Finite Fields and Their Applications ( IF 1 ) Pub Date : 2019-12-02 , DOI: 10.1016/j.ffa.2019.101619 Songsong Li , Yi Ouyang , Zheng Xu
Let be a fixed prime. For a supersingular elliptic curve E over , a result of Ibukiyama tells us that is a maximal order (resp. ) in indexed by a (non-unique) prime q satisfying and the quadratic residue if (resp. ), where is the absolute Frobenius. Let denote the minimal q for E whose -invariant and denote the maximum of for all supersingular . Firstly, we determine the neighborhood of the vertex with in the supersingular ℓ-isogeny graph if and or and : there are either or neighbors of , each of which connects to by one edge and at most two of which are defined over . We also give examples to illustrate that our bounds are tight. Next, under GRH, we obtain explicit upper and lower bounds for , which were not studied in the literature as far as we know. To make the bounds useful, we estimate the number of supersingular elliptic curves with for or . In the appendix, we compute for all numerically. Our data show that except or 23 and for all p.
中文翻译:
奇异椭圆曲线上的同态环。
让 成为固定的素数。对于超奇异椭圆曲线E over,Ibukiyama的结果告诉我们 是最大阶数 (分别 )在 由满足以下条件的(非唯一)质数q索引 和二次残基 如果 (分别 ),在哪里 是绝对的Frobenius。让表示最小q为Ë其不变的 和 表示最大 对于所有超奇 。首先,我们确定顶点的邻域 与 在超奇异ℓ -isogeny图表如果 和 要么 和 :有 要么 的邻居 ,每个都连接到 一个边缘,最多两个边缘定义 。我们还举一些例子来说明我们的界限是紧密的。接下来,在GRH下,我们获得显式的上限和下限,据我们所知在文献中并未对此进行研究。为了使边界有用,我们估计了以下奇异椭圆曲线的数量: 对于 要么 。在附录中,我们计算 对全部 数值上。我们的数据表明 除 或23和 对于所有p。