52 research outputs found
Ashtekar's variables without spin
Ashtekar's variables are shown to arise naturally from a 3+1 split of general
relativity in the Einstein-Cartan formulation. Thereby spinors are exorcised.Comment: 5 pages, unpublished paper from 198
Lensing in the Einstein-Straus solution
The analytical treatment of lensing in the Einstein-Straus solution with
positive cosmological constant by Kantowski et al. is compared to the numerical
treatment by the present author. The agreement is found to be excellent.Comment: 6 pages, 1 figure, 1 tabl
Cosmological constant and lensing
The effect of the cosmological constant on the curvature of light due to an
isolated spherical mass is recalculated without using the lens equation and
compared to a lensing cluster.Comment: 9 pages,4 figure
Krajewski diagrams and spin lifts
A classification of irreducible, dynamically non-degenerate, almost
commutative spectral triples is refined. It is extended to include centrally
extended spin lifts. Simultaneously it is reduced by imposing three
constraints: (i) the condition of vanishing Yang-Mills and mixed gravitational
anomalies, (ii) the condition that the fermion representation be complex under
the little group, while (iii) massless fermions are to remain neutral under the
little group. These constraints single out the standard model with one
generation of leptons and quarks and with an arbitrary number of colours.Comment: 19 pages LaTeX, 1 figure, will not be submitted to journal, v2:
extension of diagram 1 and suppression of electro-weak mode
Spin group and almost commutative geometry
For Connes' spectral triples, the group of automorphisms lifted to the
Hilbert space is defined and used to fluctuate the metric. A few commutative
examples are presented including Chamseddine and Connes' spectral unification
of gravity and electromagnetism. One almost commutative example is treated: the
full standard model. Here the lifted automorphisms explain O'Raifeartaigh's
reduction SU(2)\times U(3)/\zz_2.Comment: 25 pages LaTeX, 1 figure, this paper will not be submitted to any
journal, in particular not to Nucl.Phys.
The noncommutative standard model, post- and predictions
I try to assess the weak and strong points of the standard model of
electro-magnetic, weak and strong forces, how it can be derived from general
relativity by generalizing Riemannian to noncommutative geometry and what post-
and predictions this unification of all four forces entails in particle
physics.Comment: contribution to Moriond '10 electro-wea
25 years ago: the official farewell to the meter
On october 21st 1983 took place in S\`evres on the western outskirts of Paris
the official funeral of the meter. With it the notion of distance as a physical
observable was buried
Noncommutative geometry and the standard model
The aim of this contribution is to explain how Connes derives the standard
model of electromagnetic, weak and strong forces from noncommutative geometry.
The reader is supposed to be aware of two other derivations in fundamental
physics: the derivation of the Balmer-Rydberg formula for the spectrum of the
hydrogen atom from quantum mechanics and Einstein's derivation of gravity from
Riemannian geometry.Comment: 11 pages, 4 figures, contribution to Encyclopedia of Mathematical
Physics, J.-P. Francoise, G. Naber & Tsou Sheung Tsun (eds.), Elsevier
Scienc
Higgs-mass predictions
A compilation of Higgs-mass predictions is proposedComment: This is the last version. Only addition: today's update by Kahana &
Kahan
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