Abstract. This work is concerned with the fast diffusion equation ut = Δu m − u κ in R n , where 0 < m < 1 and κ < 1. A global positive solution is said to quench regularly in infinite time if u(x k , t k ) → 0 for some bounded sequence (x k ) k∈N and some t k → ∞, and if sup (x,t)∈K×(0,∞) u(x, t) < ∞ for all compact K ⊂⊂ R n . It is shown that such regular quenching in infinite time occurs for a large class of initial data if κ > m, whereas it is impossible in one space dimension when κ < −m and the solution is radially symmetric and nondecreasing for x > 0.
Mathematics Subject Classification (2000). 35K55, 35K65, 35B40.