# Positive solutions of nonlinear fourth-order boundary-value problems with local and non-local boundary conditions

Webb, J.R.L., Infante, G. and Franco, D. (2008) Positive solutions of nonlinear fourth-order boundary-value problems with local and non-local boundary conditions. Proceedings of the Royal Society of Edinburgh Section A: Mathematics, 138(2), pp. 427-446.

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## Abstract

We establish new existence results for multiple positive solutions of fourth-order nonlinear equations which model deflections of an elastic beam. We consider the widely studied boundary conditions corresponding to clamped and hinged ends and many non-local boundary conditions, with a unified approach. Our method is to show that each boundary-value problem can be written as the same type of perturbed integral equation, in the space $C[0,1]$, involving a linear functional $\alpha[u]$ but, although we seek positive solutions, the functional is not assumed to be positive for all positive $u$. The results are new even for the classic boundary conditions of clamped or hinged ends when $\alpha[u]=0$, because we obtain sharp results for the existence of one positive solution; for multiple solutions we seek optimal values of some of the constants that occur in the theory, which allows us to impose weaker assumptions on the nonlinear term than in previous works. Our non-local boundary conditions contain multi-point problems as special cases and, for the first time in fourth-order problems, we allow coefficients of both signs.

Item Type: Articles Published Yes Infante, Dr Gennaro and Webb, Professor Jeffrey Webb, J.R.L., Infante, G., and Franco, D. Q Science > QA Mathematics College of Science and Engineering > School of Mathematics and Statistics > Mathematics Proceedings of the Royal Society of Edinburgh Section A: Mathematics Cambridge University Press on behalf of the Royal Society of Edinburgh 0308-2105 1473-7124 14 July 2008 Copyright © 2008 Royal Society of Edinburgh First published in Proceedings of the Royal Society of Edinburgh: Section A Mathematics 138(2):427-446 Reproduced in accordance with the copyright policy of the publisher

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