Quantified Boolean truth and PSPACE completeness
TQBF asks whether a fully quantified finite Boolean formula is true.
Key knowledge
TQBF asks whether a fully quantified finite Boolean formula is true. Existential quantifiers branch by OR and universal quantifiers by AND; depth-first evaluation reuses polynomial workspace. TQBF is PSPACE-complete under polynomial-time many-one reductions.
Conditions and scope
- Every variable is bound; formula length determines the input size.
- Evaluation may take exponential time despite polynomial memory. PSPACE hardness uses quantified reachability constructions, rather than the exponentially large raw computation tableau.
Sources · 2
References
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Massachusetts Institute of Technology2 sources
Evidence and review
Lecture 17 slides 5–6 recursive evaluation and space depth; Lecture 18 slides 5–9 completeness definition/theorem and quantified midpoint construction (polynomial-size shared selector variables).
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Entry details
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- university-core.1
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- University core expansion