polyhedral complex
{{short description|Math concept}}
In mathematics, a polyhedral complex is a set of polyhedra in a real vector space that fit together in a specific way.{{Citation | last=Ziegler | first=Günter M. | title=Lectures on Polytopes | publisher=Springer-Verlag | location=Berlin, New York | series=Graduate Texts in Mathematics | year=1995 | volume=152}} Polyhedral complexes generalize simplicial complexes and arise in various areas of polyhedral geometry, such as tropical geometry, splines and hyperplane arrangements.
Definition
A polyhedral complex is a set of polyhedra that satisfies the following conditions:
:1. Every face of a polyhedron from is also in .
:2. The intersection of any two polyhedra is a face of both and .
Note that the empty set is a face of every polyhedron, and so the intersection of two polyhedra in may be empty.
Examples
- Tropical varieties are polyhedral complexes satisfying a certain balancing condition.{{cite book|last=Maclagan|first=Diane|authorlink=Diane Maclagan|last2=Sturmfels|first2=Bernd |title= Introduction to Tropical Geometry |title-link= Introduction to Tropical Geometry |year=2015|publisher=American Mathematical Soc.|isbn=9780821851982 }}
- Simplicial complexes are polyhedral complexes in which every polyhedron is a simplex.
- Voronoi diagrams.
- Splines.
Fans
A fan is a polyhedral complex in which every polyhedron is a cone from the origin. Examples of fans include:
- The normal fan of a polytope.
- The Gröbner fan of an ideal of a polynomial ring.{{Cite journal|title=The Gröbner fan of an ideal |language=en|doi=10.1016/S0747-7171(88)80042-7|volume=6|issue=2–3 |journal=Journal of Symbolic Computation|pages=183–208 | last2 = Robbiano | first2 = Lorenzo | last1 = Mora | first1 = Teo|year=1988 |doi-access=free }}{{Cite journal|title=Standard bases and geometric invariant theory I. Initial ideals and state polytopes|language=en|doi=10.1016/S0747-7171(88)80043-9|volume=6|issue=2–3|journal=Journal of Symbolic Computation|pages=209–217 | last1 = Bayer | first1 = David | last2 = Morrison | first2 = Ian|year=1988|doi-access=free}}
- A tropical variety obtained by tropicalizing an algebraic variety over a valued field with trivial valuation.
- The recession fan of a tropical variety.