  We introduce the notion of measurable sensitivity, a measure-theoretic
version of the condition of sensitive dependence on initial conditions. It is a
consequence of light mixing, implies a transformation has only finitely many
eigenvalues, and does not exist in the infinite measure-preserving case. Unlike
the traditional notion of sensitive dependence, measurable sensitivity carries
up to measure-theoretic isomorphism, thus ignoring the behavior of the function
on null sets and eliminating dependence on the choice of metric.
