Two Remarks on the Power of Counting

The relationship between the polynomial hierarchy and Valiant's class #P is at present unknown. We show that some low portions of the polynomial hierarchy, namely deterministic polynomial algorithms using an NP oracle at most a logarithmic number of times, can be simulated by one #P computation...

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Bibliographic Details
Main Authors: Papadimitriou, Christos H., Zachos, Stathis K.
Published: 2023
Online Access:https://hdl.handle.net/1721.1/149038
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Summary:The relationship between the polynomial hierarchy and Valiant's class #P is at present unknown. We show that some low portions of the polynomial hierarchy, namely deterministic polynomial algorithms using an NP oracle at most a logarithmic number of times, can be simulated by one #P computation. We also show that the class of problems solvable by polynomial-time nondeterministic Turing machines which accept whenever there is an odd number of accepting computations is idempotent, that is closed under usage of oracles from the same class.