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In this paper, two interesting complexity classes, PP and P, are compared with PH, the polynomial-time hierarchy. It is shown that every set in PH is polynomial-time Turing reducible to a set in PP, and PH is included in BP. 0)P. As a consequence of the results, it follows that PP PH (or 03P___ PH) implies a collapse of PH. A stronger result is also shown:… (More)

- Seinosuke Toda
- 1991

The main purpose of this paper is to exhibit non-algebraic problems that are computationally equivalent to computing the integer determinant. For this purpose, some graph-theoretic counting problems are shown to be equivalent to the integer determinant problem under suitable reducibilities. Those are the problems of counting the number of all paths between… (More)

This paper deals with the graph isomorphism (GI) problem for two graph classes: chordal bipartite graphs and strongly chordal graphs. It is known that GI problem is GI complete even for some special graph classes including regular graphs, bipar-tite graphs, chordal graphs, comparability graphs, split graphs, and k-trees with unbounded k. On the other side,… (More)

We investigate the computational power of the new counting class ModP which generalizes the classes Mod p P, p prime. We show that ModP is polynomial-time truth-table equivalent in power to #P and that ModP is contained in the class AmpMP. As a consequence, the classes PP, ModP and AmpMP are all Turing equivalent, and thus AmpMP and ModP are not low for MP… (More)