projections -- projections of a multi-projective variety

Usage:

projections X
Inputs:
- X, a multi-projective variety, a subvariety of $\mathbb{P}^{k_1}\times\mathbb{P}^{k_2}\times\cdots\times\mathbb{P}^{k_n}$
Outputs:
- the list of the projections $X\to \mathbb{P}^{k_i}$, for $i=1,\ldots,n$

Description

This function is intended for internal use. Use the projectionMaps function instead.

i1 : X = projectiveVariety(ZZ/101[x_0..x_3]) ** projectiveVariety(ZZ/101[y_0..y_2]);

o1 : ProjectiveVariety, PP^3 x PP^2

i2 : projections X

o2 = {-- rational map --                                              ,
                    ZZ                              ZZ                 
      source: Proj(---[x0 , x0 , x0 , x0 ]) x Proj(---[x1 , x1 , x1 ]) 
                   101   0    1    2    3          101   0    1    2   
                    ZZ                                                 
      target: Proj(---[x , x , x , x ])                                
                   101  0   1   2   3                                  
      defining forms: {                                                
                       x0 ,                                            
                         0                                             
                                                                       
                       x0 ,                                            
                         1                                             
                                                                       
                       x0 ,                                            
                         2                                             
                                                                       
                       x0
                         3
                      }
     ------------------------------------------------------------------------
     -- rational map --                                              }
                   ZZ                              ZZ
     source: Proj(---[x0 , x0 , x0 , x0 ]) x Proj(---[x1 , x1 , x1 ])
                  101   0    1    2    3          101   0    1    2
                   ZZ
     target: Proj(---[y , y , y ])
                  101  0   1   2
     defining forms: {
                      x1 ,
                        0
                      
                      x1 ,
                        1
                      
                      x1
                        2
                     }

o2 : List

Ways to use projections:

projections(MultiprojectiveVariety)

For the programmer

The object projections is a method function.

The source of this document is in MultiprojectiveVarieties.m2:2596:0.

projections -- projections of a multi-projective variety

Description

See also

Ways to use projections:

For the programmer