Topological $\Delta G$ homology of rings with twisted $G$-action

TL;DR

This paper introduces a unified topological homology framework for rings with twisted G-actions, generalizing existing theories like THH and THR, and explores new examples such as THQ and twisted symmetric homology.

Contribution

It constructs topological ΔG-homology for rings with twisted G-actions, generalizing and unifying various known topological homology theories and introducing new examples like THQ.

Findings

THQ of a loop space with twisted C4-action is Pin(2)-equivariantly equivalent to a twisted free loop space

Develops new crossed simplicial groups related to rings with twisted G-actions

Provides homotopical computations for these new homology theories on loop spaces

Abstract

We construct topological $\Delta G$-homology for rings with twisted $G$-action. Here a ring with twisted $G$-action is a common generalization of a ring with anti-involution and a ring with $G$-action. This construction recovers as special cases topological Hochschild homology (THH) of rings, with its $S^1$-action, and Real topological Hochschild homology (THR) of rings with anti-involution, with its $O(2)$-action. A new example of this construction is quaternionic topological Hochschild homology (THQ) of rings with twisted $C_4$-action, which carries a $Pin(2)$-action. We prove that THQ of a loop space with twisted $C_4$-action can be $Pin(2)$-equivariantly identified with a twisted free loop space. Other new examples of interest are topological symmetric homology and topological hyperoctrahedral homology and more generally topological twisted symmetric homology. We prove a homotopical version of results of Fiedorowicz, Ault, and Graves computing these new topological homology theories on loop spaces with twisted $G$-action. A key step of independent interest in this program is the construction of a new family of crossed simplicial groups, which correspond to operads that encode the structure of rings with twisted $G$-action.