Forecasts for interacting dark energy with time-dependent momentum exchange

Models of interacting dark energy and dark matter offer a possible solution to cosmological tensions. In this work, we examine a pure momentum-exchange model with a time-dependent coupling strength ξ(z) that could help to alleviate the S8 tension. We perform Fisher forecasting and MCMC analysis to constrain the coupling strength of this interaction for different redshift bins 0.0 < z < 2.1, using the specifications of upcoming DESI-like surveys. For this analysis, we examine both a model with a constant equation of state w = -0.9, as well as a thawing dark energy model with an evolving w(z). We show that, for a constant equation of state, ξ(z) can be well constrained in all redshift bins. However, due to a weaker effect at early times, the constraints are significantly reduced at high redshifts in the case of a thawing w(z) model.