Two-dimensional Potts Model Research Articles

Lattice Realization of Complex Conformal Field Theories: Two-Dimensional Potts Model with Q>4 States.

The two-dimensional Q-state Potts model with real couplings has a first-order transition for Q>4. We study a loop-model realization in which Q is a continuous parameter. This model allows for the collision of a critical and a tricritical fixed point at Q=4, which then emerge as complex conformally invariant theories at Q>4, or even complex Q, for suitable complex coupling constants. All critical exponents can be obtained as analytic continuation of known exact results for Q≤4. We verify this scenario in detail for Q=5 using transfer-matrix computations.

Learning the phase transitions of two-dimensional Potts model with a pre-trained one-dimensional neural network

Conventionally, the training of a neural network for learning phases of matter uses real physical quantities as the training set. However, it has been demonstrated in several studies that this may not be required. Here we investigate the phase transitions of the two-dimensional (2D) q-state Potts models on the square lattice using a pre-trained neural network (NN). The employed NN was trained previously using two artificially made configurations as the training set. Hence no training is conducted for the present study. Remarkably, the used NN not only calculates the critical points of the considered phase transitions precisely, but also determines the nature of these phase transitions definitely without ambiguity. Our results as well as the outcomes found previously suggest that training a NN using real physical quantities as the training set is not required to obtain a working NN. These unconventional studies also imply that if the configuration space of a system can be classified into two categories, then the NN considered here is likely applicable to study the phase transition of that system. Comparison between our approach and other known NN methods for studying the 2D q-state Potts models is briefly discussed as well.

Расчет относительных дисперсий намагниченности, теплоемкости и восприимчивости в двумерной слабо разбавленной трехкомпонентной модели Поттса

Using the Monte Carlo method, the relative dispersions of magnetization Rm, heat capacity Rc and susceptibility Rchi are calculated for a weakly diluted three-component Potts model on a square lattice at a spin concentration p=0.90. It is revealed that the introduction of disorder in the form of non-magnetic impurities into the two-dimensional Potts model leads to non-zero values for Rm, Rc, and Rchi at the critical point. It is found that these values decrease markedly for systems with linear dimensions L>80.

Phase Transitions in Two-Dimensional Potts Models on the Hexagonal Lattice

Phase Transitions in Two-Dimensional Potts Models on the Hexagonal Lattice

Энергетический анализ магнитных структур основного состояния модели Поттса

Based on the Wang-Landau algorithm, the Monte Carlo method was used to perform an energy analysis of the magnetic structures of the ground state of the two-dimensional Potts model with the number of spin states $q=4$ on a triangular lattice, taking into account the exchange interactions of the first $J_1$ and second $J_2$ nearest neighbors. The studies were carried out for the value of the interaction of the second nearest neighbors in the interval $-2.0 \leq J_2 \leq 0.0$. The magnetic structures of the ground state are determined for different values of the interaction of the second nearest neighbors. It is found that a change in the magnitude of the interaction of the second nearest neighbors in this model leads to a change in the magnetic ordering.

Phase transitions in the frustrated Potts model in the magnetic field

The influence of the magnetic field on phase transitions, magnetic and thermodynamic properties of the two-dimensional Potts model with q = 4 on a hexagonal lattice with the nearest and next-nearest neighbors interactions is studied using the replica algorithm of the Monte Carlo method . The studies are carried out in the magnetic field range −1.0 ≤ h ≤ 7.0 with a step of 0.1. A phase diagram of the magnetization dependence on magnetic field value is plotted. It is found that a first-order phase transition is observed in the ranges 0.0 ≤ h ≤ 1.0 and 2.0 ≤ h ≤ 3.5. A second-order phase transition is observed for the magnetic field value h = 1.5. It is revealed that there is no the ground-state degeneracy and the phase transition is smeared for magnetic field values of h ≥ 4.0. A phase diagram of the dependence of the critical temperature on the magnitude of the interaction of the next-nearest neighbors is constructed. • A two-dimensional frustrated Potts model are investigated. • The magnetic structures of the ground-state for considered model are obtained. • The phase diagram is plotted. • It is shown that magnetic fields destroyed the phase transition.

