Undergrad 2D Ising Model Average Number of Domain Walls

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The discussion centers on the classical Ising model on a 2-D square lattice with no external field, focusing on the average internal energy per site at criticality, which is calculated to be u = -√2 when the coupling constant J is set to 1. The query involves determining the average number of domain walls per site, given that each domain wall contributes an energy of 2. The ground state energy is established as -2N, and the goal is to find the number of domain walls needed to raise the energy to -√2N. The derived equation, n_walls/N = (2 - √2)/2, is proposed as a solution to this energy transition. The logic and calculations presented appear to be sound and consistent with the principles of the Ising model.
thatboi
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Hi all,
I'm trying to see if my question/logic makes sense. Suppose I have a classical Ising model on a 2-D Square lattice with ##N## sites and 0 external field. There is an exact formula for the average internal energy per site, and at criticality it turns out to be ##u = -\sqrt{2}## where I have set the coupling constant ##J=1##. From here, I'd like to know if it is possible to find the average number of domain walls per site. I know each domain wall contributes energy ##2##. Now suppose the system is in its ground state (say all spin-up). Then the ground state energy is ##-2N##. I want to put in domain walls until the system energy increases to ##-\sqrt{2}N##, so we just need to solve ##-2N + 2n_{\text{walls}} = -\sqrt{2}N## and I get ##\frac{n_{\text{walls}}}{N} = \frac{2-\sqrt{2}}{2}##. Does this make sense?
 
Topic about reference frames, center of rotation, postion of origin etc Comoving ref. frame is frame that is attached to moving object, does that mean, in that frame translation and rotation of object is zero, because origin and axes(x,y,z) are fixed to object? Is it same if you place origin of frame at object center of mass or at object tail? What type of comoving frame exist? What is lab frame? If we talk about center of rotation do we always need to specified from what frame we observe?

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