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- Xref: sparky sci.physics:21159 alt.sci.physics.new-theories:2547
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- From: carlip@landau.ucdavis.edu (Steve Carlip)
- Newsgroups: sci.physics,alt.sci.physics.new-theories
- Subject: Re: Feynman 32 - Ghost Busters & Quantum Gravity
- Message-ID: <20099@ucdavis.ucdavis.edu>
- Date: 14 Dec 92 22:31:42 GMT
- References: <ByzBAI.B0w@well.sf.ca.us>
- Sender: usenet@ucdavis.ucdavis.edu
- Followup-To: sci.physics
- Organization: Physics, UC Davis
- Lines: 26
-
- In article <ByzBAI.B0w@well.sf.ca.us> sarfatti@well.sf.ca.us (Jack Sarfatti) writes:
- >
- >[...] Do the ghosts [in perturbative quantum gravity]
- >follow closed time like loops and do they obey the usual spin-statistics
- >connection or are they scalar (spin0) fermions, spinor (spin1/2) bosons
- >etc. as in Yang-Mills Faddeev-Popov regulators?
-
- Feynman's ghosts in quantum gravity are precisely the same as the
- ghosts that occur in Faddeev-Popov gauge-fixing (in this case, from
- gauge-fixing the diffeomorphism group). Historically, I believe
- Feynman came first, though he was followed rather soon by Faddeev
- Popov, and DeWitt. Like the ghosts in Yang-Mills theory, gravitational
- ghosts do not obey the usual spin-statistics relationship; and like
- Yang-Mills ghosts, they cannot appear as extrnal particles --- they
- are really just fictitious particles introduced for book-keeping
- purposes, to keep track of Jacobians in the path integral. Since
- they only appear as internal lines in Feynman diagrams, the question
- of closed timelike loops doesn't really make sense.
-
- If you want to know more, you might look at the articles by Duff and
- Deser in _Quantum Gravity_ (Isham et al., editors, Clarendon Press,
- 1975).
-
- Steve Carlip
- carlip@dirac.ucdavis.edu
-
-