Kochen-Specker theorem for von Neumann algebras
  The Kochen-Specker theorem has been discussed intensely ever since its original proof in 1967. It is one of the central no-go theorems of quantum theory, showing the non-existence of a certain kind of hidden states models. In this paper, we first offer a new, non-combinatorial proof for quantum systems with a type $I_{n}$ factor as algebra of observables, including $I_{\infty}$. Afterwards, we give a proof of the Kochen-Specker theorem for an arbitrary von Neumann algebra $\mathcal{R}$ without summands of types $I_{1}$ and $I_{2}$, using a known result on two-valued measures on the projection lattice $\mathcal{P(R)}$. Some connections with presheaf formulations as proposed by Isham and Butterfield are made. 
Andreas Doering