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arXiv · 2103.07955

A new family of exceptional rational functions

Zhiguo Ding·Michael E. Zieve
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Abstract

For each odd prime power q, we construct an infinite sequence of rational functions f(X) in F_q(X), each of which is exceptional, which means that for infinitely many n the map c-->f(c) induces a bijection of P^1(F_{q^n}). Moreover, each of our functions f(X) is indecomposable, which means that it cannot be written as the composition of lower-degree rational functions in F_q(X). In case q is not a power of 3, these are the first known examples of indecomposable exceptional rational functions f(X) over F_q which have non-solvable monodromy groups and have arbitrarily large degree. These are also the first known examples of wildly ramified indecomposable exceptional rational functions f(X), other than linear changes of polynomials.

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Zhiguo Ding, Michael E. Zieve. 2021-03-14. A new family of exceptional rational functions. https://doi.org/10.1093/imrn%2Frnab315

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