Université de Fribourg

Existence, uniqueness and stability analysis of allelopathic stimulatory phytoplankton model

Abbas, Syed ; Banerjee, Malay ; Hungerbühler, Norbert

In: Journal of Mathematical Analysis and Applications, 2010, p. -

In this paper we consider the two species competitive delay plankton allelopathy stimulatory model system. We show the existence and uniqueness of the solution of the deterministic model. Moreover, we study the persistence of the model and the stability properties of its equilibrium points. We illustrate the theoretical results by some numerical simulations.

Université de Fribourg

Heat flow into spheres for a class of energies

Hungerbühler, Norbert

In: Variational Problems in Riemannian Geometry, 2004, p. 45-64

Let M and N be compact smooth Riemannian manifolds without boundaries. Then, for a map u : M→N, we consider a class of energies which includes the popular Dirichlet energy and the more general p-energy. Geometric or physical questions motivate to investigate the critical points of such an energy or the corresponding heat flow problem. In the case of the Dirichlet energy, the heat flow...

Université de Fribourg

Results on a Navier-Stokes system with applications to electrorheological fluid flow

Dreyfuss, Pierre ; Hungerbühler, Norbert

In: International Journal of Pure and Applied Mathematics, 2004, vol. 14, no. 2, p. 241-267

We study a Navier-Stokes system which is motivated by models for electrorheological fluids. Its principal features are the weak monotonicity assumptions we impose on the viscosity tensor. Moreover we allow the viscosity to depend on the velocity in order to cover some of the models in electrorheological theory. We establish existence of a weak solution of the corresponding Navier-Stokes...

Université de Fribourg

Navier-Stokes systems with quasimonotone viscosity tensor.

Dreyfuss, Pierre ; Hungerbühler, Norbert

In: International Journal of Differential Equations and Applications

We (Dreyfuss P., Hungerbühler, N., 2004, Int. J. of Pure and Appl.Math. 14(2): 241– 271) investigated a class of Navier-Stokes systems which is motivated by models for electrorheological fluids. We obtained an existence result for a weak solution under mild monotonicity assumptions for the viscosity tensor. In this article, we continue the analysis of such systems, but with various notions...

Université de Fribourg

Quasilinear elliptic systems in divergence form with weak monotonicity and nonlinear physical data

Augsburger, Fabien ; Hungerbühler, Norbert

In: Electronic Journal of Differential Equations, 2004, vol. 144, p. 1-18

We study the quasilinear elliptic system −div σ(x, u,Du) = v(x) + f(x, u) + div g(x, u) on a bounded domain of Rⁿ with homogeneous Dirichlet boundary conditions. This system corresponds to a diffusion problem with a source v in a moving and dissolving substance, where the motion is described by g and the dissolution by f. We prove existence of a weak solution of this system under classical...