Brown representability and the Eilenberg-Watts theorem in homotopical algebra
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- by Mark Hovey PDF
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Abstract:
It is well known that every homology functor on the stable homotopy category is representable, so of the form $E_{*} (X)=\pi _{*} (E\wedge X)$ for some spectrum $E$. However, Christensen, Keller, and Neeman (2001) have exhibited simple triangulated categories, such as the derived category of $k[x,y]$ for sufficiently large fields $k$, for which not every homology functor is representable. In this paper, we show that this failure of Brown representability does not happen on the model category level. That is, we show that a homology theory is representable if and only if it lifts to a well-behaved functor on the model category level. We also show that, for a reasonable model category $\mathcal {M}$, every functor that has the same formal properties as a functor of the form $X\mapsto X\otimes E$ for some cofibrant $E$ is naturally weakly equivalent to a functor of that form. This is closely related to the Eilenberg-Watts theorem in algebra, which proves that every functor with the same formal properties as the tensor product with a fixed object is isomorphic to such a functor.References
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Additional Information
- Mark Hovey
- Affiliation: Department of Mathematics, Wesleyan University, Middletown, Connecticut 06459
- Email: mhovey@wesleyan.edu
- Received by editor(s): September 24, 2013
- Received by editor(s) in revised form: December 10, 2013
- Published electronically: December 9, 2014
- Communicated by: Michael A. Mandell
- © Copyright 2014 American Mathematical Society
- Journal: Proc. Amer. Math. Soc. 143 (2015), 2269-2279
- MSC (2010): Primary 55U35; Secondary 18E30, 18G35, 55N20, 55P42
- DOI: https://doi.org/10.1090/S0002-9939-2014-12423-3
- MathSciNet review: 3314134