322,618 research outputs found
Gravity as a Gauge Theory of Translations
The Poincar\'e group can be interpreted as the group of isometries of a
minkowskian space. This point of view suggests to consider the group of
isometries of a given space as the suitable group to construct a gauge theory
of gravity. We extend these ideas to the case of maximally symmetric spaces to
reach a realistic theory including the presence of a cosmological constant.
Introducing the concept of "minimal tetrads" we deduce Einstein gravity in the
vacuum as a gauge theory of translations.Comment: 14 pages. LaTeX 2
Harry Lehmann and the analyticity unitarity programme
I try to describe the extremely fruitful interaction I had with Harry Lehmann
and the results which came out of the analyticity unitarity programme,
especially the proof of the Froissart bound, which, with recent and future
measurements of total cross-sections and real parts, remains topical.Comment: (10 pages, latex
History of Spin and Statistics
These lectures were given in the framework of the ``Dixi\`eme s\'eminaire
rhodanien de physique'' entitled ``Le spin en physique'', given at Villa
Gualino, Turin, March 2002. We have shown how the difficulties of
interpretation of atomic spectra led to the Pauli exclusion principle and to
the notion of spin, and then described the following steps: the Pauli spin with
22 matrices after the birth of "new" quantum mechanics, the Dirac
equation and the magnetic moment of the electron, the spins and magnetic
moments of other particles, proton, neutron and hyperons. Finally, we show the
crucial role of statistics in the stability of the world.Comment: latex file, 7 figures, 3 table
Extending the Coordination of Cognitive and Social Perspectives
Cognitive analyses are typically used to study individuals, whereas social analyses are typically used to study groups. In this article, I make a distinction between what one is looking with?one’s theoretical lens?and what one is looking at?e.g., an individual or a group?. By emphasizing the former, I discuss social analyses of individuals and cognitive analyses of groups, additional analyses that can enhance mathematics education research. I give examples of each and raise questions about the appropriateness of such analyses
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