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Bistellar and Edge Flip Graphs of Triangulations in the Plane - Geometry and Connectivity. Welzl, Emo
Description
The set of all triangulations of a finite point set in the plane attains structure via flips: The graph, where two triangulations are adjacent if one can be obtained from the other by an elementary flip. This is an edge flip for full triangulations, or a bistellar flip for partial triangulations (where non-extreme points can be skipped). It is well-known (Lawson, 1972) that both, the edge flip graph and the bistellar flip graph are connected. For n the number of points and general position assumed, we show that the edge flip graph is (n/2 - 2)-connected and the bistellar flip graph is (n-3)-connected. Both bounds are tight. This matches the situation for regular triangulations (a subset of the partial triangulations), where (n-3)-connectivity was known through the secondary polytope (Gelfand, Kapranov, Zelevinsky, 1990) and Balinski's Theorem. We show that the edge flip graph can be covered by 1-skeletons of polytopes of dimension at least n/2-2 (products of associahedra). Similarly, the bistellar flip graph can be covered by 1-skeletons of polytopes of dimension at least n-3 (products of secondary polytopes). (covers joint research with Uli Wagner, IST Austria)
Item Metadata
Title |
Bistellar and Edge Flip Graphs of Triangulations in the Plane - Geometry and Connectivity.
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Creator | |
Publisher |
Banff International Research Station for Mathematical Innovation and Discovery
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Date Issued |
2019-10-11T09:47
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Description |
The set of all triangulations of a finite point set in the plane attains structure via flips: The graph, where two triangulations are adjacent if one can be obtained from the other by an elementary flip. This is an edge flip for full triangulations, or a bistellar flip for partial triangulations (where non-extreme points can be skipped).
It is well-known (Lawson, 1972) that both, the edge flip graph and the bistellar flip graph are connected. For n the number of points and general position assumed, we show that the edge flip graph is (n/2 - 2)-connected and the bistellar flip graph is (n-3)-connected. Both bounds are tight.
This matches the situation for regular triangulations (a subset of the partial triangulations), where (n-3)-connectivity was known through the secondary polytope (Gelfand, Kapranov, Zelevinsky, 1990) and Balinski's Theorem. We show that the edge flip graph can be covered by 1-skeletons of polytopes of dimension at least n/2-2 (products of associahedra). Similarly, the bistellar flip graph can be covered by 1-skeletons of polytopes of dimension at least n-3 (products of secondary polytopes).
(covers joint research with Uli Wagner, IST Austria)
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Extent |
50.0 minutes
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Subject | |
Type | |
File Format |
video/mp4
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Language |
eng
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Notes |
Author affiliation: ETH Zurich
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Series | |
Date Available |
2020-04-09
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Provider |
Vancouver : University of British Columbia Library
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Rights |
Attribution-NonCommercial-NoDerivatives 4.0 International
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DOI |
10.14288/1.0389778
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URI | |
Affiliation | |
Peer Review Status |
Unreviewed
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Scholarly Level |
Faculty
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Rights URI | |
Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
Attribution-NonCommercial-NoDerivatives 4.0 International