5
$\begingroup$

This is essentially a reference request, or a request for an explanation of why this cannot be done in a useful or interesting way (i.e. an explanation of why no such reference exists!).

If I have a directed space, perhaps modeled by something like a globular complex or complicial set, is there any way to compute "homology" or "cohomology" of it with coefficients in a (commutative) monoid?

A particularly simple example might just be to think of $S^1$ as a directed 1-type, and ask whether or not there's some homology theory such that $H_1(S^1,\mathbb{N})\cong\mathbb{N}$, or something along those lines.

This seems like too simple of an idea to not have been attempted. Does anyone have a reference? If not, does anyone know what goes wrong?

One possibly silly attempt at answering this might be: write down the directed space $X$ as some kind of $(\infty,\infty)$-category, then write down the sequence of deloopings $(M,BM,B^2M,...)$ where we have to take the $n$th "delooping" here to be something like the $(\infty,n)$-category with one object and an $M$'s worth of $n$-morphisms. Then define $H^n(X,M)$ to be something like functors of $(\infty,\infty)$-categories $X\to B^nM$ modulo some notion of equivalence of $(\infty,\infty)$-functors.

$\endgroup$
3
  • 3
    $\begingroup$ I don't have a reference, and this is likely clear to you, but a reasonable definition would be to take $H_i(X,\mathbb N):= \pi_{i}({\rm hocolim}_{X} \mathbb N)$ in the category of simplicial commutative monoids (or the obvious $\infty$ equivalent). $\endgroup$ Commented Aug 30, 2021 at 20:24
  • $\begingroup$ I'm not sure if you mean what I think you mean by directed space, but if so then this paper on "natural homolgy" (and the discussion and references in the introduction) seems relevant: group-mmm.org/~dubut/papers/icalp15.pdf $\endgroup$
    – Mark Grant
    Commented Aug 31, 2021 at 11:06
  • $\begingroup$ This preprint - www2.math.upenn.edu/~ghrist/preprints/MFMC-GSIP.pdf - mentions directed homology with coefficients in N (see sec. V), and refers to a couple of further papers by Krishnan. $\endgroup$ Commented Aug 31, 2021 at 12:22

0

You must log in to answer this question.