  Heat conduction in three-dimensional nonlinear lattices is investigated using
a particle dynamics simulation. The system is a simple three-dimensional
extension of the Fermi-Pasta-Ulam $\beta$ (FPU-$\beta$) nonlinear lattices, in
which the interparticle potential has a biquadratic term together with a
harmonic term. The system size is $L\times L\times 2L$, and the heat is made to
flow in the $2L$ direction the Nose-Hoover method. Although a linear
temperature profile is realized, the ratio of enerfy flux to temperature
gradient shows logarithmic divergence with $L$. The autocorrelation function of
energy flux $C(t)$ is observed to show power-law decay as $t^{-0.98\pm 0,25}$,
which is slower than the decay in conventional momentum-cnserving
three-dimensional systems ($t^{-3/2}$). Similar behavior is also observed in
the four dimensional system.
