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18 votes
8 answers
3k views

Reference request: Equivariant Topology

I am teaching a graduate seminar in equivariant topology. The format of the course is that I will give 2-3 weeks of background lectures, then each week a student will present a topic. The students ...
15 votes
2 answers
1k views

$RO(G)$-graded homotopy groups vs. Mackey functors

Everything here is model-independent: either take co/fibrant replacements wherever appropriate, or work $\infty$-categorically. Also, I've looked through other similar MO questions, but I didn't find ...
Aaron Mazel-Gee's user avatar
13 votes
1 answer
603 views

Applications of equivariant homotopy theory to representation theory

Equivariant homotopy theory focuses on spaces together with some group action on them. Jeroen van der Meer and Richard Wong have a paper where they use equivariant methods to compute the Picard group ...
Logan Hyslop's user avatar
10 votes
0 answers
703 views

Adams Spectral Sequence for Equivariant Cohomology Theories

In ordinary algebraic topology the Adams spectral sequence can be applied for any cohomology theory $E$ and in good cases it converges to the stable homotopy classes of maps (of the E-nilpotent ...
user2146's user avatar
  • 1,233
9 votes
2 answers
1k views

Genuine equivariant ambidexterity

A particular case of Lurie and Hopkins' ambidexterity theory is that if $G$ is a finite group acting on a $K(n)$-local spectrum $X$ then the norm map $$ X_{hG} \to X^{hG} $$ is a $K(n)$-local ...
Yonatan Harpaz's user avatar
9 votes
3 answers
633 views

Homotopy group action and equivariant cohomology theories

Many of the introductory notes on generalized equivariant cohomology theories assume that one is working over the category of $G$-spaces or $G$-spectra. However, one thing that concerns me is that the ...
Arkadij's user avatar
  • 914
9 votes
1 answer
1k views

A heart for stable equivariant homotopy theory

Let $G$ be a finite group. I wonder whether the following statement is true, known and written down: There is a t-structure on the stable $G$-equivariant homotopy category such that the associated ...
user2146's user avatar
  • 1,233
9 votes
1 answer
410 views

Applications of equivariant homotopy theory in chromatic homotopy theory

I usually do computations in equivariant homotopy theory, but I would like to learn chromatic homotopy theory where one may use the equivariant techniques, e.g., slice spectral sequences, etc. For ...
Surojit Ghosh's user avatar
9 votes
1 answer
205 views

Almost free circle actions on spheres

$\DeclareMathOperator{\Fix}{\operatorname{Fix}}$I am looking for any reference regarding the following problem: Problem: Consider a smooth almost-free action of $S^1$ on a smooth sphere $S^n$. Then ...
CuriousUser's user avatar
  • 1,384
8 votes
0 answers
395 views

Equivariant K-theory of projective representation on complex projective space

Let $G$ be a group and let $V$ be a complex projective representation of $G$, so that $G$ acts on the projectivization $\mathbb{P}(V)$. Is there any way to calculate the $G$-equivariant complex $K$-...
Akhil Mathew's user avatar
  • 25.1k
6 votes
2 answers
227 views

Fibre preserving maps of Borel constructions

Let $G$ be a discrete group with universal principal bundle $EG\to BG$, and let $X$ and $Y$ be left $G$-spaces. An equivariant map $\overline{f}:X\to Y$ induces a fibre-preserving map $f:EG\times_G X\...
Mark Grant's user avatar
  • 34.9k
6 votes
1 answer
594 views

Where can I find basic "computations" of equivariant stable homotopy groups?

I am new to this subject; so please correct me if I will say something wrong or if you don't like my notation. In particular, I don't know whether it is reasonable to consider an infinite group $G$ (...
Mikhail Bondarko's user avatar
5 votes
2 answers
450 views

Burnside ring and zeroth G-equivariant stem for finite G

Let $G$ be a finite group. The theorem that the Burnside ring $A(G)$ is isomorphic to the zeroth stable stem $\pi^{G}_0(S)$ is usually said to originate from Segal. I search for a reference of a proof ...
user2146's user avatar
  • 1,233
5 votes
1 answer
590 views

Is a $G$-cell complex always a $G$-CW complex?

I recall vaguely once reading that a cell complex—constructed like a CW-complex but without assuming the cells are appended in order of increasing dimension —"is" actually a CW-complex. I ...
jdc's user avatar
  • 2,974
5 votes
0 answers
89 views

Equivariant imbedding of compact manifold

Let $G$ be a compact Lie group smoothly acting on a smooth compact manifold $X$. Is it true that there exists a smooth $G$-equivariant imbedding of $X$ into a Euclidean space acted linearly (and ...
asv's user avatar
  • 20.5k
4 votes
0 answers
146 views

Rigidity of the TMF-valued equivariant elliptic genus

Let me preface this question by saying that I wrote it at least in part to understand its statement. As such, I hope that the reader will excuse any mistakes. $\DeclareMathOperator{\ind}{ind}\...
Bertram Arnold's user avatar
3 votes
0 answers
127 views

Extensive survey of computations of equivariant stable stems

Where can I find a comprehensive survey of computations of equivariant stems? To my knowledge, the status is: Classical Work of Araki and Iriye, Osaka J. Math. 19 (1982). ...
Nicolas Boerger's user avatar
2 votes
1 answer
372 views

Universal space for the family of subgroups of a finite cyclic group

Let $G$ be a compact Lie group and let $\mathcal{P}_G$ denote the family of proper subgroups of $G$. The universal space for the family $\mathcal{P}_G$ is a cofibrant $G$-space which does not have $G$-...
fixedp's user avatar
  • 123
2 votes
1 answer
233 views

Do Mackey (co)homology functors factor through derived categories? References with details?

Let $G$ be a compact Lie group; I will write $SH_G$ for the (equivariant) stable homotopy category of $G$-spectra (say, with respect to a complete universe; does its choice affect the homotopy ...
Mikhail Bondarko's user avatar
2 votes
0 answers
74 views

Does there exist a "Margolis-type" definition of equivariant cellular towers?

I am interested in cellular towers in the equivariant stable homotopy category $SH_G$ corresponding to a compact Lie group along with a complete universe for it. Note here that a cellular tower for ...
Mikhail Bondarko's user avatar