Existence of solitons in the nonlinear beam equation

This paper concerns with the existence of solitons, namely stable solitary waves in the nonlinear beam equation (NBE) with a suitable nonlinearity. An equation of this type has been introduced by P.J. McKenna and W. Walter as a model of a suspension bridge. We prove both the existence of solitary waves for a large class of nonlinearities and their stability. As far as we know this is the first result about stability of solitary waves in NBE.Comment: 19 page

Exact meromorphic stationary solutions of the real cubic Swift-Hohenberg equation

We show that all meromorphic solutions of the stationary reduction of the real cubic Swift-Hohenberg equation are elliptic or degenerate elliptic. We then obtain them all explicitly by the subequation method, and one of them appears to be a new elliptic solution.Comment: 15 pages, 3 figures, to appear, Studies in Applied Mathematic

On the finite space blow up of the solutions of the Swift-Hohenberg equation

The aim of this paper is to study the finite space blow up of the solutions for a class of fourth order differential equations. Our results answer a conjecture in [F. Gazzola and R. Pavani. Wide oscillation finite time blow up for solutions to nonlinear fourth order differential equations. Arch. Ration. Mech. Anal., 207(2):717--752, 2013] and they have implications on the nonexistence of beam oscillation given by traveling wave profile at low speed propagation.Comment: 24 pages, 2 figure

Continuation of homoclinic orbits in the suspension bridge equation: a computer-assisted proof

In this paper, we prove existence of symmetric homoclinic orbits for the suspension bridge equation $u""+\beta u" + e^u-1=0$ for all parameter values $\beta \in [0.5,1.9]$. For each $\beta$, a parameterization of the stable manifold is computed and the symmetric homoclinic orbits are obtained by solving a projected boundary value problem using Chebyshev series. The proof is computer-assisted and combines the uniform contraction theorem and the radii polynomial approach, which provides an efficient means of determining a set, centered at a numerical approximation of a solution, on which a Newton-like operator is a contraction.Comment: 37 pages, 6 figure

Existence de connexions homoclines pour l'équation du pont suspendu : une preuve assistée par ordinateur

Tableau d'honneur de la Faculté des études supérieures et postdorales, 2015-2016Dans ce mémoire, une méthode assistée numériquement est introduite et utilisée afin de montrer l'existence d'une connexion homocline à zéro pour l'équation du pont suspendu. Cette méthode, basée sur l'utilisation du théorème de contraction de Banach, permet d'obtenir les points fixes de l'opérateur de Newton légèrement modifié. La méthode ainsi que son cadre théorique sont introduits au premier chapitre. L'espace de Banach sur lequel sera définit l'opérateur ainsi que la manière de construire l'approximation de l'inverse utilisée pour l'opérateur sont les éléments majeurs du cadre théorique. Par la suite, la méthode est utilisée dans le Chapitre 2 pour prouver rigoureusement la validité de l'approximation numérique utilisée pour la variété stable locale. Puis cette approximation est réutilisée pour prouver l'existence de la connexion homocline. Cette preuve est à nouveau effectuée en utilisant la méthode introduite au premier chapitre. Finalement, certains résultats des calculs numériques sont présentés pour conclure ce mémoire.In this work, a numerically assisted technique is introduced in order to prove the existence of a homoclinic connexion to zero for the suspension bridge equation. This technique, based on the use of the Banach fixed point theorem, can provide the fixed point of a slightly modified version of the Newton operator. The technique and its theorical background are introduced in the first chapter. The Banach space on which the operator is defined and the way to construct the approximation of the inverse needed to define the operator are the major parts of the theoretical background. The method is then used to rigorously validate the numerical approximation used to parametrize the local stable manifold. This parametrization is used to find the homoclinic connexion we are looking for. This proof is also completed using the technique from the first chapter. Finally, some results and numerical approximations will be presented in the last chapter