RELATIONSHIP BETWEEN THE STRUCTURE OF THE GROUND-LEVEL AND FRUSTRATION IN + -J ISING LATTICES/

Ground states of Ising lattices with +/-J exchange interactions (bonds ) are highly degenerate. Such degeneracy can be grouped in sets of loc al ensembles (LEGs) in which states are connected by single spin flips . Here we study LEGs in samples 6 x 6. Then we go onto the decompositi on of the total ground-state degeneracy into partial degeneracies of t he LEGs. Each LEG can be generated by flipping spins grouped into clus ters, whose sizes are directly related to the degeneracies of the LEGs . We find that all bonds attached to a cluster are frustrated in an it inerant way. Additionally, there is rigid frustration that can be loca l (associated to some LEGs) or global (associated to all LEGs). The re st of the bonds constitute the diluted (unfrustrated) lattice possessi ng interesting properties. (C) 1998 Published by Elsevier Science B.V. All rights reserved.