Håstad’s switching lemma

E120579

Håstad’s switching lemma is a fundamental result in computational complexity theory that provides powerful bounds on the simplification of Boolean formulas under random restrictions, with major applications in circuit lower bounds.

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Predicate Object
instanceOf mathematical theorem
result in computational complexity theory
appearsIn Johan Håstad’s work on almost optimal lower bounds for small-depth circuits
appliesTo CNF formulas
DNF formulas
small-depth Boolean circuits
assumption random restriction chosen independently for each variable
characterizes simplification of Boolean formulas under random restrictions
field circuit complexity
computational complexity theory
theoretical computer science
implies that random restrictions often yield shallow decision trees
importance central tool in modern circuit lower bound proofs
foundational result in the theory of AC0 circuits
influenced subsequent switching lemmas and refinements
mainConcept Boolean formulas
circuit lower bounds
decision trees
random restrictions
namedAfter Johan Håstad
provides probabilistic bounds on decision tree depth after restriction
relatedTo Ajtai’s lower bounds for constant-depth circuits
Fourier analysis of Boolean functions
Furst–Saxe–Sipser lower bounds
random restriction method
relates width of CNF or DNF to resulting decision tree depth
shows probability that restricted formula has large decision tree depth is exponentially small in depth bound
random restrictions simplify small-width CNF and DNF formulas
strengthenedBy Håstad’s switching lemma self-linksurface differs
surface form: Håstad’s multi-switching lemma

multi-switching lemmas
toolFor “Almost optimal lower bounds for small depth circuits”
surface form: Håstad’s optimal lower bounds for small-depth circuits

Razborov–Smolensky style arguments for AC0[⊕]
typicalConclusion restricted formula has small-depth decision tree with high probability
typicalDomain formulas of bounded width
usedFor AC0 circuit lower bounds
correlation bounds between AC0 circuits and parity
hardness amplification arguments in circuit complexity
hierarchy theorems for small-depth circuits
proving lower bounds for constant-depth circuits
pseudorandomness constructions for AC0
showing limitations of small-depth circuits computing majority
showing limitations of small-depth circuits computing parity

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Referenced by (3)

Full triples — surface form annotated when it differs from this entity's canonical label.

Johan Håstad knownFor Håstad’s switching lemma
Håstad’s switching lemma strengthenedBy Håstad’s switching lemma self-linksurface differs
this entity surface form: Håstad’s multi-switching lemma
“Almost optimal lower bounds for small depth circuits” relatedTo Håstad’s switching lemma
subject surface form: Almost optimal lower bounds for small depth circuits
this entity surface form: Håstad switching lemma