Accurate expansions of internal energy and specific heat of critical two-dimensional Ising model with free boundaries

TL;DR

This paper develops high-precision algorithms to accurately compute the internal energy and specific heat of the 2D Ising model with free boundaries, enabling precise estimation of edge and corner effects and finite-size scaling behaviors.

Contribution

The authors introduce the bond-propagation algorithms for internal energy and specific heat, achieving unprecedented accuracy and revealing detailed finite-size scaling and boundary effects in the 2D Ising model.

Findings

Achieved accuracy of 10^{-26} for internal energy and specific heat.

Conjectured exact values for edge and corner terms.

Identified absence of higher-order logarithmic corrections in certain lattice shapes.

Abstract

The bond-propagation (BP) algorithm for the specific heat of the two dimensional Ising model is developed and that for the internal energy is completed. Using these algorithms, we study the critical internal energy and specific heat of the model on the square lattice and triangular lattice with free boundaries. Comparing with previous works [X.-T. Wu {\it et al} Phys. Rev. E {\bf 86}, 041149 (2012) and Phys. Rev. E {\bf 87}, 022124 (2013)], we reach much higher accuracy ($10^{-26}$) of the internal energy and specific heat, compared to the accuracy $10^{-11}$ of the internal energy and $10^{-9}$ of the specific heat reached in the previous works. This leads to much more accurate estimations of the edge and corner terms. The exact values of some edge and corner terms are therefore conjectured. The accurate forms of finite-size scaling for the internal energy and specific heat are determined for the rectangle-shaped square lattice with various aspect ratios and various shaped triangular lattice. For the rectangle-shaped square and triangular lattices and the triangle-shaped triangular lattice, there is no logarithmic correction terms of order higher than 1/S, with S the area of the system. For the triangular lattice in rhombus, trapezoid and hexagonal shapes, there exist logarithmic correction terms of order higher than 1/S for the internal energy, and logarithmic correction terms of all orders for the specific heat.