Ordering in the infinite-ranged Ising spin glass—Exact solutions for small samples

A new order parameter q(2) for the infinite-ranged Ising spin glass model is introduced. q(2) can be defined without specifying any symmetry breaking field, and is a direct measure of the effect of frustration on the internal energy below the spin glass transition temperature, Tsg. An exact evaluation of q(2)(T) for small systems (with up to 20 spins) establishes the existence of Edwards-Anderson ordering, and sheds light on several of the controversies which surround this model.