Critical Behavior of theS=3/2Antiferromagnetic Heisenberg Chain

Using the density-matrix renormalization-group technique we study the long-wavelength properties of the spin $S=3\mathrm{}/2$ nearest-neighbor Heisenberg chain. We obtain an accurate value for the spin velocity $v=3.87\mathrm{}\pm 0.02$, in agreement with experiment. Our results show conclusively that the model belongs to the same universality class as the $S=1\mathrm{}/2$ Heisenberg chain, with a conformal central charge $c=1\mathrm{}$ and critical exponent $\eta =1\mathrm{}$.