Degenerate and Singular Porous Medium Type Equations with Measure Data

We consider the inhomogeneous porous medium equation
\partial_t u − \Delta u^m = \mu, m >(N−2)_+/N,
and more general equations of porous medium type with a non-negative Radon
measure \mu on the right-hand side. In a first step, we prove a priori estimates for weak
solutions in terms of a linear Riesz potential of the right-hand side measure, which
takes exactly the same form as the one for the classical heat equation. Then, we give
an optimal criterium for the continuity of weak solutions, again in terms of a Riesz
potential. Finally, we prove the existence of non-negative, very weak solutions and
show that these constructed very weak solutions satisfy the same estimates.We deal
with both the degenerate case m > 1 and the singular case (N−2)+/N < m < 1.