Phase transition in the takayasu model with desorption

We study a lattice model where particles carrying different masses diffuse and coalesce upon contact, and also unit masses adsorb to a site with rate q or desorb from a site with nonzero mass with rate p. In the limit p=0 (without desorption), our model reduces to the well studied Takayasu model where the steady-state single site mass distribution has a power-law tail P(m) approximately m(-tau) for large mass. We show that varying the desorption rate p induces a nonequilibrium phase transition in all dimensions. For fixed q, there is a critical p(c)(q) such that if pp(c)(q), P(m) approximately exp(-m/m(*)) for large m. The model is studied analytically within a mean-field theory and numerically in one dimension.