770 research outputs found
Contractions, Hopf algebra extensions and cov. differential calculus
We re-examine all the contractions related with the
deformed algebra and study the consequences that the contraction process has
for their structure. We also show using
as an example that, as in the undeformed case, the contraction may generate
Hopf algebra cohomology. We shall show that most of the different Hopf algebra
deformations obtained have a bicrossproduct or a cocycle bicrossproduct
structure, for which we shall also give their dual `group' versions. The
bicovariant differential calculi on the deformed spaces associated with the
contracted algebras and the requirements for their existence are examined as
well.Comment: TeX file, 25 pages. Macros are include
Effective actions, relative cohomology and Chern Simons forms
The explicit expression of all the WZW effective actions for a simple group G
broken down to a subgroup H is established in a simple and direct way, and the
formal similarity of these actions to the Chern-Simons forms is explained.
Applications are also discussed.Comment: 11 pages. Latex2e file. Published versio
Superconformal mechanics, black holes, and non-linear realizations
The OSp(2|2)-invariant planar dynamics of a D=4 superparticle near the
horizon of a large mass extreme black hole is described by an N=2
superconformal mechanics, with the SO(2) charge being the superparticle's
angular momentum. The {\it non-manifest} superconformal invariance of the
superpotential term is shown to lead to a shift in the SO(2) charge by the
value of its coefficient, which we identify as the orbital angular momentum.
The full SU(1,1|2)-invariant dynamics is found from an extension to N=4
superconformal mechanics.Comment: 19 pages, plain latex file. Slightly shortened version, two
references adde
Projective representation of k-Galilei group
The projective representations of k-Galilei group G_k are found by
contracting the relevant representations of k-Poincare group. The projective
multiplier is found. It is shown that it is not possible to replace the
projective representations of G_k by vector representations of some its
extension.Comment: 15 pages Latex fil
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