[time 833] RE: [time 830] Re: Does a fundamental time exist in GR and QM? The thinking of others...

Lancelot Fletcher (lance.fletcher@freelance-academy.org)
Wed, 29 Sep 1999 02:09:40 -0500


> -----Original Message-----
> From: owner-time@kitada.com [mailto:owner-time@kitada.com]On Behalf Of
> Stephen Paul King
> Sent: Tuesday, September 28, 1999 9:28 PM
> To: time@kitada.com
> Subject: [time 830] Re: Does a fundamental time exist in GR and QM? The
> thinking of others...

I was a little puzzled about why you re-posted that message by John Baez
which was originally posted on Aug. 12 on the sci.physics.research
newsgroup as message 112 in a thread containing 119 messages. Out of
curiosity I tracked down the first message in that thread, from Paul
Stewart Snyder on Aug. 6, and I have copied it below. It seems to me that
some of this, especially the second paragraph, resembles Hitoshi's approach
in ways that might be worth exploring.



From: "Paul Stewart Snyder" <ps@ws5.com>
Subject: Does a fundamental time exist in GR and QM?
Date: 06 Aug 1999 00:00:00 GMT
Message-ID: <rqe8crihq1tcq6@corp.supernews.com>
Approved: mmcirvin@world.std.com (sci.physics.research)
Sender: mmcirvin@world.std.com (Matthew J McIrvin)
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Newsgroups: sci.physics.research

I have tried to digest the basic information in the recent threads about
spacetime in GR. To me the most interesting ideas follow from what Carlo
Rovelli suggested in 1991 (Physical Review D43, 442), that in GR time
be treated as a derived and not a fundamental quantity. In extending this
the quantum world, he argues that "in the absence of a fundamental time and
of an exact Schrodinger equation, there are gauge invariant observables,
that commute with the hamiltonian constraint, which describe evolution with
respect to physical clocks. The observables are self-adjoint operators on
the space of the solutions of the Wheeler-DeWitt equation.. Evolution with
respect to physical clocks is described by self-adjoint operators
corresponding to the observables.. This extension is well-defined both in
terms of the coherence of the formalism, and from the point of view of the
viability of the standard probabilistic interpretation."

It seems to me that rethinking the answers to the questions about what is
"here and now" and what is "casuality", in terms of spatial contiguity in
atemporal universe, might resolve some of the apparent paradoxes of GR/QM?
Indeed, the idea of hamiltonian mechanics in a presymplectic space seems
"elegant" and, if this actually models nature, might provide a useful way
viewing phenomena that seem to lack temporal constraints. Are there any
clear objections or impediments in pursuing this approach?

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