We give a new proof of the following result (originally due to Linial and Post): it is undecidable whether a given calculus, that is a finite set of propositional formulas together with the rules of ...

We give a direct proof of admissibility of cut and contraction for the contraction-free sequent calculus G4ip for intuitionistic propositional logic and for a corresponding multi-succedent calculus: ...

Computational complexity and proof systems are fundamental areas in theoretical computer science that explore the limits of what can be computed and how efficiently problems can be solved. Recent ...