In 1984, Danecki proved that satisfiability in IPDL, i.e.,
Propositional Dynamic Logic (PDL) extended with an intersection
operator on programs, is decidable in deterministic double
exponential time. Since then, the exact complexity of IPDL has
remained an open problem: the best known lower bound was the
ExpTime one stemming from plain PDL until, in 2004, the first
author established ExpSpace-hardness.
In this paper, we finally close the gap and prove that IPDL is hard for
2-ExpTime, thus 2-ExpTime-complete. We then sharpen our lower bound,
showing that it even applies to IPDL without the test operator interpreted
on tree structures.