M(16,14,8)

M(16,14,8) - [math]k(A_4 \times A_4)[/math]

[[File: |250px]]

Representative:	[math]k(A_4 \times A_4)[/math]
Defect groups:	[math](C_2)^4[/math]
Inertial quotients:	[math]C_3 \times C_3[/math]
[math]k(B)=[/math]	16
[math]l(B)=[/math]	9
[math]{\rm mf}_k(B)=[/math]	1
[math]{\rm Pic}_k(B)=[/math]
Cartan matrix:	[math]\left( \begin{array}{ccccccccc} 4 & 2 & 2 & 1 & 1 & 1 & 1 & 2 & 2 \\ 2 & 4 & 1 & 2 & 1 & 2 & 1 & 1 & 2 \\ 2 & 1 & 4 & 2 & 2 & 1 & 1 & 2 & 1 \\ 1 & 2 & 2 & 4 & 2 & 2 & 1 & 1 & 1 \\ 1 & 1 & 2 & 2 & 4 & 1 & 2 & 1 & 2 \\ 1 & 2 & 1 & 2 & 1 & 4 & 2 & 2 & 1 \\ 1 & 1 & 1 & 1 & 2 & 2 & 4 & 2 & 2 \\ 2 & 1 & 2 & 1 & 1 & 2 & 2 & 4 & 1 \\ 2 & 2 & 1 & 1 & 2 & 1 & 2 & 1 & 4 \end{array} \right)[/math]
Defect group Morita invariant?	Yes
Inertial quotient Morita invariant?	Yes
[math]\mathcal{O}[/math]-Morita classes known?	Yes
[math]\mathcal{O}[/math]-Morita classes:	[math]\mathcal{O} (A_4 \times A_4)[/math]
Decomposition matrices:	See below
[math]{\rm mf}_\mathcal{O}(B)=[/math]	1
[math]{\rm Pic}_{\mathcal{O}}(B)=[/math]	[math]S_3 \wr C_2[/math]
[math]PI(B)=[/math]
Source algebras known?	No
Source algebra reps:
[math]k[/math]-derived equiv. classes known?	Yes
[math]k[/math]-derived equivalent to:	M(16,14,9), M(16,14,10)
[math]\mathcal{O}[/math]-derived equiv. classes known?	Yes
[math]p'[/math]-index covering blocks:
[math]p'[/math]-index covered blocks:
Index [math]p[/math] covering blocks:

Covering blocks and covered blocks

Let [math]N \triangleleft G[/math] with prime [math]p'[/math]-index and let [math]B[/math] be a block of [math]\mathcal{O} G[/math] covering a block [math]b[/math] of [math]\mathcal{O} N[/math].

If [math]b[/math] is in M(16,14,8), then [math]B[/math] is in M(16,14,3), M(16,14,4), M(16,14,8).

Projective indecomposable modules

Labelling the simple [math]B[/math]-modules by [math]S_1, \dots, S_9[/math], the projective indecomposable modules have Loewy structure as follows:

[math]\begin{array}{ccccccccc} \begin{array}{c} S_1 \\ S_2 S_3 S_8 S_9 \\ S_1 S_1 S_4 S_5 S_6 S_7 \\ S_2 S_3 S_8 S_9 \\ S_1 \\ \end{array} & \begin{array}{c} S_2 \\ S_1 S_4 S_6 S_9 \\ S_2 S_2 S_3 S_5 S_7 S_8 \\ S_1 S_4 S_6 S_9 \\ S_2 \\ \end{array} & \begin{array}{c} S_3 \\ S_1 S_4 S_5 S_8 \\ S_2 S_3 S_3 S_6 S_7 S_9 \\ S_1 S_4 S_5 S_8 \\ S_3 \\ \end{array} & \begin{array}{c} S_4 \\ S_2 S_3 S_5 S_6 \\ S_1 S_4 S_4 S_7 S_8 S_9 \\ S_2 S_3 S_5 S_6 \\ S_4 \\ \end{array} & \begin{array}{c} S_5 \\ S_3 S_4 S_7 S_9 \\ S_1 S_2 S_5 S_5 S_6 S_8 \\ S_3 S_4 S_7 S_9 \\ S_5 \\ \end{array} & \begin{array}{c} S_6 \\ S_2 S_4 S_7 S_8 \\ S_1 S_3 S_5 S_6 S_6 S_9 \\ S_2 S_4 S_7 S_8 \\ S_6 \\ \end{array} & \begin{array}{c} S_7 \\ S_5 S_6 S_8 S_9 \\ S_1 S_2 S_3 S_4 S_7 S_7 \\ S_5 S_6 S_8 S_9 \\ S_7 \\ \end{array} & \begin{array}{c} S_8 \\ S_1 S_3 S_6 S_7 \\ S_2 S_4 S_5 S_8 S_8 S_9 \\ S_1 S_3 S_6 S_7 \\ S_8 \\ \end{array} & \begin{array}{c} S_9 \\ S_1 S_2 S_5 S_7 \\ S_3 S_4 S_6 S_8 S_9 S_9 \\ S_1 S_2 S_5 S_7 \\ S_9 \\ \end{array} \end{array} [/math]

Irreducible characters

All irreducible characters have height zero.

Decomposition matrix

[math]\left( \begin{array}{ccccccccc} 1 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 \\ 0 & 0 & 0 & 0 & 1 & 0 & 0 & 0 & 0 \\ 0 & 0 & 0 & 0 & 0 & 0 & 0 & 1 & 0 \\ 0 & 0 & 0 & 1 & 0 & 0 & 0 & 0 & 0 \\ 0 & 0 & 0 & 0 & 0 & 0 & 1 & 0 & 0 \\ 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 1 \\ 0 & 0 & 1 & 0 & 0 & 0 & 0 & 0 & 0 \\ 0 & 0 & 0 & 0 & 0 & 1 & 0 & 0 & 0 \\ 0 & 1 & 0 & 0 & 0 & 0 & 0 & 0 & 0 \\ 1 & 0 & 1 & 0 & 0 & 0 & 0 & 1 & 0 \\ 1 & 1 & 0 & 0 & 0 & 0 & 0 & 0 & 1 \\ 0 & 0 & 0 & 0 & 0 & 1 & 1 & 1 & 0 \\ 0 & 0 & 0 & 0 & 1 & 0 & 1 & 0 & 1 \\ 0 & 1 & 0 & 1 & 0 & 1 & 0 & 0 & 0 \\ 0 & 0 & 1 & 1 & 1 & 0 & 0 & 0 & 0 \\ 1 & 1 & 1 & 1 & 1 & 1 & 1 & 1 & 1 \end{array}\right)[/math]

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