Universality Class of Directed Percolation

The universality class of Directed Percolation describes a category of systems that, despite differences in details, share the same critical behavior when transitioning from an inactive to an active state. Imagine a process where the chance of spreading (like a disease or fire) depends only on local connections and a preferred direction (time or depth). Near the critical point, different systems exhibit similar patterns of how clusters form and dissolve, characterized by specific mathematical exponents. These shared characteristics define the universality class, highlighting fundamental similarities in how such systems behave at phase transitions, regardless of their specific nature.