Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:0908.3622 · Physical Review B

Disordered Potts model on the diamond hierarchical lattice: Numerically exact treatment in the large- q limit

Ferenc Iglói, Loïc Turban

Published Oct 9, 2009• 11 citations
arXivHTMLPDF

Abstract

We consider the critical behavior of the random $q$-state Potts model in the large-$q$ limit with different types of disorder leading to either the nonfrustrated random ferromagnet regime or the frustrated spin-glass regime. The model is studied on the diamond hierarchical lattice for which the Migdal-Kadanoff real-space renormalization is exact. It is shown to have a ferromagnetic and a paramagnetic phase and the phase transition is controlled by four different fixed points. The state of the system is characterized by the distribution of the interface free energy $P(I)$ which is shown to satisfy different integral equations at the fixed points. By numerical integration we have obtained the corresponding stable laws of nonlinear combination of random numbers and obtained numerically exact values for the critical exponents.

DOI
10.1103/physrevb.80.134201

Related papers

Correlated disordered interactions on Potts models

Paulo de Tarso Muzy, André P. Vieira, Silvio R. A. Salinas

Using a weak-disorder scheme and real-space renormalization-group techniques, we obtain analytical results for the critical behavior of various q-state Potts models with correlated disordered exchange interactions along d(1) of d spatial dimensions on hierarchical (Migdal-Kadanoff) lattices. Our results indicate qualitative differences between the cases d-d(1)=1 (for which we find non-physical random fixed points, suggesting the existence of non-perturbative fixed distributions) and d-d(1)>1 (for which we do find acceptable perturbative random fixed points), in agreement with previous numerical calculations by Andelman and Aharony [Phys. Rev. B 31, 4305 (1985)]. We also rederive a criterion for relevance of correlated disorder, which generalizes the usual Harris criterion.

arXiv:cond-mat/0201575•Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics•Apr 2, 2002•5 citations

Critical behavior of interfaces in disordered Potts ferromagnets: Statistics of free-energy, energy, and interfacial adsorption

Cécile Monthus, Thomas Garel

A convenient way to study phase transitions is by considering finite spin systems of linear size $L$ with boundary conditions that produce a system-size interface. In this paper, we study the statistical properties of such an interface in a disordered Potts ferromagnet in dimension $d=2$ within Migdal--Kadanoff real-space renormalization. We first focus on the interface free-energy and energy to measure the singularities of the average and random contributions, as well as the corresponding histograms, both in the low-temperature phase and at criticality. We then consider the critical behavior of the interfacial adsorption of nonboundary states. Our main conclusion is that all singularities involve the correlation length ${\ensuremath{\xi}}_{\mathit{av}}(T)\ensuremath{\sim}{({T}_{c}\ensuremath{-}T)}^{\ensuremath{-}\ensuremath{\nu}}$ appearing in the average free-energy $\overline{F}\ensuremath{\sim}{[L∕{\ensuremath{\xi}}_{\mathit{av}}(T)]}^{{d}_{s}}$ of the interface of dimension ${d}_{s}=d\ensuremath{-}1$, except for the free-energy width $\ensuremath{\Delta}F\ensuremath{\sim}{[L∕{\ensuremath{\xi}}_{\mathit{var}}(T)]}^{\ensuremath{\theta}}$ that involves the droplet exponent $\ensuremath{\theta}$ and another correlation length ${\ensuremath{\xi}}_{\mathit{var}}(T)$ that diverges more rapidly than ${\ensuremath{\xi}}_{\mathit{av}}(T)$. We compare with the spin-glass transition in $d=3$, where ${\ensuremath{\xi}}_{\mathit{var}}(T)$ is the ``true'' correlation length and where the interface energy presents unconventional scaling with a chaos critical exponent ${\ensuremath{\zeta}}_{c}>1∕\ensuremath{\nu}$ [M. Nifle and H. J. Hilhorst, Phys. Rev. Lett. 68, 2992 (1992)]. The common feature is that in both cases, the characteristic length scale ${L}_{\mathit{ch}}(T)$ associated with the chaotic nature of the low-temperature phase diverges more slowly than the correlation length.

arXiv:0711.2878•Physical Review B•Apr 7, 2008•15 citations

Disorder-induced rounding of the phase transition in the large- q -state Potts model

Maria Teresa Mercaldo, J C Anglès d'Auriac, Ferenc Iglói

The phase transition in the q -state Potts model with homogeneous ferromagnetic couplings is strongly first order for large q, while it is rounded in the presence of quenched disorder. Here we study this phenomenon on different two-dimensional lattices by using the fact that the partition function of the model is dominated by a single diagram of the high-temperature expansion, which is calculated by an efficient combinatorial optimization algorithm. For a given finite sample with discrete randomness the free energy is a piecewise linear function of the temperature, which is rounded after averaging, however, the discontinuity of the internal energy at the transition point (i.e., the latent heat) stays finite even in the thermodynamic limit. For a continuous disorder, instead, the latent heat vanishes. At the phase transition point the dominant diagram percolates and the total magnetic moment is related to the size of the percolating cluster. Its fractal dimension is found d(f) = ( 5 + square root of 5)/4 and it is independent of the type of the lattice and the form of disorder. We argue that the critical behavior is exclusively determined by disorder and the corresponding fixed point is the isotropic version of the so-called infinite randomness fixed point, which is realized in random quantum spin chains. From this mapping we conjecture the values of the critical exponents as beta=2- d(f), beta(s) =1/2, and nu=1.

