A DETERMINATION OF THE LOW-ENERGY PARAMETERS OF THE 2-D HEISENBERG-ANTIFERROMAGNET

We perform numerical simulations of the 2-d Heisenberg antiferromagnet using a cluster algorithm. Comparing the size and temperature effects of various quantities with results from chiral perturbation theory we determine the low energy parameters of the system very precisely. We find e(0)=-0.6693(1)J/a(2) for the ground state energy density, M(s)=0 .3074(4)/a(2) for the staggered magnetization, hc=1.68(1)Ja for the sp in wave velocity and p(s)=0.186(4)J for the spin stiffness. Our result s agree with experimental data for the precursor insulators of high-T- c, superconductors.