Witte, Nikolaus (2007)
Foldable Triangulations.
Fachbereich Mathematik
Ph.D. Thesis, Primary publication
Abstract
A simplicial d-complex is foldable if it is (d+1)-colorable in the graph theoretic sense. Such a coloring defines a non-degenerated simplicial map to the d-simplex, hence the name "foldable". Foldable simplicial complexes are sometimes referred to as being "balanced". We apply foldable simplicial complexes to obtain the following two results. Any closed oriented PL d-manifold is a branched cover of the d-sphere, but no restrictions on the number of sheets nor the topology of the branching set are known for d>4 in general. As for dimension four, Piergallini [Topology 34(3):497-508, 1995] proved that every closed oriented PL 4-manifold is a 4-fold branched cover of the 4-sphere branched over an immersed PL surface. This generalizes a long standing result by Hilden and Montesinos to dimension four. Izmestiev and Joswig [Adv. Geom. 3(2):191-225, 2003] gave a combinatorial equivalent of the Hilden and Montesinos result, constructing (fairly explicit) closed oriented combinatorial 3-manifolds as unfoldings of combinatorial 3-spheres. The construction of Izmestiev and Joswig is generalized and applied to the result of Piergallini, obtaining closed oriented combinatorial 4-manifolds as unfoldings of combinatorial 4-spheres. Foldable and regular triangulations of products of lattice polytopes are constructed from foldable and regular triangulations of the factors. It is known that foldable triangulations of polytopes have a bipartite dual graph. The (weighted) size difference of this bipartition is a lower bound for the number of real roots of certain sparse polynomial systems by recent results of Soprunova and Sottile [Adv. Math. 204(1):116-151, 2006]. Special attention is paid to the cube case.
Item Type: | Ph.D. Thesis | ||||
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Erschienen: | 2007 | ||||
Creators: | Witte, Nikolaus | ||||
Type of entry: | Primary publication | ||||
Title: | Foldable Triangulations | ||||
Language: | English | ||||
Referees: | Joswig, Prof. Dr. Michael ; Ziegler, Prof. Günter M. | ||||
Advisors: | Joswig, Prof. Dr. Michael | ||||
Date: | 23 February 2007 | ||||
Place of Publication: | Darmstadt | ||||
Publisher: | Technische Universität | ||||
Collation: | IV, 128 Seiten, Illustrationen | ||||
Refereed: | 7 February 2007 | ||||
URL / URN: | urn:nbn:de:tuda-tuprints-7881 | ||||
Corresponding Links: | |||||
Abstract: | A simplicial d-complex is foldable if it is (d+1)-colorable in the graph theoretic sense. Such a coloring defines a non-degenerated simplicial map to the d-simplex, hence the name "foldable". Foldable simplicial complexes are sometimes referred to as being "balanced". We apply foldable simplicial complexes to obtain the following two results. Any closed oriented PL d-manifold is a branched cover of the d-sphere, but no restrictions on the number of sheets nor the topology of the branching set are known for d>4 in general. As for dimension four, Piergallini [Topology 34(3):497-508, 1995] proved that every closed oriented PL 4-manifold is a 4-fold branched cover of the 4-sphere branched over an immersed PL surface. This generalizes a long standing result by Hilden and Montesinos to dimension four. Izmestiev and Joswig [Adv. Geom. 3(2):191-225, 2003] gave a combinatorial equivalent of the Hilden and Montesinos result, constructing (fairly explicit) closed oriented combinatorial 3-manifolds as unfoldings of combinatorial 3-spheres. The construction of Izmestiev and Joswig is generalized and applied to the result of Piergallini, obtaining closed oriented combinatorial 4-manifolds as unfoldings of combinatorial 4-spheres. Foldable and regular triangulations of products of lattice polytopes are constructed from foldable and regular triangulations of the factors. It is known that foldable triangulations of polytopes have a bipartite dual graph. The (weighted) size difference of this bipartition is a lower bound for the number of real roots of certain sparse polynomial systems by recent results of Soprunova and Sottile [Adv. Math. 204(1):116-151, 2006]. Special attention is paid to the cube case. |
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Alternative Abstract: |
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Uncontrolled Keywords: | geometric topology, construction of combinatorial manifolds, branched covering, regular triangulations of lattice polytopes, real roots of polynomial systems, triangulations of cubes, simplicial complex | ||||
Classification DDC: | 500 Naturwissenschaften und Mathematik > 510 Mathematik | ||||
Divisions: | 04 Department of Mathematics 04 Department of Mathematics > Optimization 04 Department of Mathematics > Optimization > Discrete Optimization |
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Date Deposited: | 17 Oct 2008 09:22 | ||||
Last Modified: | 27 Jul 2023 10:58 | ||||
PPN: | |||||
Referees: | Joswig, Prof. Dr. Michael ; Ziegler, Prof. Günter M. | ||||
Refereed / Verteidigung / mdl. Prüfung: | 7 February 2007 | ||||
Corresponding Links: | |||||
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