Equilibrium and dynamical properties of the axial next-nearest-neighbor Ising chain at the multiphase point

We study the equilibrium and dynamical properties of the axial next-nearest -neighbor Ising chain at the multiphase point. An interesting property of t he system is the macroscopic degeneracy of the ground state leading to fini te zero-temperature entropy. In our equilibrium study we consider the effec t of softening the spins. We show that the degeneracy of the ground state i s lifted and there is a qualitative change in the low-temperature behavior of the system with a well-defined low-temperature peak of the specific heat that carries the thermodynamic ''weight'' of the ground state entropy. In our study of the dynamical properties, the stochastic Kawasaki dynamics is considered. The Fokker-Planck operator for the process corresponds to a qua ntum spin Hamiltonian similar to the Heisenberg ferromagnet but with constr aints on allowed states. This leads to a number of differences in its prope rties, which are obtained through exact numerical diagonalization, simulati ons, and by obtaining various analytic bounds.