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We derive exact analytical expressions for the ground-state energy and entropy of the two-dimensional $\pm J$ Ising spin glass, uncovering a nested hierarchy of frustrations. Each level in this hierarchy contributes through the kernel and…

Disordered Systems and Neural Networks · Physics 2025-04-10 Chaoming Song

We obtain the exact ground state energy of the quasi-one dimensional restricted $\pm J$ Ising spin glass in a uniform magnetic field using the transfer matrix method. Magnetic field dependence allows us to derive the magnetization as a…

Disordered Systems and Neural Networks · Physics 2024-07-30 Fateme Izadi , Reza Sepehrinia

We present an algorithm which calculates groundstates of Ising spin glasses approximately. It works by randomly selecting clusters of spins which exhibit no frustrations. The spins which were not selected, contribute to the local fields of…

Condensed Matter · Physics 2015-06-25 A. K. Hartmann

Large numbers of ground states of two-dimensional Ising spin glasses with periodic boundary conditions in both directions are calculated for sizes up to 40^2. A combination of a genetic algorithm and Cluster-Exact Approximation is used. For…

Disordered Systems and Neural Networks · Physics 2009-10-31 Alexander K. Hartmann

With the help of EXACT ground states obtained by a polynomial algorithm we compute the domain wall energy at zero-temperature for the bond-random and the site-random Ising spin glass model in two dimensions. We find that in both models the…

Disordered Systems and Neural Networks · Physics 2009-10-28 N. Kawashima , H. Rieger

A new approach known as flat histogram method is used to study the +/-J Ising spin glass in two dimensions. Temperature dependence of the energy, the entropy, and other physical quantities can be easily calculated and we give the results…

Statistical Mechanics · Physics 2009-10-31 Zhi Fang Zhan , Lik Wee Lee , Jian-Sheng Wang

We present a unified exact tensor network approach to compute the ground state energy, identify the optimal configuration, and count the number of solutions for spin glasses. The method is based on tensor networks with the Tropical Algebra…

Statistical Mechanics · Physics 2021-03-10 Jin-Guo Liu , Lei Wang , Pan Zhang

Ground states of four-dimensional (d=4) EA Ising spin glasses are calculated for sizes up to 7x7x7x7 using a combination of a genetic algorithm and cluster-exact approximation. The ground-state energy of the infinite system is extrapolated…

Disordered Systems and Neural Networks · Physics 2009-10-31 Alexander K. Hartmann

Large numbers of ground states of 3d EA Ising spin glasses are calculated for sizes up to 10^3 using a combination of a genetic algorithm and Cluster-Exact Approximation. A detailed analysis shows that true ground states are obtained. The…

Disordered Systems and Neural Networks · Physics 2009-10-31 Alexander K. Hartmann

A zero temperature dynamics of Ising spin glasses and ferromagnets on random graphs of finite connectivity is considered, like granular media these systems have an extensive entropy of metastable states. We consider the problem of what…

Statistical Mechanics · Physics 2009-11-07 David S. Dean , Alexandre Lefèvre

We study the dynamics of macroscopic observables such as the magnetization and the energy per degree of freedom in Ising spin models on random graphs of finite connectivity, with random bonds and/or heterogeneous degree distributions. To do…

Disordered Systems and Neural Networks · Physics 2009-11-11 J. P. L. Hatchett , I. Pérez Castillo , A. C. C. Coolen , N. S. Skantzos

We derive the exact ground-state energy of the one-dimensional Ising model in random fields taking values h, 0 and -h with general probabilities. The random-field Ising model on a ladder is also analyzed by showing its equivalence to the…

Disordered Systems and Neural Networks · Physics 2009-11-10 Toshiyuki Hamasaki , Hidetoshi Nishimori

The ground-state properties of quasi-one-dimensional (Q1D) Ising spin glass are investigated using an exact numerical approach and analytical arguments. A set of coupled recursive equations for the ground-state energy are introduced and…

Disordered Systems and Neural Networks · Physics 2018-03-28 Reza Sepehrinia , Fartash Chalangari

Ground states of 3d EA Ising spin glasses are calculated for sizes up to $14^3$ using a combination of genetic algorithms and cluster-exact approximation . The distribution $P(|q|)$ of overlaps is calculated. For increasing size the width…

Disordered Systems and Neural Networks · Physics 2009-10-30 Alexander K. Hartmann

The ground state energy and entropy of the dilute mean field Ising model is computed exactly by a single order parameter. An analogous exact solution is obtained in presence of a magnetic field with random locations. Results allow for a…

Disordered Systems and Neural Networks · Physics 2015-05-19 Maurizio Serva

We study the Ising spin glass on random graphs with fixed connectivity z and with a Gaussian distribution of the couplings, with mean \mu and unit variance. We compute exact ground states by using a sophisticated branch-and-cut method for…

Disordered Systems and Neural Networks · Physics 2009-11-07 Frauke Liers , Matteo Palassini , Alexander K. Hartmann , Michael Juenger

The statistics of the ground-state and domain-wall energies for the two-dimensional random-bond Ising model on square lattices with independent, identically distributed bonds of probability $p$ of $J_{ij}= -1$ and $(1-p)$ of $J_{ij}= +1$…

Disordered Systems and Neural Networks · Physics 2007-05-23 Ronald Fisch , Alexander K. Hartmann

The nature of the probability distribution function of the local energy in the $\pm J$ Ising model has been investigated. At finite temperature, it has been derived that the probability distribution function must satisfy several relations…

Disordered Systems and Neural Networks · Physics 2007-05-23 H. Kitatani , A. Aoki

Zeros of the $n$th moment of the partition function $[Z^n]$ are investigated in a vanishing temperature limit $\beta \to \infty$, $n \to 0$ keeping $y=\beta n \sim O(1)$. In this limit, the moment parameterized by $y$ characterizes the…

Disordered Systems and Neural Networks · Physics 2009-11-13 Tomoyuki Obuchi , Yoshiyuki Kabashima , Hidetoshi Nishimori

We investigate the one-dimensional long-range random-field Ising magnet with Gaussian distribution of the random fields. In this model, a ferromagnetic bond between two spins is placed with a probability $p \sim r^{-1-\sigma}$, where $r$ is…

Disordered Systems and Neural Networks · Physics 2014-11-20 Timo Dewenter , Alexander K. Hartmann
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