General framework Decay of correlation = a.a.s. Develop a machinery to calculate the probability that the root is red. Peleg Michaeli (TAU) Greedy MIS July 21, 2019 7 / 18 We wish to calculate the asymptotics of ι ( G n ) . We fjrst calculate E ( ι ( G n )) = P ( ρ n ∈ I ( G n )) for ρ n chosen u.a.r. We hope that this is determined by a small neighbourhood of ρ n . This local view of ρ n is captured by the local limit of G n .
General framework Decay of correlation = Develop a machinery to calculate the probability that the root is red. Peleg Michaeli (TAU) Greedy MIS July 21, 2019 7 / 18 We wish to calculate the asymptotics of ι ( G n ) . We fjrst calculate E ( ι ( G n )) = P ( ρ n ∈ I ( G n )) for ρ n chosen u.a.r. We hope that this is determined by a small neighbourhood of ρ n . This local view of ρ n is captured by the local limit of G n . ⇒ ι ( G n ) ∼ E ( ι ( G n )) a.a.s.
General framework Decay of correlation = Develop a machinery to calculate the probability that the root is red. Peleg Michaeli (TAU) Greedy MIS July 21, 2019 7 / 18 We wish to calculate the asymptotics of ι ( G n ) . We fjrst calculate E ( ι ( G n )) = P ( ρ n ∈ I ( G n )) for ρ n chosen u.a.r. We hope that this is determined by a small neighbourhood of ρ n . This local view of ρ n is captured by the local limit of G n . ⇒ ι ( G n ) ∼ E ( ι ( G n )) a.a.s.
Local limits Peleg Michaeli (TAU) Greedy MIS July 21, 2019 8 / 18 We say that a (random) graph sequence G n locally converges to a random rooted graph ( U, ρ ) , if for every r ≥ 0 , the ball B r ( G, ρ n ) converges in distribution to B r ( U, ρ ) , where ρ n is a uniform vertex of G n .
Local limits Peleg Michaeli (TAU) Greedy MIS July 21, 2019 8 / 18 We say that a (random) graph sequence G n locally converges to a random rooted graph ( U, ρ ) , if for every r ≥ 0 , the ball B r ( G, ρ n ) converges in distribution to B r ( U, ρ ) , where ρ n is a uniform vertex of G n .
Local limits Peleg Michaeli (TAU) Greedy MIS July 21, 2019 8 / 18 We say that a (random) graph sequence G n locally converges to a random rooted graph ( U, ρ ) , if for every r ≥ 0 , the ball B r ( G, ρ n ) converges in distribution to B r ( U, ρ ) , where ρ n is a uniform vertex of G n .
Local limits Peleg Michaeli (TAU) Greedy MIS July 21, 2019 8 / 18 We say that a (random) graph sequence G n locally converges to a random rooted graph ( U, ρ ) , if for every r ≥ 0 , the ball B r ( G, ρ n ) converges in distribution to B r ( U, ρ ) , where ρ n is a uniform vertex of G n .
Local limits Peleg Michaeli (TAU) Greedy MIS July 21, 2019 8 / 18 We say that a (random) graph sequence G n locally converges to a random rooted graph ( U, ρ ) , if for every r ≥ 0 , the ball B r ( G, ρ n ) converges in distribution to B r ( U, ρ ) , where ρ n is a uniform vertex of G n .
Local limits Peleg Michaeli (TAU) Greedy MIS July 21, 2019 8 / 18 We say that a (random) graph sequence G n locally converges to a random rooted graph ( U, ρ ) , if for every r ≥ 0 , the ball B r ( G, ρ n ) converges in distribution to B r ( U, ρ ) , where ρ n is a uniform vertex of G n . · · ·
Peleg Michaeli (TAU) Local limits Greedy MIS July 21, 2019 8 / 18 We say that a (random) graph sequence G n locally converges to a random rooted graph ( U, ρ ) , if for every r ≥ 0 , the ball B r ( G, ρ n ) converges in distribution to B r ( U, ρ ) , where ρ n is a uniform vertex of G n . · · · � ➪ ➪
Peleg Michaeli (TAU) Local limits Greedy MIS July 21, 2019 8 / 18 We say that a (random) graph sequence G n locally converges to a random rooted graph ( U, ρ ) , if for every r ≥ 0 , the ball B r ( G, ρ n ) converges in distribution to B r ( U, ρ ) , where ρ n is a uniform vertex of G n . · · · � ➪ ➪ � ➪ ➪
Local limits loc July 21, 2019 Greedy MIS Peleg Michaeli (TAU) loc 8 / 18 Examples loc We say that a (random) graph sequence G n locally converges to a random rooted graph ( U, ρ ) , if for every r ≥ 0 , the ball B r ( G, ρ n ) converges in distribution to B r ( U, ρ ) , where ρ n is a uniform vertex of G n . P n , C n − → Z [ n ] d loc → Z d − G ( n, λ / n ) loc − → T λ , a Galton-Watson Pois ( λ ) tree − → the d -regular tree G n,d → ˆ Uniform random tree T n − T 1 , a size-biased GW Pois (1) tree − → the canopy tree Finite d -ary balanced tree loc
Convergence of the greedy independence ratio Theorem (Krivelevich, Mészáros, M., Shikhelman ’19+) loc Peleg Michaeli (TAU) Greedy MIS July 21, 2019 9 / 18 Suppose G n has subfactorial growth. − → ( U, ρ ) then ι ( G n ) → ι ( U, ρ ) a.a.s. If G n
Decay of correlation Peleg Michaeli (TAU) Greedy MIS July 21, 2019 10 / 18
Decay of correlation Peleg Michaeli (TAU) Greedy MIS July 21, 2019 10 / 18
Decay of correlation Peleg Michaeli (TAU) Greedy MIS July 21, 2019 10 / 18
Decay of correlation Peleg Michaeli (TAU) Greedy MIS July 21, 2019 10 / 18
Decay of correlation Peleg Michaeli (TAU) Greedy MIS July 21, 2019 10 / 18
Decay of correlation Peleg Michaeli (TAU) Greedy MIS July 21, 2019 10 / 18
Decay of correlation Peleg Michaeli (TAU) Greedy MIS July 21, 2019 10 / 18
Decay of correlation Peleg Michaeli (TAU) Greedy MIS July 21, 2019 10 / 18
Decay of correlation Peleg Michaeli (TAU) Greedy MIS July 21, 2019 10 / 18
Decay of correlation Peleg Michaeli (TAU) Greedy MIS July 21, 2019 10 / 18
Decay of correlation Peleg Michaeli (TAU) Greedy MIS July 21, 2019 10 / 18
Decay of correlation Peleg Michaeli (TAU) Greedy MIS July 21, 2019 10 / 18
Decay of correlation Peleg Michaeli (TAU) Greedy MIS July 21, 2019 10 / 18
Decay of correlation Peleg Michaeli (TAU) Greedy MIS July 21, 2019 10 / 18
Let us therefore restrict ourselves to locally tree-like graph sequences, i.e., Locally tree-like but even is still unknown... graph sequences for which is a.s. a tree. Children of the past are roots to independent subtrees. Peleg Michaeli (TAU) Greedy MIS July 21, 2019 11 / 18 We need to calculate ι ( U, ρ ) ,
Let us therefore restrict ourselves to locally tree-like graph sequences, i.e., Locally tree-like graph sequences for which is a.s. a tree. Children of the past are roots to independent subtrees. Peleg Michaeli (TAU) Greedy MIS July 21, 2019 11 / 18 We need to calculate ι ( U, ρ ) , but even ι ( Z 2 ) is still unknown...
Locally tree-like Children of the past are roots to independent subtrees. Peleg Michaeli (TAU) Greedy MIS July 21, 2019 11 / 18 We need to calculate ι ( U, ρ ) , but even ι ( Z 2 ) is still unknown... Let us therefore restrict ourselves to locally tree-like graph sequences, i.e., graph sequences for which ( U, ρ ) is a.s. a tree.
Locally tree-like Children of the past are roots to independent subtrees. Peleg Michaeli (TAU) Greedy MIS July 21, 2019 11 / 18 We need to calculate ι ( U, ρ ) , but even ι ( Z 2 ) is still unknown... Let us therefore restrict ourselves to locally tree-like graph sequences, i.e., graph sequences for which ( U, ρ ) is a.s. a tree. u 1 u 2 · · · u d ρ
Locally tree-like Children of the past are roots to independent subtrees. Peleg Michaeli (TAU) Greedy MIS July 21, 2019 11 / 18 We need to calculate ι ( U, ρ ) , but even ι ( Z 2 ) is still unknown... Let us therefore restrict ourselves to locally tree-like graph sequences, i.e., graph sequences for which ( U, ρ ) is a.s. a tree. u 1 u 2 · · · u d ρ
Systems of ordinary difgerential equations I I I I Peleg Michaeli (TAU) Greedy MIS July 21, 2019 12 / 18 Let ( U, ρ ) be a single-type branching process.
Systems of ordinary difgerential equations I I I Peleg Michaeli (TAU) Greedy MIS July 21, 2019 12 / 18 Let ( U, ρ ) be a single-type branching process. y ( x ) = P ( ρ ∈ I ( U, ρ ) ∧ σ ρ < x )
I Systems of ordinary difgerential equations Peleg Michaeli (TAU) Greedy MIS July 21, 2019 12 / 18 Let ( U, ρ ) be a single-type branching process. y ( x ) = P ( ρ ∈ I ( U, ρ ) ∧ σ ρ < x ) = x · P ( ρ ∈ I ( U, ρ ) | σ ρ < x ) ∫ x = P ( ρ ∈ I ( U, ρ ) | σ ρ = z ) dz 0
Systems of ordinary difgerential equations Peleg Michaeli (TAU) Greedy MIS July 21, 2019 12 / 18 Let ( U, ρ ) be a single-type branching process. y ( x ) = P ( ρ ∈ I ( U, ρ ) ∧ σ ρ < x ) = x · P ( ρ ∈ I ( U, ρ ) | σ ρ < x ) ∫ x = P ( ρ ∈ I ( U, ρ ) | σ ρ = z ) dz 0 y ′ ( x ) = P ( ρ ∈ I ( U, ρ ) | σ ρ = x )
Systems of ordinary difgerential equations Peleg Michaeli (TAU) July 21, 2019 Greedy MIS 12 / 18 Let ( U, ρ ) be a single-type branching process. y ( x ) = P ( ρ ∈ I ( U, ρ ) ∧ σ ρ < x ) = x · P ( ρ ∈ I ( U, ρ ) | σ ρ < x ) ∫ x = P ( ρ ∈ I ( U, ρ ) | σ ρ = z ) dz 0 y ′ ( x ) = P ( ρ ∈ I ( U, ρ ) | σ ρ = x ) Thus, if y is a unique solution of ) ℓ )( 1 − y ( x ) ξ <x = ℓ ∑ y ′ ( x ) = ( y (0) = 0 , P , x ℓ ∈ N then, ι ( U, ρ ) = y (1) .
Systems of ordinary difgerential equations Peleg Michaeli (TAU) July 21, 2019 Greedy MIS 12 / 18 Let ( U, ρ ) be a multi-type branching process. y ( x ) = P ( ρ ∈ I ( U, ρ ) ∧ σ ρ < x ) = x · P ( ρ ∈ I ( U, ρ ) | σ ρ < x ) ∫ x = P ( ρ ∈ I ( U, ρ ) | σ ρ = z ) dz 0 y ′ ( x ) = P ( ρ ∈ I ( U, ρ ) | σ ρ = x ) Thus, if y is a unique solution of ) ℓ j )( 1 − y j ( x ) ( ∑ ∏ ξ <x y ′ k ( x ) = k → j = ℓ j y k (0) = 0 , P , x ℓ ∈ N T j ∈ T then, ι ( U, ρ ) = E ( y k (1)) .
