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Bulletin of the London Mathematical Society
Article . 1986 . Peer-reviewed
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Chern Classes of Representations

Chern classes of representations
Authors: Thomas, C. B.;

Chern Classes of Representations

Abstract

For any G-module A of the group G, we have the Eilenberg-MacLane cohomology groups \(H^*(G,A)\). In general, they are quite difficult to compute. When A is the G-trivial module \({\mathbb{Z}}\), \(H^*(G,{\mathbb{Z}})\) becomes a ring, it is possible to get some information on \(H^*(G,{\mathbb{Z}})\) through the complex representation theory of G. Namely, if \(\rho\) : \(G\to GL(n,{\mathbb{C}})\), then we can use classifying space functor and pull back the cohomology ring of \(BGL(n,{\mathbb{C}})^{top}\). This latter is known to be a polynomial ring generated by the Chern classes. The present paper is a survey of many of the results on this theme. The original theme (to the reviewer's knowledge) first appeared in a work of \textit{M. F. Atiyah} [Publ. Math., Inst. Hautes Etud. Sci. 9, 241-288 (1961; Zbl 0107.023)]. Atiyah's paper seems to have been left out of the reference section by accident. This may be caused by the fact that \(H^*(G,{\mathbb{Z}})\) has not contributed as much information to finite groups G as the representation ring R(G). In spite of this comment by the author, there are some results in this area, and further investigations would be desirable. The survey is very well done. The reviewer would like to add the comment that many interesting groups (e.g. the infinite general linear group) have very few nontrivial representations (there are groups without any). In such cases, the theme leads to nothing. In contrast, the homology group \(H_*(G,{\mathbb{Z}})\) may become more interesting. To be more precise, the divisible elements of \(H_*(G,{\mathbb{Z}})\) may be permanently lost when we pass to \(H^*(G,{\mathbb{Z}})\). Of course, as a trade-off, \(H_*(G,{\mathbb{Z}})\) usually does not enjoy a ring structure.

Keywords

Homological methods in group theory, homology group, Homology of classifying spaces and characteristic classes in algebraic topology, Chern classes, cohomology ring, survey, representation ring, Cohomology theory for linear algebraic groups, cohomology groups, classifying space

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selected citations
These citations are derived from selected sources.
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
7
Average
Average
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