Re: nonlinearities in QFT

From: Patrick Van Esch (vanesch_at_ill.fr)
Date: 09/28/04 

Date: Tue, 28 Sep 2004 15:19:59 +0000 (UTC)

Arnold Neumaier <Arnold.Neumaier@univie.ac.at> wrote in message news:<4157E1B9.5030302@univie.ac.at>...

> The standard theory gives an S-matrix (or rather an asymptotic series
> for it) but not a dynamics at finite times. Clearly, measurements happen
> in finite time, hence cannot be described at present in a fundamental way
> (i.e., beyond the nonrelativistic QM approximation).

Isn't this a too pessimistic view ? After all, the framework formally
allows us to have the finite time evolution, it is just that it is
plagued by infinities and inconsistencies (Haag ?). But as a "picture
in the mind" cannot quantum fields be considered as having an evolving
quantum state in Hilbert space (even if it screws up each time you
want to write it out explicitly) ?

cheers,
patrick.