Miha Nemevšek (IJS) and Yue Zhang (Carleton U.) find significant generic constraints on models of dark matter coming from large scale structure formation. Their work, published in Physical Review Letters, gives analytic estimates, followed by precise numerical calculations that set stringent constraints on a class of models with entropy dilution.

Abstract: Entropy production is a necessary ingredient for addressing the overpopulation of thermal relics. It is widely employed in particle physics models for explaining the origin of dark matter. A long-lived particle that decays to the known particles, while dominating the universe, plays the role of the dilutor. We point out the impact of its partial decay to dark matter on the primordial matter power spectrum. For the first time, we derive a stringent limit on the branching ratio of the dilutor to dark matter from large scale structure observation using the sloan digital sky survey data. This offers a novel tool for testing models with a dark matter dilution mechanism. We apply it to the left-right symmetric model and show that it firmly excludes a large portion of parameter space for right-handed neutrino warm dark matter.

PRL link: Dark Matter Dilution Mechanism through the Lens of Large-Scale Structure