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[Phys-l] Some Comments and Open Questions Concerning QG and time



FROM ANOTHER LIST. May be of interest.



I thought a wrap up relating how I view the questions concerning the early
Universe , time, and a possible theory of quantum gravity might be useful.

1) Topos Theory.

Any comments on a quantum theory of gravity , in other words a quantum
model of the Universe should at least mention Topos Theory. Topos theory is a
meta-logical branch of Mathematics which,if Chris Isham is correct , we need
to talk meaningfully about ultimate theories of the Universe. Isham who is
one of most profound thinkers on the fundamental questions in physics may
well be correct , though to date this effort has produced little of value.
Nevertheless , the work has begun only very recently and it may well revolutionize
our view of nature. However, what follows doesn't consider Topos theory.

2) The Quantum Nature of the Early Universe.

It seems reasonable to assume that we must talk about the Universe as a
quantum entity. Our classical world is only our local coarse grained
viewpoint of reality. No Classical model can be applied to the Universe taken as a
whole.

3) The Early Universe and Decoherence.

Based on our best understanding of Quantum theory any closed quantum system
must be a pure quantum state. Therefore the emergence of our classical
Universe must be the result of the Decoherence process. Because the Decoherence
functional is time symmetric there is no basis for assuming that local coarse
grained viewpoints emerge in one time direction only. In addition if the
Universe is created by tunneling from nothing into existence , in terms of its
dynamic description , its positive energy content must be balanced with its
negative energy content , requiring a local time evolution in both time
directions.

4) Conformal Symmetry equals constant entropy.

As has been demonstrated by Bruce and myself, a Universe consisting
of only massless particles has a constant entropy hence seems to be
timeless. This basic point was going to be brought out in Vic's "Comprehensible
Cosmos". However, concerns about how energy was conserved in such a Universe
caused this to be pulled from the book, unfortunately. I think any questions here
about energy conservation can be solved by properly drawn boundaries. The
issues of boundaries is why energy conservation can be a question in General
Relativity itself. If this is done there are no energy conservation issues
with this proposal in my opinion.

It might be argued that a Conformally symmetric Universe does have a time
like parameter, the scale factor. But I would reply that this parameter is
meaningless in the early Universe because time is what is measured on a clock
and here measured is the operative term.

In the early Universe we may possibly be able to connect three parameters
together though how exactly remains to be discovered. These are the breaking of
conformal symmetry, the decoherence of the gravity field ( assuming C Kiefer
and others are correct) and the onset of inflation. How exactly these are
connected, if indeed they are , remains an open and very interesting question.

5) What Does It mean to have no time parameter in the Wheeler De Witt
Equation?

It's my proposal that the significance of the lack of time in the
Schrodinger Equation of the Universe is that describing the entire Universe as a
closed quantum system necessarily means describing it in terms of a coherent
superposition of time reversed quantum states. Critic may argue that this
conflates the arrow of time with the existence of time. To these critics I respond
please explain what time might be absent an arrow of time. Time is what we
"measure" on a clock, in terms of position or in terms of the emission of light
quanta or using any other irreversible event.

Therefore time emerges locally , or more accurately , the possibility of
irreversible events emerges locally when the time reversed wavefunctions of
the Universe Decohere , though of course they remain coherent globally.



6) CPT Violation

Based on some preliminary models of a Quantum theory of gravity we
may expect CPT violation to appear in our experiments. Does this also relate
to the Decoherence of forward and time reversed wavefunctions? Is this why in
our Universe matter predominates over anti matter? Is this the origin of the
arrow of time in our universe from which all other arrows of time are derived
from? ( CP violation <> T violation)

There are some tentative indications that the anomalous neutrino flavor
mixing observed at LSND may not
be simply due to the existence of Sterile Neutrinos , but possibly involve
CPT violation. See Link.

_www.Fnal.gov/pub/presspass/press_releases/BooNE-box.html_
(http://www.fnal.gov/pub/presspass/press_releases/BooNE-box.html)


Bob Zannelli






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