Variation in the fine-structure constant, distance-duality relation and the next generation of high-resolution spectrograph

Understand

The possibility of variation of the fundamental constants of nature has been a long-standing question, with important consequences for fundamental physics and cosmology.

• In particular, it has been shown that variations in the fine-structure constant, $\alpha$, are directly related to violation of the distance duality relation (DDR), which holds true as long as photons travel on unique null geodesics and their number is conserved.
• In this paper we use the currently available measurements of ${\Delta \alpha}/{\alpha}$ to impose the most stringent constraints on departures of the DDR to date, here quantified by the parameter $\eta$.
• We also perform a forecast analysis to discuss the ability of the new generation of high-resolution spectrograph, like ESPRESSO/VLT and E-ELT-HIRES, to constrain the DDR parameter $\eta$.