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7.5.23.0. allExtOfRight
Procedure from librarypurityfiltration.lib (see purityfiltration_lib).
- Usage:
- allExtOfRight(R), R matrix representing the right Module M=D^q/RD^p over a ring D
M module with finite right projective dimension n - Return:
- list, entries are ext-modules
- Purpose:
- computes a list T, which entries are representations of the left modules ext^i(M,D)
T[i] gives the repr. matrix of ext^(i-1)(M,D), i=1,..,n+1
LIB "purityfiltration.lib"; ring D = 0,(x,y,z),dp; matrix R[6][4]= 0,-2*x,z-2*y-x,-1, 0,z-2*x,2*y-3*x,1, z,-6*x,-2*y-5*x,-1, 0,y-x,y-x,0, y,-x,-y-x,0, x,-x,-2*x,0; // coker(R) considered as right module projectiveDimension(R,1)[2]; ==> 1 list T=allExtOfRight(R); print(T[1]); ==> 4x, ==> -4y, ==> -z, ==> z print(T[2]); ==> 1,0,0, 0,0, 0, ==> 0,0,4y-z,0,4x-z,0, ==> 0,z,0, y,0, x // left modules coker(.T[i])!! |