Family 243Mathematical logicLeanNot yet digested
Separating choiceless counting from polynomial time and witnessed choice
Confirms the Blass–Gurevich–Shelah noncapture conjecture: consistency of a linear system over 𝔽 defines a polynomial-time query on unordered finite structures that choiceless polynomial time with counting cannot express. A separate result shows that adding witnessed symmetric choice strictly increases expressive power. Both separations hold for the full counting formalism, allowing hereditarily finite sets of arbitrary finite rank.
Manuscripts in this family · 2
Choiceless polynomial time with counting does not capture polynomial time
Sep 23, 2026·paper.pdfLean
We prove that choiceless polynomial time with counting does not capture polynomial time on unordered finite structures, confirming the noncapture conjecture of Blass, Gurevich and Shelah. A linear-consistency query over 𝔽 in a fixed binary vocabulary is decidable in polynomial time but not in the full counting formalism.
Witnessed symmetric choice is strictly stronger than choiceless polynomial time with counting
Sep 24, 2026·paper.pdf
We prove that witnessed symmetric choice strictly increases the expressive power of choiceless polynomial time with counting. A fixed sentence with one witnessed-choice occurrence defines a Boolean query on every finite input that is not definable in the original counting formalism.