A survey on counting classes

Consideration is given to polynomial-time machines. Among these classes are EP and PP. The authors prove P/sup EP(log)/ 25 PP, investigate the Boolean closure BC(EP) of EP, and give a relativization principle which allows them to completely separate BC(EP) in a suitable relativized world and to give simple proofs for known relativization results. Further results concerning the relationships of such classes in unrelativized and relativized worlds are given.<
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