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A characterization of alternating links in thickened surfaces

Published online by Cambridge University Press:  13 December 2021

Hans U. Boden
Affiliation:
Mathematics & Statistics, McMaster University, Hamilton, Ontario, (boden@mcmaster.ca; karimih@math.mcmaster.ca)
Homayun Karimi
Affiliation:
Mathematics & Statistics, McMaster University, Hamilton, Ontario, (boden@mcmaster.ca; karimih@math.mcmaster.ca)

Abstract

We use an extension of Gordon–Litherland pairing to thickened surfaces to give a topological characterization of alternating links in thickened surfaces. If $\Sigma$ is a closed oriented surface and $F$ is a compact unoriented surface in $\Sigma \times I$, then the Gordon–Litherland pairing defines a symmetric bilinear pairing on the first homology of $F$. A compact surface in $\Sigma \times I$ is called definite if its Gordon–Litherland pairing is a definite form. We prove that a link $L$ in a thickened surface is non-split, alternating, and of minimal genus if and only if it bounds two definite surfaces of opposite sign.

Information

Type
Research Article
Copyright
Copyright © The Author(s), 2021. Published by Cambridge University Press on behalf of The Royal Society of Edinburgh

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