It is well known that the homology of a CW-complex with cells only in even dimensions is free. The equivariant analog of this result for $G$-cell complexes is, however, not obvious, since $RO(G)$-graded homology cannot be computed using cellular chains. This book considers $G = \mathbb{Z}/p$ and studies $G$-cell complexes.

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It is well known that the cohomology of a finite CW-complex with cells only in even dimensions is free. The equivariant analog of this result for generalized G-cell complexes is, however, not obvious, since RO(G)-graded cohomology cannot be computed using cellular chains. We consider G = Z/p and study G-spaces that can be built as cell complexes using the unit disks of finite dimensional G-representations as cells. Our main result is that, if X is a G-complex containing only even dimensional representation cells and satisfying certain finite type assumptions, then the RO(G)-graded equivariant ordinary cohomology is free as a graded module over the cohomology of a point. This extends a result due to Gaunce Lewis about equivariant complex projective spaces with linear Z/p actions. Our new result applies more generally to equivariant complex Grassmannians with linear Z/p actions.

It is well known that the homology of a CW-complex with cells only in even dimensions is free. The equivariant analog of this result for $G$-cell complexes is, however, not obvious, since $RO(G)$-graded homology cannot be computed using cellular chains. We consider $G = \mathbb{Z}/p$ and study $G$-cell complexes constructed using the unit disks of finite dimensional $G$-representations as cells. Our main result is that, if $X$ is a $G$-complex containing only even-dimensional representation cells and satisfying certain finiteness assumptions, then its $RO(G)$-graded equivariant ordinary homology $H_\ast^G(X;A>$ is free as a graded module over the homology $H_\ast$ of a point.This extends a result due to the second author about equivariant complex projective spaces with linear $\mathbb{Z}/p$-actions. Our new result applies more generally to equivariant complex Grassmannians with linear $\mathbb{Z}/p$-actions. Two aspects of our result are particularly striking. The first is that, even though the generators of $H^G_\ast(X;A)$ are in one-to-one correspondence with the cells of $X$, the dimension of each generator is not necessarily the same as the dimension of the corresponding cell. This shifting of dimensions seems to be a previously unobserved phenomenon. However, it arises so naturally and ubiquitously in our context that it seems likely that it will reappear elsewhere in equivariant homotopy theory. The second unexpected aspect of our result is that it is not a purely formal consequence of a trivial algebraic lemma.Instead, we must look at the homology of $X$ with several different choices of coefficients and apply the Universal Coefficient Theorem for $RO(G)$-graded equivariant ordinary homology. In order to employ the Universal Coefficient Theorem, we must introduce the box product of $RO(G)$-graded Mackey functors. We must also compute the $RO(G)$-graded equivariant ordinary homology of a point with an arbitrary Mackey functor as coefficients. This, and some other basic background material on $RO(G)$-graded equivariant ordinary homology, is presented in a separate part at the end of the memoir.

The cohomology of groups has, since its beginnings in the 1920s and 1930s, been the stage for significant interaction between algebra and topology and has led to the creation of important new fields in mathematics, like homological algebra and algebraic K-theory. This is the first book to deal comprehensively with the cohomology of finite groups: it introduces the most important and useful algebraic and topological techniques, and describes the interplay of the subject with those of homotopy theory, representation theory and group actions. The combination of theory and examples, together with the techniques for computing the cohomology of important classes of groups including symmetric groups, alternating groups, finite groups of Lie type, and some of the sporadic simple groups, enable readers to acquire an in-depth understanding of group cohomology and its extensive applications.

Discrete Mathematics combines a balance of theory and applications with mathematical rigor and an accessible writing style. The author uses a range of examples to teach core concepts, while corresponding exercises allow students to apply what they learn. Throughout the text, engaging anecdotes and topics of interest inform as well as motivate learners. The text is ideal for one- or two-semester courses and for students who are typically mathematics, mathematics education, or computer science majors. Part I teaches student how to write proofs; Part II focuses on computation and problem solving. The second half of the book may also be suitable for introductory courses in combinatorics and graph theory. Important Notice: Media content referenced within the product description or the product text may not be available in the ebook version.