Modifications to the Standard Freeze-out Picture

Speaker: Alexandre Poulin

Although Dark Matter (DM) makes up a significant part of the all the 

energy in the Universe, lack experimental DM measurements means that there is

 no clear path or direction for theorists. Because of this,there are many particle 

physics models and ways to theoretically produce DM, one such mechanism is 

thermal freeze-out. In this scenario, the DM was in thermal contact with the 

Standard Model and decoupled once the rate of reaction became comparable to 

the expansion rate of the Universe. This can be a complicated calculation and 

many approximations are typically made, obscuring the physics when making 

modifications to the standard picture. We will explore the concepts behind 

freeze-out in such a way that generalizations to the standard picture become 

clear, well-motivated path for continued research. We will then go down two such

 path by considering modified expansion rate and will be shown that the results 

are not obtain as simply as one would expect if they were only looking at the 

typical freeze-out equations. Next, we will look at the case with multiple DM  

species as a generalization to the single particle case revealing that general 

interactions between DM species can lead to potentially many important effects.