Janko Boehm, boehm at mathematik.uni-kl.de
Simon Keicher, keicher at mail.mathematik.uni-tuebingen.de
Yue Ren, ren at mathematik.uni-kl.de
Overview:
This library allows you to calculate GIT-fans, torus orbits and GKZ-fans.
In provides features to make use of symmetries of the torus action under consideration.
The main procedure is GITfan which can be directly applied to an ideal and a grading matrix
encoding the torus action, and returns a fan, the associated GIT-fan.
We also provide various procedures implementing substeps of the algorithm
to deal with large computations.
The library uses the package 'gfanlib' by Anders N. Jensen.
For notation, background, and algorithms see [BKR16].
Functions produce debug output if printlevel is positive.
Elements of the symmetric group Sn of type permutation can be created by
the function permutationFromIntvec.
The images of 1,...,n can be obtained by permutationToIntvec.
Composition of permutations can be done by the *-Operator,
also powers can be computed in the usual way.
References:
[BKR16] J. Boehm, S. Keicher, Y. Ren: Computing GIT-Fans with Symmetry and the Mori Chamber Decomposition of M06bar, https://arxiv.org/abs/1603.09241
Online Manual
