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In [[statistical mechanics]], the '''Temperley–Lieb algebra''' is an algebra from which are built certain [[transfer matrix|transfer matrices]], invented by [[Harold Neville Vazeille Temperley|Neville Temperley]] and [[Elliott H. Lieb|Elliott Lieb]]. It is also related to  [[integrable model]]s, [[knot theory]] and the [[braid group]], [[quantum groups]] and [[subfactor]]s of [[von Neumann algebra]]s.
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==Definition==
 
Let <math>R</math> be a [[commutative ring]] and fix <math>\delta \in R</math>. The Temperley–Lieb algebra <math>TL_n(\delta)</math> is the [[algebra (ring theory)|<math>R</math>-algebra]] generated by the elements <math>U_1, U_2, \ldots, U_{n-1}</math>, subject to the Jones relations:
*<math>U_i^2 = \delta U_i</math> for all <math>1 \leq i \leq n-1</math>
*<math>U_i U_{i+1} U_i = U_i</math> for all <math>1 \leq i \leq n-2</math>
*<math>U_i U_{i-1} U_i = U_i</math> for all <math>2 \leq i \leq n-1</math>
*<math>U_i U_j = U_j U_i</math> for all <math>1 \leq i,j \leq n-1</math> such that <math>|i-j| \neq 1</math>
 
<math>TL_n(\delta)</math> may be represented diagrammatically as the vector space over noncrossing pairings on a rectangle with ''n'' points on two opposite sides.  The five basis elements of <math>TL_3(\delta)</math> are the following:
 
[[File:Temperley-lieb (horizontal).svg|340px|Basis of the Temperley–Lieb algebra <math>TL_3(\delta)</math>]].
 
Multiplication on basis elements can be performed by placing two rectangles side by side, and replacing any closed loops by a factor of ''δ'', for example:
 
[[File:Factor-a.svg|50px]]  ×  [[File:Factor-b.svg|50px]]  =  [[File:Factor-a.svg|50px]][[File:Factor-b.svg|50px]]  =  δ  [[File:Concatenation-ab.svg|50px]].
 
The identity element is the diagram in which each point is connected to the one directly across the rectangle from it, and the generator <math>U_i</math> is the diagram in which the ''i''th point is connected to the ''i+1''th point, the ''2n − i + 1''th point is connected to the ''2n − i''th point, and all other points are connected to the point directly across the rectangle.  The generators of <math>TL_5(\delta)</math> are:
 
[[File:Temperley-Lieb (generateurs).svg|340px|Generators of the Temperley–Lieb algebra <math>TL_5(\delta)</math>]]
 
From left ot right, the unit 1 and the generators U<sub>1</sub>, U<sub>2</sub>, U<sub>3</sub>, U<sub>4</sub>.
 
The Jones relations can be seen graphically:
 
[[File:E 2 Temperley.svg|50px]] [[File:E 2 Temperley.svg|50px]]  =  δ  [[File:E 2 Temperley.svg|50px]]
 
[[File:E 2 Temperley.svg|50px]] [[File:E 3 Temperley.svg|50px]] [[File:E 2 Temperley.svg|50px]]  =  [[File:E 2 Temperley.svg|50px]]
 
[[File:E 1 Temperley.svg|50px]] [[File:E 4 Temperley.svg|50px]]  =  [[File:E 4 Temperley.svg|50px]] [[File:E 1 Temperley.svg|50px]]
 
==The Temperley-Lieb Hamiltonian==
 
Consider an interaction-round-a-face model e.g. a square [[Lattice model (physics)|lattice model]] and let <math>L</math> be the number of sites on the lattice. Following Temperley and Lieb<ref>Temperley N. and Lieb E., (1971), Proc. R. Soc. A 322 251.</ref> we define the Temperley-Lieb [[Hamiltonian (quantum mechanics)|hamiltonian]] (the TL hamiltonian) as
 
<math> \mathcal{H} = \sum_{j=1}^{L-1} (1 - e_j) </math>
 
where <math>e_j =  U(\lambda)/\sin\lambda</math>, for some spectral parameter <math>\lambda \in R</math>.
 
===Applications===
 
We will firstly consider the case <math>L = 3</math>. The TL hamiltonian is <math>\mathcal{H} = 2 - e_1 - e_2 </math>, namely
 
<math>\mathcal{H}</math>  =  2  [[File:Unit 3 Temperley.svg|50px]]  -  [[File:E 1 3 Temperley.svg|50px]]  -  [[File:E 2 3 Temperley.svg|50px]].
 
We have two possible states,
 
[[File:BS1-Temperley-Lieb.svg|40px]] and [[File:BS2-Temperley-Lieb.svg|40px]].
 
In acting by <math>\mathcal{H}</math> on these states, we find
 
<math>\mathcal{H}</math> [[File:BS1-Temperley-Lieb.svg|40px]]  =  2  [[File:Unit 3 Temperley.svg|50px]][[File:BS1-Temperley-Lieb.svg|40px]]  -  [[File:E 1 3 Temperley.svg|50px]][[File:BS1-Temperley-Lieb.svg|40px]]  -  [[File:E 2 3 Temperley.svg|50px]][[File:BS1-Temperley-Lieb.svg|40px]]  =  [[File:BS1-Temperley-Lieb.svg|40px]]  -  [[File:BS2-Temperley-Lieb.svg|40px]],
 
and
 
<math>\mathcal{H}</math> [[File:BS2-Temperley-Lieb.svg|40px]]  =  2  [[File:Unit 3 Temperley.svg|50px]][[File:BS2-Temperley-Lieb.svg|40px]]  -  [[File:E 1 3 Temperley.svg|50px]][[File:BS2-Temperley-Lieb.svg|40px]]  -  [[File:E 2 3 Temperley.svg|50px]][[File:BS2-Temperley-Lieb.svg|40px]]  =  -  [[File:BS1-Temperley-Lieb.svg|40px]]  +  [[File:BS2-Temperley-Lieb.svg|40px]].
 
