fixed points and feedback cycles in boolean networks
play

Fixed Points and Feedback Cycles in Boolean Networks Adrien Richard - PowerPoint PPT Presentation

Fixed Points and Feedback Cycles in Boolean Networks Adrien Richard Laboratoire I3S, CNRS & Universit e de Nice-Sophia Antipolis Joint work with Julio Aracena & Lilian Salinas Universidad de Concepci on, Chile Groupe de travail


  1. Remark If H ⊆ G then τ ( H ) ≤ τ ( G ) thus φ ( H ) ≤ 2 τ ( H ) ≤ 2 τ ( G ) → connexion with Network Coding from Information Theory ֒ Binary network coding problem Given a digraph G , is there exists H ⊆ G such that φ ( H ) = 2 τ ( G ) ? Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 12/25

  2. Remark If H ⊆ G then τ ( H ) ≤ τ ( G ) thus φ ( H ) ≤ 2 τ ( H ) ≤ 2 τ ( G ) → connexion with Network Coding from Information Theory ֒ Binary network coding problem Given a digraph G , is there exists H ⊆ G such that φ ( H ) = 2 τ ( G ) ? Surprisingly, the following question has deserved very few attention Given a digraph G , do we have φ ( G ) = 2 τ ( G ) ? Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 12/25

  3. Upper bounds on φ ( G σ ) Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 13/25

  4. In G σ the sign of a cycle (or path) is the product of the sign of its arcs τ + ( G σ ) := positive transversal number := minimum size of a set of vertices meeting every non-negative cycle Remark 1 τ + ≤ τ Remark 2 τ + is invariant under subdivisions of arcs preserving signs Remark 2 e.g. → replaced by →→ , or → replaced by →→ Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 13/25

  5. Theorem (signed version of the classical bound) [Aracena, 2008] For every signed digraph G σ φ ( G σ ) ≤ 2 τ + Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 14/25

  6. Theorem (signed version of the classical bound) [Aracena, 2008] For every signed digraph G σ φ ( G σ ) ≤ 2 τ + G σ has only negative cycles ⇒ τ + = 0 ⇒ φ ( G σ ) ≤ 1 Remark 1 Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 14/25

  7. Theorem (signed version of the classical bound) [Aracena, 2008] For every signed digraph G σ φ ( G σ ) ≤ 2 τ + G σ has only negative cycles ⇒ τ + = 0 ⇒ φ ( G σ ) ≤ 1 Remark 1 Also true for differential equation systems [Soul´ e 03] ! Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 14/25

  8. Theorem (signed version of the classical bound) [Aracena, 2008] For every signed digraph G σ φ ( G σ ) ≤ 2 τ + G σ has only negative cycles ⇒ τ + = 0 ⇒ φ ( G σ ) ≤ 1 Remark 1 Also true for differential equation systems [Soul´ e 03] ! Remark 2 We recover the classical upper-bound: 2 τ + ( G σ ) = 2 τ ( G ) φ ( G ) = max φ ( G σ ) ≤ max σ σ Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 14/25

  9. Theorem (signed version of the classical bound) [Aracena, 2008] For every signed digraph G σ φ ( G σ ) ≤ 2 τ + G σ has only negative cycles ⇒ τ + = 0 ⇒ φ ( G σ ) ≤ 1 Remark 1 Also true for differential equation systems [Soul´ e 03] ! Remark 2 We recover the classical upper-bound: 2 τ + ( G σ ) = 2 τ ( G ) φ ( G ) = max φ ( G σ ) ≤ max σ σ This is the state of the art for upper bounds that depend on the cycle structure Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 14/25

  10. Theorem (signed version of the classical bound) [Aracena, 2008] For every signed digraph G σ φ ( G σ ) ≤ 2 τ + G σ has only negative cycles ⇒ τ + = 0 ⇒ φ ( G σ ) ≤ 1 Remark 1 Also true for differential equation systems [Soul´ e 03] ! Remark 2 We recover the classical upper-bound: 2 τ + ( G σ ) = 2 τ ( G ) φ ( G ) = max φ ( G σ ) ≤ max σ σ This is the state of the art for upper bounds that depend on the cycle structure No lower bounds on φ ( G ) neither φ ( G σ ) ! Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 14/25