Phase Transitions in the Diluted Two-Dimensional Potts Model with the Number of Spin States q = 3 on a Square Lattice

Phase Transitions in the Diluted Two-Dimensional Potts Model with the Number of Spin States q = 3 on a Square Lattice

Computer simulation of phase transitions in low-dimensional Potts models

The Monte Carlo method is used to study phase transitions in the two-dimensional Potts model with the number of states spin q=3 on square and hexagonal lattices. Considered systems with linear dimensions Lx L=N, L=21/102. The obtained numerical data indicate that in the considered In the Potts model, a second-order phase transition is observed in accordance with the analytical theory. The Binder cumulants method of the fourth order determines the values of the critical points of the Potts model on different lattices. Keywords: Phase transitions, Potts model, Monte Carlo, thermodynamic parameters, critical temperature.

Компьютерное моделирование фазовых переходов в низкоразмерных моделях Поттса

The Monte Carlo method is used to study phase transitions in the two-dimensional Potts model with the number of states spin q = 3 on square and hexagonal lattices. Considered systems with linear dimensions L × L = N, L = 21 ÷ 102. The obtained numerical data indicate that in the considered In the Potts model, a second-order phase transition is observed in accordance with the analytical theory. The Binder cumulants method of the fourth order determines the values ​​of the critical points of the Potts model on different lattices.

Energy analysis of magnetic structures of the ground state of the Potts model with competing exchange interactions

Based on the Wang--Landau algorithm, the Monte Carlo method was used to study the magnetic structures of the ground state and the thermodynamic properties of the two-dimensional Potts model with the number of spin states q=4 on a triangular lattice, taking into account the exchange interactions of the first J1 and second J2 nearest neighbors. The studies were carried out for the value of the interaction of the second nearest neighbors in the range -2.0≤ J2≤0.0. The magnetic structures of the ground state are constructed in the interval considered. An energy analysis of the magnetic structures of the ground state has been carried out. A phase diagram of the dependence of the critical temperature on the value of J2 is constructed. It is shown that taking into account the interactions of the second nearest neighbors leads to the appearance of frustrations and violation of the magnetic ordering. Keywords: Frustrations, magnetic structures, Monte Carlo method, Potts model.

Исследование влияния слабых магнитных полей на термодинамические свойства модели Поттса с числом состояний спина q=4 на гексагональной решетке

The replica exchange algorithm of the Monte Carlo method was used to study phase transitions and thermodynamic properties of the two-dimensional Potts model with the number of spin states q = 4 on a hexagonal lattice in weak magnetic fields. The studies were carried out for the interval of the magnetic field value 0.0 ≤ Н ≤ 3.0 with a step of 1.0. It is found that a first-order phase transition is observed in the considered range of field values.

Investigation of the influence of weak magnetic fields on thermodynamic properties of the Potts model with the number of spin states q=4 on a hexagonal lattice

The replica exchange algorithm of the Monte Carlo method was used to study phase transitions and thermodynamic properties of the two-dimensional Potts model with the number of spin states q=4 on a hexagonal lattice in weak magnetic fields. The studies were carried out for the interval of the magnetic field value 0.0≤ H≤3.0 with a step of 1.0. It is found that a first-order phase transition is observed in the considered range of field values. Keywords: Frustration, Phase transitions, Monte Carlo method, Potts model.

Энергетический анализ магнитных структур основного состояния модели Поттса с конкурирующими обменными взаимодействиями

Based on the Wang-Landau algorithm, the Monte Carlo method was used to study the magnetic structures of the ground state and the thermodynamic properties of the two-dimensional Potts model with the number of spin states q=4 on a triangular lattice, taking into account the exchange interactions of the first J1 and second J2 nearest neighbors. The studies were carried out for the value of the interaction of the second nearest neighbors in the range -2.0≤ J2≤0.0. The magnetic structures of the ground state are constructed in the interval considered. An energy analysis of the magnetic structures of the ground state has been carried out. A phase diagram of the dependence of the critical temperature on the value of J2 is constructed. It is shown that taking into account the interactions of the second nearest neighbors leads to the appearance of frustrations and violation of the magnetic ordering.

