Spin-glass effects on critical behavior in systems with extended quenched disorder

A renormalization-group approach is used for investigating the effects of t he Parisi replica symmetry breaking ("spin-glass effects") on critical prop erties of d-dimensional systems with extended quenched disorder along Ed di rections. Within a double expansion scheme to first order in (epsilon=4-d, epsilon(d)) it is found that for d less than or equal to 4 + epsilon(d) and order-parameter dimensionalities n less than or equal to 4, a full fixed-p oint instability with a consequent runaway towards a strong-coupling regime occurs in the parameter space while, for d<4 and n>4, compatibly with the modified Harris criterion, an additional marginally stable fixed point exis ts which might control a new anisotropic random critical behavior. In any c ase, the traditional replica-symmetric Dorogovtsev-like solution for classi cal and quantum systems is unstable against the replica symmetry-breaking m odes. [S0163-1829(99)07501-3].