M(8,3,3)

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M(8,3,3) - [math]kS_4[/math]
M(8,3,3)quiver.png
Representative: [math]kS_4[/math]
Defect groups: [math]D_8[/math]
Inertial quotients: [math]1[/math]
[math]k(B)=[/math] 5
[math]l(B)=[/math] 2
[math]{\rm mf}_k(B)=[/math] 1
[math]{\rm Pic}_k(B)=[/math]
Cartan matrix: [math]\left( \begin{array}{cc} 4 & 2 \\ 2 & 3 \\ \end{array} \right)[/math]
Defect group Morita invariant? Yes
Inertial quotient Morita invariant? Yes
[math]\mathcal{O}[/math]-Morita classes known? No
[math]\mathcal{O}[/math]-Morita classes:
Decomposition matrices: [math]\left( \begin{array}{c} 1 & 0 \\ 1 & 0 \\ 0 & 1 \\ 1 & 1 \\ 1 & 1 \\ \end{array}\right)[/math]
[math]{\rm mf}_\mathcal{O}(B)=[/math]
[math]{\rm Pic}_{\mathcal{O}}(B)=[/math]
[math]PI(B)=[/math] {{{PIgroup}}}
Source algebras known? No
Source algebra reps:
[math]k[/math]-derived equiv. classes known? Yes
[math]k[/math]-derived equivalent to: M(8,3,2)
[math]\mathcal{O}[/math]-derived equiv. classes known?
[math]p'[/math]-index covering blocks:
[math]p'[/math]-index covered blocks:
Index [math]p[/math] covering blocks: {{{pcoveringblocks}}}

These are tame blocks, and appear in the family [math]D(2 {\cal B})[/math] in Erdmann's classification (see [Er87] ). Derived equivalences over [math]k[/math] are established in [Ho97].

Basic algebra

Quiver: a:<1,1>, b:<1,2>, c:<2,1>, d:<2,2>,

Relations w.r.t. [math]k[/math]: [math]a^2=bd=dc=cb=0[/math], [math]abc=bca[/math], [math]cab=d^2[/math]

Other notatable representatives

Projective indecomposable modules

Labelling the simple [math]B[/math]-modules by [math]1, 2[/math], the projective indecomposable modules have Loewy structure as follows:

[math]\begin{array}{cc} \begin{array}{ccc} & 1 & \\ \begin{array}{c} 1 \\ 2 \\ \end{array} & \oplus & \begin{array}{c} 2 \\ 1 \\ \end{array} \\ & 1 & \\ \end{array}, & \begin{array}{ccc} & 2 & \\ \begin{array}{c} 1 \\ 1 \\ \end{array} & \oplus & \begin{array}{c} 2 \\ \end{array} \\ & 2 & \\ \end{array} \\ \end{array} [/math]

Irreducible characters

[math]k_0(B)=4, k_1(B)=1[/math]