Moebius transformations in noncommutative conformal geometry


Bongaarts, P.J.M. and Brodzki, J. (1999) Moebius transformations in noncommutative conformal geometry. Communications in Mathematical Physics, 201, (1), 35-60. (doi:10.1007/s002200050548).

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Original Publication URL: http://dx.doi.org/10.1007/s002200050548

Description/Abstract

We study the projective linear group PGL2(A) associated with an arbitrary algebra A and its subgroups from the point of view of their action on the space of involutions in A. This action formally resembles Möbius transformations known from complex geometry. By specifying A to be an algebra of bounded operators in a Hilbert space H, we rediscover the Möbius group wev(M) defined by Connes and study its action on the space of Fredholm modules over the algebra A. There is an induced action on the K-homology of A, which turns out to be trivial. Moreover, this action leads naturally to a simpler object, the polarized module underlying a given Fredholm module, and we discuss this relation in detail. Any polarized module can be lifted to a Fredholm module, and the set of different lifts forms a category, whose morphisms are given by generalized Möbius tranformations. We present an example of a polarized module canonically associated with the differentiable structure of a smooth manifold V. Using our lifting procedure we obtain a class of Fredholm modules characterizing the conformal structures on V. Fredholm modules obtained in this way are a special case of those constructed by Connes, Sullivan and Teleman.

Item Type: Article
ISSNs: 0010-3616 (print)
Related URLs:
Subjects: Q Science > QA Mathematics
Q Science > QC Physics
Divisions: University Structure - Pre August 2011 > School of Mathematics > Pure Mathematics
Item ID: 29845
Date Deposited: 27 Jul 2006
Last Modified: 02 Mar 2012 12:27
Contributors: Bongaarts, P.J.M. (Author)
Brodzki, J. (Author)
Date: 1999
Status: Published
URI: http://eprints.soton.ac.uk/id/eprint/29845

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