The relative importance of the contributions of droplet excitations and
domain walls on the ordering of short-range Edwards-Anderson spin glasses in
three and four dimensions is studied. We compare the overlap distributions of
periodic and free boundary conditions using population annealing Monte Carlo.
For system sizes up to about 1000 spins, spin glasses show non-trivial spin
overlap distributions. Periodic boundary conditions can trap diffusive domain
walls which can contribute to small spin overlaps, and the other contribution
is the existence of low-energy droplet excitations within the system. We use
free boundary conditions to minimize domain-wall effects, and show that
low-energy droplet excitations are the major contribution to small overlaps in
numerical simulations. Free boundary conditions has stronger finite-size
effects, and is likely to have the same thermodynamic limit with periodic
boundary conditions.Comment: 5 pages, 4 figure
