Recent content by A. Neumaier

Any relativistic quantum field theory needs an underlying globally hyperbolic manifold.

I am beyond this stage and therefore have more freedom!

This is a bug in the rendering by the preprint server. Look at https://arnold-neumaier.at/ms/Laplace.pdf for my own, good version.

The (strongly modified) submitted version is here. A poster for a conference next week in Vienna summarizes everything on one page.

So it is extra structure assumed, beyond the textbook requirenments for a quantum system. Not a good sign for an interpretation of quantum mechanics.

The statement is basis-independent. For example, any ##\rho=\pi\psi^*## with normalized ##\psi## is a rank 1 projector. Given a Hilbert space and a Hamiltonian (and hence a physical system), what is a definite configuration?

One can prove that every finite- rank density matrix can be written as a convex combination of projectors, and that every density matrix can be written as the limit of a family of convex combinations of projectors.

Of course they are well-defined. In a long distance Bell experiment, Alice sees the effects of one of the entangled photons, not even knowing whether there is an entangled partner somewhere. For her, the only system is the subsystem, and it has all the properties a single photon has. This is...

But they amount to unverifiable speculation.

Bohmian mechanics is a different interpretation, limited to nonrelativistic quantum mechanics. Thus this incompatibilty is a plus for the new approach! Yes. This is discussed In Section 13 of my paper.

But only the quasiclassical ones are checkable by us, and hence only these convey an objective physical meaning in the sense used by the physics community.

I gave references in my paper here.

I had written this from memory, and was wrong. Actually.Hida distributions can be used to construct the Feynman path integral (which is done in the paper you cited), but only for anharmonic oscillators, which corresponds to a field theory in 1-dimensional spacetime. The real problems appear in...

The latter is (as the name says) an approximation of the former, where only the first order term in the Born series is taken into account.

This is the Euclidean (Feynman-Kac) path integral, which is mathematically better behaved. But QFT needs the Minkowski (Feynman) path integral, which has an extra factor i in the exponent that makes the intergrals heavily oscillating and mathematically intractable in infinite dimensions, except...