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Isogenous decomposition of the Jacobian of generalized Fermat curves

2015/07/10 by Carvacho, Mariela, Hidalgo, Rubén A., Quispe, Saúl
#30F10 #30F40 #Algebraic Geometry (math.AG) #FOS: Mathematics

paper · doi:10.48550/arxiv.1507.02903

Abstract

A closed Riemann surface S is called a generalized Fermat curve of type (p,n), where p,n ≥ 2 are integers, if it admits a group H ≅ \mathbb Zpn of conformal automorphisms so that S/H is an orbifold of genus zero with exactly n+1 cone points, each one of order p. It is known that S is a fiber product of (n-1) classical Fermat curves of degree p and, for (p-1)(n-1)>2, that it is a non-hyperelliptic Riemann surface. In this paper, assuming p to be a prime integer, we provide a decomposition, up to isogeny, of the Jacobian variety JS as a product of Jacobian varieties of certain cyclic p-gonal curves. Explicit equations for these p-gonal curves are provided in terms of the equations for S. As a consequence of this decomposition, we are able to provide explicit positive-dimensional families of closed Riemann surfaces whose Jacobian variety is isogenous to the product of elliptic curves.

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