SINGULAR / A Computer Algebra System for Polynomial Computations / version 2-0-1 0< by: G.-M. Greuel, G. Pfister, H. Schoenemann \ June 2001 FB Mathematik der Universitaet, D-67653 Kaiserslautern \ // ** loaded /local/math/Singular/2-0-1/LIB/primdec.lib (1.98.2.4,2001/06/18) // ** loaded /local/math/Singular/2-0-1/LIB/matrix.lib (1.26,2001/01/18) // ** loaded /local/math/Singular/2-0-1/LIB/ring.lib (1.17,2001/01/16) // ** loaded /local/math/Singular/2-0-1/LIB/inout.lib (1.21,2001/01/16) // ** loaded /local/math/Singular/2-0-1/LIB/random.lib (1.16,2001/01/16) // ** loaded /local/math/Singular/2-0-1/LIB/poly.lib (1.33,2001/01/16) // ** loaded /local/math/Singular/2-0-1/LIB/elim.lib (1.14,2001/01/16) // ** loaded /local/math/Singular/2-0-1/LIB/general.lib (1.38.2.1,2001/04/24) This is the degree of the original ideal; which has irrelevant components as well as relevant ones that we wish to study // codimension = 6 // dimension = 4 // degree = 8 We saturate by the ideal of rank 1 quadrics // codimension = 7 // dimension = 3 // degree = 20 Now we saturate by an ideal defining a trivial 2,2 curve Saturate by (g,f,e,d,c,b,a). // codimension = 7 // dimension = 3 // degree = 10 Now we saturate by an ideal defining a trivial 2,2 curve Saturate by (y,x,h,g,f,d,c). // codimension = 8 // dimension = 2 // degree = 24 Thus we have finaly obtain an ideal of dimension 2, so that it defines curves. The first component of the ideal has degree 4, and is reducible, but does not contain any real points _[1]=3*x^2+3*x*y+y^2 _[2]=h+2*x+y _[3]=f+g _[4]=e*y^2-3*g^2*x-3*g^2*y _[5]=e*x+g^2 _[6]=d*y-6*g*x-3*g*y _[7]=d*x+3*g*x+2*g*y _[8]=d*g-2*e*y+3*g^2 _[9]=d^2+3*g^2 _[10]=c+g _[11]=b*y-2*e*y+3*g^2 _[12]=b*x+e*y-g^2 _[13]=2*b*g-d*e-e*g _[14]=2*b*d-d*e+3*e*g _[15]=b^2-b*e+e^2 _[16]=a-2*b+e // codimension = 8 // dimension = 2 // degree = 4 ///////////////////////////////////////// The same is true for the second component _[1]=3*x^2+3*x*y+y^2 _[2]=h+2*x+y _[3]=f+g _[4]=e*y^2-3*g^2*x-3*g^2*y _[5]=e*x+g^2 _[6]=d*y+6*g*x+3*g*y _[7]=d*x-3*g*x-2*g*y _[8]=d*g+2*e*y-3*g^2 _[9]=d^2+3*g^2 _[10]=c-g _[11]=b*y+2*e*y-3*g^2 _[12]=b*x-e*y+g^2 _[13]=2*b*g-d*e+e*g _[14]=2*b*d+d*e+3*e*g _[15]=b^2+b*e+e^2 _[16]=a+2*b+e // codimension = 8 // dimension = 2 // degree = 4 ///////////////////////////////////////// And the third component _[1]=3*x^2-3*x*y+y^2 _[2]=h-2*x+y _[3]=f-g _[4]=e*y^2+3*g^2*x-3*g^2*y _[5]=e*x-g^2 _[6]=d*y-6*g*x+3*g*y _[7]=d*x-3*g*x+2*g*y _[8]=d*g+2*e*y-3*g^2 _[9]=d^2+3*g^2 _[10]=c+g _[11]=b*y+2*e*y-3*g^2 _[12]=b*x+e*y-g^2 _[13]=2*b*g-d*e+e*g _[14]=2*b*d+d*e+3*e*g _[15]=b^2+b*e+e^2 _[16]=a+2*b+e // codimension = 8 // dimension = 2 // degree = 4 ///////////////////////////////////////// And the fourth component _[1]=3*x^2-3*x*y+y^2 _[2]=h-2*x+y _[3]=f-g _[4]=e*y^2+3*g^2*x-3*g^2*y _[5]=e*x-g^2 _[6]=d*y+6*g*x-3*g*y _[7]=d*x+3*g*x-2*g*y _[8]=d*g-2*e*y+3*g^2 _[9]=d^2+3*g^2 _[10]=c-g _[11]=b*y-2*e*y+3*g^2 _[12]=b*x-e*y+g^2 _[13]=2*b*g-d*e-e*g _[14]=2*b*d-d*e+3*e*g _[15]=b^2-b*e+e^2 _[16]=a-2*b+e // codimension = 8 // dimension = 2 // degree = 4 ///////////////////////////////////////// The last 4 components each have degree 2 and are defined over the real numbers, defining RATIONAL components ! _[1]=x _[2]=h+y _[3]=g _[4]=f _[5]=d _[6]=c^2+4*e*y _[7]=b _[8]=a-3*e // codimension = 8 // dimension = 2 // degree = 2 ///////////////////////////////////////// _[1]=x _[2]=h+y _[3]=g _[4]=f _[5]=d^2+4*e*y _[6]=c _[7]=b _[8]=a+e // codimension = 8 // dimension = 2 // degree = 2 ///////////////////////////////////////// _[1]=x _[2]=3*h-y _[3]=g _[4]=4*e*y-3*f^2 _[5]=d _[6]=c _[7]=b _[8]=a-3*e // codimension = 8 // dimension = 2 // degree = 2 ///////////////////////////////////////// _[1]=x _[2]=3*h-y _[3]=f _[4]=4*e*y-3*g^2 _[5]=d _[6]=c _[7]=b _[8]=a+e // codimension = 8 // dimension = 2 // degree = 2 ///////////////////////////////////////// 10 Auf Wiedersehen.