I would like to understand the mathematical content of Kochen-Specker theorem. This theorem states the following:
If the dimension of a Hilbert space $\mathcal{H}$ is $>2$ then there is no valuation $\lambda:\mathcal{B}(\mathcal{H}) \to \mathbb{C}$.
Recall that a valuation is the function with the following properties:
(1) for each observable (meaning: self-adjoint operator) $A$ the value $\lambda(A)$ belongs to the spectrum of $A$
(2) if two observables $B,A$ are such that $B=h(A)$ for some Borel real valued function then $\lambda(B)=h(\lambda(A))$.
Q1: What is the significance of the condition (1) above?
Am I right saying that the reason for condition (1) is only due to the fact that if $B=h(A)$ then $h$ is defined on the spectrum of $A$ thus in order to write $h \circ \lambda(A)$ we assume that $\lambda(A) \in \sigma(A)$? This enables us to define valuation as a function which is an algebra homomorphism on each commutative subalgebra.
The second question concerns the proof: each proof which I have found assumes that $\mathcal{H}$ is finite dimensional (usually of dimension 4 or 8).
Q2: Is there a simple way to proof this theorem for the $n$-dimensional space $\mathcal{H}$ provided we have proved it for some dimension less than $n$? In particular, does this theorem follow for infinite dimensional $\mathcal{H}$ once we have proved it for dimension $4$?
I will be very grateful if someone could clarify those issues for me