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Consortium of Swiss Academic Libraries

Invariant measures of homeomorphisms and applications to the stability of an hyperbolic PDE

Aassila, Mohammed

In: Bulletin of the Brazilian Mathematical Society, New Series, 2004, vol. 35, no. 1, p. 83-122

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

The linear barycentric rational method for a class of delay Volterra integro-differential equations

Abdi, Ali ; Berrut, Jean-Paul ; Hosseini, Seyyed Ahmad

In: Journal of Scientific Computing, 2018, vol. 75, no. 3, p. 1757-1775

A method for solving delay Volterra integro-differential equations is introduced. It is based on two applications of linear barycentric rational interpolation, barycentric rational quadrature and barycentric rational finite differences. Its zero–stability and convergence are studied. Numerical tests demonstrate the excellent agreement of our implementation with the predicted convergence...

Université de Fribourg

A Koebe distortion theorem for quasiconformal mappings in the Heisenberg group

Adamowicz, Tomasz ; Fässler, Katrin ; Warhurst, Ben

In: Annali di Matematica Pura ed Applicata (1923 -), 2020, vol. 199, no. 1, p. 147–186

We prove a Koebe distortion theorem for the average derivative of a quasiconformal mapping between domains in the sub-Riemannian Heisenberg group H1. Several auxiliary properties of quasiconformal mappings between subdomains of H1 are proven, including BMO estimates for the logarithm of the Jacobian. Applications of the Koebe theorem include diameter bounds for images of curves, comparison of...

Université de Fribourg

Convexity of complements of tropical varieties, and approximations of currents

Adiprasito, Karim ; Babaee, Farhad

In: Mathematische Annalen, 2019, vol. 373, no. 1, p. 237–251

The goal of this note is to affirm a local version of conjecture of Nisse–Sottile [19] on higher convexity of complements of tropical varieties, while providing a family of counter-examples for the global Nisse–Sottle conjecture in any codimension and dimension higher than one. Moreover, it is shown that, surprisingly, this family also provides a family of counter-examples for the...

Université de Fribourg

Mappings of finite distortion: boundary extensions in uniform domains

Äkkinen, Tuomo ; Guo, Chang-Yu

In: Annali di Matematica Pura ed Applicata (1923 -), 2017, vol. 196, no. 1, p. 65–83

In this paper, we consider mappings on uniform domains with exponentially integrable distortion whose Jacobian determinants are integrable. We show that such mappings can be extended to the boundary, and moreover, these extensions are exponentially integrable with quantitative bounds. This extends previous results of Chang and Marshall (Am J Math 107(5):1015–1033, 1985) on analytic...

Université de Fribourg

The Regge symmetry, confocal conics, and the Schläfli formula

Akopyan, Arseniy ; Izmestiev, Ivan

In: Bulletin of the London Mathematical Society, 2019, p. blms.12276

The Regge symmetry is a set of remarkable relations between two tetrahedra whose edge lengths are related in a simple fashion. It was first discovered as a consequence of an asymptotic formula in mathematical physics. Here, we give a simple geometric proof of Regge symmetries in Euclidean, spherical, and hyperbolic geometry.

Université de Fribourg

On the inclusion of the quasiconformal Teichmüller space into the length-spectrum Teichmüller space

Alessandrini, Daniele ; Liu, L. ; Papadopoulos, A. ; Su, W.

In: Monatshefte für Mathematik, 2016, vol. 179, no. 2, p. 165–189

This paper is about surfaces of infinite topological type. Unlike the case of surfaces of finite type, there are several deformation spaces associated with a surface S of infinite topological type. Such spaces depend on the choice of a basepoint (that is, the choice of a fixed conformal structure or hyperbolic structure on S) and they also depend on the choice of a distance on the set of...

Université de Fribourg

The Â-genus of S¹-manifolds with finite second homotopy group

Amann, Manuel ; Dessai, Anand

In: Comptes rendus Mathematique

We construct simply connected smooth manifolds M of dimension 4k ≤ 8 with the following properties: the second homotopy group π₂(M) is finite, M admits a smooth action by the circle S¹ and the Â-genus Â(M) is non-zero.

Université de Fribourg

Small filling sets of curves on a surface

Anderson, James W. ; Parlier, Hugo ; Pettet, Alexandra

In: Topology and its Applications, 2011, vol. 158, no. 1, p. 84-92

We show that the asymptotic growth rate for the minimal cardinality of a set of simple closed curves on a closed surface of genus g which fill and pairwise intersect at most Kgreater-or-equal, slanted1 times is View the MathML source as g→∞. We then bound from below the cardinality of a filling set of systoles by g/log(g). This illustrates that the topological condition that a set of curves...