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K-theory and Noncommutative Geometry.pdf

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A Schwartz type algebra for the tangent groupoid 1892. The tangent groupoid of a smooth vector bundle. Let E p ! X be a smoothvector bundle over a (connected) C 1 manifold X. We can consider the Lie groupoidE X induced by the vector structure of the fibers, i:e:, s./ D p./ D r./ and thecomposition is given by the vector sum ı D C . In this case the normal vectorbundle associated to the zero section can be identified to E itself. Hence, as a set thetangent groupoid is E Œ0; 1, but the C 1 -structure at zero is given locally as in (3).3. The tangent groupoid of a C 1 -manifold. Let M a C 1 -manifold. We canconsider the product groupoid G M WD M M M . The tangent groupoid in thiscase takes the following form:G T MD TM f0g tM M .0; 1:This is called the tangent groupoid to M and it was introduced by Connes for giving avery conceptual proof of the Atiyah–Singer index theorem (see [8] and [10]).4 An algebra for the tangent groupoidIn this section we will show how to construct an algebra for the tangent groupoid whichconsists of C 1 functions that satisfy a rapid decay condition at zero while out of zerothey satisfy a compact support condition. This algebra is the main construction in thiswork.4.1 Schwartz type spaces for deformation to the normal cone manifolds. Ouralgebra for the tangent groupoid will be a particular case of a construction associated toany deformation to the normal cone. We start by defining a space for DNCs associatedto open subsets of R p R q .Definition 4.1. Let p; q 2 N and U R p R q an open subset, and let VU \ .R p f0g/.D(1) Let K U Œ0; 1 be a compact subset. We say that K is a conic compact subsetof U Œ0; 1 relative to V ifK 0 D K \ .U f0g/ V:(2) Let g 2 C 1 . U V/. We say that f has compact conic support K, if there exists aconic compact K of U Œ0; 1 relative to V such that if t ¤ 0 and .x; t; t/ … Kthen g.x; ; t/ D 0.(3) We denote by S c . U V / the set of functions g 2 C 1 . U V/ that have compact conicsupport and that satisfy the following condition:.s 1 ) for all k; m 2 N, l 2 N p and ˛ 2 N q there exists C .k;m;l;˛/ >0such that.1 Ckk 2 / k k@ l x @˛ @m t g.x; ; t/k C .k;m;l;˛/:

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