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January 31, 2026 17:05


Secant-Quandle and Its Generalization: Loop-Quandle as an Invariant of Knots

Liu Yangzhou

Abstract: We construct an interesting invariant for braids, the secant-quandle (SQ), derived from homotopy classes of generic secants and generic trisecants. We provide an algebraic-topological interpretation of this invariant by showing that each generator in SQ corresponds to a special element of the fundamental group of the braid complement, specifically, a meridian encircling exactly two braid strands. This interpretation enables a natural generalization of the secant-quandle to an invariant of knots and links, the loop-quandle (LQ). Furthermore, we extend the construction to the virtual braids. As an application, we compute the SQ and LQ for the Hopf link.

Language: English

Website: https://us02web.zoom.us/j/81866745751?pwd=bEFqUUlZM1hVV0tvN0xWdXRsV2pnQT09


© Steklov Math. Inst. of RAS, 2026