  11. The bound φ ≤ 2 τ + is very perfectible Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 15/25

  12. The bound φ ≤ 2 τ + is very perfectible · · · • • • • • • φ = 1 2 τ + ∼ 2 n/ 4 • • • • Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 15/25

  13. The bound φ ≤ 2 τ + is very perfectible · · · • • • • • • φ = 1 2 τ + ∼ 2 n/ 4 • • • • We think that improvements could be obtained by considering negative cycles too. This is a difficult problem... What happen when there is only positive cycles ? ֒ → This essentially corresponds to the case where f is monotone Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 15/25

  14. Monotone networks Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 16/25

  15. { 0 , 1 } n is equipped with the usual partial order x ≤ y ⇐ ⇒ x i ≤ y i for all i f is monotone if for all x, y ∈ { 0 , 1 } n x ≤ y ⇒ f ( x ) ≤ f ( y ) Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 16/25

  16. { 0 , 1 } n is equipped with the usual partial order x ≤ y ⇐ ⇒ x i ≤ y i for all i f is monotone if for all x, y ∈ { 0 , 1 } n x ≤ y ⇒ f ( x ) ≤ f ( y ) Remark f is monotone ⇐ ⇒ G σ has only positive arcs φ ( G + ) = maximum number of fixed points in a monotone boolean network with G as interaction graph Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 16/25

  17. { 0 , 1 } n is equipped with the usual partial order x ≤ y ⇐ ⇒ x i ≤ y i for all i f is monotone if for all x, y ∈ { 0 , 1 } n x ≤ y ⇒ f ( x ) ≤ f ( y ) Remark f is monotone ⇐ ⇒ G σ has only positive arcs φ ( G + ) = maximum number of fixed points in a monotone boolean network with G as interaction graph Proposition If G σ is strong and has only positive cycles then φ ( G σ ) = φ ( G + ) Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 16/25

  18. Fixed points in monotone networks Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 17/25

  19. Theorem [Knaster-Tarski, 1928] If f is monotone then Fixe ( f ) is a non-empty lattice Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 17/25

  20. Theorem [Knaster-Tarski, 1928] If f is monotone then Fixe ( f ) is a non-empty lattice To go further we need another graph parameter about cycles ν ( G ) := packing number := maximum number of vertex-disjoint cycles Remark ν ≤ τ Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 17/25

  21. Theorem [Aracena-Salinas-R, 2016 + ] If f is monotone then Fixe ( f ) a isomorphic to a subset L ⊆ { 0 , 1 } τ s.t. 1. L is a non-empty lattice 2. L has no chains of size ν + 2 Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 18/25

  22. Theorem [Aracena-Salinas-R, 2016 + ] If f is monotone then Fixe ( f ) a isomorphic to a subset L ⊆ { 0 , 1 } τ s.t. 1. L is a non-empty lattice 2. L has no chains of size ν + 2 Proof of the isomorphism • • • • • • • • Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 18/25

  23. Theorem [Aracena-Salinas-R, 2016 + ] If f is monotone then Fixe ( f ) a isomorphic to a subset L ⊆ { 0 , 1 } τ s.t. 1. L is a non-empty lattice 2. L has no chains of size ν + 2 Proof of the isomorphism FVS of size τ I • • • • • • • • Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 18/25

  24. Theorem [Aracena-Salinas-R, 2016 + ] If f is monotone then Fixe ( f ) a isomorphic to a subset L ⊆ { 0 , 1 } τ s.t. 1. L is a non-empty lattice 2. L has no chains of size ν + 2 Proof of the isomorphism FVS of size τ I • • • • • • • • Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 18/25

  25. Theorem [Aracena-Salinas-R, 2016 + ] If f is monotone then Fixe ( f ) a isomorphic to a subset L ⊆ { 0 , 1 } τ s.t. 1. L is a non-empty lattice 2. L has no chains of size ν + 2 ∀ x, y ∈ Fixe ( f ) x I ≤ y I ⇐ ⇒ x ≤ y Proof of the isomorphism FVS of size τ I • • • • • • • • Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 18/25

