Bull. Austral. Math. Soc. 72(1) pp.7--15, 2005.

A strong excision theorem for
generalised Tate cohomology

N. Mramor Kosta

Received: 13th January, 2005

Supported in part by the Ministry for Education, Science and Sport of the Republic of Slovenia Research Program No. 101-509.

Abstract

We consider the analogue of the fixed point theorem of A. Borel in the context of Tate cohomology. We show that for general compact Lie groups G the Tate cohomology of a G-CW complex X with coefficients in a field of characteristic 0 is in general not isomorphic to the cohomology of the fixed point set, and thus the fixed point theorem does not apply. Instead, the following excision theorem is valid: if X' is the subcomplex of all G-cells of orbit type G/H where dim H > 0, and V is a ring such that for every finite isotropy group H the order |H| is invertible in V, then $ \widehat {{H}}^{*}_{G}$(X;V) $ \cong $ $ \widehat {{H}}^{*}_{G}$(X';V). In the special cases G = $ \mathbb {T}$, the circle group, and G = $ \mathbb {U}$, the group of unit quaternions, a more elementary geometric proof, using a cellular model of $ \widehat {{H}}^{*}_{\mathbb }$U is given.

Click to download PDF of this article (free access until July 2006)

or get the no-frills version

[an error occurred while processing this directive]
(Metadata: XML, RSS, BibTeX) MathSciNet: MR2162289 Z'blatt-MATH: 02212181

References

  1. K.S. Brown;
    Cohomology pf groups (Springer-Verlag, New York, 1982). MR672956
  2. M. Cencelj;
    Jones-Petrack cohomology,
    Quart. J. Math. Oxford (2) 46 (1995), pp. 409--415. MR1366613
  3. M. Cencelj and N. Mramor Kosta;
    CW decompositions of equivariant complexes,
    Bull. Austr. Math. Soc. 65 (2002), pp. 45--53. MR1889377
  4. M. Cencelj, N. Mramor Kosta and A. Vavpetič;
    G-complexes with a compatible CW structure,
    J. Math. Kyoto Univ 43 (2003), pp. 585--597. MR2028668
  5. T.G. Goodwillie;
    Cyclic homology, derivations, and the free loop space,
    Topology 24 (1985), pp. 187--215. MR793184
  6. J.P.C. Greenlees and J.P. May;
    Generalized Tate cohomology,
    Memoirs of the American Mathematical Society 113 (American Mathematical Society, Providence, R.I., 1995). MR1230773
  7. W.Y. Hsiang;
    Cohomology theory of topological transformation groups (Springer-Verlag, Berlin, Heidelberg, New York, 1975). MR423384
  8. J.D.S. Jones;
    Cyclic homology and equivariant homology,
    Invent. Math. 87 (1987), pp. 403--423. MR870737
  9. J.D.S. Jones and S.B. Petrack;
    Le théorème des points fixes en cohomologie équivariante en dimension infinite,
    C.R. Acad. Sci. Paris Ser. I 306 (1988), pp. 75--78. MR929113
  10. J.D.S. Jones and S.B. Petrack;
    The fixed point theorem in equivariant cohomology,
    Trans. Amer. Math. Soc. 322 (1990), pp. 35--50. MR1010411
  11. I. Suzuki;
    Group theory I (Springer-Verlag, Berlin, Heidelberg, New York, 1982). MR648772
  12. T. tom Dieck;
    Transformation groups and representation theory,
    Lecture Notes in Mathematics 766 (Springer-Verlag, Berlin, Heidelberg, New York, 1979). MR551743

ISSN 0004-9727