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Chebycheff and Belyi polynomials, dessins dénfants, Beauville surfaces and group theory. (English) Zbl 1167.14300

Summary: We start discussing the group of automorphisms of the field of complex numbers, and describe, in the special case of polynomials with only two critical values, Grothendieck’s program of ‘Dessins d’ enfants’, aiming at giving representations of the absolute Galois group. We describe Chebycheff and Belyi polynomials, and other explicit examples. As an illustration, we briefly treat difference and Schur polynomials. Then we concentrate on a higher dimensional analogue of the triangle curves, namely, Beauville surfaces and varieties isogenous to a product. We describe their moduli spaces, and show how the study of these varieties leads to new interesting questions in the theory of finite (simple) groups.

MSC:

14D05 Structure of families (Picard-Lefschetz, monodromy, etc.)
14G32 Universal profinite groups (relationship to moduli spaces, projective and moduli towers, Galois theory)
14J10 Families, moduli, classification: algebraic theory
14H30 Coverings of curves, fundamental group
33C45 Orthogonal polynomials and functions of hypergeometric type (Jacobi, Laguerre, Hermite, Askey scheme, etc.)

Online Encyclopedia of Integer Sequences:

Triangle whose (i,j)-th entry is binomial(i,j)*4^(i-j)*4^j.