257 research outputs found
Computation of highly ramified coverings
An almost Belyi covering is an algebraic covering of the projective line,
such that all ramified points except one simple ramified point lie above a set
of 3 points of the projective line. In general, there are 1-dimensional
families of these coverings with a fixed ramification pattern. (That is,
Hurwitz spaces for these coverings are curves.) In this paper, three almost
Belyi coverings of degrees 11, 12, and 20 are explicitly constructed. We
demonstrate how these coverings can be used for computation of several
algebraic solutions of the sixth Painleve equation.Comment: 26 page
Dessins d'enfants for analysts
We present an algorithmic way of exactly computing Belyi functions for
hypermaps and triangulations in genus 0 or 1, and the associated dessins, based
on a numerical iterative approach initialized from a circle packing combined
with subsequent lattice reduction. The main advantage compared to previous
methods is that it is applicable to much larger graphs; we use very little
algebraic geometry, and aim for this paper to be as self-contained as possible
On computing Belyi maps
We survey methods to compute three-point branched covers of the projective
line, also known as Belyi maps. These methods include a direct approach,
involving the solution of a system of polynomial equations, as well as complex
analytic methods, modular forms methods, and p-adic methods. Along the way, we
pose several questions and provide numerous examples.Comment: 57 pages, 3 figures, extensive bibliography; English and French
abstract; revised according to referee's suggestion
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