Zeros of the Partition Function and Pseudospinodals in a Near-Mean-Field Ising Model

Chikao Kawabata, Masuo Suzuki, Syû Ono +1 more

John Stephenson

John Stephenson, Jan Van Aalst

Shigetoshi Katsura, Yoshihiko Abe, Masami Yamamoto

To study the relations between Yang-Lee's theory of the phase transitions and the distribution of the zeros of the partition functions in the antiferromagnetic case, the partition functions of finite (4×4 and 4×6) Ising model with the nearest and the next nearest neighbor interactions are calculated. The distributions of the zeros in the fugacity z plane of the partition function for various combinations of the values of J / k T - J '/ k T or tanh ( J /2 k T )-tanh ( J '/2 k T ) are investigated. The patterns of the distribution of the zeros show several types corresponding to ferromagnetic state, antiferromagnetic state and superantiferromagnetic state. In the antiferromagnetic ordered state the locus of the zeros is found to be nearly two concentric circles and to cross the positive real axis at two points z c and 1/ z c when the next neighbor ferromagnetic interaction is introduced. This means that our system shows the phase transitions at finite critical fields H c and - H c . The locus of zeros of Fisher's model of super-exchange antiferromagnet is also shown to cross the positive real axis at z c and 1/ z c below the Néel temperature.

Nelson A. Alves, J. R. Drugowich de Felício, Ulrich H. E. Hansmann

The density of states for the three-dimensional Ising model is calculated with high precision by means of multicanonical simulations. This allows us to estimate the leading partition function zeros for lattice sizes up to L = 32. We have evaluated the critical exponent ν and the correction to scaling through an analysis of a multi-parameter fit and of the Bulirsch-Stoer (BST) extrapolation algorithm. The performance of the BST algorithm is also explored in case of the 2D Ising model, where the exact partition function zeros are known.

Seung‐Yeon Kim, Wooseop Kwak

The partition function zeros of the Ising model on a kagomé lattice in the complex magnetic-field plane are obtained. The properties of the Ising model on a kagomé lattice are not known in an external magnetic field. We estimate the joint density of states for the Ising model on a kagomé lattice in an external magnetic field by using the Wang-Landau sampling method. From the joint density of states, we evaluate its partition function zeros (so-called the Yang-Lee zeros) in the complex magnetic-field plane. For the first time, we investigate the unknown properties of the Ising model on a kagomé lattice in an external magnetic field by using its Yang-Lee zeros.