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arXiv · 2510.07659

The homotopy type of the Poincar\'e cobordism category for surfaces

Azélie Picot
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Abstract

We define a version of the surface cobordism category $\mathrm{Cob}_2^{\mathrm{SG}}(X)$ over a base space $X$ where surfaces are considered up to self homotopy equivalences instead of diffeomorphisms. We prove the induced functor $B\mathrm{Cob}_2^{\mathrm{SG}}(-): \mathcal{S} \rightarrow \mathcal{S}$ is not $1$-excisive. We show its first derivative $\partial_1 B\mathrm{Cob}_2^{\mathrm{SG}}(-)$ in the Goodwillie sense is equivalent to a Thom spectrum over $B\mathrm{haut}_*^+(S^2)$.

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Azélie Picot. 2025-10-09. The homotopy type of the Poincar\'e cobordism category for surfaces. https://arxiv.org/abs/2510.07659

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