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D.4.8.19 tensorMod
Procedure from library homolog.lib (see homolog_lib).
- Usage:
- tensorMod(M,N); M,N modules
- Compute:
- presentation matrix A of the tensor product T of the modules
M'=coker(M), N'=coker(N): if matrix(M) defines a map M: R^r-->R^s and
matrix(N) defines a map N: R^p-->R^q, then A defines a presentation
| | R^(sp+rq) --A-> R^(sq) --> T --> 0 .
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- Return:
- matrix A satisfying coker(A) = tensorprod(coker(M),coker(N)) .
Example:
| | LIB "homolog.lib";
ring A=0,(x,y,z),dp;
matrix M[3][3]=1,2,3,4,5,6,7,8,9;
matrix N[2][2]=x,y,0,z;
print(M);
==> 1,2,3,
==> 4,5,6,
==> 7,8,9
print(N);
==> x,y,
==> 0,z
print(tensorMod(M,N));
==> x,y,0,0,0,0,1,0,2,0,3,0,
==> 0,z,0,0,0,0,0,1,0,2,0,3,
==> 0,0,x,y,0,0,4,0,5,0,6,0,
==> 0,0,0,z,0,0,0,4,0,5,0,6,
==> 0,0,0,0,x,y,7,0,8,0,9,0,
==> 0,0,0,0,0,z,0,7,0,8,0,9
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