The Stack Overflow podcast is back! Listen to an interview with our new CEO.

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.

Filter by
Sorted by
Tagged with
0
votes
1answer
37 views

(Transverse) Ising Model Higher Than Four Dimensions

First question: Wiki says Ising Model higher than four dimensions can be described by mean field theory. What is the reason for this? Does this mean there is no phase transition for higher dimensions ...
1
vote
1answer
58 views

Magnetization of the Ising model for an asymptotic vanishing magnetic field

I am considering the following ferromagnetic Hamiltonian for the 2-d Ising Model, say with periodic boundary condition in the torus $\Lambda_n=\mathbb{T}^2_n := (\mathbb{Z}/ \mathbb{Z}_n)^2$: $$ H_n(\...
-2
votes
0answers
33 views

Partition function of Ising model?

Hello, I am taking a stat mechanics course from a non physics background and above picture is the question I am trying to solve for your reference. I was wondering for the partition function of Ising ...
3
votes
1answer
52 views

Understanding Periodic and Anti-periodic boundary condition for Jordan-Wigner transformation

In the study of spin chains with periodic boundary condition ($S_{N+1}=S_{1}$) when one applies Jordan-Wigner transformation to map the spin chain to spinless fermion chain, one needs to make sure in ...
1
vote
0answers
59 views

Critical exponent mean field Ising model

I am given the following expression for the free energy: $$f = \frac{1}{2}r_0 m^2+um^4+vm^6,$$ where $r_0=k_B (T-T_c)$ with $T_c$ the critical temperature and $u=\frac{1}{12}k_B T$ and $v=\frac{1}{...
1
vote
1answer
63 views

1D Ising model thermodynamic limit

The partition function for the infinite range Ising model is $$Z(\beta ,h)=\int_{-\infty}^{\infty}dm \frac{1}{\sqrt{2\pi/N\beta J}} e^{-Ng(m)}$$ where $g(m) = \frac{\beta J}{2}m^2 - \ln\left[2\cosh(\...
0
votes
0answers
35 views

Correlation functions of quantum Ising models

I have a single technical question regarding a statement on page 7 of the paper "Dynamical quantum correlations of Ising models on an arbitrary lattice and their resilience to decoherence". The paper ...
2
votes
0answers
32 views

Eigenfunctions and eigenvalues XY Ising model

In the XY Ising model we have the following Hamiltonian: $$H=-J\sum_i \cos(\theta_i-\theta_{i+1}).$$ From this I found that $\langle \theta_i| T | \theta_{i+1}\rangle = \exp(\beta J \cos(\theta_i-\...
0
votes
0answers
58 views

Eigenvalues of transfer matrix Ising model spin 1 system

I am calculating the partition function of an Ising model with spin 1 ($\sigma_i \in \{-1,0,1\}$) for $n$ sites. The following Hamiltonian has been used: $$H = -J \sum_{i=1}^{n} \sigma_i\sigma_{i+1},$...
1
vote
0answers
58 views

Calculating the local energy in neural network quantum state

given a Hamiltonian of Heisenberg 1D model as following: $$H = -J\sum_{I}\sigma_{i}^{z}\sigma_{i+1}^{z}$$ I am trying to solve it with a neural network function given by Restricted Boltzmann machine ...
0
votes
0answers
64 views

Generalised Ising models?

Are there generalised Ising models: The underslying mesh/connectivity is completely arbitrary - non rectangular, 3D...ND, complete connectivity should be possible The interaction potential is ...
2
votes
0answers
38 views

Mathematical Rigorousness of Taking the Thermodynamical limit of a finite size quantum model

Suppose I have nearest Neighbour Quantum Ising model with a transverse field. $$\hat{H} = \sum_{i}S^{x}_iS^{x}_{i+1} + h\sum_i S^{z}_i$$ Through Jordan-Wigner and Bogoliubov transformation, one finds ...
0
votes
0answers
40 views

Quantum Monte Carlo Loop Algorithm for quantum spin: why is the freezing graph present in ferromagnetic Ising model?

I study the loop algorithm (Evertz et al). I cannot understand, why the freezing graph type where we have to flip all 4 spins together is not present for the quantum-XY model and the anti-/...
7
votes
2answers
255 views

Correlation length anisotropy in the 2D Ising model

In the Ising model, the two-spin correlation function is $$ C(\vec{r}) = \langle \sigma_{\vec{r}_0+\vec{r}}\sigma_{\vec{r}_0}\rangle - \langle \sigma_{\vec{r}_0+\vec{r}}\rangle \langle \sigma_{\vec{r}...
0
votes
0answers
26 views

RG of Ising model whose Hamiltonian is represented with Kronecker delta

Let $H$ be hamiltonian, $i$ the index of a spin, and $S_i = \pm 1 $ the $i$-th spin's value. When 1D Ising model's hamiltonian is represented as $$ H = - J \sum _i S_i S_{i + 1}\ \ \ (J > 0), $$ ...
1
vote
1answer
35 views

Why are the autocorrelations larger for the energy at the critical temperature?

