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Compact symmetric spaces are probably one of the most prominent class of formal spaces, i.e. of spaces where the rational homotopy type is a formal consequence of the rational cohomology algebra. As a generalisation, it is even known that…

Algebraic Topology · Mathematics 2023-03-08 Manuel Amann , Andreas Kollross

We build model structures on the category of equivariant simplicial operads with a fixed set of colors, with weak equivalences determined by families of subgroups. In particular, by specifying to the family of graph subgroups (or, more…

Algebraic Topology · Mathematics 2022-04-20 Peter Bonventre , Luis Alexandre Pereira

We provide and study an equivariant theory of group (co)homology of a group G with coefficients in a gamma-equivariant G-module A, when a separate group "gamma" acts on G and A, generalizing the classical Eilenberg-MacLane (co)homology of…

K-Theory and Homology · Mathematics 2007-05-23 H. Inassaridze

These notes are based on a series of three lectures given (online) by the first named author at the workshop "Higher Structures and Operadic Calculus" at CRM Barcelona in June 2021. The aim is to give a concise introduction to rational…

Algebraic Topology · Mathematics 2025-05-08 Alexander Berglund , Robin Stoll

We develop model categories of rational equivariant spectra whose homotopy categories are equivalent to the category of rational equivariant cohomology theories. We prove that given an orthogonal decomposition of the unit in the rational…

Algebraic Topology · Mathematics 2008-02-08 David Barnes

We introduce the notion of the \emph{equivariant covering type} of a space $X$ on which a finite group $G$ acts, and study its properties. The equivariant covering type measures the size of $G$-equivariant good covers of $X$ and is thus an…

Algebraic Topology · Mathematics 2024-11-27 Dejan Govc , Waclaw Marzantowicz , Petar Pavesic

Bivariant (equivariant) K-theory is the standard setting for non-commutative topology. We may carry over various techniques from homotopy theory and homological algebra to this setting. Here we do this for some basic notions from…

K-Theory and Homology · Mathematics 2015-10-23 Ralf Meyer , Ryszard Nest

We give an explicit formula for the rational category of an elliptic space whose minimal model has a homogeneous-length differential. We also show that for such a space, there are no gaps in the sequence of integers realized as the rational…

Algebraic Topology · Mathematics 2007-05-23 Gregory Lupton

We develop an algebraic model for the relative sectional category of a continuous map in rational homotopy theory using commutative differential graded algebras (CDGAs). Our main result establishes that for formal maps, the rational…

Algebraic Topology · Mathematics 2026-04-28 Lekha Das , Bittu Singh

We regard the classification of rational homotopy types as a problem in algebraic deformation theory: any space with given cohomology is a perturbation, or deformation, of the "formal" space with that cohomology. The classifying space is…

Quantum Algebra · Mathematics 2012-11-08 Mike Schlessinger , Jim Stasheff

Shipley and the author have given an algebraic model for free rational G-spectra for a compact Lie group G. In the present note we describe, at the level of homotopy categories, the algebraic models for induction, restriction and…

Algebraic Topology · Mathematics 2015-01-27 J. P. C. Greenlees

We investigate group actions on homotopy coherent diagrams. This is used to prove an equivalence between realizations of equivariant cubical flow categories and external actions on Burnside functors. In particular, the results imply that…

Geometric Topology · Mathematics 2024-02-01 Jakub Paliga

We set up an algebraic framework for the study of pseudoholomorphic discs bounding nonorientable Lagrangians, as well as equivariant extensions of such structures arising from a torus action. First, we define unital cyclic twisted…

Symplectic Geometry · Mathematics 2023-03-15 Amitai Netser Zernik

For a semisimple complex algebraic group $G$ we determine the rational cohomology and the Hodge-Tate structure of the moduli stack ${\mathscr B}un_{G,X}$ of principal $G$-bundles over a connected smooth complex projective variety $X$ of…

Algebraic Geometry · Mathematics 2025-08-06 Pedro L. del Angel R. , Frank Neumann

Let G be a general (not necessarily finite dimensional compact) Lie group, let g be its Lie algebra, let Cg be the cone on g in the category of differential graded Lie algebras, and consider the functor which assigns to a chain complex V…

Differential Geometry · Mathematics 2008-10-02 Johannes Huebschmann

For a $C^{*}$-category with a strict $G$-action we construct examples of equivariant coarse homology theories. To this end we first introduce versions of Roe categories of objects in $C^{*}$-categories which are controlled over bornological…

K-Theory and Homology · Mathematics 2023-06-21 Ulrich Bunke , Alexander Engel

For manifolds equipped with group actions, we have the following natural question: To what extent does the equivariant cohomology determine the equivariant diffeotype? We resolve this question for Hamiltonian circle actions on compact,…

Symplectic Geometry · Mathematics 2024-12-20 Tara S. Holm , Liat Kessler , Susan Tolman

The real singular cohomology ring of a homogeneous space $G/K$, interpreted as the real Borel equivariant cohomology $H^*_K(G)$, was historically the first computation of equivariant cohomology of any nontrivial connected group action.…

Algebraic Topology · Mathematics 2023-12-05 Jeffrey D. Carlson

We introduce equivariant versions of uniform rationality: given an algebraic group G, a G-variety is called G-uniformly rational (resp. G-linearly uniformly rational) if every point has a G-invariant open neighborhood equivariantly…

Algebraic Geometry · Mathematics 2017-03-28 Charlie Petitjean

Goresky, Kottwitz and MacPherson have recently shown that the computation of the equivariant cohomology ring of a G-manifold can be reduced to a computation in graph theory. This opens up the possibility that many of the fundamental…

Differential Geometry · Mathematics 2007-05-23 Victor Guillemin , Catalin Zara