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authorSebastiano Tronto <sebastiano.tronto@gmail.com>2019-04-19 11:38:07 +0200
committerSebastiano Tronto <sebastiano.tronto@gmail.com>2019-04-19 11:38:07 +0200
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1# Kummer Degrees 1# Kummer Degrees
2A SageMath script that computes the degrees of Kummer Extensions of the rational numbers. 2A SageMath script that computes the degrees of Kummer Extensions of the rational numbers.
3It contains the following useful functions:
4
5+-----------------------+
6|TotalKummerFailure( G )|
7+-----------------------+
8
9Outputs the description of the failure of maximality
10for all possible values of M and N. Here G is given as a list of generators
11(not necessarily a basis). G can also contain torsion. If G = <-1>, the program
12stops immediately.
13
14Example:
15
16sage: TotalKummerFailure([-36,12,-1])
17output:
18M_0 = 24
19N_0 = 8
20
21The following table shows the total failure of Kummer degrees in
22 case the quotient M/N is EVEN.
23Columns correspond to values of M, rows to values of N
24
25The degree of the Kummer extension (M,N) can be extracted by taking
26the value f (failure) of the entry at (gcd(N,N0),gcd(M,M0)) and
27simply computing ed(M,N) / f, where ed(M,N) is the expected degree
28of the Kummer extension.
29In this case (-1 is in G), we have ed(M,N) = 2^e*phi(M)*N^r,
30where e=1 if N is even and e=0 if N is odd.
31where r is the rank of G.
32
33 | 1 2 3 4 6 8 12 24
34 - - - - - - - - - -
35 1 | 1 1 1 1 1 1 1 1
36 2 | 4 4 4 4 4 4 8 8
37 4 | 4 4 4 4 4 8 8 16
38 8 | 8 8 8 8 8 16 16 32
39
40The following table shows the total failure of Kummer degrees in
41case the quotient M/N is ODD.
42This table can be read exactly as the first one.
43
44 | 1 2 3 4 6 8 12 24
45 - - - - - - - - - -
46 1 | 1 1 1 1 1 1 1 1
47 2 | 2 2 2 2 4 2 4 4
48 4 | 2 2 2 4 4 4 8 8
49 8 | 4 4 4 8 8 8 16 16
50
51-------------------------------------------------------------------------------
52
53+-----------------------+
54|KummerDegree( G, M, N )|
55+-----------------------+
56
57Returns the degree of the Kummer extension Q_{M,N}. Again, G is given simply as
58a list of generators and it may contain torsion.
59
60sage: KummerDegree([-36,12,-1],120,24)
61output:
622304
63
64-------------------------------------------------------------------------------

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