RT Dissertation/Thesis T1 Existence of solutions for non-linear boundary value problems A1 Saavedra López, Lorena K1 boundary value problems K1 Green's functions K1 constant sign solutions K1 spectral theory AB This Thesis contains a detailed collection of the different results proved by the author in her predoctoral stage.The interest of the non-linear differential equations is well-known. This is due to their applications in different fields, such as physics, economy, medicine, biology or chemistry.It is very important to make a precise study of the existence of solutions for this kind of problems, as well as their uniqueness or multiplicity. We focus on the qualitative analysis of diverse boundary value problems, both linear and non-linear ones. Indeed, in most of the cases, our aim is to prove the existence of constant sign solutions in their definition interval. This interest comes from the constant sign of many of the magnitudes which are modelled by this kind of problems. YR 2017 FD 2017 LK http://hdl.handle.net/10347/16505 UL http://hdl.handle.net/10347/16505 LA eng DS Minerva RD 23 abr 2026