QUANTUM SPHERICAL DESCRIPTION OF AN ISING SPIN-GLASS IN A TRANSVERSE FIELD

We study the competition between bond randomness and quantum fluctuati on in the infinite-range Ising model in the transverse field Delta rel evant for a number of pseudospin and magnetic quantum spin-glass syste ms. By introducing a mapping of the quantum Hamiltonian of the model o nto a soft-spin action we consider it truncated version in a form of t he solvable quantized spherical model. The resulting critical phase bo undary T-crit(Delta) is in considerable agreement with the numerical e stimates based on the Trotter-Suzuki and Monte Carlo methods. The equa tion of state for the system is also given.