CASA Function: passGenCurve

Generates a general curve and passing it through specified points.

Calling Sequence:

• C := passGenCurve(deg,points,c)
• C := passGenCurve(deg,points,c,vars)
• C := passGenCurve(deg,points,c,vars, ext)

Parameters:

deg : posint

• Degree of the resulting curve.

points : list(list)

• List of points through which the curve should pass.

c : table

• name of a global table to holding coefficients

vars : list(name)

• List of variables.

ext : list

• List of field extensions.

Result:

C : algset

• A curve (or a system of curves) in projective space of degree deg passing through the specified points points.

Description:

• The function returns a curve (or a system of curves) in projective 3-space of degree deg passing through specified points. The resulting curve will contain vars as variables.
• The third parameter is used as a name of a table holding coefficients of the resulting curve (system).
• If some points have algebraic coordinates, the fifth argument has to list extensions, where the coordinates of the points are lying. Precisely, for each point there has to be a list describing the extension of the coordinate field over the rational numbers. If all coordinates of a point are rational, the empty list has to be supplied. If some points have non-rational coordinates the procedure expects as the fifth argument a list of the same length as points where each element (list) specifies a tower of extensions [alpha_1,...,alpha_k] such that the corresponding point lies in Q(alpha_1,...,alpha_k) and the minimal polynomial for alpha_i (argument of the RootOf) is irreducible over Q(alpha_1,...,alpha_{i-1}).
• A point in points is given either as a list [x0,x1,x2] (denoting a simple point) or as a nested list [[x0,x1,x2],m] (denoting a singular point with multiplicity m). Note that m = 1 is possible.

Examples:

> points := [[[RootOf(z^2+1),1,0],2],[[0,0,1],3],[[-1,-1,1],2]]:

> fieldExtensions := [[RootOf(z^2+1)],[],[]]:

> c1:=passGenCurve(5,points,u,[x,y,z],fieldExtensions);

> c2:=setRandomParameters(c1);

> singularities(c2);

See Also: