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# Visualizing diagram factorizations in Temperley–Lieb algebras, Part 2

This talk is a continued exploration and discussion of new results from "Visualizing diagram factorizations in Temperley--Lieb algebras, Part 1" by Michael Hastings (NAU). The diagrammatic representation is like that of type A (introduced in Part 1) with a relation decorated diagrams. Multiplying diagram is easy to do. However, taking a given diagram and finding the corresponding reduced factorization is generally difficult. We have an efficient (and colorful) algorithm for obtaining a reduced factorization for Temperley-Lieb diagrams of type B.

This talk was given by my undergraduate research student Sarah Salmon (Northern Arizona University) on March 1, 2014 at the Southwestern Undergraduate Mathematics Research Conference (SUnMaRC) at Mesa Community College, Mesa, AZ. This joint work with Michael Hastings. March 01, 2014

## Transcript

1. ### Visualizing diagram factorizations in Temperley–Lieb algebras, Part 2 Sarah Salmon

Northern Arizona University Department of Mathematics and Statistics [email protected] Southwestern Undergraduate Mathematics Research Conference March 1, 2014 Joint work with Michael Hastings S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 1 / 19
2. ### Type A Temperley–Lieb diagrams A diagram in type An must

satisfy the following requirements: • The diagram starts with a box with n + 1 nodes along the north face and n + 1 nodes along the south face. • Every node must be connected to exactly one other node by a single edge. • The edges cannot cross. • The edges cannot leave the box. Example Here is a 6-diagram. This is not a diagram. S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 2 / 19
3. ### The type A Temperley–Lieb diagram algebra TL(An ) is the

Z[δ]-algebra having (n + 1)-diagrams as a basis. When multiplying diagrams, it is possible to obtain a loop. In this case, we replace each loop with a coeﬃcient δ. = δ2 S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 3 / 19
4. ### The type A Temperley–Lieb diagram algebra Here is another example

of diagram multiplication. = δ4 S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 4 / 19
5. ### Type A diagrams Example For TL(A3 ), we have the

following set of 4-diagrams as a basis: Theorem In TL(An ), there are Catalan-many diagrams. S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 5 / 19
6. ### Type A diagrams Example For TL(A3 ), we have the

following set of 4-diagrams as a basis: Theorem In TL(An ), there are Catalan-many diagrams. S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 5 / 19
7. ### Products of simple diagrams Example Consider the product d1 d2

d1 d3 d2 d4 d3 in TL(A4 ). = = Note that d1 d2 d1 d3 d2 d4 d3 = d1 d3 d2 d4 d3. S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 6 / 19
8. ### Products of simple diagrams Example Consider the product d1 d2

d1 d3 d2 d4 d3 in TL(A4 ). = = Note that d1 d2 d1 d3 d2 d4 d3 = d1 d3 d2 d4 d3. S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 6 / 19
9. ### Factorization of type A We have discovered an algorithm to

determine the factorization given a diagram. S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 7 / 19
10. ### Factorization of type A We have discovered an algorithm to

determine the factorization given a diagram. ←→ S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 7 / 19
11. ### Factorization of type A We have discovered an algorithm to

determine the factorization given a diagram. ←→ S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 7 / 19
12. ### Factorization of type A We have discovered an algorithm to

determine the factorization given a diagram. ←→ S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 7 / 19
13. ### Factorization of type A We have discovered an algorithm to

determine the factorization given a diagram. ←→ S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 7 / 19
14. ### Factorization of type A We have discovered an algorithm to

determine the factorization given a diagram. ←→ S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 7 / 19
15. ### Factorization of type A We have discovered an algorithm to

determine the factorization given a diagram. ←→ By our algorithm, the diagram equals d4 d7 d3 d5 d8 d2 d6 d1 d7 . S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 7 / 19
16. ### Factorization of type A Let’s verify our calculation. d4 d7

d3 d5 d8 d2 d6 d1 d7 = = S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 8 / 19
17. ### Type B Temperley–Lieb diagrams A diagram must satisfy the restrictions

for type A and the following: • All decorations must be exposed to the west face; • There are a few technical restrictions on what decorations can occur where; • All loops (decorated or not) are replaced with a coeﬃcient, δ. S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 9 / 19
18. ### Type B Temperley–Lieb diagrams In TL(Bn ), we multiply diagrams

as in type A subject to the following relations: = = = 2 = 2 = 2 S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 10 / 19
19. ### Type B diagrams Example For TL(B3 ), we have the

following set of 4-diagrams as a basis: S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 11 / 19
20. ### Type B diagrams Example For TL(B3 ), we have the

following set of 4-diagrams as a basis: S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 11 / 19
21. ### Type B generators and relations For TL(Bn ), we deﬁne

n simple diagrams as follows (i ≥ 2): d1 = · · · 1 2 n n + 1 , di = 1 n + 1 · · · · · · i i + 1 S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 12 / 19
22. ### Type B generators and relations For TL(Bn ), we deﬁne

n simple diagrams as follows (i ≥ 2): d1 = · · · 1 2 n n + 1 , di = 1 n + 1 · · · · · · i i + 1 Theorem TL(Bn ) satisﬁes the following: S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 12 / 19
23. ### Type B generators and relations For TL(Bn ), we deﬁne

n simple diagrams as follows (i ≥ 2): d1 = · · · 1 2 n n + 1 , di = 1 n + 1 · · · · · · i i + 1 Theorem TL(Bn ) satisﬁes the following: • d2 i = δdi ; • di dj = dj di when |i − j| > 1; • di dj di = di when |i − j| = 1 and i, j = 1; S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 12 / 19
24. ### Type B generators and relations For TL(Bn ), we deﬁne

