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Divisor :: torsionSubmodule

torsionSubmodule -- Finds the torsion submodule of a given module

Synopsis

Usage:
M2 = torsionSubmodule( M1 )
Inputs:
- M1, a module
Outputs:
- M2, a module

Description

Finds the torsion submodule of a given module. It does this by computing the kernel of the map from M1 to its double dual

i1 : R = QQ[x,y]

o1 = R

o1 : PolynomialRing

i2 : m = ideal(x,y)

o2 = ideal (x, y)

o2 : Ideal of R

i3 : M = (R^1/m) ++ R^1

o3 = cokernel | x y |
              | 0 0 |

                            2
o3 : R-module, quotient of R

i4 : prune torsionSubmodule M

o4 = cokernel | y x |

                            1
o4 : R-module, quotient of R

See also

reflexifyModuleWithMap -- Compute the canonical map from a module to its double-dual

Ways to use `torsionSubmodule` :

torsionSubmodule(Module)