Loading...
5 results
Search Results
Now showing 1 - 5 of 5
- Bifurcation structures in a 2D exponential diffeomorphism with Allee effectPublication . Rocha, J. Leonel; Taha, Abdel-KaddousAn embedding of one-dimensional generic growth functions into a two-dimensional diffeomorphism is considered. This family of unimodal maps naturally incorporates a key item of ecological and biological research: the Allee effect. Consequently, the presence of this species extinction phenomenon leads us to a new definition of bifurcation for this two-dimensional exponential diffeomorphism: Allee’s effect bifurcation. The stability and the nature of the fixed points of the two-dimensional diffeomorphism are analyzed, by studying the corresponding contour lines. Fold and flip bifurcation structures of this exponential diffeomorphism are investigated, in which there are flip codimension-2 bifurcation points and cusp points, when some parameters evolve. Numerical studies are included.
- Generalized r-Lambert function in the analysis of fixed points and bifurcations of homographic 2-Ricker mapsPublication . Rocha, J. Leonel; TAHA, Abdel-KaddousThis paper aims to study the nonlinear dynamics and bifurcation structures of a new mathematical model of the γ-Ricker population model with a Holling type II per-capita birth function, where the Allee effect parameter is γ = 2. A generalized r-Lambert function is defined on the 3D parameters space to determine the existence and variation of the number of nonzero fixed points of the homographic 2-Ricker maps considered. The singularity points of the generalized r-Lambert function are identified with the cusp points on a fold bifurcation of the homographic 2-Ricker maps. In this approach, the application of the transcendental generalized r-Lambert function is demonstrated based on the analysis of local and global bifurcation structures of this three-parameter family of homographic maps. Some numerical studies are included to illustrate the theoretical results.
- Homoclinic and big bang bifurcations of an embedding of 1D Allee's functions into a 2D diffeomorphismPublication . Rocha, J. Leonel; Taha, Abdel-Kaddous; Fournier-Prunaret, D.In this work a thorough study is presented of the bifurcation structure of an embedding of one-dimensional Allee's functions into a two-dimensional diffeomorphism. A complete classification of the nature and stability of the fixed points, on the contour lines of the two-dimensional diffeomorphism, is provided. A necessary and sufficient condition so that the Allee fixed point is a snapback repeller is established. Sufficient conditions for the occurrence of homoclinic tangencies of a saddle fixed point of the two-dimensional diffeomorphism are also established, associated to the snapback repeller bifurcation of the endomorphism defined by the Allee functions. The main results concern homoclinic and big bang bifurcations of the diffeomorphism as "germinal" bifurcations of the Allee functions. Our results confirm previous predictions of structures of homoclinic and big bang bifurcation curves in dimension one and extend these studies to "local" concepts of Allee effect and big bang bifurcations to this two-dimensional exponential diffeomorphism.
- Dynamics and bifurcations of a map of homographic Ricker typePublication . Rocha, J. Leonel; TAHA, Abdel-Kaddous; Fournier-Prunaret, D.A dynamical system of the type homographic Ricker map is considered; this is a particular case of a new extended gamma-Ricker population model with a Holling type II per-capita birth function. The purpose of this paper is to investigate the nonlinear dynamics and bifurcation structure of the proposed model. The existence, nature and stability of the fixed points of the homographic Ricker map are analyzed, by using a Lambert W function. Fold and flip bifurcation structures of the homographic Ricker map are investigated, in which there are flip codimension-2 bifurcation points and cusp points, while some parameters evolve. Some communication areas and big bang bifurcation curves are also detected. Numerical studies are included.
- Bifurcation analysis of the γ-Ricker population model using the Lambert W functionPublication . Rocha, J. Leonel; TAHA, Abdel-KaddousIn this work, we present the dynamical study and the bifurcation structures of the γ-Ricker population model. Resorting to the Lambert W function, the analytical solutions of the positive fixed point equation for the γ-Ricker population model are explicitly presented and conditions for the existence and stability of these fixed points are established. The main focus of this work is the definition and characterization of the Allee effect bifurcation for the γ-Ricker population model, which is not a pitchfork bifurcation. Consequently, we prove that the phenomenon of Allee effect for the γ-Ricker population model is associated with the asymptotic behavior of the Lambert W function in a neighborhood of zero. The theoretical results describe the global and local bifurcations of the γ-Ricker population model, using the Lambert W function in the presence and absence of the Allee effect. The Allee effect, snapback repeller and big bang bifurcations are investigated in the parameters space considered. Numerical studies are included.