Download this article
 Download this article For screen
For printing
Recent Issues

Volume 25
Issue 5, 2527–3144
Issue 4, 1917–2526
Issue 3, 1265–1915
Issue 2, 645–1264
Issue 1, 1–644

Volume 24, 9 issues

Volume 23, 9 issues

Volume 22, 8 issues

Volume 21, 7 issues

Volume 20, 7 issues

Volume 19, 7 issues

Volume 18, 7 issues

Volume 17, 6 issues

Volume 16, 6 issues

Volume 15, 6 issues

Volume 14, 6 issues

Volume 13, 6 issues

Volume 12, 4 issues

Volume 11, 5 issues

Volume 10, 4 issues

Volume 9, 4 issues

Volume 8, 4 issues

Volume 7, 4 issues

Volume 6, 5 issues

Volume 5, 4 issues

Volume 4, 2 issues

Volume 3, 2 issues

Volume 2, 2 issues

Volume 1, 2 issues

The Journal
About the journal
Ethics and policies
Peer-review process
 
Submission guidelines
Submission form
Editorial board
 
Subscriptions
 
ISSN (electronic): 1472-2739
ISSN (print): 1472-2747
 
Author index
To appear
 
Other MSP journals
Equivariant intrinsic formality

Rekha Santhanam and Soumyadip Thandar

Algebraic & Geometric Topology 25 (2025) 2851–2882
Abstract

Algebraic models for equivariant rational homotopy theory were developed by Triantafillou and Scull for finite group actions and S1 action, respectively. They showed that given a diagram of rational cohomology algebras from the orbit category of a group G, there is a unique minimal system of DGAs representing a unique G-rational homotopy type that is weakly equivalent to it. However, there can be several equivariant rational homotopy types with the same diagram of cohomology algebras. Halperin, Stasheff, and others studied the problem of classifying rational homotopy types up to cohomology in the nonequivariant case. In this article, we consider this question in the equivariant case. For the case G = Cp, for prime p, under suitable conditions, we are able to determine the equivariant rational homotopy types with isomorphic diagram of cohomology algebras in terms of nonequivariant data. We give explicit examples to demonstrate how these theorems can be applied to classify equivariant rational homotopy types with isomorphic cohomology.

Keywords
systems of DGAs, minimal systems, equivariantly formal, intrinsically formal, unstable equivariant rational homotopy theory.
Mathematical Subject Classification
Primary: 55P62, 55P91
Secondary: 16E45, 18G10
References
Publication
Received: 16 June 2023
Revised: 23 May 2024
Accepted: 28 June 2024
Published: 17 September 2025
Authors
Rekha Santhanam
Department of Mathematics
Indian Institute of Technology Bombay
Mumbai
India
https://iitb.irins.org/profile/155793
Soumyadip Thandar
School of Mathematics
Tata Institute of Fundamental Research
Mumbai
India
https://sites.google.com/view/soumyadip-thandar-math/home

Open Access made possible by participating institutions via Subscribe to Open.