Calculation of ground states of four-dimensional +/-J Ising spin glasses.

Ground states of four-dimensional (d=4) Edwards-Anderson Ising spin glasses are calculated for sizes up to 7 x 7 x 7 x 7 using a combination of a genetic algorithm and cluster-exact approximation. The ground-state energy of the infinite system is extrapolated as e0(infinity)=-2.095(1). The ground-state stiffness (or domain wall) energy Delta is calculated. A delta approximately L(theta(S)) behavior with theta(S)=0.64(5) is found which confirms that the d=4 model has an equilibrium spin-glass-paramagnet transition for nonzero T(c).