Abstract
We study categories of d -dimensional cobordisms from the perspective of Tillmann [14] and Galatius, Madsen, Tillman and Weiss [6]. There is a category Cθ of closed smooth (d - 1)-manifolds and smooth d -dimensional cobordisms, equipped with generalised orientations specified by a map θ: X → BO(d). The main result of [6] is a determination of the homotopy type of the classifying space BCθ. The goal of the present paper is a systematic investigation of subcategories D ⊆ Cθ with the property that BD ≃ BCθ the smaller such D the better. We prove that in most cases of interest, D can be chosen to be a homotopy commutative monoid. As a consequence we prove that the stable cohomology of many moduli spaces of surfaces with θ -structure is the cohomology of the infinite loop space of a certain Thom spectrum MTθ. This was known for certain special θ, using homological stability results; our work is independent of such results and covers many more cases.
Original language | English |
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Journal | Geometry & Topology |
Volume | 14 |
Pages (from-to) | 1243-1302 |
ISSN | 1465-3060 |
DOIs | |
Publication status | Published - 2010 |
Keywords
- Faculty of Science