Group Approach in Spin Dynamics

A. I. Solomon, Joseph L. Birman

Stam Nicolis, Pascal Thibaudeau, Thomas Nussle

M. A. Contínentino, S. Moss de Oliveira

Recent dynamic experiments on spin glasses, in which contours of constant relaxation time are obtained in the plane of magnetic field versus temperature, are discussed from a renormalization-group point of view. We show that two fixed points control the critical behavior of spin glasses and the critical exponents associated with them can be determined through the dynamic experiments. We give a renormalization-group formulation of the fractal cluster model of spin glasses.

Xiao-Chuan Wu, Ran Cheng, Di Xiao

Satoshi Nishimoto, M. ARIKAWA

We study the one-dimensional S = 1/2 Heisenberg model with an uniform and a staggered magnetic fields, using the dynamical density-matrix renormalization group (DDMRG) technique. The DDMRG enables us to investigate the dynamical properties of chain with lengths up to a few hundreds, and the results are numerically exact in the same sense as 'exact diagonalization' results are. Thus, we can analyze the low-energy spectrum almost in the thermodynamic limit. In this work, we calculate the dynamical spin structure factor and demonstrate the performance of the DDMRG method applying the open-end boundary conditions as well as the periodic boundary conditions.

Ilya Kuprov