combination of ζ and the present dark energy equation of state w 0 . Moreover, in these models the new degree of freedom inevitably couples to nucleons (through the α dependence of their masses) and leads to violations of the Weak Equivalence Principle. We obtain indirect bounds on the Eötvös parameter η that are typically stronger than the current direct ones. We discuss the model-dependence of our results and briefly comment on how the forthcoming generation of high-resolution ultra-stable spectrographs will enable significantly tighter constraints.

Is there a connection between “dark” and “light” physics?

“…In fact, several models incorporating non-minimal couplings between dark energy and the electromagnetic sector have already been proposed in the literature, as solutions to problems in contemporary cosmology [65][66][67][68][69]. Although a thorough analysis of the cosmological implications of the DE-UP has not yet been attempted, the cosmological implications of Λ ∝ α −6 e cosmology were investigated in [70,71], in the context of a time-varying fine structure constant.…”

Search for a Variation of the Fine Structure Constant around the Supermassive Black Hole in Our Galactic Center

“…While both theories have been extremely successful, they are expected to break down at a certain point. In particular, a breaking of the Einstein equivalence principle is expected in various unification scenarios [1,2], in higher dimensional theories [3], and by some models of dark matter [4,5] and dark energy [6,7]. On a more philosophical note, the "principle of absence of absolute structure" led to many developments of extensions of physics where the constants of physics become dynamical entities, explicitly breaking the equivalence principle (see the discussion in section 2 of [8]).…”

Fine-structure constant constraints on late-time dark energy transitions

“…The dimensionless parameter ζ quantifies the strength of the coupling. With these assumptions one can explicitly relate the evolution of α to that of dark energy [32,33] as follows…”

“…which improves the MICROSCOPE bound by more than a factor of three. This is an indirect and somewhat modeldependent constraint, but nevertheless the model dependence is expected to be relatively mild-see [33] for additional discussion of this point.…”