Where can I read more about the Cauchy problem, i.e. solutions to
$$ \frac{\partial u}{\partial t}+Lu=0 \text{ and } u(0,x)=f(x)$$
for some parabolicelliptic differential operator $L$ where $f$ is not continuous?
Or about the stochastic representations in terms of a diffusion $X$,
$$ u(t,x) = E^{t,x}(f(X_T)), $$
where $f$ is not continuous?
What about the case where the set of discontinuities has measure zero?