University of Paderborn Department of Mathematics Diploma Thesis ...
University of Paderborn Department of Mathematics Diploma Thesis ...
University of Paderborn Department of Mathematics Diploma Thesis ...
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4.5. COMPUTING STABLE IDEALS TO A GIVEN HILBERT POLYNOMIAL 101contractMon:= 0;for j from nops(J) downto 1 doif J[j][n] > 0 thencontractMon:= J[j];break;end_if;end_for;/* If there is no monomial contractible, return theset, which contains only the input ideal */if contractMon = 0 thenreturn({J});end_if:/* Find all expandable monomials in the set <strong>of</strong> generators.Use procedure ’test_expandable’ to check, whether any <strong>of</strong>the monomials generators is expandable. */expandable:= {};for i from 1 to nops(J) doif test_expandable(J, J[i], n) = TRUE andcontains(J, contractMon) > i thenexpandable:= expandable union {J[i]};end_if;end_for;contractMon[n]:= contractMon[n] - 1;included:= FALSE;/* Perform all possible pairs <strong>of</strong> contractions andexpansions, if the set ’expandable’ <strong>of</strong> expandablemonomials is not the empty set*/if expandable {} thenfor mon in expandable doif test_contractible(J, contractMon, n) = TRUE andtest_expandable(compute_contraction(J, contractMon, n),mon, n) = TRUE thenIdeal:= compute_contraction(J, contractMon, n);