## gitfanlib - a package for GIT-fans

#### (for Maple or polymake-Singular or Singular 3.1.6)

Current version: (May / October / November, 2012),

### Software Systems

At the moment there are versions for
• Maple by Simon Keicher (requires Maple 10 or above and the package convex by Matthias Franz).
• polymake/Singular by Simon Keicher and Thomas Kremer (The Polymake/Singular-version of gitfanlib needs at least polymake 2.11 and Singular 3.1.3 installed),
• Singular 3.1.6 by Janko Böhm, Simon Keicher and Yue Ren (requires at leat Singular 3.1.6).
There also is an early first Macaulay2-implementation here.

### Description

Given the action of a torus $$H$$ on an affine variety $$X$$, this package provides functions to compute
• GIT-chambers,
• the GIT-fan of the $$H$$-action on $$X$$,
• toric orbits intersecting $$X$$.
We assume that $$X$$ is given by equations and $$H$$ is given by a grading matrix.

### Installation

• Maple-version: Download the files gitfanlib.ind and gitfanlib.lib, and put them into a directory where Maple can find them. In a new Maple-session enter "with(gitfanlib);" after loading convex.
• polymake/Singular-version: Download the current version and load the extension in polymake by using the command 'found_extension('pathtofolder')'.