- $\Gamma$-spaces are pointed functors $X\colon(\Gamma^\op,\l0\r)\to(\mathcal{S},*)$ from Segal's category to the category $\mathcal{S}$ of spaces. Moreover, we call $X$
$\Gamma$-spaces are pointed functors $X\colon(\Gamma^\op,\l0\r)\to(\mathcal{S},*)$ from Segal's category to the category $\mathcal{S}$ of spaces. Moreover, we call $X$ (see Definition 7.1 here)
- special if, for each $X$ sends coproducts to products;$\l n\r,\l m\r\in\mathrm{Obj}(\Gamma)$, the map $$X_{\l n\r\vee\l m\r}\to X_{\l n\r}\times X_{\l m\r}$$ induced by the inert surjections $\l n\r\vee\l m\r\to\l n\r$ and $\l n\r\vee\l m\r\to\l m\r$ is a weak equivalence.
- very special if $\pi_0(X_{\l1\r})$it is a group.special and equivalently
- $\pi_0(X_{\l1\r})$ is a group.
- The map $$X_{\l 2\r}\to X_{\l1\r}\times X_{\l1\r}$$ induced by the total map $\l2\r\to\l1\r$ and one of the two inert surjections $\l2\r\to\l1\r$ is a weak equivalence.
- Spectra are reduced excisive functors $E\colon\mathcal{S}^\fin_*\to\S$ of $\infty$-categories, where
Spectra are reduced excisive functors $E\colon\mathcal{S}^\fin_*\to\S$ of $\infty$-categories, where
- $E$ is excisive if it sends pushouts to pullbacks.
- $E$ is reduced if $E(*)\simeq *$;
One could imagine also more generally expanding the definition of $\infty$-operad, replacing $\mathrm{N}_{\bullet}(\mathsf{Fin}_*)$ by $\S^\fin_*$ and variants. For spans in $m$-finite spaces, this should give a notion of $m$-operad, as pointed out by Shachar Carmeli on the homotopy Discord.
Edit: This question has been mostly answer by Marc Hoyois and Dmitri Pavlov below (thanks!). The only remaining part is what are reduced excisive functors $\mathcal{S}^{\mathrm{fin}}_{*,\leq n}\to\mathcal{S}$, which I've split into a separate question here.