M(4,2,2)
quiver.png)
| Representative: | [math]B_0(kA_5)[/math] |
|---|---|
| Defect groups: | [math]C_2 \times C_2[/math] |
| Inertial quotients: | [math]C_3[/math] |
| [math]k(B)=[/math] | 4 |
| [math]l(B)=[/math] | 3 |
| [math]{\rm mf}_k(B)=[/math] | 1 |
| [math]{\rm Pic}_k(B)=[/math] | [math]k^* \wr C_2[/math][1] |
| Cartan matrix: | [math]\left( \begin{array}{ccc} 2 & 2 & 1 \\ 2 & 4 & 2 \\ 1 & 2 & 2 \\ \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]B_0(\mathcal{O}A_5)[/math] |
| Decomposition matrices: | [math]\left( \begin{array}{ccc} 0 & 1 & 0 \\ 1 & 1 & 0 \\ 0 & 1 & 1 \\ 1 & 1 & 1 \\ \end{array}\right)[/math] |
| [math]{\rm mf}_\mathcal{O}(B)=[/math] | 1 |
| [math]{\rm Pic}_{\mathcal{O}}(B)=[/math] | [math]\mathcal{T}(B)=C_2[/math][2] |
| [math]PI(B)=[/math] | [math]S_4 \times C_2[/math][3] |
| Source algebras known? | Yes |
| Source algebra reps: | [math]B_0(\mathcal{O}A_5)[/math] |
| [math]k[/math]-derived equiv. classes known? | Yes |
| [math]k[/math]-derived equivalent to: | M(4,2,3) |
| [math]\mathcal{O}[/math]-derived equiv. classes known? | Yes |
| [math]p'[/math]-index covering blocks: | M(4,2,2) (complete) |
| [math]p'[/math]-index covered blocks: | M(4,2,2) (complete) |
| Index [math]p[/math] covering blocks: | M(8,3,2), M(8,5,2) (complete)[4] |
Contents
Basic algebra
Quiver: a:<1,2>, b:<2,3>, c:<3,2>, d:<2,1>
Relations w.r.t. [math]k[/math]: ad=cb=bcda+dabc=0
Other notatable representatives
Projective indecomposable modules
Labelling the simple [math]B[/math]-modules by [math]S_1, S_2, S_3[/math], the projective indecomposable modules have Loewy structure as follows:
[math]\begin{array}{ccc} \begin{array}{c} S_1 \\ S_2 \\ S_3 \\ S_2 \\ S_1 \\ \end{array}, & \begin{array}{ccc} & S_2 & \\ \begin{array}{c} S_1 \\ S_2 \\ S_3 \\ \end{array} & \oplus & \begin{array}{c} S_3 \\ S_2 \\ S_1 \\ \end{array} \\ & S_2 & \\ \end{array}, & \begin{array}{c} S_3 \\ S_2 \\ S_1 \\ S_2 \\ S_3 \\ \end{array} \end{array} [/math]
Irreducible characters
All irreducible characters have height zero.
Back to [math]C_2 \times C_2[/math]
Notes
- ↑ This is an elementary calculation
- ↑ Every Morita equivalence is a source algebra equivalence by [CEKL13], so [math]{\rm Pic}(B)=\mathcal{T}(B)[/math]
- ↑ This follows from the result for M(4,2,3) since blocks in these classes are derived equivalent and so perfectly isometric
- ↑ A covering block cannot have defect group [math]C_4 \times C_2[/math].
