4 problems

A Kochen–Specker (KS) set is a set of rays, or equivalently projectors, together with their orthogonality relations. Such a set is rigid if any set of projectors, not necessarily o…

Let a non-Kochen–Specker set in dimension $d$ be a measurable subset $A\subseteq S^{d-1}$ admitting a valuation map $v:A\to\{0,1\}$ such that $v(-n)=v(n)$, every mutually orthogona…

Noncoordinatization conjecture. The critical Kochen–Specker MMPH 19-5 has no coordinatization from $\{0,\pm1\}$.

Noncoordinatization conjecture. The 7-dimensional MMPH 13-6 has no coordinatization.