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Recursive regularity and the finest regular coarsening of a polyhedral subdivision Rafel Jaume joint work with G unter Rote Overview Basic definition and tools Recursive regularity and finest regular coarsening Properties of recursively


  1. Proposition Recursively regular subdivisions are a superset of the regular subdivisions and a subset of the acyclic ones Proof Assume that it exists a cycle in a recursively regular subdivision. We can assume that the cycle belongs to more than one cell of the FRC and apply recursion otherwise. Then, the FRC cannot be regular, since a cycle cannot be destroyed by means of merging cells.

  2. Proposition There is a 5-dimensional point set with at least 12 recursively regular triangulations pairwise disconnected and disconnected from any regular triangulation in the graph of flips

  3. Applications Floodlights Homothecies Graph embeddings Spider webs

  4. Floodlights polyhedral fan with n cells

  5. Floodlights n points polyhedral fan with n cells

  6. Floodlights n points one to one polyhedral fan with n cells

  7. Floodlights n points one to one polyhedral fan with n cells covering assignment

  8. Covering fans A polyhedral fan is universally covering if for any point set there exists a covering assignment

  9. Covering fans A polyhedral fan is universally covering if for any point set there exists a covering assignment Theorem (Galperin & Galperin, 1981) Regular fans are universally covering

  10. Covering fans A polyhedral fan is universally covering if for any point set there exists a covering assignment Theorem (Galperin & Galperin, 1981) Regular fans are universally covering Theorem Recursively regular fans are universally covering Cyclic fans are not universally covering

  11. Fans Cyclic Rec. regular Regular

  12. Fans Cyclic Rec. regular Regular Universally covering

  13. Fans Cyclic Rec. regular Regular Universally covering

  14. Fans Cyclic Rec. regular Regular Universally covering

  15. Fans Cyclic Rec. regular Regular Universally covering

  16. Overlapping condition

  17. Overlapping condition

  18. Overlapping condition

  19. Directional graph embeddings → − V = { 1 , ..., n } E ⊂ V × V

  20. Directional graph embeddings → − V = { 1 , ..., n } E ⊂ V × V P = { p 1 , ...p n } ⊂ R d

  21. Directional graph embeddings → − N : − → → R d V = { 1 , ..., n } E ⊂ V × V E − P = { p 1 , ...p n } ⊂ R d

  22. Directional graph embeddings → − N : − → → R d V = { 1 , ..., n } E ⊂ V × V E − P = { p 1 , ...p n } ⊂ R d proper embedding Is there a σ : V ↔ P N ( i, j ) · p i ≥ N ( i, j ) · p j ∀ ( i, j ) ∈ − → E ?

  23. Directional graph embeddings → − N : − → → R d V = { 1 , ..., n } E ⊂ V × V E − P = { p 1 , ...p n } ⊂ R d proper embedding Is there a σ : V ↔ P N ( i, j ) · p i ≥ N ( i, j ) · p j ∀ ( i, j ) ∈ − → E ? A path is always embeddable

  24. Directional graph embeddings → − N : − → → R d V = { 1 , ..., n } E ⊂ V × V E − P = { p 1 , ...p n } ⊂ R d proper embedding Is there a σ : V ↔ P N ( i, j ) · p i ≥ N ( i, j ) · p j ∀ ( i, j ) ∈ − → E ? A path is always embeddable A cycle is not always embeddable

  25. Directional graph embeddings → − N : − → → R d V = { 1 , ..., n } E ⊂ V × V E − P = { p 1 , ...p n } ⊂ R d proper embedding Is there a σ : V ↔ P N ( i, j ) · p i ≥ N ( i, j ) · p j ∀ ( i, j ) ∈ − → E ? A path is always embeddable A cycle is not always embeddable A tree?

  26. Proposition If the graph is the normal graph (or a projection of a subgraph) of a fan and there is a covering assignment for P , there is a proper graph embedding for P . If there is no assignment satisfying OC for... , there is no proper embedding

  27. Proposition If the graph is the normal graph (or a projection of a subgraph) of a fan and there is a covering assignment for P , there is a proper graph embedding for P . If there is no assignment satisfying OC for... , there is no proper embedding Corollary The graph of a polytope is always embeddable.

  28. Homothecies 1,3 1,1 1,2 0,6 0,9 1,5

  29. Homothecies 1,3 1,1 1,2 0,6 0,9 1,5

  30. Homothecies

  31. Homothecies

  32. Homothecies

  33. Homothecies

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