Size-biased Galton-Watson branching processes Kolchin, Grimmett: the sequence of uniform random trees locally Peleg Michaeli (TAU) Greedy MIS July 21, 2019 13 / 18 converges to the size-biased Galton-Watson Pois (1) tree.
Size-biased Galton-Watson branching processes Kolchin, Grimmett: the sequence of uniform random trees locally Peleg Michaeli (TAU) Greedy MIS July 21, 2019 13 / 18 converges to the size-biased Galton-Watson Pois (1) tree.
Size-biased Galton-Watson branching processes Kolchin, Grimmett: the sequence of uniform random trees locally Peleg Michaeli (TAU) Greedy MIS July 21, 2019 13 / 18 converges to the size-biased Galton-Watson Pois (1) tree.
Size-biased Galton-Watson branching processes Kolchin, Grimmett: the sequence of uniform random trees locally Peleg Michaeli (TAU) Greedy MIS July 21, 2019 13 / 18 converges to the size-biased Galton-Watson Pois (1) tree.
Size-biased Galton-Watson branching processes Kolchin, Grimmett: the sequence of uniform random trees locally Peleg Michaeli (TAU) Greedy MIS July 21, 2019 13 / 18 converges to the size-biased Galton-Watson Pois (1) tree.
Size-biased Galton-Watson branching processes Kolchin, Grimmett: the sequence of uniform random trees locally Peleg Michaeli (TAU) Greedy MIS July 21, 2019 13 / 18 converges to the size-biased Galton-Watson Pois (1) tree.
Size-biased Galton-Watson branching processes Kolchin, Grimmett: the sequence of uniform random trees locally Peleg Michaeli (TAU) Greedy MIS July 21, 2019 13 / 18 converges to the size-biased Galton-Watson Pois (1) tree.
Size-biased Galton-Watson branching processes Kolchin, Grimmett: the sequence of uniform random trees locally Peleg Michaeli (TAU) Greedy MIS July 21, 2019 13 / 18 converges to the size-biased Galton-Watson Pois (1) tree.
Size-biased Galton-Watson branching processes Kolchin, Grimmett: the sequence of uniform random trees locally Peleg Michaeli (TAU) Greedy MIS July 21, 2019 13 / 18 converges to the size-biased Galton-Watson Pois (1) tree.
Size-biased Galton-Watson branching processes Kolchin, Grimmett: the sequence of uniform random trees locally Peleg Michaeli (TAU) Greedy MIS July 21, 2019 13 / 18 converges to the size-biased Galton-Watson Pois (1) tree.
Uniform random trees , s t s hence s , and for s s , and we get s Peleg Michaeli (TAU) Greedy MIS July 21, 2019 t s 14 / 18 ∞ ) d ( λx ) d ( 1 − y t ( x ) ∑ = e − λy t ( x ) . y ′ t ( x ) = e λx d ! x d =0 hence y t ( x ) = ln (1 + λx )/ λ . Thus ι ( G ( n, λ / n )) → ι ( T λ ) = y t (1) = ln (1 + λ ) . λ
Uniform random trees and we get July 21, 2019 Greedy MIS Peleg Michaeli (TAU) 14 / 18 ∞ ) d ( λx ) d ( 1 − y t ( x ) ∑ = e − λy t ( x ) . y ′ t ( x ) = e λx d ! x d =0 hence y t ( x ) = ln (1 + λx )/ λ . Thus ι ( G ( n, λ / n )) → ι ( T λ ) = y t (1) = ln (1 + λ ) . λ t ( x ) = (1 − y s ( x )) e − λy t ( x ) = 1 − y s ( x ) y ′ s ( x ) = (1 − y s ( x )) y ′ 1 + λx , hence y s ( x ) = 1 − (1 + λx ) − 1/ λ , and for λ = 1 , y s (1) = 1 − (1 + x ) − 1 , T 1 ) = y s (1) = 1 ι ( T n ) → ι ( ˆ 2 .
