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Cup-one algebras and $1$-minimal models

Richard D. Porter and Alexander I. Suciu

Algebraic & Geometric Topology 26 (2026) 65–134
DOI: 10.2140/agt.2026.26.65
Abstract

Previously we introduced the notion of binomial cup-one algebras, which are differential graded algebras endowed with Steenrod 1-products and compatible binomial operations. In this paper we show that binomial cup-one algebras capture homotopy 1-type. In particular, given such an R-dga, (A,dA), defined over the ring R = or 𝔽p (for p a prime), with H0(A) = R and with H1(A) a finitely generated, free R-module, we show that A admits a functorially defined 1-minimal model, ρ : ((A),d) (A,dA), which is unique up to isomorphism. Furthermore, we associate to this model a pronilpotent group, whose continuous cohomology is isomorphic to that of (A). These constructions, which refine classical notions from rational homotopy theory, allow us to distinguish spaces with isomorphic torsion-free integral cohomology rings. Moreover, we show that there is an equivalence of categories between isomorphism classes of finitely generated, torsion-free-nilpotent groups and isomorphism classes of finitely generated 1-minimal models over the integers.

Keywords
differential graded algebras, cochain algebras, Steenrod cup-$i$ products, binomial rings, Hirsch extensions, minimal models, Massey products, nilmanifolds
Mathematical Subject Classification
Primary: 16E45, 55P62, 55S05
Secondary: 13F20, 20F18, 20J05, 55N45, 55U10
References
Publication
Received: 8 August 2023
Revised: 20 July 2024
Accepted: 22 January 2025
Published: 16 January 2026
Authors
Richard D. Porter
Department of Mathematics
Northeastern University
Boston, MA
United States
Alexander I. Suciu
Department of Mathematics
Northeastern University
Boston, MA
United States

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