We study charge and heat transport in the square lattice Hubbard model at
strong coupling using the finite-temperature Lanczos method. We construct the
diffusion matrix and estimate the effect of thermoelectric terms on the
diffusive time evolution. The thermoelectric terms prevent the interpretation
of the diffusion in terms of a single time scale. We discuss our results in
relation to cold-atom experiments and measurements of heat conductivity based
on the measurements of heat diffusion.Comment: 10 page