Considering a simulation with the Swendsen-Wang algorithm for the 3-D cubic lattice I wanted to have a look at the auto-correlations, and expecting it to be quite small considering Swendsen-Wang is a ...
2
votes
1answer
58 views

References and papers to distinguish between the Heisenberg and Ising Model

Does anybody have any good papers or references to explain the differences between the Heisenberg model and Ising model? To the best of my knowledge, I am aware that the Hamiltonians are similar, ...
1
vote
0answers
24 views

Why do the Binder Cumulants of different system sizes intersect at the critical point?

When Monte Carlo simulations are performed for spin models (Ising model etc.) the critical temperature can be found by simulating for different lattice sizes and plotting the Binder Cumulant for them. ...
1
vote
2answers
58 views

Different concepts of phase transitions in spin models

I am currently revising the lecture notes in which different spin systems are analyzed, focussing on the occurrence (or absence) of phase transitions. Different techniques are applied to analyze the ...
0
votes
0answers
70 views

Questions on mean field theory and the enforcement of local spin conserving constraints

Hello Physics StackExchange community, I've recently been working on a problem that seems like it should be straightforward, but I can't seem to overcome what seems to be a basic obstacle. I'll try ...
0
votes
0answers
31 views

How to get mean field critical exponents for this Hamiltonian?

$$ \mathcal{H} = -J \sum_{\langle ij\rangle} \sum_{\alpha=1}^N s_i{}^\alpha s_j{}^\alpha -g \sum_{\langle ij\rangle} \sum_{\alpha\beta} (s_i{}^\alpha s_j{}^\alpha) (s_i{}^\beta s_j{}^\beta) $$ Above ...
0
votes
0answers
31 views

Order parameter for spin-1 ising model

I'm curious what the order parameter would be for a spin-1 Ising model for magnetism and anti-ferromagnetism. So if spin's can take the value's -1,0 and 1.
0
votes
0answers
44 views

Derivation of the Ising free energy close to a critical point

In "Statistical physics of fields" Mehran Kardar states that the Ising free energy scales with, $$ f(t,h)\sim t^\alpha g_f\left(\frac{h}{t^\Delta}\right), $$ wherein $t=\vert T-T_c\vert/T_c$ ...
5
votes
0answers
67 views

What are the excitations in the near critical 2D-Ising model in a magnetic field?

Apparently it is well known that the 2D Ising model with $T=T_C$ in a small magnetic field has a mass gap and correlation length $\xi \sim h^{- \frac{8}{15}} $. Further, in a paper in 1989 ...
1
vote
0answers
41 views

Asymmetric hysteresis loop in Ising Model

I am doing simulations using Monte Carlo of the 2 dimensional square lattice with periodic boundary conditions Ising model, and i obtain hysteresis loops, which are asymmetric. Meaning i obtain a ...
0
votes
0answers
56 views

How to calculate the autocorrelation function of magnetic susceptibility for the Ising model?

In the paper Wolff U. 1989. Physics Letters B. 228(3):379–82, the autocorrelation time of susceptibility, $\tau_\chi$ was calculated, but the way to do so was not clearly explained in the paper. To ...
4
votes
1answer
78 views

Water boiling and 3D Ising model

I've been told for a long time that water boiling near critical temperature and the 3D Ising model near critical temperature are described by the same laws, and give a CFT. This is usually mentioned ...
0
votes
1answer
54 views

How to deduce the formula of the Correlation Length on a periodic lattice?

Sometimes in Monte Carlo simulations we need to compute the correlation length, but this is a hard task without a formula. However, for instance, in an periodic cubic lattice of $L^3$ spins, some ...
1
vote
0answers
34 views

Magnetic susceptibility vs Monte Carlo step

I have some difficulties in understanding how to compute the magnetic susceptibility from a Monte Carlo simulation of the Ising model. I know that it is related to the magnetisation of the system by $\...
1
vote
1answer
31 views

Ginzburg Criterion (Ising model)

In my statistical field theory class, we were told that we want the magnetization fluctuations in the Ising model to be smaller than their background. Specifically this was written as $$\langle\phi^2\...
0
votes
1answer
35 views

Average magnetisation in the Ising Model

The Ising Model has energy given by $$ E=-B \sum_{i} s_{i}-J \sum_{\langle i, j\rangle} s_{i} s_{j} $$ where $\langle i, j\rangle$ indicates that the second sum is over each pair of nearest ...
4
votes
0answers
81 views

Renormalization Group - Scaling fields and physical critical exponents (1D Ising model)

This is related to this question: Critical exponents and scaling dimensions from RG theory. TLDR: How to compute physical critical exponents $\alpha, \beta, \gamma, etc$ from the RG exponents when ...
1
vote
0answers
58 views

Length of domain wall in Ising model

A subquestion of a homework for my statistical mechanics class this week asked of the 2d Domain wall Ising model approximation: "Now argue that for the formation of a domain wall separating the ...
0
votes
2answers
56 views

