Abstract
By defining combinatorial moves, we can define an equivalence relation on Gauss words called homotopy. In this paper we define a homotopy invariant of Gauss words. We use this to show that there exist Gauss words that are not homotopic to the empty Gauss word, disproving a conjecture by Turaev. In fact, we show that there are an infinite number of equivalence classes of Gauss words under homotopy.
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This work was supported by a Scholarship from the Ministry of Education, Culture, Sports, Science and Technology of Japan.
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Gibson, A. Homotopy invariants of Gauss words. Math. Ann. 349, 871–887 (2011). https://doi.org/10.1007/s00208-010-0536-0
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DOI: https://doi.org/10.1007/s00208-010-0536-0