Random oracles separate PSPACE from the polynomial-time hierarchy

1987 ◽  
Vol 26 (1) ◽  
pp. 51-53 ◽  
Author(s):  
Lászió Babai
Keyword(s):  
Polynomial Time ◽  
Random Oracles ◽  
Polynomial Time Hierarchy

scholarly journals Polynomial-Time Random Oracles and Separating Complexity Classes

2021 ◽  
Vol 13 (1) ◽  
pp. 11-16
Author(s):  
John M. Hitchcock ◽  
Adewale Sekoni ◽  
Hadi Shafei
Keyword(s):  
Polynomial Time ◽  
Open Problem ◽  
Random Oracle ◽  
Complexity Class ◽  
Complexity Classes ◽  
Random Oracles ◽  
Class Separation ◽  
Polynomial Time Hierarchy

Bennett and Gill [1981] showed that P A ≠ NP A ≠ coNP A for a random oracle A , with probability 1. We investigate whether this result extends to individual polynomial-time random oracles. We consider two notions of random oracles: p-random oracles in the sense of martingales and resource-bounded measure [Lutz 1992; Ambos-Spies et al. 1997], and p-betting-game random oracles using the betting games generalization of resource-bounded measure [Buhrman et al. 2000]. Every p-betting-game random oracle is also p-random; whether the two notions are equivalent is an open problem. (1) We first show that P A ≠ NP A for every oracle A that is p-betting-game random. Ideally, we would extend (1) to p-random oracles. We show that answering this either way would imply an unrelativized complexity class separation: (2) If P A ≠ NP A relative to every p-random oracle A , then BPP ≠ EXP. (3) If P A ≠ NP A relative to some p-random oracle A , then P ≠ PSPACE. Rossman, Servedio, and Tan [2015] showed that the polynomial-time hierarchy is infinite relative to a random oracle, solving a longstanding open problem. We consider whether we can extend (1) to show that PH A is infinite relative to oracles A that are p-betting-game random. Showing that PH A separates at even its first level would also imply an unrelativized complexity class separation: (4) If NP A ≠ coNP A for a p-betting-game measure 1 class of oracles A , then NP ≠ EXP. (5) If PH A is infinite relative to every p-random oracle A , then PH ≠ EXP. We also consider random oracles for time versus space, for example: (6) L A ≠ P A relative to every oracle A that is p-betting-game random.

The polynomial-time hierarchy and sparse oracles

1986 ◽  
Vol 33 (3) ◽  
pp. 603-617 ◽  
Author(s):  
Jose L. Balcázar ◽  
Ronald V. Book ◽  
Uwe Schöning
Keyword(s):  
Polynomial Time ◽  
Polynomial Time Hierarchy

ON HIGHER ARTHUR-MERLIN CLASSES

2004 ◽  
Vol 15 (01) ◽  
pp. 3-19
Author(s):  
JIN-YI CAI ◽  
DENIS CHARLES ◽  
A. PAVAN ◽  
SAMIK SENGUPTA
Keyword(s):  
Polynomial Time ◽  
Upper Bounds ◽  
Complexity Classes ◽  
Polynomial Time Hierarchy

We study higher Arthur-Merlin classes defined via several natural probabilistic operators BP, R and coR. We investigate the complexity classes they define, and a number of interactions between these operators and the standard polynomial time hierarchy. We prove a hierarchy theorem for these higher Arthur-Merlin classes involving interleaving operators, and a theorem giving non-trivial upper bounds to the intersection of the complementary classes in the hierarchy.

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