Evaluating the quality of Monte Carlo simulations for 3D Ising model

Suppose I have developed a new Monte Carlo method, and I plan to test this method on studying the magnetization of a 3D Ising model at some non-zero temperature $T$. The coupling is nearest neighbor, ...
0
votes
1answer
57 views

Correlation function at zero distance

I'm confused about the definition of the correlation function (at equal time). I know it is defined from the thermal average of the scalar product of two random variables (for example the spins of a ...
1
vote
0answers
42 views

Scaling limit of the Ising model with nonzero order parameter

I'm interested in simulating the continuum limit of the 2D Ising model $$H=J\sum_{\langle i j\rangle} s_i s_j+ h \sum_i s_i$$ In one dimension I can fix average magnetization $m=\langle s\rangle$ and ...
2
votes
1answer
40 views

Magnetic susceptibility error by binning Monte Carlo

I am studying the 2D Ising model using Monte Carlo simulations and I have learned the binning (or batching) method for the error statistical analysis. Following this discussion https://books.google.it/...
1
vote
1answer
60 views

Microscopic origin of Ising model

A typical Hamiltonian for Ising model is $$ H=-\sum_{i,j} J_{ij}S_iS_j - K \sum_i S_i.$$ In many references we can find exact solutions for special cases, mean-field approach, phase transition, and ...
5
votes
1answer
154 views

Symmetry transformations that are self-inverse and global symmetries of the Hamiltonian

I have the simplified Ising model. The Hamiltonian is given by $$ \mathcal{H} = -\mathrm{J}\sum_{<ij,i' j'>} \sigma_{ij} \sigma_{i'j'}. $$ Where the sum over $<ij,i'j'>$ means just the ...
0
votes
1answer
92 views

Ferromagnetism - computational physics

The autocorrelation of the magnetisation is plotted for the Ising model of a ferromagnet. The critical temperature is 2.3 J/k Is this the expected behaviour? as in, it decays super fast for ...
1
vote
0answers
28 views

Critical parameter for 1D quantum system corresponding to $T_c$ of 2D Classical model

Utilizing the fact that there is a correspondence between a $d$ dimensional quantum system and a $d+1$ dimensional classical system (c.f. Trotter Decomposition), my question regards what the critical ...
4
votes
1answer
55 views

Dynamics of the Ising model and its Monte Carlo sampling

The Ising model is a statistical mechanical model of ferromagnetism that defines the energy of a collection of magnetic dipoles arranged in a lattice, hence, through the Boltzmann distribution, also ...
0
votes
1answer
563 views

What is the Kitaev Model and why it became so popular? [closed]

I am seeing Kitaev Model everywhere. It feels like the spin-glass model of our time. How the Kitaev model differ from spin-glass and why it can be used everywhere? Looking at equation 1 here suggests ...
0
votes
0answers
49 views

Total momentum of multiparticle eigenstates of discrete translation operator

I will try to frame my question using the transverse field Ising model in the low spin-coupling limit as motivation. I'll begin by discussing a case I believe I understand, that of eigenstates of ...
0
votes
1answer
122 views

Does the critical dynamical exponent z of a 2D Ising model (simulated with Metropolis) vary with the temperature?

I have found in the literature that the critical dynamical exponent $z$ of an Ising model simulated with a local algorithm (such as Metropolis) is something around 2 near the critical temperature, ...
1
vote
0answers
46 views

RG of 2D Ising with nonzero magnetic field on triangular lattice

I am given the Ising Hamiltonian \begin{align} H = K \sum_{<ij>}S_i S_j + h \sum_i S_i, \quad K>0 \end{align} to set up a real-space block-spin RG, where the renormalized spins are ...
2
votes
0answers
39 views

How to quantify frustration for spin models with long range interactions?

Consider the following Hamiltonian: $$ H=-\sum_{i\neq j}J_{ij}S_iS_j-\sum_i H_iS_i $$ where $S_i\in\{-1,1\}$, and the summed pair $i,j$ can be any two distinct indices (not necessary adjacent spins)....
0
votes
1answer
39 views

Using FFT for spins in a non-cubic crystal lattice

Classical Ising/XY/Heisenberg models on a crystal lattice are commonly used to model magnetic materials. These can be studied using Monte Carlo simulations on a computer. Magnetic systems are often ...
1
vote
0answers
61 views

How do we understand the results of $1/N$ or $\epsilon$ expansion beyond leading orders?

When we do $1/N$ expansions in, say, 2+1$D$ $O(N)$ models and try to extract all kinds of critical exponents from it, we get the following results for the scaling dimensions of various operators up to ...
3
votes
0answers
47 views

Correlation length amplitudes in Ising 2D model

I am reading the article about Universal amplitude ratios in the 2D Ising model (https://arxiv.org/abs/hep-th/9710019) by G. Delfino. I have a question about page 3 of the paper. For a magnetic ...