PSL(2,31) Modulo 3
The Hecke algebra for the Projective Special Linear Group of dimension 2
over GF(31) with point stabilizer being the normalizer of a
Sylow 3-subgroup
in characteristic 3
.
The Module M
The module M is the permutation module over the prime
field of chacteristic 3, having point stablilizer
of order 30
The dimension of M is 496
.
The dimensions of the irreducible submodules modules are
120,
64,
31,
1
.
The module M has radical filtration (Loewy series)
1,
1,
2,
3,
4
2,
4
2,
3
The module M has socle filtration (socle series)
2,
3
2,
4
1,
1,
2,
3,
4
The module M has simple direct summands:
2 copies of simple module number 1
1 copy of simple module number 4
The remaining indecomposable components of M
have radical and socle filtrations as follows:
1).
radical layers
3
4
3
socle layers
3
4
3
2).
radical layers
2
2
2
socle layers
2
2
2
The Action Algebra
The action algebra A is the image of kG in the
k-endomorphism ring of M. It's simple modules are the irreducible
submodules of M.
The dimensions of the projective modules are
120,
192,
63,
32
.
The cartan matrix of A is
1,
0,
0,
0
0,
3,
0,
0
0,
0,
2,
1
0,
0,
1,
1
The determinant of the Cartan matrix is 3.
The blocks of A consist of the following irreducible
modules:
Projective module number 1 is simple.
The radical and socle filtrations of the remaining
projective modules for A are the following:
Projective module number 2
radical layers
2
2
2
socle layers
2
2
2
Projective module number 3
radical layers
3
4
3
socle layers
3
4
3
Projective module number 4
radical layers
4
3
socle layers
4
3
The degrees of the splitting fields are
4,
2,
1,
1
.
The Hecke Algebra
The Hecke algebra H of the module M is the A-endomorphism
ring of M.
The dimension of H is
25
.
The dimensions of the irreducible H-modules are
8,
2,
1,
1
.
The degrees of the splitting fields are
4,
2,
1,
1
.
The dimensions of the projective modules of H are
8,
6,
2,
1
.
The cartan matrix of H is
1,
0,
0,
0
0,
3,
0,
0
0,
0,
2,
0
0,
0,
0,
1
The determinant of the Cartan matrix is 6.
The blocks of H consist of the following irreducible
modules:
(1).
1
(2).
2
(3).
3
(4).
4
Projective modules number
1,
4
are simple.
The radical and socle filtrations of the remaining
projective modules for H are the following:
Projective module number 2
radical layers
2
2
2
socle layers
2
2
2
Projective module number 3
radical layers
3
3
socle layers
3
3