Supersingular Elliptic Curves Without Inseparable Small Degree Endomorphisms
Abstract
For a fixed characteristic p, let δ(p) denote the smallest degree needed to guarantee the existence of an isogeny from any supersingular curve E to its Frobenius conjugate E(p). We translate existence questions concerning δ(p) into questions about positive definite integral ternary quadratic forms and use Voronoi's theory of perfect forms in dimension three to characterize when δ(p) is nearly maximal. For sufficiently large primes, we show that δ(p) attains its upper bound precisely when p is represented by one of nine explicit cubic polynomials, reducing the infinitude of such primes to whether one of these cubics takes prime values infinitely often. We also prove that, for almost all primes, δ(p) lies at least p1/6−o(1) below its upper bound.
Related
- Iwasawa theory of CM elliptic curves at potentially supersingular primes
- On Sun's Conjectures for Truncated Jacobi-Symbol Determinants via Supersingular Elliptic Curves
- An Explicit Sextic Twist of a Supersingular Elliptic Curve in Characteristic Two
- Higher rank elliptic sieve via CM endomorphisms
- Torsion points in families of elliptic curves
BibTeX
@misc{swanson2026supersingular,
title = {{Supersingular Elliptic Curves Without Inseparable Small Degree Endomorphisms}},
author = {Nicolas Swanson},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.03839},
eprint = {2609.03839},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.03839},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Supersingular Elliptic Curves Without Inseparable Small Degree Endomorphisms
AU - Nicolas Swanson
PY - 2026
DA - 2026/09/03
PB - arXiv
DO - 10.48550/arxiv.2609.03839
UR - https://arxiv.org/abs/2609.03839
AB - For a fixed characteristic p, let δ(p) denote the smallest degree needed to guarantee the existence of an isogeny from any supersingular curve E to its Frobenius conjugate E^(p). We translate existence questions concerning δ(p) into questions about positive definite integral ternary quadratic forms and use Voronoi's theory of perfect forms in dimension three to characterize when δ(p) is nearly maximal. For sufficiently large primes, we show that δ(p) attains its upper bound precisely when p is represented by one of nine explicit cubic polynomials, reducing the infinitude of such primes to whether one of these cubics takes prime values infinitely often. We also prove that, for almost all primes, δ(p) lies at least p^1/6−o(1) below its upper bound.
ER -