Simulations don’t lie red: 125 (50%), green: 92 ( 37%), blue: 32 ( 13%), black: 1 Peleg Michaeli (TAU) Greedy MIS July 21, 2019 15 / 18
Simulations don’t lie Peleg Michaeli (TAU) Greedy MIS July 21, 2019 15 / 18 red: 125 (50%), green: 92 ( ≈ 37%), blue: 32 ( ≈ 13%), black: 1
Simulations don’t lie (but I do) Peleg Michaeli (TAU) Greedy MIS July 21, 2019 15 / 18 red: 125 (50%), green: 92 ( ≈ 37%), blue: 32 ( ≈ 13%), black: 1
Greedy independence ratio – results Flory ’39, Page ’59 July 21, 2019 Greedy MIS Peleg Michaeli (TAU) (same for functional digraphs) KMMS ’19+ Lauer & Wormald ’07 16 / 18 McDiarmid ’84 Wormald ’95 ι ( P n ) → 1 2 (1 − e − 2 ) ι ( G ( n, λ / n )) → ln (1 + λ )/ λ ι ( G n,d ) → 1 ( 1 − ( d − 1) − 2/( d − 2) ) 2 ( d -regular graphs with girth → ∞ )
Greedy independence ratio – results Flory ’39, Page ’59 July 21, 2019 Greedy MIS Peleg Michaeli (TAU) (same for functional digraphs) KMMS ’19+ Lauer & Wormald ’07 16 / 18 McDiarmid ’84 Wormald ’95 ✓ ι ( P n ) → 1 2 (1 − e − 2 ) ι ( G ( n, λ / n )) → ln (1 + λ )/ λ ι ( G n,d ) → 1 ( 1 − ( d − 1) − 2/( d − 2) ) 2 ( d -regular graphs with girth → ∞ )
Greedy independence ratio – results Flory ’39, Page ’59 July 21, 2019 Greedy MIS Peleg Michaeli (TAU) (same for functional digraphs) KMMS ’19+ Lauer & Wormald ’07 16 / 18 Wormald ’95 McDiarmid ’84 ✓ ι ( P n ) → 1 2 (1 − e − 2 ) ✓ ι ( G ( n, λ / n )) → ln (1 + λ )/ λ ι ( G n,d ) → 1 ( 1 − ( d − 1) − 2/( d − 2) ) 2 ( d -regular graphs with girth → ∞ )
Greedy independence ratio – results Flory ’39, Page ’59 July 21, 2019 Greedy MIS Peleg Michaeli (TAU) (same for functional digraphs) KMMS ’19+ Lauer & Wormald ’07 16 / 18 Wormald ’95 McDiarmid ’84 ✓ ι ( P n ) → 1 2 (1 − e − 2 ) ✓ ι ( G ( n, λ / n )) → ln (1 + λ )/ λ 1 − ( d − 1) − 2/( d − 2) ) ✓ ι ( G n,d ) → 1 ( 2 ( d -regular graphs with girth → ∞ )
Greedy independence ratio – results Flory ’39, Page ’59 July 21, 2019 Greedy MIS Peleg Michaeli (TAU) (same for functional digraphs) KMMS ’19+ Lauer & Wormald ’07 16 / 18 Wormald ’95 McDiarmid ’84 ✓ ι ( P n ) → 1 2 (1 − e − 2 ) ✓ ι ( G ( n, λ / n )) → ln (1 + λ )/ λ 1 − ( d − 1) − 2/( d − 2) ) ✓ ι ( G n,d ) → 1 ( 2 ( d -regular graphs with girth → ∞ ) ✓
Greedy independence ratio – results Flory ’39, Page ’59 July 21, 2019 Greedy MIS Peleg Michaeli (TAU) (same for functional digraphs) KMMS ’19+ Lauer & Wormald ’07 16 / 18 McDiarmid ’84 Wormald ’95 ✓ ι ( P n ) → 1 2 (1 − e − 2 ) ✓ ι ( G ( n, λ / n )) → ln (1 + λ )/ λ 1 − ( d − 1) − 2/( d − 2) ) ✓ ι ( G n,d ) → 1 ( 2 ( d -regular graphs with girth → ∞ ) ✓ ✸ ι ( T n ) → 1 2
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