“…In particular, if f : X → Y is isotrivial, then δ(f ) = 0. Modular invariants are basic in the study of fibrations of algebraic surfaces and moduli spaces of algebraic curves, see [Ta10,LT13,Li16,No07]. In arithmetic algebraic geometry, modular invariants are some heights of algebraic curves, and can be used to give uniformity properties of curves, see [LT17].…”