Let $\Gamma^{op}$ (see Segal's category) be the skeleton of the category of finite pointed sets. We write $\underline{n}$ for the finite pointed set with $n$ non-basepoint elements. Then a **$\Gamma$-set** is a functor $X\colon \Gamma^{op}\to Set$.

The topos $\Set^{\Gamma^{op}}$ of $\Gamma$-sets is the classifying topos for pointed objects (MO question). For more on this see also at *classifying topos for the theory of objects*.

Related $n$Lab entries include Gamma-space, Segal's category.

- Graeme Segal,
*Categories and cohomology theories*, Topology 13 (1974). - Alain Connes, Caterina Consani,
*Absolute algebra and Segal’s Gamma sets*, arxiv/1502.05585

Created on November 5, 2016 at 14:56:15. See the history of this page for a list of all contributions to it.