Soft photons and the ETH interpretation of QM

[DrDu]

As the thread on Jürg Fröhlich's paper on the "ETH interpretation" of QM has been closed, I want to consider here a specific point.
Fröhlich points out that this interpretation requires the inclusion of massless particles and I think this is the key to getting a physical understanding.
Especially, to get rid of infrared divergences one has to sum over soft photons. But, as states in the sum differ by infinitely many soft photons, these states live in different Hilbert spaces and this constitutes a source of decoherence. The interaction with soft photons has always been one of the directions of research at the ETH. E.g. it was used to explain Hund's paradox, that we do not observe superpositions of molecules of different chirality. This was seen a prototypical example of how classical properties emerge in a quantum world.

 

[vanhees71]

Alternatively you can also just use the right asymptotic free states, which in a specific sense describe particles as "bare particles" with its em. field around them. This (virtual) photon cloud is what is taken into consideration through the soft-photon resummation to get rid of IR and collinear singularities.

 

[DrDu]

Yes, and coincidentially, this is what Fröhlich has studied in one of his most oftenly cited papers:
http://www.numdam.org/article/AIHPA_1973__19_1_1_0.pdf

 

[A. Neumaier]

But, as states in the sum differ by infinitely many soft photons, these states live in different Hilbert spaces and this constitutes a source of decoherence.

Can you be more specific about how ''this constitutes a source of decoherence'' follows from you premise?