3 problems

Let the nested pushdown tree hierarchy be the hierarchy introduced in the paper, and let the higher-order pushdown and collapsible higher-order pushdown hierarchies be the correspo…

Let the higher-order nested pushdown tree hierarchy consist of nested pushdown trees at all finite levels, equipped with their tree structure and jump relations. The modal $\mu$-ca…

Let $n$-NPT denote the class of level $n$ nested pushdown trees, and let level $n$ collapsible pushdown graphs be the corresponding graph class. An interpretation is a logical inte…