  26. Theorem [Aracena-Salinas-R, 2016 + ] If f is monotone then Fixe ( f ) a isomorphic to a subset L ⊆ { 0 , 1 } τ s.t. 1. L is a non-empty lattice 2. L has no chains of size ν + 2 ∀ x, y ∈ Fixe ( f ) x I ≤ y I ⇐ ⇒ x ≤ y Proof of the isomorphism Fixe ( f ) is isomorphic to L = { x I : x ∈ Fixe ( f ) } I • • • • • • • • Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 18/25

  27. Theorem [Aracena-Salinas-R, 2016 + ] If f is monotone then Fixe ( f ) a isomorphic to a subset L ⊆ { 0 , 1 } τ s.t. 1. L is a non-empty lattice 2. L has no chains of size ν + 2 ∀ x, y ∈ Fixe ( f ) x I ≤ y I ⇒ x ≤ y Proof of the isomorphism = I • • • • • • • • Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 18/25

  28. Theorem [Aracena-Salinas-R, 2016 + ] If f is monotone then Fixe ( f ) a isomorphic to a subset L ⊆ { 0 , 1 } τ s.t. 1. L is a non-empty lattice 2. L has no chains of size ν + 2 ∀ x, y ∈ Fixe ( f ) x I ≤ y I ⇒ x ≤ y Proof of the isomorphism = x I ≤ y I 0 1 0 1 1 0 I • • • • • • • • • • Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 18/25

  29. Theorem [Aracena-Salinas-R, 2016 + ] If f is monotone then Fixe ( f ) a isomorphic to a subset L ⊆ { 0 , 1 } τ s.t. 1. L is a non-empty lattice 2. L has no chains of size ν + 2 ∀ x, y ∈ Fixe ( f ) x I ≤ y I ⇒ x ≤ y Proof of the isomorphism = x I ≤ y I 0 1 0 1 1 0 I J • • • • • • • • • • Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 18/25

  30. Theorem [Aracena-Salinas-R, 2016 + ] If f is monotone then Fixe ( f ) a isomorphic to a subset L ⊆ { 0 , 1 } τ s.t. 1. L is a non-empty lattice 2. L has no chains of size ν + 2 ∀ x, y ∈ Fixe ( f ) x I ≤ y I ⇒ x ≤ y Proof of the isomorphism = x I ≤ y I 0 1 0 1 1 0 I i i J • • • • • • • • Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 18/25

  31. Theorem [Aracena-Salinas-R, 2016 + ] If f is monotone then Fixe ( f ) a isomorphic to a subset L ⊆ { 0 , 1 } τ s.t. 1. L is a non-empty lattice 2. L has no chains of size ν + 2 ∀ x, y ∈ Fixe ( f ) x I ≤ y I ⇒ x ≤ y Proof of the isomorphism = x I ≤ y I 0 1 0 1 1 0 I f i ( x ) ≤ f i ( y ) i i J • • • • • • • • Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 18/25

  32. Theorem [Aracena-Salinas-R, 2016 + ] If f is monotone then Fixe ( f ) a isomorphic to a subset L ⊆ { 0 , 1 } τ s.t. 1. L is a non-empty lattice 2. L has no chains of size ν + 2 ∀ x, y ∈ Fixe ( f ) x I ≤ y I ⇒ x ≤ y Proof of the isomorphism = x I ≤ y I 0 1 0 1 1 0 I x i ≤ y i i i J • • • • • • • • Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 18/25

  33. Theorem [Aracena-Salinas-R, 2016 + ] If f is monotone then Fixe ( f ) a isomorphic to a subset L ⊆ { 0 , 1 } τ s.t. 1. L is a non-empty lattice 2. L has no chains of size ν + 2 ∀ x, y ∈ Fixe ( f ) x I ≤ y I ⇒ x ≤ y Proof of the isomorphism = x I ≤ y I 0 1 0 1 1 0 I x J ≤ y J 0 1 1 1 J • • • • • • Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 18/25

  34. Theorem [Aracena-Salinas-R, 2016 + ] If f is monotone then Fixe ( f ) a isomorphic to a subset L ⊆ { 0 , 1 } τ s.t. 1. L is a non-empty lattice 2. L has no chains of size ν + 2 ∀ x, y ∈ Fixe ( f ) x I ≤ y I ⇒ x ≤ y Proof of the isomorphism = x I ≤ y I 0 1 0 1 1 0 I x J ≤ y J 0 1 1 1 J K • • • • • • Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 18/25