Компьютерное моделирование двумерной модели Поттса с конкурирующими обменными взаимодействиями

The phase transitions and thermodynamic properties of the two-dimensional Potts model with the number of spin states $q = 4$ on a hexagonal lattice with competing exchange interactions have been investigated on the basis of the Wang-Landau algorithm by the Monte Carlo method. It is shown that taking into account the antiferromagnetic interactions of the next-nearest neighbors leads to a violation of the magnetic ordering and to the appearance of frustration.

Low-temperature universal dynamics of the bidimensional Potts model in the large q limit

We study the low temperature quench dynamics of the two-dimensional Potts model in the limit of a large number of states, q ≫ 1. We identify a q-independent crossover temperature (the pseudo spinodal) below which no high-temperature metastability stops the curvature driven coarsening process. At short length scales, the latter is decorated by freezing for some lattice geometries, notably the square one. With simple analytic arguments, we evaluate the relevant time-scale in the coarsening regime, which turns out to be of Arrhenius form and independent of q for large q. Once taken into account, dynamic scaling is universal.

Multiple metastable states in an off-lattice Potts model

The interactions between a group of components are commonly studied in several areas of science (social science, biology, material science, complex dynamical systems, among others) using the methods of thermodynamics and statistical mechanics. In this work we study the properties of the recently proposed off-lattice, two-dimensional Potts model (Davis et al., 2014), originally motivated by the dynamics of agent opinions, and which is described by a Hamiltonian obtained by a maximum entropy inference procedure. We performed microcanonical and canonical Monte Carlo simulations of the first-order phase transition in the model, revealing a caloric curve with metastable regions. Furthermore, we report a “switching” behavior between multiple metastable states. We also note that the thermodynamics of the model has striking similarities with systems having long-range interactions, even though the interactions are short-ranged.

Inverse renormalization group based on image super-resolution using deep convolutional networks

The inverse renormalization group is studied based on the image super-resolution using the deep convolutional neural networks. We consider the improved correlation configuration instead of spin configuration for the spin models, such as the two-dimensional Ising and three-state Potts models. We propose a block-cluster transformation as an alternative to the block-spin transformation in dealing with the improved estimators. In the framework of the dual Monte Carlo algorithm, the block-cluster transformation is regarded as a transformation in the graph degrees of freedom, whereas the block-spin transformation is that in the spin degrees of freedom. We demonstrate that the renormalized improved correlation configuration successfully reproduces the original configuration at all the temperatures by the super-resolution scheme. Using the rule of enlargement, we repeatedly make inverse renormalization procedure to generate larger correlation configurations. To connect thermodynamics, an approximate temperature rescaling is discussed. The enlarged systems generated using the super-resolution satisfy the finite-size scaling.

Calculation of relative dispersions of magnetization, susceptibility, and heat capacity in a two-dimensional weakly diluted Potts model based on computer simulation methods

The Monte Carlo method was used to calculate the relative dispersions of the magnetization Rm, susceptibility Rχ, and heat capacity RC for a weakly diluted impurity Potts model with the number of spin states q = 4. It is shown that the introduction of disorder in the form of nonmagnetic impurities into the two-dimensional Potts model with q = 4 on square lattice leads to nonzero values for Rm, Rχ, and RC at the critical point.

Effect of quenched non-magnetic impurities on phase transitions in a two-dimensional Potts model

The Wolff cluster Monte Carlo algorithm is used to investigate the effect of frozen nonmagnetic canonically distributed impurities on the phase transitions in a two-dimensional Potts model with the spin state q = 5. Systems with linear dimensions L = 20–160 at spin concentrations p = 1.0 and 0.9 are considered. Using the fourth-order Binder cumulant method and the histogram analysis method it is shown that if a weak quenched disorder in the form of non-magnetic impurities (p = 0.9) is introduced in the system, the first-order phase transition changes to a second-order phase transition.

Phase Transitions in the Two-Dimensional Slightly Diluted Five-Vertex Potts Model

Phase transitions in the two-dimensional slightly diluted Potts model on a square lattice at q = 5 have been studied using the computer simulation method. The systems with linear sizes L × L = N, L = 10–120 are considered. It is shown based on the forth-order Binder cumulants and using the histogram analysis of the data that the introduction of nonmagnetic impurities to a spin system described by the two-dimensional Potts model with q = 5 leads to a change of the first-order phase transition to a second-order phase transition.