The transfer integral formalism is used to study the statistical mechanical properties of a two-component field defined on a two-dimensional lattice. This field, taken to have anisotropic elasticity, is subject to both a nonlinear local potential and an external field. The free energy and...

Phase transitions at absolute zero temperature can take place as some parameter in the Hamiltonian of the system is varied. For the Hamiltonian of N-electron atoms, this parameter is taken to be the nuclear charge. As the nuclear charge reaches a critical point, the quantum ground state changes...