Uniqueness and exact multiplicity results for two classes of semilinear problems

1998 ◽  
Vol 31 (7) ◽  
pp. 849-865 ◽  
Author(s):  
Philip Korman
2001 ◽  
Vol 131 (5) ◽  
pp. 1167-1182 ◽  
Author(s):  
Philip Korman ◽  
Junping Shi

We obtain some new exact multiplicity results for the Dirichlet boundary-value problem on a unit ball Bn in Rn. We consider several classes of nonlinearities f(u), including both positive and sign-changing cases. A crucial part of the proof is to establish positivity of solutions for the corresponding linearized problem. As an application we obtain exact multiplicity results for the Holling-Tanner population model.


2003 ◽  
Vol 3 (2) ◽  
Author(s):  
Philip Korman ◽  
Yi Li ◽  
Tiancheng Ouyang

AbstractWe revisit the question of exact multiplicity of positive solutions for a class of Dirichlet problems for cubic-like nonlinearities, which we studied in [6]. Instead of computing the direction of bifurcation as we did in [6], we use an indirect approach, and study the evolution of turning points. We give conditions under which the critical (turning) points continue on smooth curves, which allows us to reduce the problem to the easier case of f (0) = 0. We show that the smallest root of f (u) does not have to be restricted.


2013 ◽  
Vol 2013 ◽  
pp. 1-9
Author(s):  
Yulian An

Using bifurcation techniques and Sturm comparison theorem, we establish exact multiplicity results of sign-changing or constant sign solutions for the boundary value problemsu″+a(t)f(u)=0,t∈(0,1),u(0)=0, andu(1)=0, wheref∈C(ℝ,ℝ)satisfiesf(0)=0and the limitsf∞=lim|s|→∞(f(s)/s),f0=lim|s|→0(f(s)/s)∈{0,∞}. Weight functiona(t)∈C1[0,1]satisfiesa(t)>0on[0,1].


Author(s):  
Philip Korman

Using techniques of bifurcation theory, we give exact multiplicity and uniqueness results for the fourth-order Dirichlet problem, which describes deflection of an elastic beam, subjected to a nonlinear force, and clamped at the end points. The crucial part of this approach was to show positivity of non-trivial solutions of the corresponding linearized problem.


2003 ◽  
Vol 46 (1) ◽  
pp. 229-249 ◽  
Author(s):  
Leszek Gasiński ◽  
Nikolaos S. Papageorgiou

AbstractIn this paper we examine periodic problems driven by the scalar $p$-Laplacian. Using non-smooth critical-point theory and a recent multiplicity result based on local linking (the original smooth version is due to Brezis and Nirenberg), we prove three multiplicity results, the third for semilinear problems with resonance at zero. We also study a quasilinear periodic eigenvalue problem with the parameter near resonance. We prove the existence of three distinct solutions, extending in this way a semilinear and smooth result of Mawhin and Schmitt.AMS 2000 Mathematics subject classification: Primary 34C25


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