Abstract
We prove that a knot is the unknot if and only if its reduced Khovanov cohomology has rank 1. The proof has two steps. We show first that there is a spectral sequence beginning with the reduced Khovanov cohomology and abutting to a knot homology defined using singular instantons. We then show that the latter homology is isomorphic to the instanton Floer homology of the sutured knot complement: an invariant that is already known to detect the unknot.
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The work of the first author was supported by the National Science Foundation through NSF grants DMS-0405271 and DMS-0904589.
The work of the second author was supported by NSF grant DMS-0805841.
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Kronheimer, P.B., Mrowka, T.S. Khovanov homology is an unknot-detector. Publ.math.IHES 113, 97–208 (2011). https://doi.org/10.1007/s10240-010-0030-y
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DOI: https://doi.org/10.1007/s10240-010-0030-y