Consider the Goodwillie calculus of a homotopy functor $F : \mathrm{Sp} \to \mathrm{Sp}$, where $\mathrm{Sp}$ denotes an appropriate model for spectra (... orthogonal spectra for instance).

Then Goodwillie (and others) produced a Taylor tower of approximations to $F$, where the levels of the tower are spectra with a $\Sigma_n$-action.

Calculus of functors was also developed by Johnson and McCarthy, for additive categories, which produces an analogous tower associated to functors between additive categories.

I am aware that Johnson and McCarthy consider when the two towers are the same, or more precisely when the functors in their additive sense, fit into a Goodwillie tower. My question concerns the opposite direction:

When we consider the homotopy category of spectra, it is a triangulated category, hence additive. Has anyone ever considered how the Goodwillie and Johnson-McCarthy towers relate in this instance?

That is, given a homotopy functor $F: \mathrm{Sp} \to \mathrm{Sp}$ it will produce a tower in the sense of Goodwillie, but we can consider $F$ as a functor between homotopy cateogories, $ F:\mathrm{Ho}(\mathrm{Sp}) \to \mathrm{Ho}(\mathrm{Sp})$, and we get another tower in the sense of Johnson-McCarthy. As such my question may be rephrased as follows:

When does the Goodwillie tower and the Johnson-McCarthy tower coincide for a homotopy functor $F: \mathrm{Sp} \to \mathrm{Sp}$?

  • 6
    $\begingroup$ If I am not mistaken, the construction of Johnson-McCarthy requires the existence of certain colimits (e.g., quotients). I am not sure you can apply it to a functor between homotopy categories. $\endgroup$ – Gregory Arone Oct 19 '18 at 5:33

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.