Resumen de Some extensions of the modular method and Fermat equations of signature (13,13,n)

Nicolas Billerey , Imin Chen, Lassina Dembélé, Luis Victor Dieulefait , Nuno Freitas

• We provide several extensions of the modular method which were motivated by the problem of completing previous work to prove that, for any integer n ≥ 2, the equation x13 + y 13 = 3zn has no non-trivial primitive solutions. In particular, we present four elimination techniques which are based on: (1) establishing reducibility of certain residual Galois representations over a totally real field; (2) generalizing image of inertia arguments to the setting of abelian surfaces; (3) establishing congruences of Hilbert modular forms without the use of often impractical Sturm bounds; and (4) a unit sieve argument which combines information from classical descent and the modular method. The extensions are of broader applicability and provide further evidence that it is possible to obtain a complete resolution of a family of generalized Fermat equations by remaining within the framework of the modular method. As a further illustration of this, we complete a theorem of Anni–Siksek to show that, for `, m ≥ 5, the only primitive solutions to the equation x 2` + y 2m = z 13 are trivial.