Time-Space Tradeoffs for Satisfiability (1997)
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| Venue: | Journal of Computer and System Sciences |
| Citations: | 25 - 1 self |
BibTeX
@ARTICLE{Fortnow97time-spacetradeoffs,
author = {Lance Fortnow},
title = {Time-Space Tradeoffs for Satisfiability},
journal = {Journal of Computer and System Sciences},
year = {1997},
volume = {60},
pages = {2000}
}
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Abstract
We give the first nontrivial model-independent time-space tradeoffs for satisfiability. Namely, we show that SAT cannot be solved simultaneously in n 1+o(1) time and n 1\Gammaffl space for any ffl ? 0 on general random-access nondeterministic Turing machines. In particular, SAT cannot be solved deterministically by a Turing machine using quasilinear time and p n space. We also give lower bounds for log-space uniform NC 1 circuits and branching programs. Our proof uses two basic ideas. First we show that if SAT can be solved nondeterministically with a small amount of time then we can collapse a nonconstant number of levels of the polynomial-time hierarchy. We combine this work with a result of Nepomnjascii that shows that a nondeterministic computation of super linear time and sublinear space can be simulated in alternating linear time. A simple diagonalization yields our main result. We discuss how these bounds lead to a new approach to separating the complexity classes NL a...
