The bare necessities of a physically reasonable mathematical model for quantum theory

The physical foundation of the mathematical formalism of quantum theory is still an iffy mystery.

Here it is presumed that a physically reasonable mathematical model needs only three basic features.

The first one are the transition probabilities, which are so typical of quantum theory.

The other two constitute a variation of the postulate that continuous reversible dynamical processes exist and act transitively on the underlying space.

One class of mathematical models with these features arises from the atomic JBW factors, which include the atomic von Neumann factors and become identical with the Jordan matrix algebras, when the dimension is finite.

A further model is known, on which the exceptional Lie group E6 acts transitively.

Interestingly, E6 is sometimes considered a candidate for internal symmetries in particle physics, but many familiar features of quantum theory get lost in this case (particularly the general existence of post-measurement states).

The paper concludes with some open issues, concerning this problem and the classification of the mathematical structures with the three features.