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Main Authors: Freitas, Nuno, Mocanu, Diana, Sanchez-Rodriguez, Ignasi
Format: Preprint
Published: 2025
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Online Access:https://arxiv.org/abs/2512.10781
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author Freitas, Nuno
Mocanu, Diana
Sanchez-Rodriguez, Ignasi
author_facet Freitas, Nuno
Mocanu, Diana
Sanchez-Rodriguez, Ignasi
contents Let $E/\mathbb Q$ be an elliptic curve and $p \geq 3$ a prime. The modular curve $X_E^-(p)$ parameterizes elliptic curves with $p$-torsion modules anti-symplectically isomorphic to $E[p]$. The work of Freitas--Naskręcki--Stoll uses the modular method to show that all primitive non-trivial solutions of the Fermat-type equation $x^2 + y^3 = z^p$ give rise to rational points on $X_E^-(p)$ with $E \in \{27a1,54a1,96a1,288a1,864a1,864b1,864c1 \}$. Using a criterion classifying the existence of local points due to the first two authors, we show that, for $E$ any of the curves with conductor 864 and certain primes $p \equiv 19 \pmod{24}$, we have $X_E^-(p)(\mathbb Q_\ell) = \emptyset$. Furthermore, for each $E$ in the list and any $p$, we prove that either $X_E^-(p)$ can be discarded using the same criterion, or it cannot be discarded using purely local information.
format Preprint
id arxiv_https___arxiv_org_abs_2512_10781
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Revisiting the equation $x^2+y^3=z^p$
Freitas, Nuno
Mocanu, Diana
Sanchez-Rodriguez, Ignasi
Number Theory
Let $E/\mathbb Q$ be an elliptic curve and $p \geq 3$ a prime. The modular curve $X_E^-(p)$ parameterizes elliptic curves with $p$-torsion modules anti-symplectically isomorphic to $E[p]$. The work of Freitas--Naskręcki--Stoll uses the modular method to show that all primitive non-trivial solutions of the Fermat-type equation $x^2 + y^3 = z^p$ give rise to rational points on $X_E^-(p)$ with $E \in \{27a1,54a1,96a1,288a1,864a1,864b1,864c1 \}$. Using a criterion classifying the existence of local points due to the first two authors, we show that, for $E$ any of the curves with conductor 864 and certain primes $p \equiv 19 \pmod{24}$, we have $X_E^-(p)(\mathbb Q_\ell) = \emptyset$. Furthermore, for each $E$ in the list and any $p$, we prove that either $X_E^-(p)$ can be discarded using the same criterion, or it cannot be discarded using purely local information.
title Revisiting the equation $x^2+y^3=z^p$
topic Number Theory
url https://arxiv.org/abs/2512.10781