Classical spin liquid:: Exact solution for the infinite-component antiferromagnetic model on the kagome lattice

Thermodynamic quantities and correlation functions (CF's) of the classical antiferromagnet on the kagome lattice are studied for the exactly solvable infinite-component spin-vector model, 0-->infinity. In this limit, the critical coupling of fluctuations dies out and the critical behavior simplifies, but the effect of would-be Goldstone modes preventing ordering at any nonzero temperature is properly accounted for. In contrast to conventional two-dimensional magnets with continuous symmetry showing extended short-range order at distances smaller than the correlation length, r less than or similar to xi(c)proportional to exp(T*/T), correlations in the kagome-lattice model decay already at the scale of the lattice spacing due to the strong degeneracy of the ground state characterized by a macroscopic number of strongly fluctuating local degrees of freedom. At low temperatures, spin CF's decay as [S0Sr] proportional to 1/r(2) in the range a(0)much less than r much less than xi(c)proportional to T-1/2, where a(0) is the lattice spacing. Analytical results for the principal thermodynamic quantities in our model are in fairly good quantitative agreement with the Monte Carlo simulations for the classical Heisenberg model, D=3. The neutron-scattering cross section has its maxima beyond the first Brillouin zone; at T-->0 it becomes nonanalytic but does not diverge at any q. [S0163-1829(99)01601-X].