9,331 research outputs found
Probing the small distance structure of canonical quantum gravity using the conformal group
In canonical quantum gravity, the formal functional integral includes an
integration over the local conformal factor, and we propose to perform the
functional integral over this factor before doing any of the other functional
integrals. By construction, the resulting effective theory would be expected to
be conformally invariant and therefore finite. However, also the conformal
integral itself diverges, and the effects of a renormalization counter term are
considered. It generates problems such as unitarity violation, due to a
Landau-like ghost, and conformal anomalies. Adding (massive or massless) matter
fields does not change the picture. Various alternative ideas are offered,
including a more daring speculation, which is that no counter term should be
allowed for at all. This has far-reaching and important consequences, which we
discuss. A surprising picture emerges of quantized elementary particles
interacting with a gravitational field, in particular gravitons, which are
"partly classical". This approach was inspired by a search towards the
reconciliation of Hawking radiation with unitarity and locality, and it offers
basic new insights there.Comment: 22 pages (incl. title page), 1 figure. Substantial changes in the
discussion sections, minor errors corrected, and references adde
Confinement at Large Nc
A discussion is given of the confinement mechanism in terms of the Abelian
projection scheme, for a general number Nc of colors. There is a difficulty in
the Nc to infinity limit that requires a careful treatment, as the charges of
the condensing magnetic monopoles tend to infinity. We suggest that Bose
condensation of electric or magnetic charges is indicative for the kind of
confinement that takes place, but the actual mechanism of confinement depends
on other features as well.Comment: 11 pages, 3 figures. Presented at "Large N QCD", trento, July 200
Canonical Quantization of Gravitating Point Particles in 2+1 Dimensions
A formalism previously introduced by the author using tesselated Cauchy
surfaces is applied to define a quantized version of gravitating point
particles in 2+1 dimensions. We observe that this is the first model whose
quantum version automatically discretizes time. But also spacelike distances
are discretized in a very special way.Comment: 14 pages (TeX), 3 figures (Postscript), Utrecht THU-93/1
The Grand View of Physics
Abdus Salam was known for his `grand views', grand views of science as well
as grand views of society. In this talk the grand view of theoretical physics
is put in perspective.Comment: 5 pages, 1 figure. Presented at Salam +50, Imperial College, London,
July 7, 200
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