n simple diagrams as follows (i ≥ 2): d1 = · · · 1 2 n n + 1 , di = 1 n + 1 · · · · · · i i + 1 Theorem TL(Bn ) satisﬁes the following: • d2 i = δdi ; • di dj = dj di when |i − j| > 1; • di dj di = di when |i − j| = 1 and i, j = 1; • di dj di dj = 2di dj if {i, j} = {1, 2}. S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 12 / 19
25. ### Type B generators and relations For TL(Bn ), we deﬁne

n simple diagrams as follows (i ≥ 2): d1 = · · · 1 2 n n + 1 , di = 1 n + 1 · · · · · · i i + 1 Theorem TL(Bn ) satisﬁes the following: • d2 i = δdi ; • di dj = dj di when |i − j| > 1; • di dj di = di when |i − j| = 1 and i, j = 1; • di dj di dj = 2di dj if {i, j} = {1, 2}. Theorem The set of simple diagrams generate all diagrams in the Temperley–Lieb algebra of type Bn . S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 12 / 19
26. ### Proof of last relation Proof For i = 1 and

j = 2, d1 d2 d1 d2 = · · · · · · · · · · · · S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 13 / 19
27. ### Proof of last relation Proof For i = 1 and

j = 2, d1 d2 d1 d2 = · · · · · · · · · · · · = 2 · · · S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 13 / 19
28. ### Proof of last relation Proof For i = 1 and

j = 2, d1 d2 d1 d2 = · · · · · · · · · · · · = 2 · · · = 2 · · · · · · S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 13 / 19
29. ### Proof of last relation Proof For i = 1 and

j = 2, d1 d2 d1 d2 = · · · · · · · · · · · · = 2 · · · = 2 · · · · · · = 2d1 d2 S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 13 / 19
30. ### Product of simple diagrams in type B Example Here is

an example of a product of several simple diagrams in TL(B4 ). d1 d2 d4 d1 d3 d2 = = S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 14 / 19
31. ### Factorization of type B Example Using a diagram, let’s work

towards the factorization. S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 15 / 19
32. ### Factorization of type B Example Using a diagram, let’s work

towards the factorization. ←→ S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 15 / 19
33. ### Factorization of type B Example Using a diagram, let’s work

towards the factorization. ←→ S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 15 / 19
34. ### Factorization of type B Example Using a diagram, let’s work

towards the factorization. ←→ S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 15 / 19
35. ### Factorization of type B Example Using a diagram, let’s work

towards the factorization. ←→ S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 15 / 19
36. ### Factorization of type B Example Using a diagram, let’s work

towards the factorization. ←→ S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 15 / 19
37. ### Factorization of type B Example Using a diagram, let’s work

towards the factorization. ←→ S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 15 / 19
38. ### Factorization of type B Example Using a diagram, let’s work

towards the factorization. ←→ S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 15 / 19
39. ### Factorization of type B Example Using a diagram, let’s work

towards the factorization. ←→ S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 15 / 19
40. ### Factorization of type B Example Using a diagram, let’s work

towards the factorization. ←→ S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 15 / 19
41. ### Factorization of type B Example Using a diagram, let’s work

towards the factorization. ←→ Therefore, the original diagram equals d1 d4 d8 d10 d3 d5 d9 d2 d4 d6 d1 d3 d5 d7 d2 d4 d6 d8 d1 d3 d5 d2 d4 . S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 15 / 19
42. ### Factorization of type B Let’s check our calculation: d1 d4

d8 d10 d3 d5 d9 d2 d4 d6 d1 d3 d5 d7 d2 d4 d6 d8 d1 d3 d5 d2 d4 = = S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 16 / 19
43. ### An exception Example There is one case where we must

slightly adjust our algorithm. S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 17 / 19
44. ### An exception Example There is one case where we must

slightly adjust our algorithm. ←→ S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 17 / 19
45. ### An exception Example There is one case where we must

slightly adjust our algorithm. ←→ S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 17 / 19
46. ### An exception Example There is one case where we must

slightly adjust our algorithm. ←→ S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 17 / 19
47. ### An exception Example There is one case where we must

slightly adjust our algorithm. ←→ S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 17 / 19
48. ### An exception Example There is one case where we must

slightly adjust our algorithm. ←→ S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 17 / 19
49. ### An exception Example There is one case where we must

slightly adjust our algorithm. ←→ S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 17 / 19
50. ### An exception Example There is one case where we must

slightly adjust our algorithm. ←→ S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 17 / 19
51. ### An exception Example There is one case where we must

slightly adjust our algorithm. ←→ S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 17 / 19
52. ### An exception Example There is one case where we must

slightly adjust our algorithm. ←→ S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 17 / 19
53. ### An exception Example There is one case where we must

slightly adjust our algorithm. ←→ This diagram equals d5 d4 d6 d3 d2 d1 d2 d3 S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 17 / 19
54. ### An exception Here is the product of simple diagrams: d5

d4 d6 d3 d2 d1 d2 d3 = = S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 18 / 19
55. ### An exception Here is the product of simple diagrams: d5

d4 d6 d3 d2 d1 d2 d3 = = S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 18 / 19
56. ### Further work and acknowledgements Further work Will our algorithm work

on other types where diagrammatic representations are known to exist? For example, TL(Cn ): Acknowledgements • Northern Arizona University • Department of Mathematics and Statistics • Dr. Dana Ernst S. Salmon Visualizing diagram factorizations in TL algebras, Part 2 19 / 19