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楼主 |
发表于 2025-7-21 20:37:29
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主要是magma返回的生成元列表 会包括 扰子群的生成元. 然后看到一个生成元是整数,高度疑似扰子群的生成元, 就想当然了/
刚才验证了一下PARI/Gp, PARI/Gp计算的rank也是2.
- a=2026;b=1;
- E=ellinit([0,-27*a^2*b^2*(a + b)^2/4]);
- (250721.20:32:18)> ellrank(E,1)
- %17 = [2, 2, 0, [[4106703, 8322227550]]]
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我的magma代码
- SetClassGroupBounds("GRH");
- a:=2026;
- b:=1;
- E := EllipticCurve([0,-27*a^2*b^2*(a + b)^2/4]);
- time rank, gens, sha := MordellWeilShaInformation(E :Effort := 10);
- print "Rank:", rank;
- print "Generators:", gens;
- print "Sha information:", sha;
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返回的结果是
- Using model [ 0, 0, 0, 0, -113838758888427 ]
- Torsion Subgroup is trivial
- The 2-Selmer group has rank 2
- New point of infinite order (x = 4106703)
- After 2-descent:
- 1 <= Rank(E) <= 2
- Sha(E)[2] <= (Z/2)^1
- (Searched up to height 10000 on the 2-coverings.)
- New point of infinite order (x = 1593462484636951396357229451101533533429521203\
- 971283371577/1636149542007351853070414842976186503226847976880784)
- After 4-descent:
- 2 <= Rank(E) <= 2
- Sha(E)[4] is trivial
- (Searched up to height 10^5 on the 4-coverings.)
- Time: 4.270
- Rank: [ 2, 2 ]
- Generators: [ (4106703 : -8322227550 : 1),
- (1593462484636951396357229451101533533429521203971283371577/1636149542007351853\
- 070414842976186503226847976880784 : -636042305388456468929604763503295503957362\
- 08682901211206839820657814072393955419434515/6618117792479635904690921613416924\
- 9039568440832223385995613883844083171018048 : 1) ]
- Sha information: [
- <2, [ 0, 0 ]>,
- <4, [ 0, 0 ]>
- ]
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