  35. Theorem [Aracena-Salinas-R, 2016 + ] If f is monotone then Fixe ( f ) a isomorphic to a subset L ⊆ { 0 , 1 } τ s.t. 1. L is a non-empty lattice 2. L has no chains of size ν + 2 ∀ x, y ∈ Fixe ( f ) x I ≤ y I ⇒ x ≤ y Proof of the isomorphism = x I ≤ y I 0 1 0 1 1 0 I x J ≤ y J 0 1 1 1 J x K ≤ y K K 0 1 0 1 1 0 Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 18/25

  36. Theorem [Aracena-Salinas-R, 2016 + ] If f is monotone then Fixe ( f ) a isomorphic to a subset L ⊆ { 0 , 1 } τ s.t. 1. L is a non-empty lattice 2. L has no chains of size ν + 2 Proof of 2 If Fixe ( f ) has a chain of size k then ν ≥ k − 1 Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 19/25

  37. Theorem [Aracena-Salinas-R, 2016 + ] If f is monotone then Fixe ( f ) a isomorphic to a subset L ⊆ { 0 , 1 } τ s.t. 1. L is a non-empty lattice 2. L has no chains of size ν + 2 Proof of 2 If Fixe ( f ) has a chain of size k then ν ≥ k − 1 x 5 = 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 x 4 = 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 x 3 = 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 x 2 = 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 x 1 = 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 19/25

  38. Theorem [Aracena-Salinas-R, 2016 + ] If f is monotone then Fixe ( f ) a isomorphic to a subset L ⊆ { 0 , 1 } τ s.t. 1. L is a non-empty lattice 2. L has no chains of size ν + 2 Proof of 2 If Fixe ( f ) has a chain of size k then ν ≥ k − 1 x 5 = 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 x 4 = 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 x 3 = 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 x 2 = 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 x 1 = 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ∆( x 1 , x 2 ) ∆( x 2 , x 3 ) ∆( x 3 , x 4 ) ∆( x 4 , x 5 ) Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 19/25

  39. Theorem [Aracena-Salinas-R, 2016 + ] If f is monotone then Fixe ( f ) a isomorphic to a subset L ⊆ { 0 , 1 } τ s.t. 1. L is a non-empty lattice 2. L has no chains of size ν + 2 Proof of 2 If Fixe ( f ) has a chain of size k then ν ≥ k − 1 x 5 = 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 x 4 = 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 x 3 = 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 x 2 = 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 x 1 = 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ∆( x 1 , x 2 ) ∆( x 2 , x 3 ) ∆( x 3 , x 4 ) ∆( x 4 , x 5 ) C 1 C 2 C 3 C 4 Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 19/25

  40. Theorem [Aracena-Salinas-R, 2016 + ] If f is monotone then Fixe ( f ) a isomorphic to a subset L ⊆ { 0 , 1 } τ s.t. 1. L is a non-empty lattice 2. L has no chains of size ν + 2 Proof of 2 If Fixe ( f ) has a chain of size k then ν ≥ k − 1 Thus Fixe ( f ) has no chains of length ν + 2 and so L x 5 = 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 x 4 = 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 x 3 = 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 x 2 = 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 x 1 = 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ∆( x 1 , x 2 ) ∆( x 2 , x 3 ) ∆( x 3 , x 4 ) ∆( x 4 , x 5 ) C 1 C 2 C 3 C 4 Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 19/25

  41. Theorem [Erd˝ os, 1945] If X ⊆ { 0 , 1 } n has no chains of size ℓ + 1 then � n | X | ≤ the sum of the ℓ largest binomial coefficients � k Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 20/25

  42. Theorem [Erd˝ os, 1945] If X ⊆ { 0 , 1 } n has no chains of size ℓ + 1 then � n | X | ≤ the sum of the ℓ largest binomial coefficients � k Remark The case ℓ = 1 is Sperner’s lemma on antichains Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 20/25

