Constraining Variations in the Fine Structure Constant in the presence of Early Dark Energy

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We discuss present and future cosmological constraints on variations of the fine structure constant $\alpha$ induced by an early dark energy component having the simplest allowed (linear) coupling to electromagnetism.

• We find that current cosmological data show no variation of the fine structure constant at recombination respect to the present-day value, with $\alpha$ / $\alpha_0$ = 0.975 \pm 0.020 at 95 % c.l., constraining the energy density in early dark energy to $\Omega_e$ < 0.060 at 95 % c.l..
• Moreover, we consider constraints on the parameter quantifying the strength of the coupling by the scalar field.
• We find that current cosmological constraints on the coupling are about 20 times weaker than those obtainable locally (which come from Equivalence Principle tests).