Uniqueness Of Distributional Solutions Research Articles

Waves in viscoelastic media described by a linear fractional model

Recently, the classical wave equation has been generalized for the case of viscoelastic media described by the fractional Zener model (cf. [S. Konjik, Lj. Oparnica, and D. Zorica, Waves in fractional Zener type viscoelastic media, J. Math. Anal. Appl. (2009), doi:10.1016/j.jma.2009.10.043]). In this article, we use a more general fractional model for a viscoelastic body to describe the wave equation for viscoelastic infinite media, and prove existence and uniqueness of distributional solutions to the corresponding generalized Cauchy problem.

Lagrangian flows and the one-dimensional Peano phenomenon for ODEs

We consider the one-dimensional ordinary differential equation with a vector field which is merely continuous and nonnegative, and satisfies a condition on the amount of zeros. Although it is classically known that this problem lacks uniqueness of classical trajectories, we show that there is uniqueness for the so-called regular Lagrangian flow (by now usual notion of flow in nonsmooth situations), as well as uniqueness of distributional solutions for the associated continuity equation. The proof relies on a space reparametrization argument around the zeros of the vector field.

Distributional solution concepts for the Euler–Bernoulli beam equation with discontinuous coefficients§

We study existence and uniqueness of distributional solutions w to the ordinary differential equation with discontinuous coefficients and right-hand side. For example, if a and w are non-smooth the product a · w″ has no obvious meaning. When interpreted on the most general level of the hierarchy of distributional products discussed by Oberguggenberger, M. [1992, Multiplication of distributions and applications to partial differential equations (Harlow: Longman Scientific & Technical)], it turns out that existence of a solution w forces it to be at least continuously differentiable. Curiously, the choice of the distributional product concept is thus incompatible with the possibility of having a discontinuous displacement function as a solution. We also give conditions for unique solvability. §Supported by Ministry of Science of Serbia, project 144016, and the Austrian Science Fund (FWF) START program Y237 on ‘Nonlinear distributional geometry’.