scholarly journals Pairs of solutions of constant sign for nonlinear periodic equations with unbounded nonlinearity

2005 ◽  
Vol 12 (2) ◽  
pp. 193-208
Author(s):  
Shouchuan Hu ◽  
Nikolaos S. Papageorgiou
Keyword(s):  
Constant Sign ◽  
Solutions Of Constant Sign

Nonlinear Parametric Robin Problems with Combined Nonlinearities

2015 ◽  
Vol 15 (3) ◽  
Author(s):  
Nikolaos S. Papageorgiou ◽  
Vicenţiu D. Rădulescu
Keyword(s):  
Growth Condition ◽  
Morse Theory ◽  
Constant Sign ◽  
Robin Problem ◽  
Three Solutions ◽  
Multiplicity Theorem ◽  
Solutions Of Constant Sign ◽  
Semilinear Problem ◽  
Concave Term

AbstractWe consider a nonlinear parametric Robin problem driven by the p-Laplacian. We assume that the reaction exhibits a concave term near the origin. First we prove a multiplicity theorem producing three solutions with sign information (positive, negative and nodal) without imposing any growth condition near ±∞ on the reaction. Then, for problems with subcritical reaction, we produce two more solutions of constant sign, for a total of five solutions. For the semilinear problem (that is, for p = 2), we generate a sixth solution but without any sign information. Our approach is variational, coupled with truncation, perturbation and comparison techniques and with Morse theory.

A variational approach to nonlinear logistic equations

2015 ◽  
Vol 17 (03) ◽  
pp. 1450021 ◽  
Author(s):  
Leszek Gasiński ◽  
Donal O'Regan ◽  
Nikolaos S. Papageorgiou
Keyword(s):  
Positive Solutions ◽  
Variational Approach ◽  
Continuous Dependence ◽  
Type Equation ◽  
Logistic Equation ◽  
Extremal Solutions ◽  
Constant Sign ◽  
Nontrivial Solutions ◽  
Logistic Equations ◽  
Solutions Of Constant Sign

We consider a nonlinear logistic type equation. For all big values of the parameter, we show that the problem admits nontrivial solutions of constant sign and in fact we establish the existence of extremal constant sign solutions. Using these extremal solutions, we produce a nodal (sign-changing) solution. We also investigate the uniqueness and continuous dependence on the parameter of positive solutions. Finally, we study the degenerate p-logistic equation.

scholarly journals Two constant sign solutions for a nonhomogeneous Neumann boundary value problem

2015 ◽  
Vol 14 (1) ◽  
pp. 47-62
Author(s):  
Liliana Klimczak
Keyword(s):  
Differential Operator ◽  
Boundary Value Problem ◽  
Neumann Boundary ◽  
Constant Sign ◽  
Elliptic Differential Operator ◽  
Nontrivial Solutions ◽  
Natural Conditions ◽  
Neumann Boundary Value Problem ◽  
Nonlinear Neumann Problem ◽  
Solutions Of Constant Sign

Abstract We consider a nonlinear Neumann problem with a nonhomogeneous elliptic differential operator. With some natural conditions for its structure and some general assumptions on the growth of the reaction term we prove that the problem has two nontrivial solutions of constant sign. In the proof we use variational methods with truncation and minimization techniques.

Three Solutions of Constant Sign for a System of Discrete Equations

2004 ◽  
Vol 84 (2) ◽  
pp. 121-162 ◽  
Author(s):  
Ravi P. Agarwal ◽  
Donal O’Regan ◽  
Patricia J. Y. Wong
Keyword(s):  
Constant Sign ◽  
Three Solutions ◽  
Discrete Equations ◽  
Solutions Of Constant Sign

scholarly journals A note on the eigenvalue free intervals of some classes of signed threshold graphs

2019 ◽  
Vol 7 (1) ◽  
pp. 218-225
Author(s):  
Milica Anđelić ◽  
Tamara Koledin ◽  
Zoran Stanić
Keyword(s):  
Tridiagonal Matrix ◽  
Constant Sign ◽  
Equitable Partition ◽  
Elementary Matrix ◽  
Matrix Operations ◽  
Threshold Graphs ◽  
The Matrix ◽  
Threshold Graph

Abstract We consider a particular class of signed threshold graphs and their eigenvalues. If Ġ is such a threshold graph and Q(Ġ ) is a quotient matrix that arises from the equitable partition of Ġ , then we use a sequence of elementary matrix operations to prove that the matrix Q(Ġ ) – xI (x ∈ ℝ) is row equivalent to a tridiagonal matrix whose determinant is, under certain conditions, of the constant sign. In this way we determine certain intervals in which Ġ has no eigenvalues.

Constant-Sign Lp Solutions for a System of Integral Equations

2004 ◽  
Vol 46 (3-4) ◽  
pp. 195-219 ◽  
Author(s):  
Ravi P. Agarwal ◽  
Donal O’Regan ◽  
Patricia J. Y. Wong
Keyword(s):  
Integral Equations ◽  
Constant Sign ◽  
System Of Integral Equations ◽  
Lp Solutions

scholarly journals Green's function of the clamped punctured disk

1977 ◽  
Vol 20 (2) ◽  
pp. 175-181 ◽  
Author(s):  
Mitsuru Nakai ◽  
Leo Sario
Keyword(s):  
Green’S Function ◽  
Circular Plate ◽  
Green's Function ◽  
American Mathematical Society ◽  
Point Load ◽  
Thin Elastic Plate ◽  
Constant Sign ◽  
Boundary Circle ◽  
Simply Supported ◽  
Image Position

If a thin elastic circular plate B: ∣z∣ < 1 is clamped (simply supported, respectively) along its edge ∣z∣ = 1, its deflection at z ∈ B under a point load at ζ ∈ B, measured positively in the direction of the gravitational pull, is the biharmonic Green's function β(z, ζ) of the clamped plate (γ(z, ζ) of the simply supported plate, respectively). We ask: how do β(z, ζ) and γ(z, ζ) compare with the corresponding deflections β0(z, ζ) and γ0(z, ζ) of the punctured circular plate B0: 0 < ∣ z ∣ < 1 that is “clamped” or “simply supported”, respectively, also at the origin? We shall show that γ(z, ζ) is not affected by the puncturing, that is, γ(·, ζ) = γ0(·, ζ), whereas β(·, ζ) is:on B0 × B0. Moreover, while β((·, ζ) is of constant sign, β0(·, ζ) is not. This gives a simple counterexmple to the conjecture of Hadamard [6] that the deflection of a clampled thin elastic plate be always of constant sign:The biharmonic Gree's function of a clampled concentric circular annulus is not of constant sign if the radius of the inner boundary circle is sufficiently small.Earlier counterexamples to Hadamard's conjecture were given by Duffin [2], Garabedian [4], Loewner [7], and Szegö [9]. Interest in the problem was recently revived by the invited address of Duffin [3] before the Annual Meeting of the American Mathematical Society in 1974. The drawback of the counterexample we will present is that, whereas the classical examples are all simply connected, ours is not. In the simplicity of the proof, however, there is no comparison.

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