# veering
Python code (using regina, snappy, and sage) for working with transverse taut
and veering ideal triangulations -- implemented by Anna Parlak, Saul Schleimer,
and Henry Segerman. We thank Nathan Dunfield for many helpful comments (and
for some code).
### Installation
To install (or uninstall) veering inside Sage via the command line, using pip, type:
sage -pip install veering
or
sage -pip uninstall veering
For installation into your system's Python, replace `sage -pip` by `pip3`.
Note that the github repository of veering contains further data and scripts
which are not installed by pip.
Almost all of the veering code relies on regina; some of it relies on
snappy and some relies on SageMath. Other parts rely on the Python
vector graphics package pyx. Installation instructions for SageMath,
snappy, and regina can be found at the following webpages:
https://doc.sagemath.org/html/en/installation/ \
https://snappy.math.uic.edu/installing.html \
https://github.com/3-manifolds/regina_wheels
### Testing
After installation start a sage session and run the following:
sage: import veering
sage: from veering import test_suite
sage: test_suite.run_tests()
Each test should take at most a few seconds.
### Usage
As a simple example:
sage: census = veering.veering_census(); len(census)
87047
The veering census contains the 87047 taut isomorphism signatures
of the veering triangulations with at most 16 tetrahedra. These are
ordered lexicographically.
sage: sig = census[1]; sig
'cPcbbbiht_12'
This is the taut isomorphism signature for the only veering
structure on the figure eight knot complement. The string before the
underscore is the isomorphism signature for the triangulation; the
string after the underscore records, for each tetrahedron, which two
edges have dihedral angle pi; the other four edges have dihedral angle
zero.
sage: from veering import taut_polytope
sage: taut_polytope.is_layered(sig)
True
This taut structure is layered; thus the figure-eight knot is fibered.
sage: from veering import taut_polynomial
sage: taut_polynomial.taut_polynomial_via_tree(sig)
a^2 - 3*a + 1
sage: taut_polynomial.taut_polynomial_via_tree(sig, mode = 'alexander')
a^2 - 3*a + 1
sage: from veering import veering_polynomial
sage: veering_polynomial.veering_polynomial(sig)
a^3 - 4*a^2 + 4*a - 1
The taut and veering polynomials are defined by Michael Landry, Yair
Minsky and Sam Taylor. Note that the taut polynomial divides the veering
polynomial; this is true in general. The taut polynomial of this veering
triangulation is equal to the Alexander polynomial of the underlying
manifold; this is not true in general.
sage: sig = census[257]; sig
'iLLLQPcbeegefhhhhhhahahha_01110221'
sage: taut_polytope.cone_in_homology(sig)
[N(1, -1), N(1, 1)]
The cone of homology classes carried by the veering triangulation
`iLLLQPcbeegefhhhhhhahahha_01110221` is spanned by the rays passing
through (1,-1) and (1,1). Landry, Minsky, and Taylor proved that,
if nonempty, this cone is equal to a cone on a (not necessarily top-dimensional)
face of the Thurston norm ball. The chosen basis on H^1 is dual to the
basis of H_1 used to compute the taut and veering polynomials.
### Webpage
For references, for information about the census, and for many diagrams,
please see:
https://math.okstate.edu/people/segerman/veering.html
### Citation
When citing the codebase, please use the following (updating the
version number and the year).
```
@Misc{Veering,
author = {Anna Parlak and Saul Schleimer and Henry Segerman},
title = {veering x.y, code for studying taut and veering ideal triangulations},
howpublished = {\url{https://github.com/henryseg/Veering}},
year = {20zz},
}
```
### Contact
Please contact us with any and all suggestions, questions, and/or corrections.
### Licence
This work is in the public domain. See the LICENCE for details.
