Juan G. Escudero

Folding polynomials of degree d with integer coefficients were used by S. Chmutov to generate complex algebraic surfaces with many nodes ("Examples of projective surfaces with many singularities". J. Algebraic Geom. Vol.1, p.191 (1992)). For d=3n, there is a family of complex surfaces having more singularities, which can be obtained by using certain bivariate polynomials Q with complex coefficients. As the folding polynomials, Q are related to the generalized cosine associated to the affine Weyl group of the root system A2. (On a family of complex algebraic surfaces of degree 3n. C. R. Math. Acad. Sci. Paris. Vol.351, n.17-18, p.699 (2013), Zbl 1283.14013).