Exact product form for the anisotropic simple cubic lattice Green function

2006 ◽  
Vol 39 (16) ◽  
pp. 4119-4145 ◽  
Author(s):  
R T Delves ◽  
G S Joyce

The analytical properties of the simple cubic lattice Green function G ( t ) = 1 π 3 ∫ ∫ ∫ 0 π [ t − ( cos x 1 + cos x 2 + cos x 3 ) ] − 1 d x 1 d x 2 d x 3 are investigated. In particular, it is shown that tG(t) can be written in the form t G ( t ) = [ F ( 9 , − 3 4 ; 1 4 , 3 4 , 1 , 1 2 ; 9 / t 2 ) ] 2 , where F ( a , b ;α, β, γ, β; z) denotes a Heun function. The standard analytic continuation formulae for Heun functions are then used to derive various expansions for the Green function G − ( s ) ≡ G R ( s ) + i G I ( s ) = lim ∈→ 0 + G ( s − i ∈ ) ( 0 ≤ s < ∞ ) about the points s = 0,1 and 3. From these expansions accurate numerical values of G R ( s ) and G I ( s ) are obtained in the range 0≤ s ≤3, and certain new summation formulae for Heun functions of unit argum ent are deduced. Quadratic transformation formulae for the Green function G(t) are discussed, and a connexion between G(t) and the Lamé-Wangerin differential equation is established. It is also proved that G(t) can be expressed as a product of two complete elliptic integrals of the first kind. Finally, several applications of the results are made in lattice statistics.


2014 ◽  
Vol 31 (7) ◽  
pp. 070503 ◽  
Author(s):  
Shun Wang ◽  
Zhi-Yuan Xie ◽  
Jing Chen ◽  
Bruce Normand ◽  
Tao Xiang

1990 ◽  
Vol 59 (5-6) ◽  
pp. 1397-1429 ◽  
Author(s):  
M. Fukugita ◽  
H. Mino ◽  
M. Okawa ◽  
A. Ukawa

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