Electronic Journal of Differential Equations, 
Vol. 2020 (2020), No. 59, pp. 1-27.

Title: Nonnegative controllability for a class of nonlinear degenerate parabolic
       equations with application to climate science
       
Author: Giuseppe Floridia (Univ. Mediterranea di Reggio Calabria, Italy)

Abstract:
 We consider a nonlinear degenerate reaction-diffusion equation.
 First we prove that if the initial state is nonnegative, then
 the solution remains nonnegative for all time.
 Then we prove the approximate  controllability between nonnegative states
 via multiplicative  controls, this is done using the reaction coefficient
 as control.
 
Submitted March 10, 2020. Published June 15, 2020.
Math Subject Classifications: 93C20, 35K10, 35K65, 35K57, 35K58.
Key Words: Semilinear degenerate reaction-diffusion equations;
           energy balance models in climate science; approximate controllability;
           multiplicative controls; nonnegative states.