Re: Ground state and QFT

From: Frank Hellmann (Certhas -at- gmail -dot- com) (Certhas_at_gmail.com)
Date: 12/14/04 

Date: Tue, 14 Dec 2004 16:18:24 +0000 (UTC)

Nope Observer independent has a rather specific meaning. It says
(roughly) that if two observers in different physical states observe
the same phenomenon it must reduce to a common fundamental event,
independently of the state of observers, meaning that no contradiction
between the relations between events can be derived from observations
of different observers.
If we limit ourselfs to classes of observers related by Lorentz
transformations, we get the non accelerated observers of Special
Relativity, and observer independence is manifest in the formal
invariance of physical laws under transformation into the
"observational system".
In GR where we consider all possible observers but not any two of them
are equivalent, which makes things rather more subtle.

Unfortunately observer independence and symmetry are often thrown in to
argue for the invariance under coordinate transformations, this in
itself is missing the assumption that each coordinate system
corresponds to an observational mode in some sense.
If I model the observation completely in the mathematical framework,
then I can always subject any theory to any mathematical transformation
without changing it.
It's not immidiately clear to me if this is significant for covariant
Quantum Mechanics.

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