On the ring of cooperations for real hermitian K-theory

Fuente: arXiv
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Main Author: Morris, Jackson
Format: Preprint
Published: 2025
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_version_ 1866909040722837504
author Morris, Jackson
author_facet Morris, Jackson
contents Let kq denote the very effective cover of the motivic Hermitian K-theory spectrum. We analyze the ring of cooperations $π^\mathbb{R}_{**}(\text{kq} \otimes \text{kq})$ in the stable motivic homotopy category $\text{SH}(\mathbb{R})$, giving a full description in terms of Brown--Gitler comodules. To do this, we decompose the $E_2$-page of the motivic Adams spectral sequence and show that it must collapse. The description of the $E_2$-page is accomplished by a series of algebraic Atiyah--Hirzebruch spectral sequences which converge to the summands of the $E_2$-page. Along the way, we prove a splitting result for the very effective symplectic K-theory ksp over any base field of characteristic not two.
format Preprint
id arxiv_https___arxiv_org_abs_2506_16672
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle On the ring of cooperations for real hermitian K-theory
Morris, Jackson
Algebraic Topology
Algebraic Geometry
K-Theory and Homology
14F42, 55Q10, 55Q51, 55T15, 19G38
Let kq denote the very effective cover of the motivic Hermitian K-theory spectrum. We analyze the ring of cooperations $π^\mathbb{R}_{**}(\text{kq} \otimes \text{kq})$ in the stable motivic homotopy category $\text{SH}(\mathbb{R})$, giving a full description in terms of Brown--Gitler comodules. To do this, we decompose the $E_2$-page of the motivic Adams spectral sequence and show that it must collapse. The description of the $E_2$-page is accomplished by a series of algebraic Atiyah--Hirzebruch spectral sequences which converge to the summands of the $E_2$-page. Along the way, we prove a splitting result for the very effective symplectic K-theory ksp over any base field of characteristic not two.
title On the ring of cooperations for real hermitian K-theory
topic Algebraic Topology
Algebraic Geometry
K-Theory and Homology
14F42, 55Q10, 55Q51, 55T15, 19G38
url https://arxiv.org/abs/2506.16672