A Steenrod square on Khovanov homology and a cup-i product

Fuente: arXiv
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Autor principal: Rajapakse, Advika
Formato: Preprint
Publicado: 2026
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author Rajapakse, Advika
author_facet Rajapakse, Advika
contents Lipshitz-Sarkar defined a stable homotopy type refining Khovanov homology, producing cohomology operations $\text{Sq}^i$ on the Khovanov homology $Kh(L)$ of a link $L$. Later, Morán proposed a sequence of cup-i products on the $\mathbb{F}_2$-coefficient cochain complex of any augmented semi-simplicial object in the Burnside category. Applied to the Khovanov functor, he obtained another sequence of operations $\mathfrak{sq}^n$ on $Kh(L)$, where $\mathfrak{sq}^0$, $\mathfrak{sq}^1$ agree with the usual Steenrod squares. We prove that Lipshitz-Sarkar's $\text{Sq}^2$, the first Steenrod operation that cannot be computed from merely homological data, agrees with Morán's $\mathfrak{sq}^2$.
format Preprint
id arxiv_https___arxiv_org_abs_2603_16221
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle A Steenrod square on Khovanov homology and a cup-i product
Rajapakse, Advika
Geometric Topology
Algebraic Topology
57K18 (Primary) 55P42, 55S10 (Secondary)
Lipshitz-Sarkar defined a stable homotopy type refining Khovanov homology, producing cohomology operations $\text{Sq}^i$ on the Khovanov homology $Kh(L)$ of a link $L$. Later, Morán proposed a sequence of cup-i products on the $\mathbb{F}_2$-coefficient cochain complex of any augmented semi-simplicial object in the Burnside category. Applied to the Khovanov functor, he obtained another sequence of operations $\mathfrak{sq}^n$ on $Kh(L)$, where $\mathfrak{sq}^0$, $\mathfrak{sq}^1$ agree with the usual Steenrod squares. We prove that Lipshitz-Sarkar's $\text{Sq}^2$, the first Steenrod operation that cannot be computed from merely homological data, agrees with Morán's $\mathfrak{sq}^2$.
title A Steenrod square on Khovanov homology and a cup-i product
topic Geometric Topology
Algebraic Topology
57K18 (Primary) 55P42, 55S10 (Secondary)
url https://arxiv.org/abs/2603.16221