Parametric equation in pi-calculus
The paper “On Recursion, Replication and Scope Mechanisms in Process Calculi” by Jesús Aranda, Cinzia Di Giusto, Catuscia Palamidessi, and Frank D. Valencia gives an encoding of the polyadic pi-calculus with recursive definitions in terms of the polyadic pi-calculus with replication and vice versa. The essence of the encoding (in the first direction) is to replace the recursive definition by the replication of a process, so that each invocation of the recursive definition results in a new process.