The smooth classification of 4-dimensional complete intersections

Fuente: arXiv
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Main Authors: Crowley, Diarmuid, Nagy, Csaba
Format: Preprint
Published: 2020
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author Crowley, Diarmuid
Nagy, Csaba
author_facet Crowley, Diarmuid
Nagy, Csaba
contents We prove the "Sullivan Conjecture" on the classification of 4-dimensional complete intersections up to diffeomorphism. Here an $n$-dimensional complete intersection is a smooth complex variety formed by the transverse intersection of $k$ hypersurfaces in $CP^{n+k}$. Previously Kreck and Traving proved the 4-dimensional Sullivan Conjecture when 64 divides the total degree (the product of the degrees of the defining hypersurfaces) and Fang and Klaus proved that the conjecture holds up to the action of the group of homotopy 8-spheres $Θ_8 = Z/2$. Our proof involves several new ideas, including the use of the Hambleton-Madsen theory of degree-$d$ normal maps, which provide a fresh perspective on the Sullivan Conjecture in all dimensions. This leads to an unexpected connection between the Segal Conjecture for $S^1$ and the Sullivan Conjecture.
format Preprint
id arxiv_https___arxiv_org_abs_2003_09216
institution arXiv
publishDate 2020
record_format arxiv
spellingShingle The smooth classification of 4-dimensional complete intersections
Crowley, Diarmuid
Nagy, Csaba
Geometric Topology
57R65, 57R55, 14M10
We prove the "Sullivan Conjecture" on the classification of 4-dimensional complete intersections up to diffeomorphism. Here an $n$-dimensional complete intersection is a smooth complex variety formed by the transverse intersection of $k$ hypersurfaces in $CP^{n+k}$. Previously Kreck and Traving proved the 4-dimensional Sullivan Conjecture when 64 divides the total degree (the product of the degrees of the defining hypersurfaces) and Fang and Klaus proved that the conjecture holds up to the action of the group of homotopy 8-spheres $Θ_8 = Z/2$. Our proof involves several new ideas, including the use of the Hambleton-Madsen theory of degree-$d$ normal maps, which provide a fresh perspective on the Sullivan Conjecture in all dimensions. This leads to an unexpected connection between the Segal Conjecture for $S^1$ and the Sullivan Conjecture.
title The smooth classification of 4-dimensional complete intersections
topic Geometric Topology
57R65, 57R55, 14M10
url https://arxiv.org/abs/2003.09216