i1 : kk = ZZ/101; |
i2 : S = kk[a..f]; |
i3 : I = minors(2, genericSymmetricMatrix(S, 3)) 2 2 o3 = ideal (- b + a*d, - b*c + a*e, - c*d + b*e, - b*c + a*e, - c + a*f, - ------------------------------------------------------------------------ 2 c*e + b*f, - c*d + b*e, - c*e + b*f, - e + d*f) o3 : Ideal of S |
i4 : pts = randomPointsOnRationalVariety(I, 4) o4 = {| 1 49 24 -23 -36 -30 |, | 23 -29 -29 19 19 19 |, | 38 -11 -10 -42 -29 ------------------------------------------------------------------------ -8 |, | -37 -35 -22 -14 -29 -24 |} o4 : List |
i5 : for p in pts list sub(I, p) == 0 o5 = {true, true, true, true} o5 : List |
i6 : S = kk[a..d]; |
i7 : F = groebnerFamily ideal"a2,ab,ac,b2" 2 2 2 o7 = ideal (a + t b*c + t a*d + t c + t b*d + t c*d + t d , a*b + t b*c + 1 3 2 4 5 6 7 ------------------------------------------------------------------------ 2 2 2 t a*d + t c + t b*d + t c*d + t d , a*c + t b*c + t a*d + t c + 9 8 10 11 12 13 15 14 ------------------------------------------------------------------------ 2 2 2 t b*d + t c*d + t d , b + t b*c + t a*d + t c + t b*d + t c*d 16 17 18 19 21 20 22 23 ------------------------------------------------------------------------ 2 + t d ) 24 o7 : Ideal of kk[t , t , t , t , t , t , t , t , t , t , t , t , t , t , t , t , t , t , t , t , t , t , t , t ][a..d] 6 5 12 2 4 11 18 24 1 3 8 10 17 23 7 9 14 16 20 22 13 15 19 21 |
i8 : J = groebnerStratum F; o8 : Ideal of kk[t , t , t , t , t , t , t , t , t , t , t , t , t , t , t , t , t , t , t , t , t , t , t , t ] 6 5 12 2 4 11 18 24 1 3 8 10 17 23 7 9 14 16 20 22 13 15 19 21 |
i9 : compsJ = decompose J; |
i10 : compsJ = compsJ/trim; |
i11 : #compsJ == 2 o11 = true |
i12 : compsJ/dim o12 = {11, 8} o12 : List |
There are 2 components. We attempt to find points on each of these two components. We are successful. This indicates that the corresponding varieties are both rational. Also, if we can find one point, we can find as many as we want.
i13 : netList randomPointsOnRationalVariety(compsJ_0, 10) +-------------------------------------------------------------------------------------+ o13 = || 13 15 3 36 2 48 44 -35 -34 39 5 -32 34 19 -42 -47 -16 -34 -39 -13 -18 -43 21 -38 | | +-------------------------------------------------------------------------------------+ || -43 48 14 29 -47 -10 47 22 8 -47 15 -26 2 16 -49 22 -28 -18 45 -48 -34 -47 38 -15 || +-------------------------------------------------------------------------------------+ || -3 45 42 47 -50 16 -30 28 43 -16 24 19 15 -23 37 39 19 -8 43 -11 -17 48 7 47 | | +-------------------------------------------------------------------------------------+ || -49 7 32 -6 -30 -41 -10 2 44 11 -25 4 33 40 -19 11 35 -17 46 1 -28 -3 -38 36 | | +-------------------------------------------------------------------------------------+ || 35 -48 -2 45 -35 29 34 12 -32 -23 50 2 2 29 -3 -47 -47 -34 15 -13 -37 -10 -7 22 | | +-------------------------------------------------------------------------------------+ || 47 8 -14 6 -1 -13 -7 16 -20 39 -34 -22 -22 32 17 -9 -18 -6 -32 24 -20 -30 27 30 | | +-------------------------------------------------------------------------------------+ || -2 -36 -39 41 -6 34 -10 42 5 39 20 33 33 -49 -15 -33 -15 41 -19 -20 17 44 0 -48 | | +-------------------------------------------------------------------------------------+ || -30 37 -9 16 -36 19 -13 -14 -19 9 -33 5 4 13 44 -26 36 -12 22 -11 -49 -8 -39 -39 | | +-------------------------------------------------------------------------------------+ || 27 41 32 -44 40 -20 41 33 28 36 44 31 -22 -30 9 41 -8 30 16 -6 -28 35 -3 43 | | +-------------------------------------------------------------------------------------+ || 37 -2 17 -42 -42 -12 18 -31 33 6 19 -31 3 -31 -11 25 -35 28 -2 -49 -41 -13 40 -9 | | +-------------------------------------------------------------------------------------+ |
i14 : netList randomPointsOnRationalVariety(compsJ_1, 10) +---------------------------------------------------------------------------------------+ o14 = || -41 -1 -48 25 40 4 35 16 26 -41 -28 -16 27 -14 -39 4 4 30 -40 37 -31 -35 -47 0 | | +---------------------------------------------------------------------------------------+ || -1 19 -3 12 50 3 4 25 48 50 34 -6 -29 6 -5 36 -39 -31 -48 30 47 -37 -48 0 | | +---------------------------------------------------------------------------------------+ || -27 -3 -40 22 27 3 -28 -41 -12 -34 -10 40 46 29 30 24 -49 28 1 40 10 -22 -18 0 | | +---------------------------------------------------------------------------------------+ || -26 -6 24 28 -27 26 34 47 13 50 3 -42 -17 5 4 -35 7 30 -13 3 8 -41 13 0 | | +---------------------------------------------------------------------------------------+ || 49 -7 48 1 48 25 25 -10 49 36 -16 35 -46 -5 25 -33 8 -29 49 -18 23 42 30 0 | | +---------------------------------------------------------------------------------------+ || -35 28 -6 22 50 -49 2 -5 -11 -39 30 27 -16 34 -9 -34 -28 15 -46 12 27 -18 18 0 | | +---------------------------------------------------------------------------------------+ || -49 -44 -16 -10 48 18 22 33 -35 -48 -28 -8 -23 -48 -25 -3 -21 23 44 -39 19 20 -37 0 || +---------------------------------------------------------------------------------------+ || -33 -14 -18 10 2 -43 -26 45 10 19 -15 25 47 9 -15 -22 0 -47 -28 6 -33 -9 -28 0 | | +---------------------------------------------------------------------------------------+ || 20 -27 -17 2 -47 -23 13 40 -19 -13 39 -23 5 -3 47 -6 28 -29 -37 -33 42 -28 26 0 | | +---------------------------------------------------------------------------------------+ || 19 10 -10 47 41 20 -43 -34 -43 2 44 29 22 35 -42 16 44 30 5 -20 -29 -13 4 0 | | +---------------------------------------------------------------------------------------+ |
This routine expects the input to represent an irreducible variety