Published online by Cambridge University Press: 09 January 2023
We consider the global existence for the following fully parabolic chemotaxis system with two populations or $\Omega =B_R(0)\subset \mathbb {R}^2$
supplemented with homogeneous Neumann boundary conditions, $\kappa _i,\chi _i>0,$
$i=1,2$
. The global existence remains open for the fully parabolic case as far as the author knows, while the existence of global solution was known for the parabolic-elliptic reduction with the second equation replaced by $0=\Delta v-v+u_1+u_2$
or $0=\Delta v+u_1+u_2$
. In this paper, we prove that there exists a global solution if the initial masses satisfy the certain sub-criticality condition. The proof is based on a version of the Moser–Trudinger type inequality for system in two dimensions.