We devote this paper to proving non-existence and existence of stable solutions to weighted Lane-Emden equations on the Euclidean space ℝN, N ⩾ 2. We first prove some new Liouville-type theorems for stable solutions which recover and considerably improve upon the known results. In particular, our approach applies to various weighted equations, which naturally appear in many applications, but that are not covered by the existing literature. A typical example is provided by the well-know Matukuma's equation. We also prove an existence result for positive, bounded and stable solutions to a large family of weighted Lane–Emden equations, which indicates that our Liouville-type theorems are somehow sharp.

We consider a possibly anisotropic integrodifferential semilinear equation, driven by a non-decreasing nonlinearity. We prove that if the solution grows less than the order of the operator at infinity, then it must be affine (possibly constant).

We prove pointwise gradient bounds for entire solutions of pde’s of the form

     ℒu(x) = ψ(x, u(x), ∇u(x)),

where ℒ is an elliptic operator (possibly singular or degenerate). Thus, we obtain some Liouville type rigidity results. Some classical results of J. Serrin are also recovered as particular cases of our approach.

We consider the functional in a periodic setting. We discuss whether the minimizers or the stable solutions satisfy some symmetry or monotonicity properties, with special emphasis on the autonomous case when F is x-independent. In particular, we give an answer to a question posed by Victor Bangert when F is autonomous in dimension n≤3 and in any dimension for non-zero rotation vectors.

The main goal of this paper is the investigation of a relevant property which appears in the various definition of deterministic topological chaos for discrete time dynamical system: transitivity. Starting from the standard Devaney's notion of topological chaos based on regularity, transitivity, and sensitivity to the initial conditions, the critique formulated by Knudsen is taken into account in order to exclude periodic chaos from this definition. Transitivity (or some stronger versions of it) turns out to be the relevant condition of chaos and its role is discussed by a survey of some important results about it with the presentation of some new results. In particular, we study topological mixing, strong transitivity, and full transitivity. Their applications to symbolic dynamics are investigated with respect to the relationships with the associated languages.

We investigate the relationships among all currently known X-ray structures of crystalline pentacene by calculating their “inherent” structures of minimum potential energy. We are thus able to show that two distinct bulk crystalline phases of pentacene exist, with very subtle but clear di.erences. We then assess the effects of temperature on the crystal structures, by including both inter- molecular and low-frequency intra-molecular phonons in the framework of quasi harmonic lattice dynamics methods. In this way we properly reproduce the experimental thermal expansion, and obtain a reliable description of the phonon dynamics and of its temperature dependence. The calculated phonon frequencies compare well with the experimental Raman spectrum.

The struggle against death is one of the main themes in human history. Mortality as it declined in recent times, became a central factor behind population growth. In this context, childhood mortality was the key, not only because deaths at these young ages often constituted more than half of all deaths, but also because any decrease in it brought about fundamental changes in the age structure and the size of the population and in fertility.