Seminarium "Teoria cząstek elementarnych i kosmologia"

The CP asymmetries necessary for explaining the observed baryon asymmetry of the universe require irreducible complex phases in couplings and imaginary kinematics from loop diagrams. Furthermore, they must obey the so-called CPT and unitarity constraints - for a particular initial state, summing the asymmetries over all possible final states yields zero. In this seminar, we use unitarity and holomorphic cutting rules to reformulate these constraints diagrammatically in any perturbative order. As a result, the number of terms to be evaluated is reduced and tracking the asymmetry cancellations is simplified. After briefly commenting on handling the s- and t-channel singularities within the same framework, we approach the inclusion of thermal corrections in the Boltzmann equation. Studying the density matrix evolution, we argue that, surprisingly, thermal effects enter via modified cutting rules while still using zero-temperature Feynman rules for the matrix elements.

slides: https://mycloud.fuw.edu.pl/index.php/s/6ZdkfYCkZcXTfwA