8 research outputs found
Liouville's theorems for L\'evy operators
Let be a L\'evy operator. A function is said to be harmonic with
respect to if in an appropriate sense. We prove Liouville's
theorem for positive functions harmonic with respect to a general L\'evy
operator : such functions are necessarily mixtures of exponentials. For
signed harmonic functions we provide a fairly general result, which encompasses
and extends all Liouville-type theorems previously known in this context, and
which allows to trade regularity assumptions on for growth restrictions on
. Finally, we construct an explicit counterexample which shows that
Liouville's theorem for signed functions harmonic with respect to a general
L\'evy operator does not hold.Comment: 43 page