  43. Theorem [Erd˝ os, 1945] If X ⊆ { 0 , 1 } n has no chains of size ℓ + 1 then � n | X | ≤ the sum of the ℓ largest binomial coefficients � k Corollary If f is monotone then � τ | Fixe ( f ) | − 2 ≤ the sum of the ν − 1 largest � k Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 20/25

  44. Theorem [Erd˝ os, 1945] If X ⊆ { 0 , 1 } n has no chains of size ℓ + 1 then � n | X | ≤ the sum of the ℓ largest binomial coefficients � k Corollary If f is monotone then � τ | Fixe ( f ) | − 2 ≤ the sum of the ν − 1 largest � k Proof Let L ⊆ { 0 , 1 } τ be a non-empty lattice isomorphic to Fixe ( f ) max b • no chains L of size ν + 2 • min a Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 20/25

  45. Theorem [Erd˝ os, 1945] If X ⊆ { 0 , 1 } n has no chains of size ℓ + 1 then � n | X | ≤ the sum of the ℓ largest binomial coefficients � k Corollary If f is monotone then � τ | Fixe ( f ) | − 2 ≤ the sum of the ν − 1 largest � k Proof Let L ⊆ { 0 , 1 } τ be a non-empty lattice isomorphic to Fixe ( f ) max b • no chains L \ { a, b } of size ν • min a Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 20/25

  46. Theorem [Erd˝ os, 1945] If X ⊆ { 0 , 1 } n has no chains of size ℓ + 1 then � n | X | ≤ the sum of the ℓ largest binomial coefficients � k Corollary If f is monotone then � τ | Fixe ( f ) | − 2 ≤ the sum of the ν − 1 largest � k Proof Let L ⊆ { 0 , 1 } τ be a non-empty lattice isomorphic to Fixe ( f ) max b • no chains � τ ≤ � L \ { a, b } the sum of the ν − 1 largest k of size ν • min a Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 20/25

  47. � τ � Corollary φ ( G + ) ≤ the sum of the ν − 1 largest + 2 k Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 21/25

  48. � τ � Corollary φ ( G + ) ≤ the sum of the ν − 1 largest + 2 k � τ � τ � τ � � � τ/ 2 0 τ τ − 1 coefficients Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 21/25

  49. � τ � Corollary φ ( G + ) ≤ the sum of the ν − 1 largest + 2 k 2 τ � τ � τ � τ � � � τ/ 2 0 τ τ − 1 coefficients Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 21/25

  50. � τ � Corollary φ ( G + ) ≤ the sum of the ν − 1 largest + 2 k � τ � τ � τ � � � τ/ 2 0 τ ν − 1 coefficients τ − 1 coefficients φ ( G + ) = 2 τ ⇒ ν = τ Corollary Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 21/25

  51. � τ � Corollary φ ( G + ) ≤ the sum of the ν − 1 largest + 2 k The upper bound is interesting when ν is much more smaller that τ The largest gap known is ν log ν ≤ 30 τ [Seymour 93] Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 21/25

  52. � τ � Corollary φ ( G + ) ≤ the sum of the ν − 1 largest + 2 k The upper bound is interesting when ν is much more smaller that τ The largest gap known is ν log ν ≤ 30 τ [Seymour 93] For a fixed ν , τ cannot be arbitrarily large... Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 21/25

  53. � τ � Corollary φ ( G + ) ≤ the sum of the ν − 1 largest + 2 k The upper bound is interesting when ν is much more smaller that τ The largest gap known is ν log ν ≤ 30 τ [Seymour 93] For a fixed ν , τ cannot be arbitrarily large... Theorem [Reed-Robertson-Seymour-Thomas, 1995] There exists h : N → N such that, for every digraph G , τ ≤ h ( ν ) The upper-bound on h ( ν ) is astronomique (iterated use of Ramsey theorem) Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 21/25

  54. � τ � Corollary φ ( G + ) ≤ the sum of the ν − 1 largest + 2 k The upper bound is interesting when ν is much more smaller that τ The largest gap known is ν log ν ≤ 30 τ [Seymour 93] For a fixed ν , τ cannot be arbitrarily large... Theorem [Reed-Robertson-Seymour-Thomas, 1995] There exists h : N → N such that, for every digraph G , τ ≤ h ( ν ) The upper-bound on h ( ν ) is astronomique (iterated use of Ramsey theorem) φ ( G ) ≤ 2 τ ≤ 2 h ( ν ) Corollary Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 21/25

