Asselah, A.Brito, RicardoLebowitz, J. L.2023-06-202023-06-201997-060022-471510.1007/BF02181276https://hdl.handle.net/20.500.14352/58569© 1997 Plenum Publishing Corporation. We thank C. Landim, S. Olla, M. S. Ripoll, and H. T. Yau for useful discussions. This work was supported by NSF Grant 92-13424 4-20946. R.B. was also supported by D.G.I.C. y T. (Spain), project PB94-0265.We review some exact results for the morion of a tagged particle in simple models. Then, we study the density dependence of the sill-diffusion coefficient D_(N)(ρ) in lattice systems with simple symmetric exclusion in which the particles can jump, with equal rates, to a set of N neighboring sites. We obtain positive upper and lower bounds on F_(N)(ρ) = N{(1 - ρ) - [D_(N)(ρ)/D_(N)(0)]}/[ρ(1 - ρ)] for ρ is an element of [0, 1]. Computer simulations for the square, triangular, and one-dimensional lattices suggest that FN becomes effectively independent of N for N greater than or equal to 20.engjournal articlehttp://link.springer.com/content/pdf/10.1007%2FBF02181276http://link.springer.com/http://arxiv.org/pdf/cond-mat/9809175v1open access536Simple exclusionTagged particleEquationLimitTermodinámica2213 Termodinámica