Varying couplings in the early universe: correlated variations of $\alpha$ and $G$

Understand

The Cosmic Microwave Background anisotropies provide a unique opportunity to constrain simultaneous variations of the fine-structure constant $\alpha$ and Newton's gravitational constant $G$.

• Those correlated variations are possible in a wide class of theoretical models.
• In this brief paper we show that the current data, assuming that particle masses are constant, gives no clear indication for such variations, but already prefers that any relative variations in $\alpha$ should be of the same sign of those of $G$ for variations of $\sim 1 %$.
• We also show that a cosmic complementarity is present with Big Bang Nucleosynthesis and that a combination of current CMB and BBN data strongly constraints simultaneous variations in $\alpha$ and $G$.