On the existence of positive solutions for nonlinear differential equations with periodic boundary conditions

WOS: 000169651500010We prove the existence of positive solutions of second-order nonlinear differential equations on a finite interval with periodic boundary conditions and give upper and lower bounds for these positive solutions. Obtained results yield positive periodic solutions of the equation on the whole real axis, provided that the coefficients are periodic. (C) 2001 Elsevier Science B.V. All rights reserved