Results known to date. One goal of our database is to provide fields with small (absolute value of the) discriminant for each Galois group and signature. In small degrees it is even possible to determine the field(s) with smallest discriminant. Let's comment on the present state of knowledge in this area.
It is very easy to enumerate the discriminants of quadratic fields.
Degree 3:
Belabas [Bel] gives a very efficient algorithm to enumerate cubic number fields.
Degree 4:
In [BFP] all quartic fields with absolute discriminant smaller than 106 are enumerated.
Degree 5:
There are huge tables of the smallest quintic fields due to [SPD]. These tables are sufficient to extract the smallest discriminants for all Galois groups and classes of involutions for degree 5.
Degree 6:
The minimal discriminants for all signatures of degree 6 are computed in [Poh2]. [Oli2, FoPo1, FoPo2, FPD] have finished the computation of minimal discriminants of all signatures and all primitive Galois groups of degree 6. [BMO, Oli1] compute the minimal fields for imprimitive groups of degree 6. This yields enough information to determine the minimal fields for all groups and all conjugacy classes of that degree.
Degree 7:
In degree 7 the minimal fields of each signature are known due to [Dia1, Dia2, Poh1].
This covers all signatures of the symmetric groups.
Degree 8:
For imprimitive octic fields with a quartic subfield [CDO] compute huge tables using class field theory which cover all imprimitive groups and all possible signatures such that the corresponding field has a quartic subfield. These tables are not sufficient to find all minimal fields of that shape such that complex conjugation lies in a given class of involutions.
In [FiKl] the minima for octic fields having a quadratic subfield are computed. Altogether, we cover all possible signatures for all solvable groups.
The minimal discriminants for the symmetric group have been found in [Dia3, Bat1, Bat2]. We remark that in [Mal] we find a list of all totally real primitive number fields of discriminant up to 10^9 which is sufficient to prove the totally real S_n case in degree 8. The two other minima in the table below are proved in [JoRo].
In the following table we list the groups with at least one unproven minimal discriminant in degree 8. Here, we only know two minima, which are marked in green. The black discriminants are the smallest ones known to us.
Degree |
Name |
0 |
2 |
4 |
6 |
8 |
L(8)=PSL(2,7) |
37822859361 |
- |
- |
- |
134579395898896 |
|
L(8):2=PGL(2,7) |
418195493 |
1997331875 |
- |
- |
20418048738368 |
|
E(8):L7=AL(8) |
32684089 |
- |
293471161 |
- |
81366421504 |
|
A(8) |
16410601 |
- |
144889369 |
- |
46664208361 |
(*) = the green values are proven
(*) = the black values are open
Degree 9:
In degree 9 there are some partial results for imprimitive fields [DiOl]. Furthermore some totally real minimal discriminants are determined [Tak]. In a recent work, [JON] finished the computation of all minima for all solvable groups.
The known minima for the symmetric group have been proved in [Bat2,Tak].
In the following table we list the groups with at least one unproven minimal discriminant in degree 9. The black discriminants are the smallest ones known to us. The green values are already proven.
Degree |
Name |
1 |
3 |
5 |
7 |
9 |
L(9)=PSL(2,8) |
79082438656 |
- |
- |
- |
113186808198805... |
|
L(9):3=P|L(2,8) |
22663495936 |
- |
- |
- |
628373976482826... |
|
A(9) |
92371321 |
- |
3200504329 |
- |
11729467378561 |
|
S(9) |
29510281 |
109880167 |
453771377 |
1904081383 |
9685993193 |
(*) = the green values are proven
(*) = the black values are open
Degree 10:
For many imprimitive groups the minimal discriminants are determined in [DrJo]. In the meantime these computations have been extended to all fields with absolute discriminant smaller than 1.2*1011.
Note that the groups with missing minima are either primitive or only admit a block of size 5 which corresponds to a quadratic subfield.
In the following table we list the groups with at least one unproven minimal discriminant in degree 10. The black discriminants are the smallest ones known to us. The green values are already proven.
