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D.4.3.11 isFlatProcedure from library
Example: LIB "homolog.lib"; ring A = 0,(x,y),dp; matrix M[3][3] = x-1,y,x,x,x+1,y,x2,xy+x+1,x2+y; print(M); → x-1,y, x, → x, x+1, y, → x2, xy+x+1,x2+y isFlat(M); // coker(M) is not flat over A=Q[x,y] → 0 qring B = std(x2+x-y); // the ring B=Q[x,y]/<x2+x-y> matrix M = fetch(A,M); isFlat(M); // coker(M) is flat over B → 1 setring A; qring C = std(x2+x+y); // the ring C=Q[x,y]/<x2+x+y> matrix M = fetch(A,M); isFlat(M); // coker(M) is not flat over C → 0 |
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