source: git/Tst/Manual/Deformations.tst @ c2f6bd

LIB "tst.lib"; tst_init();
  LIB "deform.lib";
  ring R=32003,(x,y,z),ds;
  //----------------------------------------------------
  // hypersurface case (from series T[p,q,r]):
  int p,q,r = 3,3,4;
  poly f = x^p+y^q+z^r+xyz;
  print(deform(f));
  // the miniversal deformation of f=0 is the projection from the
  // miniversal total space to the miniversal base space:
  // { (A,B,C,D,E,F,G,H,x,y,z) | x3+y3+xyz+z4+A+Bx+Cxz+Dy+Eyz+Fz+Gz2+Hz3 =0 }
  //  --> { (A,B,C,D,E,F,G,H) }
  //----------------------------------------------------
  // complete intersection case (from series P[k,l]):
  int k,l =3,2;
  ideal j=xy,x^k+y^l+z2;
  print(deform(j));
  def L=versal(j);            // using default names
  def Px=L[1]; setring Px;
  show(Px);                   // show is a procedure from inout.lib
  listvar(matrix);
  // ___ Equations of miniversal base space ___:
  Js;
  // ___ Equations of miniversal total space ___:
  Fs;
  // the miniversal deformation of V(j) is the projection from the
  // miniversal total space to the miniversal base space:
  // { (A,B,C,D,E,F,x,y,z) | xy+F+Ez=0, y2+z2+x3+D+Cx+Bx2+Ay=0 }
  //  --> { (A,B,C,D,E,F) }
  //----------------------------------------------------
  // general case (cone over rational normal curve of degree 4):
  kill L;
  ring r1=0,(x,y,z,u,v),ds;
  matrix m[2][4]=x,y,z,u,y,z,u,v;
  ideal i=minor(m,2);                 // 2x2 minors of matrix m
  int time=timer;
  // Call parameters of the miniversal base A(1),A(2),...:
  def L=versal(i,0,"","A(");
  "// used time:",timer-time,"sec";   // time of last command
  def Def_rPx=L[1]; setring Def_rPx;
  Fs;
  Js;
  // the miniversal deformation of V(i) is the projection from the
  // miniversal total space to the miniversal base space:
  // { (A(1..4),x,y,z,u,v) |
  //         -u^2+x*v+A(2)*u+A(4)*v=0, -z*u+y*v-A(1)*u+A(3)*u=0,
  //         -y*u+x*v+A(3)*u+A(4)*z=0,  z^2-y*u+A(1)*z+A(2)*y=0,
  //          y*z-x*u+A(2)*x-A(3)*z=0, -y^2+x*z+A(1)*x+A(3)*y=0 }
  //  --> { A(1..4) |
  //          A(2)*A(4) = -A(3)*A(4) = -A(1)*A(4)+A(4)^2 = 0 }
  //----------------------------------------------------
tst_status(1);$