  55. � τ � Corollary φ ( G + ) ≤ the sum of the ν − 1 largest + 2 k The upper bound is interesting when ν is much more smaller that τ The largest gap known is ν log ν ≤ 30 τ [Seymour 93] For a fixed ν , τ cannot be arbitrarily large... Theorem [Reed-Robertson-Seymour-Thomas, 1995] There exists h : N → N such that, for every digraph G , τ ≤ h ( ν ) The upper-bound on h ( ν ) is astronomique (iterated use of Ramsey theorem) ν + 1 ≤ φ ( G ) ≤ 2 τ ≤ 2 h ( ν ) Corollary Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 21/25

  56. More on fixed points in monotone networks Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 22/25

  57. Special packing Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 22/25

  58. Special packing v • • u Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 22/25

  59. Special packing • u • v Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 22/25

  60. Special packing v • • P u Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 22/25

  61. Special packing • P ′ v • • P u Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 22/25

  62. Special packing • P ′ v • • P u We denote by ν ∗ ( G ) the maximum size of a special packing Remark ν ∗ ≤ ν ≤ τ Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 22/25

  63. A k -pattern in X ⊆ { 0 , 1 } n is a sequence ( x 1 , . . . , x k ) ∈ X k such that x p ≤ x q ( x 1 , . . . , x k ) ∈ X k and ⇐ ⇒ p � = q Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 23/25

  64. A k -pattern in X ⊆ { 0 , 1 } n is a sequence ( x 1 , . . . , x k ) ∈ X k such that x p ≤ x q ( x 1 , . . . , x k ) ∈ X k and ⇐ ⇒ p � = q Example ( e 1 , e 2 , e 3 ) is a 3 -pattern of { 0 , 1 } 3 e 1 = 011 e 2 = 101 e 3 = 110 e 1 = 100 e 2 = 010 e 3 = 001 Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 23/25

  65. A k -pattern in X ⊆ { 0 , 1 } n is a sequence ( x 1 , . . . , x k ) ∈ X k such that x p ≤ x q ( x 1 , . . . , x k ) ∈ X k and ⇐ ⇒ p � = q Example ( e 1 , e 2 , e 3 ) is a 3 -pattern of { 0 , 1 } 3 e 1 = 011 e 2 = 101 e 3 = 110 e 1 = 100 e 2 = 010 e 3 = 001 Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 23/25

  66. A k -pattern in X ⊆ { 0 , 1 } n is a sequence ( x 1 , . . . , x k ) ∈ X k such that x p ≤ x q ( x 1 , . . . , x k ) ∈ X k and ⇐ ⇒ p � = q Example ( e 1 , e 2 , e 3 ) is a 3 -pattern of { 0 , 1 } 3 e 1 = 011 e 2 = 101 e 3 = 110 e 1 = 100 e 2 = 010 e 3 = 001 Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 23/25

  67. A k -pattern in X ⊆ { 0 , 1 } n is a sequence ( x 1 , . . . , x k ) ∈ X k such that x p ≤ x q ( x 1 , . . . , x k ) ∈ X k and ⇐ ⇒ p � = q Example ( e 1 , e 2 , e 3 ) is a 3 -pattern of { 0 , 1 } 3 e 1 = 011 e 2 = 101 e 3 = 110 e 1 = 100 e 2 = 010 e 3 = 001 Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 23/25

  68. A k -pattern in X ⊆ { 0 , 1 } n is a sequence ( x 1 , . . . , x k ) ∈ X k such that x p ≤ x q ( x 1 , . . . , x k ) ∈ X k and ⇐ ⇒ p � = q Example ( e 1 , e 2 , e 3 ) is a 3 -pattern of { 0 , 1 } 3 e 1 = 011 e 2 = 101 e 3 = 110 e 1 = 100 e 2 = 010 e 3 = 001 More generally ( e 1 , e 2 , . . . , e n ) is an n -pattern of { 0 , 1 } n Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 23/25

