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MultiprojectiveVarieties :: projectiveDegrees(MultirationalMap)

projectiveDegrees(MultirationalMap) -- projective degrees of a multi-rational map

Synopsis

Description

This computation is performed by converting the multi-rational map to a standard rational map (using segre) and then applying the corresponding method for rational maps.

i1 : ZZ/300007[x_0..x_3], f = rationalMap {x_2^2-x_1*x_3, x_1*x_2-x_0*x_3, x_1^2-x_0*x_2}, g = rationalMap {x_1^2-x_0*x_2, x_0*x_3, x_1*x_3, x_2*x_3, x_3^2};
i2 : Phi = last graph multirationalMap {f,g}

o2 = Phi

o2 : MultirationalMap (rational map from threefold in PP^3 x PP^2 x PP^4 to PP^2 x PP^4)
i3 : time projectiveDegrees Phi
     -- used 5.09782 seconds

o3 = {66, 46, 31, 20}

o3 : List
i4 : (degree source Phi,degree image Phi)

o4 = (66, 20)

o4 : Sequence

See also