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Low temperature series for spin-1/2 Ising specific heat on 2D square lattice.
4

%I #27 Apr 28 2024 04:56:18

%S 16,72,288,1200,5376,25480,125504,634608,3269680,17086168,90282240,

%T 481347152,2585485504,13974825960,75941188736,414593263952,

%U 2272626444528,12502223573304,68996534259040,381858968527680,2118806030647328,11783826597027256,65674579024955904

%N Low temperature series for spin-1/2 Ising specific heat on 2D square lattice.

%D S. R. Finch, Mathematical Constants, Cambridge, 2003, pp. 391-406.

%H G. A. Baker, <a href="https://doi.org/10.1103/PhysRev.129.99">Further application of the Padé approximant method to the Ising and Heisenberg models</a>, Phys. Rev. 129 (1963) 99-102.

%H I. G. Enting, A, J. Guttmann and I. Jensen, <a href="https://arxiv.org/abs/hep-lat/9410005">Low-Temperature Series Expansions for the Spin-1 Ising Model</a>, arXiv:hep-lat/9410005, 1994; J. Phys. A. 27 (1994) 6987-7006.

%H Steven R. Finch, <a href="http://www.people.fas.harvard.edu/~sfinch/constant/ising/ising.html">Lenz-Ising Constants</a> [broken link]

%H Steven R. Finch, <a href="http://web.archive.org/web/20010207201511/http://www.mathsoft.com:80/asolve/constant/ising/ising.html">Lenz-Ising Constants</a> [From the Wayback Machine]

%H <a href="/index/Sp#specific_heat">Index entries for sequences related to specific heat</a>

%F G.f.: ((u^4 + 30*u^2 + 1) * K(x) / Pi - (u+1)^4 * E(x) / Pi - 2*u*(u+1)^2) / (u^2 * (u^2-1)^2) = 4 * (f(u) * (f'(u)/u + f''(u)) - (f'(u))^2) / f(u)^2, where f(u) is the g.f. of A002890, K(x) and E(x) are the complete elliptic integrals, x = 4*(1-u)*sqrt(u)/(1+u)^2. - _Andrey Zabolotskiy_, Feb 15 2022

%F a(n) ~ 2 * (1 + sqrt(2))^(2*n+4) / (Pi*n). - _Vaclav Kotesovec_, Apr 28 2024

%t CoefficientList[Series[1/(Pi*x^2*(-1 + x^2)^2) * (-2*Pi*x*(1 + x)^2 - (1 + x)^4 * EllipticE[16*(-1 + x)^2*x/(1 + x)^4] + (1 + 30*x^2 + x^4) * EllipticK[16*(-1 + x)^2*x/(1 + x)^4]), {x, 0, 25}], x] (* _Vaclav Kotesovec_, Apr 28 2024 *)

%Y Cf. A002890 (partition function).

%Y Equals A029873/4 or A029874*8.

%K nonn

%O 0,1

%A _Steven Finch_

%E Terms a(18) and beyond from _Andrey Zabolotskiy_, Feb 15 2022