Boundary contributions of the magnetizations of several isotropic magnets, which are generalized antiferromagnetic Heisenberg models in open chains, are evaluated. The boundary magnetization approaches zero logarithmically as the external field goes to zero, in each of the models, namely the...

The properties of the ground state and the low-lying states of the antiferromagnetic Heisenberg model on the kagomé lattice are discussed by an effective linear-spin-wave scheme. A novel scheme is introduced in the present paper. By using this scheme, the staggered magnetization of one of the...

The magnetization and the electron number at the edge site are analytically calculated in the repulsive Hubbard model with a small magnetic field near the half-filling. Such quantities in the strong-coupling limit are evaluated. The relationship between the repulsive and the attractive Hubbard...

A reentrant phase transition in a frustrated Ising model is studied. By the finite-size scaling technique based on the conformal field theory, the universality class of the present phase transition is discussed. Our results suggest that the universality class of the present model is the same as...

By the finite-size scaling technique, the dynamical critical exponent of the one-dimensional random transverse-Ising model is evaluated. The finite-size scaling of the average and the distribution of the energy gap in each sample are also discussed. The exponent seems to vary depending on the...

Properties of the one-dimensional Hubbard model with a boundary field are studied. The present model realizes a strongly correlated electron system with almost localized impurity spins at the boundary. Physical quantities of the present model, e.g. the compressibility, the susceptibility and the...

In the present study, we propose a new perspective on thermal dissipation based on the thermo field dynamics. From the view point of the renormalization theory, there appear effective interactions between the original and tilde spaces on thermo field dynamics with reducing thermal disturbances....

In the present study, we focus on the parity of the order parameters and clarify the order formation process in a system including two order parameters. Each order parameter shows different parity under a gauge transformation, namely even and odd order parameters. For example, in a spin-glass...

We have found the conditions under which some spin S Ising models on the honeycomb lattice have the same partition functions as the exactly solvable S = 12 Ising model. The exact critical temperatures for the S = 32 and S = 2 models have been found as solutions of nonlinear equations.

We investigate a simple system of two coupled discrete stochastic resonators in the following two cases, to clarify the role of coupling. Case A: an oscillating force is applied to the whole system. Case B: an oscillating force is applied to one of the coupled resonators. We have obtained...