30,958 research outputs found
Multiplicity of positive solutions for a fourth-order quasilinear singular differential equation
This paper is concerned with the multiplicity of positive solutions of boundary value problem for the fourth-order quasilinear singular differential equation
where , . We apply the fixed point index theory and the upper and lower solutions method to investigate the multiplicity of positive solutions. We have found a threshold , such that if , then the problem admits at least one positive solution; while if , then the problem has no positive solution. In particular, there exist at least two positive solutions for
Rotating Electromagnetic Waves in Toroid-Shaped Regions
Electromagnetic waves, solving the full set of Maxwell equations in vacuum,
are numerically computed. These waves occupy a fixed bounded region of the
three dimensional space, topologically equivalent to a toroid. Thus, their
fluid dynamics analogs are vortex rings. An analysis of the shape of the
sections of the rings, depending on the angular speed of rotation and the major
diameter, is carried out. Successively, spherical electromagnetic vortex rings
of Hill's type are taken into consideration. For some interesting peculiar
configurations, explicit numerical solutions are exhibited.Comment: 27 pages, 40 figure
Positive solutions of nonlinear fourth-order boundary-value problems with local and non-local boundary conditions
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 , involving a linear functional but, although we seek positive solutions, the functional is not assumed to be positive for all positive . The results are new even for the classic boundary conditions of clamped or hinged ends when , 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
Inverse problems connected with two-point boundary value problems
For the purpose of studying those properties of a nonlinear function for which the two-point boundary value problem , the authors construct a number of kinds of special examples. "Inverse" in the title refers to the fact that the multiplicity is specified first and then a suitable function is constructed
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