Hidden Goldstone mechanism in the kagome lattice antiferromagnet

In this paper, we study the phases of the Heisenberg model on the kagome la ttice with antiferromagnetic nearest-neighbor coupling J(1) and ferromagnet ic next-neighbor coupling J(2). Analyzing the long wavelength, low-energy e ffective action that describes this model, we arrive at the phase diagram a s a function of chi = (J(2)/J(1)) The interesting part of this phase diagra m is that for small chi, which includes chi=0, there is a phase with no lon g-range spin order and with gapless and spin-zero low-lying excitations. We discuss our results in the context of earlier, numerical and experimental work.