Affleck-Dine and thermal equilibrium

[302021895]

Hi, I am currently studying Cosmology on my own, and I am learning about the Affleck-Dine mechanism of baryogenesis. I understand that in this case the baryon asymmetry is generated by the decay of a supersymmetric flat direction carrying B, which is excited during inflation.

Regarding Sakharov's conditions, B and CP violation come explicitly from soft supersymmetry breaking induced terms in the Lagrangian (the so-called A-terms). However, a mention of the third Sakharov condition is nowhere to be found. How is thermal equilibrium lost in this particular model of baryogenesis?

 

[AndyW]

Hello,

Thank you for your question. The Affleck-Dine mechanism is a fascinating model for baryogenesis and it is great to see that you are studying it on your own.

To answer your question, the third Sakharov condition, which states that there must be a departure from thermal equilibrium, is indeed present in the Affleck-Dine mechanism. In this model, the flat direction carrying B is excited during inflation, which is a period of rapid expansion in the early universe. This rapid expansion can cause the thermal equilibrium to be lost, as the particles in the universe are not able to interact and reach a state of equilibrium.

Furthermore, as the flat direction decays, it produces a large amount of entropy, which also contributes to the departure from thermal equilibrium. This increase in entropy leads to a dilution of the baryon asymmetry, making it more difficult to create a significant amount of baryons.

Overall, the Affleck-Dine mechanism satisfies all three Sakharov conditions, with the loss of thermal equilibrium being a crucial aspect of the model. I hope this helps clarify your understanding of this mechanism.