Stratification of arithmetic formulas by alternation depth of quantifiers over a Δ₀ (bounded) kernel. Σ₁ = r.e. sets, Π₁ = Con(T)-style statements, Δ₁ = computable sets. The hierarchy is proper (Post, Kleene).
Stratification of arithmetic formulas by alternation depth of quantifiers over a Δ₀ (bounded) kernel. Σ₁ = r.e. sets, Π₁ = Con(T)-style statements, Δ₁ = computable sets. The hierarchy is proper (Post, Kleene).