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Semicanonical basis generators of the cluster algebra of type \(A_1^{(1)}\). (English) Zbl 1144.16015

Summary: We study the cluster variables and “imaginary” elements of the semicanonical basis for the coefficient-free cluster algebra of affine type \(A_1^{(1)}\). A closed formula for the Laurent expansions of these elements was given by P. Caldero and the author [Mosc. Math. J. 6, No. 3, 411-429 (2006; Zbl 1133.16012)]. As a by-product, there was given a combinatorial interpretation of the Laurent polynomials in question, equivalent to the one obtained by G. Musiker and J. Propp [Electron. J. Comb. 14, No. 1, Research paper R15 (2007; Zbl 1140.05053)]. The original argument by P. Caldero and the author used a geometric interpretation of the Laurent polynomials due to P. Caldero and F. Chapoton [Comment. Math. Helv. 81, No. 3, 595-616 (2006; Zbl 1119.16013)]. This note provides a quick, self-contained and completely elementary alternative proof of the same results.

MSC:

16G20 Representations of quivers and partially ordered sets
05E99 Algebraic combinatorics