Liouville–Neumann series

The Liouville–Neumann series is a mathematical series used in the context of solving linear differential equations, specifically in the theory of differential operators. It is closely associated with the study of linear time-dependent systems and can be used for analyzing the solutions of linear ordinary differential equations (ODEs). **Definition and Context:** Consider a linear differential operator \( L(t) \), which typically depends on time \( t \).