Motivated by the theory of proof complexity generators we consider the following $Σ^p_2$ search problem $\mbox{DD}_P$ determined by a propositional proof system $P$: given a $P$-proof $π$ of a disjunction $\bigvee_i α_i$, no two $α_i$ having an atom in common, find $i$ such that $α_i \in \mbox{TAUT}$. We formulate a hypothesis (ST) that for some strong proof system $P$ the problem $\mbox{DD}_P$ is not solvable in the student-teacher model with a $p$-time student and a constant number of rounds. The hypothesis follows from the existence of hard one-way permutations. We prove, using a model-theoretic assumption, that (ST) implies $NP \neq coNP$. The assumption concerns the existence of extensions of models of a bounded arithmetic theory and it is open at present if it holds.

@article{paperbot3993,
  title = {On $NP \cap coNP$ proof complexity generators},
  author = {Jan Krajicek},
  journal = {Logical Methods in Computer Science},
  volume = {Volume 22, Issue 2},
  year = {2026},
  doi = {10.46298/lmcs-22(2:14)2026}
}