Writing <math>\mathcal{H}</math> as a matrix in the basis of possible states we have,
 
<math> \mathcal{H} = \left(\begin{array}{rr}
1 & -1\\
-1 & 1
\end{array}\right)
</math>
 
The eigenvector of <math>\mathcal{H}</math> with the ''lowest'' [[Eigenvalues and eigenvectors|eigenvalue]] is known as the [[ground state]]. In this case, the lowest eigenvalue <math>\lambda_0</math> for <math>\mathcal{H}</math> is <math>\lambda_0 = 0</math>. The corresponding [[Eigenvalues and eigenvectors|eigenvector]] is <math>\psi_0 = (1, 1)</math>. As we vary the number of sites <math>L</math> we find the following table<ref name="bach">Batchelor M., de Gier J. and Nienhuis B., (2001), The quantum symmetric <math>XXZ</math> chain at <math>\Delta = -1/2</math>, alternating-sign matrices and plane partitions, J. Phys. A 34, L265-L270.</ref>
 
{| class="wikitable"
|-
! <math>L</math>
! <math>\psi_0</math>
! <math>L</math>
! <math>\psi_0</math>
|-
| 2
| (1)
|3
|(1, 1)
|-
| 4
|(2, 1)
|5
|<math>(3_3, 1_2)</math>
|-
| 6
| <math>(11, 5_2,4, 1)</math>
|7
|<math>(26_4, 10_2, 9_2, 8_2, 5_2, 1_2)</math>
|-
|8
|<math>(170, 75_2, 71, 56_2, 50, 30, 14_4, 6, 1)</math>
|9
|<math>(646, \ldots)</math>
|-
|<math>\vdots</math>
|<math>\vdots</math>
|<math>\vdots</math>
|<math>\vdots</math>
|-
|}
 
where we have use the notation <math>m_n = (m, \ldots, m)</math> <math>n</math>-times i.e. <math>5_2 = (5, 5)</math>.
 
===Combinatorial Properties===
An interesting observation is that the largest components of the ground state of <math>\mathcal{H}</math> have a combinatorial enumeration as we vary the number of sites,<ref>de Gier J., (2005), Loops, matchings and alternating-sign matrices, Discrete Mathematics Volume 298, Issues 1-3, Pages 365-388.</ref> as was first observed by [[Murray Batchelor]], Jan de Gier and Bernard Nienhuis.<ref name="bach">Batchelor M., de Gier J. and Nienhuis B., (2001), The quantum symmetric <math>XXZ</math> chain at <math>\Delta = -1/2</math>, alternating-sign matrices and plane partitions, J. Phys. A 34, L265-L270.</ref> Using the resources of the [[on-line encyclopedia of integer sequences]], Batchelor ''et al.'' found, for an even numbers of sites 
 
<math>
1, 2, 11, 170, \ldots = \prod_{j=0}^{n-1} \left( 3j + 1\right)\frac{ (2j)!(6j)!}{(4j)!(4j + 1)!}
</math>
 
and for an odd numbers of sites
 
<math>
1, 3, 26, 646, \ldots = \prod_{j=0}^{n-1} (3j+2)\frac{ (2j + 2)!(6j + 3)!}{(4j + 2)!(4j + 3)!}.
</math>
 
Surprisingly, these sequences corresponded to well known combinatorial objects. For <math>L</math> even, this sequence corresponded to cyclically symmetric transpose complement plane partitions and for <math>L</math> odd these corresponded to <math>(2n+1)\times(2n+1)</math> [[Alternating sign matrix|alternating sign matrices]] symmetric about the vertical axis.
 
==References==
 
<references/>
 
==Further reading==
*[[Louis H. Kauffman]], [http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V1J-45DHSCR-J&_user=10&_coverDate=12%2F31%2F1987&_rdoc=9&_fmt=high&_orig=browse&_srch=doc-info(%23toc%235676%231987%23999739996%23292694%23FLP%23display%23Volume)&_cdi=5676&_sort=d&_docanchor=&_ct=9&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=cca311a0762fc3d6a7a6f284a10a5c68 ''State Models and the Jones Polynomial''.] [[Topology (journal)|Topology]], 26(3):395-407, 1987.
*[[Rodney J. Baxter|R.J. Baxter]], [http://tpsrv.anu.edu.au/Members/baxter/book ''Exactly solved models in statistical mechanics''] Academic Press Inc. (1982)
*[[Harold Neville Vazeille Temperley|N. Temperley]], [[Elliott H. Lieb|E. Lieb]], [http://www.jstor.org/stable/77727 ''Relations between the percolation and colouring problem and other graph-theoretical problems associated with regular planar lattices: some exact results for the percolation problem''.] Proceedings of the Royal Society Series A 322 (1971), 251-280.
 
{{DEFAULTSORT:Temperley-Lieb algebra}}
[[Category:Von Neumann algebras]]
[[Category:Algebra]]
[[Category:Knot theory]]
[[Category:Braids]]
[[Category:Diagram algebras]]

Latest revision as of 15:18, 29 November 2014

Emilia Shryock is my title but you can call me anything you like. For a whilst I've been in South Dakota and my parents live close by. To play baseball is the pastime he will never quit doing. My day job is a meter reader.

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