  69. Theorem [Aracena-Salinas-R, 2016 + ] If f is monotone then Fixe ( f ) a isomorphic to a subset L ⊆ { 0 , 1 } τ s.t. 1. L is a non-empty lattice 2. L has no chains of size ν + 2 3. L has no ( ν ∗ + 1) -pattern Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 24/25

  70. Theorem [Aracena-Salinas-R, 2016 + ] If f is monotone then Fixe ( f ) a isomorphic to a subset L ⊆ { 0 , 1 } τ s.t. 1. L is a non-empty lattice 2. L has no chains of size ν + 2 3. L has no ( ν ∗ + 1) -pattern Remark If L = { 0 , 1 } τ then L has a has a τ -pattern, so τ < ν ∗ + 1 . Remark Thus τ ≤ ν ∗ and since ν ∗ ≤ τ we deduce that ν ∗ = τ . Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 24/25

  71. Theorem [Aracena-Salinas-R, 2016 + ] If f is monotone then Fixe ( f ) a isomorphic to a subset L ⊆ { 0 , 1 } τ s.t. 1. L is a non-empty lattice 2. L has no chains of size ν + 2 3. L has no ( ν ∗ + 1) -pattern Remark If L = { 0 , 1 } τ then L has a has a τ -pattern, so τ < ν ∗ + 1 . φ ( G + ) = 2 τ ⇒ ν ∗ = τ Corollary Remark Thus τ ≤ ν ∗ and since ν ∗ ≤ τ we deduce that ν ∗ = τ . Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 24/25

  72. Theorem [Aracena-Salinas-R, 2016 + ] If f is monotone then Fixe ( f ) a isomorphic to a subset L ⊆ { 0 , 1 } τ s.t. 1. L is a non-empty lattice 2. L has no chains of size ν + 2 3. L has no ( ν ∗ + 1) -pattern Remark If L = { 0 , 1 } τ then L has a has a τ -pattern, so τ < ν ∗ + 1 . φ ( G + ) = 2 τ ⇒ ν ∗ = τ ⇒ ν = τ Corollary Remark Thus τ ≤ ν ∗ and since ν ∗ ≤ τ we deduce that ν ∗ = τ . Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 24/25

  73. Theorem [Aracena-Salinas-R, 2016 + ] If f is monotone then Fixe ( f ) a isomorphic to a subset L ⊆ { 0 , 1 } τ s.t. 1. L is a non-empty lattice 2. L has no chains of size ν + 2 3. L has no ( ν ∗ + 1) -pattern Remark If L = { 0 , 1 } τ then L has a has a τ -pattern, so τ < ν ∗ + 1 . φ ( G + ) = 2 τ ⇒ ν ∗ = τ ⇒ ν = τ Corollary Remark Thus τ ≤ ν ∗ and since ν ∗ ≤ τ we deduce that ν ∗ = τ . Theorem [Aracena-Salinas-R, 2016 + ] 2 ν ∗ ≤ φ ( G + ) Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 24/25

  74. Theorem [Aracena-Salinas-R, 2016 + ] If f is monotone then Fixe ( f ) a isomorphic to a subset L ⊆ { 0 , 1 } τ s.t. 1. L is a non-empty lattice 2. L has no chains of size ν + 2 3. L has no ( ν ∗ + 1) -pattern Remark If L = { 0 , 1 } τ then L has a has a τ -pattern, so τ < ν ∗ + 1 . φ ( G + ) = 2 τ ⇒ ν ∗ = τ ⇒ ν = τ Corollary Remark Thus τ ≤ ν ∗ and since ν ∗ ≤ τ we deduce that ν ∗ = τ . Theorem [Aracena-Salinas-R, 2016 + ] 2 ν ∗ ≤ φ ( G + ) ν ∗ = τ φ ( G + ) = 2 τ Corollary ⇐ ⇒ Adrien RICHARD Fixed Points in Boolean Networks Paris 2016 24/25

Download Presentation
Download Policy: The content available on the website is offered to you 'AS IS' for your personal information and use only. It cannot be commercialized, licensed, or distributed on other websites without prior consent from the author. To download a presentation, simply click this link. If you encounter any difficulties during the download process, it's possible that the publisher has removed the file from their server.

Recommend


More recommend