Integral means of solutions of the one-dimensional Poisson equation with Robin boundary conditions

Consider the one-dimensional Poisson equation -u ''=f on the interval [-pi,pi], where f is an non-negative integrable function, with Robin boundary conditions -u '(-pi)+alpha u(-pi)=u '(pi)+alpha u(pi)=0, where alpha>0 is a constant. In this paper we prove inequalities for the convex integral means of solutions of this problem, using the polarization of functions and its properties. We find solutions with maximal convex integral means and prove their uniqueness. (c) 2024 Elsevier Inc. All rights are reserved, including those for text and data mining, AI training, and similar technologies.