Questions tagged [ising-model]
The Ising model of ferromagnetism in statistical mechanics consists of discrete bimodal (+1 or −1) "spin" (moment) variables in a simple Hamiltonian interacting with their next neighbors on a lattice. The one-dimensional variant does not evince a phase transition, but the two-dimensional square-lattice one does. Use for analog and generalized discrete models on several lattices and dimensions.
746 questions
1 vote
1 answer
66 views
Phase transition for first moments in the 2D random-bond Ising model
I have a very basic confusion about the 2D random-bond Ising model on a square lattice with Boltzmann weight $$\omega(J_{ij},\sigma_j)=\prod_{ij}(1-p)^{\delta_{J_{ij}=1}} p^{\delta_{J_{ij}=-1}} e^{-\...
4 votes
1 answer
137 views
Belief propagation equations for 2d Ising model
I'm working through Chapter 14 of Mezard and Montanari's Information,Physics,and Computation ("Belief Propagation"). I'm stuck on Exercise 14.10 in Section 14.4 about the 2d Ising model. In ...
9 votes
1 answer
304 views
Do we have good general models for solid-liquid phase transitions?
When reading about phase transitions, one quickly encounters the Ising model and its variants (spin glass, Potts, etc.). This model is used to explain ferromagnetism in a very satisfying way. It is ...
2 votes
0 answers
99 views
How do you represent Hamiltonian in Matrix Product Operator (MPO) representation?
I'm totally new to tensor networks, and I'm currently learning on my own from papers, tutorials, and videos. Right now, I'm trying to understand how to construct a Matrix Product Operator (MPO) for a ...
2 votes
0 answers
73 views
Parity transformation of Ising model (Di Francecso exercise)
I’m working on exercise 11.6 (a) in Conformal Field Theory by Di Francesco, Mathieu & Sénéchal (the “yellow book”). The problem defines the parity operation as $$ P:\qquad \psi(z)\longrightarrow\...
1 vote
1 answer
79 views
Kronecker's Delta definition in Ginzburg-Landau Ising Model
Introduction I'm studying the Ising Model described by the partition function: $$ Z = \sum_{\{s_{i}\}} \exp \bigg\{ \dfrac{1}{2} \, \vec{s} \, \mathbf{J} \, \vec{s}^{\,\scriptscriptstyle T} \bigg\} ...
2 votes
1 answer
129 views
Spectral gap lower-bound for transverse Ising model?
Not a physicist, apologies in case I lack rigor. Consider the following Hamiltonian: $$H=\sum_j \gamma_j\sigma^z_j\sigma^z_{j+1} + h\sum_j \sigma^x_j.$$ I am looking for a lower-bound to the spectral ...
3 votes
0 answers
113 views
Is it possible to analytically continue magnetization in one-dimensional Ising models?
I am asking about the infinitely long layered Ising model with a finite number of layers. The model is assumed to be invariant under translations along the direction in which it is infinite. All ...
1 vote
0 answers
122 views
Does Jordan-Wigner transformation produce the eigenvectors of Ising model?
Does Jordan-Wigner transformation produce the eigenvectors of Ising model? My understanding of diagonalisation for quantum mechanics is that it can help you calculate the propagator of a Hamiltonian ...
1 vote
0 answers
245 views
How is the general expression for critical exponents established?
The Wikipedia page on the critical exponents of the Ising model presents the following table: This page lists the critical exponents ($\alpha$, $\beta$, $\gamma$, ...) and their values for some ...
7 votes
2 answers
392 views
Is the susceptibility of a ferromagnet defined below the critical temperature?
The susceptibility is defined by $\chi = \partial M/ \partial H$ and for a ferromagnet above the critical temperature $T_C$, it is given by the Curie--Weiss law, $\chi \propto (T-T_C)^{-1}$. What ...
2 votes
0 answers
118 views
Can the index in the pre-exponential factor in the correlation function depend on the direction?
There is quite a lot of discussion on SE about correlation functions in lattice models. So I would say that it is well known that the two-spin (two-point) correlation function has the following ...
5 votes
0 answers
206 views
Coleman-Weinberg mechanism in $\phi^4$ theories in $d=4$
I'm not versed at all in high energy physics, I come from a statistical mechanics background, hence, all of what follow is far from my comfort zone. I will also talk about what is, I believe, the lore ...
2 votes
1 answer
159 views
Clarification about random field energy in Imry-Ma argument
Consider the Ising model in $d$ dimensions with a random local magnetic field $H_i$: $$ \mathcal{H} = -\frac{J}{2} \sum_{\langle i, j \rangle} S_i S_j - \sum_i H_i S_i $$ where $\langle i, j \rangle$ ...
0 votes
1 answer
135 views
Why the 2D Ising model shows a phase transition while the 1D does not? [duplicate]
I'm reading this article which shows the breakdown of the Mermin-Wagner theorem for a 2D system with finite size. In short, the Mermin-Wagner theorem states that no system with dimensionality d $\leq2$...