# Fisher matrix forecasts for astrophysical tests of the stability of the fine-structure constant

## TL;DR

This paper forecasts how upcoming astrophysical spectrographs can improve constraints on the stability of the fine-structure constant and related fundamental physics, using Fisher Matrix analysis.

## Contribution

It applies Fisher Matrix techniques to predict the impact of future spectrographs on tests of fundamental physics and dark energy.

## Key findings

- ESPRESSO can improve bounds on the Eötvös parameter by up to two orders of magnitude.
- E-ELT constraints will be competitive with the STEP satellite.
- Potential detection of α variations would significantly constrain dark energy dynamics.

## Abstract

We use Fisher Matrix analysis techniques to forecast the cosmological impact of astrophysical tests of the stability of the fine-structure constant to be carried out by the forthcoming ESPRESSO spectrograph at the VLT (due for commissioning in late 2017), as well by the planned high-resolution spectrograph (currently in Phase A) for the European Extremely Large Telescope. Assuming a fiducial model without $\alpha$ variations, we show that ESPRESSO can improve current bounds on the E\"{o}tv\"{o}s parameter---which quantifies Weak Equivalence Principle violations---by up to two orders of magnitude, leading to stronger bounds than those expected from the ongoing tests with the MICROSCOPE satellite, while constraints from the E-ELT should be competitive with those of the proposed STEP satellite. Should an $\alpha$ variation be detected, these measurements will further constrain cosmological parameters, being particularly sensitive to the dynamics of dark energy.