Degree |
Name |
0 |
2 |
4 |
6 |
8 |
10 |
[5^2]2 |
224415603 |
- |
- |
- |
- |
6194123253125 |
|
[1/2.D(5)^2]2 |
217799879264163 |
104256800000 |
- |
- |
- |
106599209867706368 |
|
1/2[D(5)^2]2 |
- |
292820000000 |
- |
- |
- |
33422341377520625 |
|
[5^2:4]2 |
2626093750000 |
1229312000000 |
- |
- |
- |
43789058048000000 |
|
[5^2:4]2_2 |
- |
9040581643536 |
- |
- |
- |
6105273987852349696 |
|
[5^2:4_2]2 |
1966899200000 |
3768595808256 |
- |
- |
- |
220292710400000000 |
|
[5^2:4_2]2_2 |
- |
234925181632512 |
- |
- |
- |
114661785600000000 |
|
[D(5)^2]2 |
593019904 |
1128753125 |
- |
34424253125 |
- |
3256446753125 |
|
L(10)=PSL(2,9) |
- |
11284439629824 |
- |
- |
- |
304061824840300... |
|
[1/2.F(5)^2]2 |
67162921875 |
2242969600000 |
- |
15680000000000 |
- |
728703488000000 |
|
1/2[F(5)^2]2 |
- |
640000000000 |
- |
45562500000000 |
- |
3399254384765625 |
|
L(10):2=PGL(2,9) |
35664401793024 |
55267035185152 |
- |
- |
- |
314547523847251... |
|
M(10)=L(10)'2 |
- |
268435456000000 |
- |
- |
- |
856766180266359... |
|
S_6(10)=L(10):2 |
- |
95820414976 |
1508214295232 |
- |
- |
525501674708224 |
|
[F(5)^2]2 |
9300278979 |
47280848896 |
- |
9932496465625 |
- |
277597456433152 |
|
L(10).2^2=P|L(2,9) |
662747776000 |
24207794634752 |
163840000000000 |
- |
- |
397310382895823... |
|
[A(5)^2]2 |
5841576387 |
6652128125 |
- |
1919520800000 |
- |
51717300078125 |
|
[1/2.S(5)^2]2=[A(5):2]2 |
4859704512 |
12462528125 |
- |
194242050000 |
- |
109268775200000 |
|
1/2[S(5)^2]2 |
- |
11103890625 |
- |
85629390625 |
- |
207699287474176 |
|
[S(5)^2]2 |
216670707 |
875003125 |
3405971875 |
14339628125 |
85992371875 |
911025153125 |
|
A(10) |
- |
1844444809 |
- |
51471358129 |
- |
1464365125816576 |
|
S(10) |
236438047 |
802448461 |
3316535227 |
19388527573 |
94822656283 |
513087549389 |
(*) = the green values are proven
(*) = the black values are open
Degree 11:
In the following table we list the groups with at least one unproven minimal discriminant in degree 11. The black discriminants are the smallest ones known to us.
Note that all of these missing groups are not solvable. The minima of the solvable groups in degree 11 have been found with the methods described in [FiKl].
Degree |
Name |
1 |
3 |
5 |
7 |
9 |
11 |
L(11)=PSL(2,11)(11) |
- |
11239665258721 |
- |
- |
- |
313765182433896... |
|
M(11) |
- |
95241470237660224 |
- |
- |
- |
118769262421915... |
|
A(11) |
- |
64283038681 |
- |
47353198025956 |
- |
952203981320302... |
|
S(11) |
5939843699 |
24963663301 |
132326332471 |
610429790897 |
7530807227563 |
48706494267293 |
(*) = the black values are open
Degree 13:
In the following table we list the groups with at least one unproven minimal discriminant in degree 13. The black discriminants are the smallest ones known to us.
Note that all of these missing groups are not solvable. The minima of the solvable groups in degree 13 have been found with the methods described in [FiKl].
Degree |
Name |
1 |
3 |
5 |
7 |
9 |
11 |
13 |
L(13)=PSL(3,3) |
- |
- |
8423789045905096704 |
- |
- |
- |
362838554526023... |
|
A(13) |
57655000561921 |
- |
5749519947196921 |
- |
810753495582814... |
- |
308767218127767... |
|
S(13) |
1325925503633 |
5570916369223 |
28261626739249 |
137400291790087 |
737652920184769 |
4161299413431551 |
50359924122392641 |
(*) = the black values are open
In order to see the statistics for other degrees, please click on Statistics and then on "Groups with unproven minimal discriminants".
References:
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