# Revision history [back]

### Can SAGE calculate with projective (indecomposable) A-modules (A is a finite dimensional Q-algebra)?

Hi, I have the following question:

Given a $\mathbb{Q}$-algebra A by generators (the generators are matrices) and knowing 5 primitive orthogonal idempotents $e_1$,...,$e_5$ (as matrices), which sum up to $1_R$ (the identity matrix), is there a way / procedure in SAGE, that can compute the projective indecomposable modules $P_1=e_1\cdot R$,...,$P_5=e_5\cdot R$ and then test, whether $P_i$ and $P_j$ are isomorphic as $R$-modules for $i\neq j$?

Thank you very much.

### Can SAGE calculate with projective (indecomposable) A-modules (A is a finite dimensional Q-algebra)?

Hi, I have the following question:

Given a $\mathbb{Q}$-algebra A by generators (the generators are matrices) and knowing 5 primitive orthogonal idempotents $e_1$,...,$e_5$ (as matrices), which sum up to $1_R$ $1_A$ (the identity matrix), is there a way / procedure in SAGE, that can compute the projective indecomposable modules $P_1=e_1\cdot R$,...,$P_5=e_5\cdot R$ A$,...,$P_5=e_5\cdot A$and then test, whether$P_i$and$P_j$are isomorphic as$R$-modules$A$-modules for$i\neq j\$?

Thank you very much.