Before revision: \nref Mathematical definitions Definition 1: A system mapping to is causal if and only if, for any pair of input signals , and any choice of , such that the corresponding outputs satisfy Definition 2: Suppose is the impulse response of any system described by a linear constant coefficient differential equation.
After revision: <:bhaskar>\nref Mathematical definitions Definition 1: A system mapping to is causal if and only if, for any pair of input signals , and any choice of , such that the corresponding outputs satisfy Definition 2: Suppose is the impulse response of any system described by a linear constant coefficient differential equation.