In the memory of Professor Tetsuro Miyakawa
MSC: 35K55We shall show existence of global strong solution to the semilinear Keller-Segel system in R n , n 3, of parabolic-parabolic type with small initial data u 0 ∈ H n r −2,r (R n ) and v 0 ∈ H n r ,r (R n ) for max{1, n/4} < r < n/2. Our method is based on the perturbation of linealization together with the L p -L q estimates of the heat semigroup and the fractional powers of the Laplace operator. As a by-product of our method, we shall prove the decay property of solutions as the time goes to infinity.In this paper, we consider the Cauchy problem of the semi-linear Keller-Segel system of parabolicparabolic type in R n for n 3,where u = u(x, t) denotes the density of amoebae and v = v(x, t) denotes the concentration of the chemo-attractant, while u 0 = u 0 (x) and v 0 = v 0 (x) are the given initial data and γ is a non-negative constant.