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"description": "# veering\n\nPython code (using regina, snappy, and sage) for working with transverse taut\nand veering ideal triangulations -- implemented by Anna Parlak, Saul Schleimer,\nand Henry Segerman. We thank Nathan Dunfield for many helpful comments (and\nfor some code).\n\n### Installation\n\nTo install (or uninstall) veering inside Sage via the command line, using pip, type:\n\n sage -pip install veering\n\nor\n\n sage -pip uninstall veering\n\nFor installation into your system's Python, replace `sage -pip` by `pip3`.\nNote that the github repository of veering contains further data and scripts\nwhich are not installed by pip.\n\nAlmost all of the veering code relies on regina; some of it relies on\nsnappy and some relies on SageMath. Other parts rely on the Python\nvector graphics package pyx. Installation instructions for SageMath,\nsnappy, and regina can be found at the following webpages:\n\nhttps://doc.sagemath.org/html/en/installation/ \\\nhttps://snappy.math.uic.edu/installing.html \\\nhttps://github.com/3-manifolds/regina_wheels\n\n### Testing\n\nAfter installation start a sage session and run the following:\n\n sage: import veering\n sage: from veering import test_suite\n sage: test_suite.run_tests()\n\nEach test should take at most a few seconds.\n\n### Usage\n\nAs a simple example:\n\n sage: census = veering.veering_census(); len(census)\n 87047\n\nThe veering census contains the 87047 taut isomorphism signatures\nof the veering triangulations with at most 16 tetrahedra. These are\nordered lexicographically.\n\n sage: sig = census[1]; sig\n 'cPcbbbiht_12'\n\nThis is the taut isomorphism signature for the only veering\nstructure on the figure eight knot complement. The string before the\nunderscore is the isomorphism signature for the triangulation; the\nstring after the underscore records, for each tetrahedron, which two\nedges have dihedral angle pi; the other four edges have dihedral angle \nzero.\n\n sage: from veering import taut_polytope\n sage: taut_polytope.is_layered(sig)\n True\n\nThis taut structure is layered; thus the figure-eight knot is fibered.\n\n sage: from veering import taut_polynomial\n sage: taut_polynomial.taut_polynomial_via_tree(sig)\n a^2 - 3*a + 1\n sage: taut_polynomial.taut_polynomial_via_tree(sig, mode = 'alexander')\n a^2 - 3*a + 1\n sage: from veering import veering_polynomial\n sage: veering_polynomial.veering_polynomial(sig)\n a^3 - 4*a^2 + 4*a - 1\n\nThe taut and veering polynomials are defined by Michael Landry, Yair \nMinsky and Sam Taylor. Note that the taut polynomial divides the veering \npolynomial; this is true in general. The taut polynomial of this veering \ntriangulation is equal to the Alexander polynomial of the underlying \nmanifold; this is not true in general.\n\n sage: sig = census[257]; sig\n 'iLLLQPcbeegefhhhhhhahahha_01110221'\n sage: taut_polytope.cone_in_homology(sig)\n [N(1, -1), N(1, 1)]\n \nThe cone of homology classes carried by the veering triangulation\n`iLLLQPcbeegefhhhhhhahahha_01110221` is spanned by the rays passing \nthrough (1,-1) and (1,1). Landry, Minsky, and Taylor proved that, \nif nonempty, this cone is equal to a cone on a (not necessarily top-dimensional) \nface of the Thurston norm ball. The chosen basis on H^1 is dual to the \nbasis of H_1 used to compute the taut and veering polynomials.\n\n### Webpage\n\nFor references, for information about the census, and for many diagrams, \nplease see:\n\nhttps://math.okstate.edu/people/segerman/veering.html\n\n### Citation\n\nWhen citing the codebase, please use the following (updating the \nversion number and the year). \n\n```\n@Misc{Veering,\n author = {Anna Parlak and Saul Schleimer and Henry Segerman},\n title = {veering x.y, code for studying taut and veering ideal triangulations},\n howpublished = {\\url{https://github.com/henryseg/Veering}},\n year = {20zz},\n}\n```\n\n### Contact\n\nPlease contact us with any and all suggestions, questions, and/or corrections.\n\n### Licence\n\nThis work is in the public domain. See the LICENCE for details.",
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