arXiv:cond-mat/0312532•Physical Review E•May 24, 2004•25 citations

The Random Field Ising Model on Hierarchical Lattices II: Ground State Critical Properties

Alexandre Rosas, S. Coutinho

The ground state critical properties of the Random Field Ising Model (RFIM) on the diamond hierarchical lattice are investigated via a combining method encompassing real space renormalization group and an exact recurrence procedure. The local magnetization and the nearest neighbors pair correlation function are exactly calculated. The fixed-point joint probability distribution of couplings and local fields are numerically obtained and analyzed, indicating that the critical behavior of the model is governed by the zero temperature disorder fixed point. The critical exponents associated with the order parameter and correlation length are estimated showing an universal behavior regarding the choice of the initial probability distribution for initial local fields being the symmetric continuous Gaussian or discrete delta-bimodal.

arXiv:cond-mat/0107407•Jul 19, 2001•0 citations

Phase Transition in the 2D Random Potts Model in the Large- q Limit

J C Anglès d'Auriac, Ferenc Iglói

Phase transition in the two-dimensional q-state Potts model with random ferromagnetic couplings is studied in the large-q limit by a combinatorial optimization algorithm and by approximate mappings. We conjecture that the critical behavior of the model is controlled by the isotropic version of the infinite randomness fixed point of the random transverse-field Ising spin chain and the critical exponents are exactly given by beta=(3-sqrt[5])/4, beta(s)=1/2, and nu=1. The specific heat has a logarithmic singularity, but at the transition point there are very strong sample-to-sample fluctuations. Discretized randomness results in discontinuities in the internal energy.

arXiv:cond-mat/0211543•Physical Review Letters•May 13, 2003•32 citations

Phase transitions of the anisotropic Ashkin-Teller model on a family of diamond-type hierarchical lattices

Le Jian-Xin, Zhao‐Di Yang

The phase transitions of the anisotropic Ashkin-Teller model on a family of diamond-type hierarchical lattices is studied by means of the transfer-matrix method and the real-space renormalization-group transformation. We find that the phase diagram, for the ferromagnetic case, consists of five phases, i.e., the fully disordered paramagnetic phase P, the fully ordered ferromagnetic phase F, and three partially ordered ferromagnetic phases F(s), F(sigma), and F(s sigma), as well as ten nontrivial fixed points. The correlation length critical exponents and the crossover exponents are also calculated. In addition, we also investigate the variations of the critical exponents with the fractal dimension d(f), the number of branches m, and the number of bonds per branch b of the generator of the family of diamond-type hierarchical lattices. Finally we give a brief discussion about universality.

Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics•Dec 17, 2003•8 citations
We consider the critical behavior of the random qqq-state Potts model in the large-qqq limit with different types of disorder leading to either the nonfrustrated random ferromagnet regime or the frustrated spin-glass regime. The model is studied on the diamond hierarchical lattice for which the Migdal-Kadanoff real-space renormalization is exact. It is shown to have a ferromagnetic and a paramagnetic phase and the phase transition is controlled by four different fixed points. The state of the system is characterized by the distribution of the interface free energy P(I)P(I)P(I) which is shown to satisfy different integral equations at the fixed points. By numerical integration we have obtained the corresponding stable laws of nonlinear combination of random numbers and obtained numerically exact values for the critical exponents.
Using a weak-disorder scheme and real-space renormalization-group techniques, we obtain analytical results for the critical behavior of various q-state Potts models with correlated disordered exchange interactions along d(1) of d spatial dimensions on hierarchical (Migdal-Kadanoff) lattices. Our results indicate qualitative differences between the cases d-d(1)=1 (for which we find non-physical random fixed points, suggesting the existence of non-perturbative fixed distributions) and d-d(1)>1 (for which we do find acceptable perturbative random fixed points), in agreement with previous numerical calculations by Andelman and Aharony [Phys. Rev. B 31, 4305 (1985)]. We also rederive a criterion for relevance of correlated disorder, which generalizes the usual Harris criterion.
A convenient way to study phase transitions is by considering finite spin systems of linear size LLL with boundary conditions that produce a system-size interface. In this paper, we study the statistical properties of such an interface in a disordered Potts ferromagnet in dimension d=2d=2d=2 within Migdal--Kadanoff real-space renormalization. We first focus on the interface free-energy and energy to measure the singularities of the average and random contributions, as well as the corresponding histograms, both in the low-temperature phase and at criticality. We then consider the critical behavior of the interfacial adsorption of nonboundary states. Our main conclusion is that all singularities involve the correlation length ${\ensuremath{\xi}}_{\mathit{av}}(T)\ensuremath{\sim}{({T}_{c}\ensuremath{-}T)}^{\ensuremath{-}\ensuremath{\nu}}$ appearing in the average free-energy $\overline{F}\ensuremath{\sim}{[L∕{\ensuremath{\xi}}_{\mathit{av}}(T)]}^{{d}_{s}}$ of the interface of dimension ${d}_{s}=d\ensuremath{-}1$, except for the free-energy width $\ensuremath{\Delta}F\ensuremath{\sim}{[L∕{\ensuremath{\xi}}_{\mathit{var}}(T)]}^{\ensuremath{\theta}}$ that involves the droplet exponent $\ensuremath{\theta}$ and another correlation length ${\ensuremath{\xi}}_{\mathit{var}}(T)$ that diverges more rapidly than ${\ensuremath{\xi}}_{\mathit{av}}(T)$. We compare with the spin-glass transition in d=3d=3d=3, where ${\ensuremath{\xi}}_{\mathit{var}}(T)$ is the ``true'' correlation length and where the interface energy presents unconventional scaling with a chaos critical exponent ${\ensuremath{\zeta}}_{c}>1∕\ensuremath{\nu}$ [M. Nifle and H. J. Hilhorst, Phys. Rev. Lett. 68, 2992 (1992)]. The common feature is that in both cases, the characteristic length scale Lch(T){L}_{\mathit{ch}}(T)Lch​(T) associated with the chaotic nature of the low-temperature phase diverges more slowly than the correlation length.
The phase transition in the q -state Potts model with homogeneous ferromagnetic couplings is strongly first order for large q, while it is rounded in the presence of quenched disorder. Here we study this phenomenon on different two-dimensional lattices by using the fact that the partition function of the model is dominated by a single diagram of the high-temperature expansion, which is calculated by an efficient combinatorial optimization algorithm. For a given finite sample with discrete randomness the free energy is a piecewise linear function of the temperature, which is rounded after averaging, however, the discontinuity of the internal energy at the transition point (i.e., the latent heat) stays finite even in the thermodynamic limit. For a continuous disorder, instead, the latent heat vanishes. At the phase transition point the dominant diagram percolates and the total magnetic moment is related to the size of the percolating cluster. Its fractal dimension is found d(f) = ( 5 + square root of 5)/4 and it is independent of the type of the lattice and the form of disorder. We argue that the critical behavior is exclusively determined by disorder and the corresponding fixed point is the isotropic version of the so-called infinite randomness fixed point, which is realized in random quantum spin chains. From this mapping we conjecture the values of the critical exponents as beta=2- d(f), beta(s) =1/2, and nu=1.
The ground state critical properties of the Random Field Ising Model (RFIM) on the diamond hierarchical lattice are investigated via a combining method encompassing real space renormalization group and an exact recurrence procedure. The local magnetization and the nearest neighbors pair correlation function are exactly calculated. The fixed-point joint probability distribution of couplings and local fields are numerically obtained and analyzed, indicating that the critical behavior of the model is governed by the zero temperature disorder fixed point. The critical exponents associated with the order parameter and correlation length are estimated showing an universal behavior regarding the choice of the initial probability distribution for initial local fields being the symmetric continuous Gaussian or discrete delta-bimodal.
Phase transition in the two-dimensional q-state Potts model with random ferromagnetic couplings is studied in the large-q limit by a combinatorial optimization algorithm and by approximate mappings. We conjecture that the critical behavior of the model is controlled by the isotropic version of the infinite randomness fixed point of the random transverse-field Ising spin chain and the critical exponents are exactly given by beta=(3-sqrt[5])/4, beta(s)=1/2, and nu=1. The specific heat has a logarithmic singularity, but at the transition point there are very strong sample-to-sample fluctuations. Discretized randomness results in discontinuities in the internal energy.
The phase transitions of the anisotropic Ashkin-Teller model on a family of diamond-type hierarchical lattices is studied by means of the transfer-matrix method and the real-space renormalization-group transformation. We find that the phase diagram, for the ferromagnetic case, consists of five phases, i.e., the fully disordered paramagnetic phase P, the fully ordered ferromagnetic phase F, and three partially ordered ferromagnetic phases F(s), F(sigma), and F(s sigma), as well as ten nontrivial fixed points. The correlation length critical exponents and the crossover exponents are also calculated. In addition, we also investigate the variations of the critical exponents with the fractal dimension d(f), the number of branches m, and the number of bonds per branch b of the generator of the family of diamond-type hierarchical lattices. Finally we give a brief discussion about universality.