 Sphaleron

A sphaleron is an unstable static electroweak field configuration at the top of the barrier between vacua of different topological number. Thermal transitions across this barrier violate $B+L$ while preserving $B-L$.

A sphaleron is a theoretical concept in particle physics that refers to a type of non-perturbative solution to the equations of the Standard Model, particularly in the context of electroweak theory. The term "sphaleron" is derived from the Greek word "sphaleo," meaning "to fall" or "to topple," which reflects its property of being a saddle point in the energy landscape of field configurations.