diff --git a/.gitignore b/.gitignore new file mode 100644 index 0000000..e4e5f6c --- /dev/null +++ b/.gitignore @@ -0,0 +1 @@ +*~ \ No newline at end of file diff --git a/README.md b/README.md new file mode 100644 index 0000000..78590f8 --- /dev/null +++ b/README.md @@ -0,0 +1,48 @@ +# Mildly Interesting Triangulations + +This repository contains triangulations in [polymake][polymake] JSON +format of various closed, orientable 4-dimensional manifolds. The +triangulations were obtained by conversion of [Regina][regina] +isomorphism signatures taken from a [census of manifolds][lofano] into +polymake files, and then simplifying them using `edge_contraction` and +`bistellar_simplification`. For each isomporphism signature, the +smallest triangulation by number of vertices was chosen, and then +duplicates (combinatorially isomorphic triangulations) were removed. + +## Contents + +The triangulations are sorted by topological/PL-type, which was +determined by comparing them to a reference triangulation (or in the +case of the topology-ℂP², by computing the intersection form). The +triangulations are further sorted by number of vertices. + +### ℂP² + +The triangulation with 9 vertices is combinatorially isomorphic to the +[minimal triangulation][lutz-cp2] found in Frank H. Lutz's library of +triangulations. The triangulations with a larger amount of vertices +are triangulations which have been found to be PL-homeomorphic to ℂP² +using Regina's [retriangulate][retriangulate] tool, but elude +polymake's simplification capabilities. + +#### ℂP² (top) + +This category are four triangulations which have been shown to be +homoeomorphic to ℂP² by computing the intersection form, however, it +is unknown whether they are also PL-homoeomorphic to ℂP² as they elude +all methods tried on them so far. + +### ℂP²#S³xS¹ + +These 1464 triangulations have all been shown to be PL-Homeomorphic to +each other using retriangulate, however, polymake has big difficulties +in finding the PL-homeomorphisms between them. + + + + +[polymake]: https://polymake.org/doku.php/start +[regina]: https://regina-normal.github.io/ +[lofano]: https://github.com/davelofa/Census6Pentachora +[lutz-cp2]: https://www3.math.tu-berlin.de/IfM/Nachrufe/Frank_Lutz/stellar/library_of_triangulations/CP2.txt +[retriangulate]: https://regina-normal.github.io/docs/man-retriangulate.html