The Motivic Cofiber of $\tau$
Documenta mathematica, Tome 23 (2018), pp. 1077-1127
Consider the Tate twist τ∈H0,1(S0,0) in the mod 2 cohomology of the motivic sphere. After 2-completion, the motivic Adams spectral sequence realizes this element as a map τ:S0,−1→S0,0, with cofiber Cτ. We show that this motivic 2-cell complex can be endowed with a unique E∞ ring structure. Moreover, this promotes the known isomorphism π∗,∗Cτ≅ExtBP∗BP∗,∗(BP∗,BP∗) to an isomorphism of rings which also preserves higher products. We then consider the closed symmetric monoidal category of Cτ-modules (CτMod,−∧Cτ−) which lives in the kernel of Betti realization. Given a motivic spectrum X, the Cτ-induced spectrum X∧Cτ is usually better behaved and easier to understand than X itself. We specifically illustrate this concept in the examples of the mod 2 Eilenberg-Maclane spectrum HF2, the mod 2 Moore spectrum S0,0/2 and the connective hermitian K-theory spectrum kq.
Classification :
14F42, 55P43, 55S10
Mots-clés : motivic cohomology, motivic homotopy theory, cofibre of τ, E∞-structure, hermitian K-theory
Mots-clés : motivic cohomology, motivic homotopy theory, cofibre of τ, E∞-structure, hermitian K-theory
@article{10_4171_dm_642,
author = {Bogdan Gheorghe},
title = {The {Motivic} {Cofiber} of $\tau$},
journal = {Documenta mathematica},
pages = {1077--1127},
year = {2018},
volume = {23},
doi = {10.4171/dm/642},
url = {http://geodesic.mathdoc.fr/articles/10.4171/dm/642/}
}
Bogdan Gheorghe. The Motivic Cofiber of $\tau$. Documenta mathematica, Tome 23 (2018), pp. 1077-1127. doi: 10.4171/dm/642
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