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Paper:

TR26-078 | 3rd May 2026 10:26

Superpolynomial Length Lower Bounds for Tree-Like Semantic Proof Systems with Bounded Line Size

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TR26-078
Authors: Susanna F. de Rezende, David Engström, Yassine Ghannane, Kilian Risse
Publication: 17th May 2026 06:11
Downloads: 115
Keywords: 


Abstract:

We prove superpolynomial length lower bounds for the semantic tree-like Frege refutation system with bounded line size. Concretely, for any function $n^{2-\varepsilon} \leq s(n) \leq \exp\bigl(n^{1-\varepsilon}\bigr)$ we exhibit an explicit family $\mathcal{A}$ of $n$-variate CNF formulas $A$, each of size $|A| \le s(n)^{1+\varepsilon}$, such that if $A$ is chosen uniformly from $\mathcal{A}$, then asymptotically almost surely any tree-like Frege refutation of $A$ in line-size $s(n)$ is of length super-polynomial in $|A|$. Our lower bounds apply also to tree-like degree $d$ threshold systems, for $d \approx \log\bigl(s(n)\bigr)$, that is, for $d$ up to $n^{1-\varepsilon}$. More generally, our lower bounds apply to the semantic version of these systems and to any semantic tree-like proof system where the number of distinct lines is bounded by $\exp\bigl(s(n)\bigr)$.



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