Michele Coti Zelati

The primitive equations of the atmosphere in presence of vapour saturation

A modification of the classical primitive equations of the atmosphere is considered in order to take into account important phase transition phenomena due to air saturation and condensation. We provide a mathematical formulation of the problem that appears to be new in this setting, by making use of differential inclusions and variational inequalities, and which allows to develop a rather complete theory for the solutions to what turns out to be a nonlinearly coupled system of non-smooth partial differential equations. Specifically we prove global existence of quasi-strong and strong solutions, along with uniqueness results and maximum principles of physical interest.

Minimality Properties of Set-Valued Processes and their Pullback Attractors

We discuss the existence of pullback attractors for multivalued dynamical systems on metric spaces. Such attractors are shown to exist without any assumptions in terms of continuity of the solution maps, based only on minimality properties with respect to the notion of pullback attraction. When invariance is required, a very weak closed graph condition on the solving operators is assumed. The presentation is complemented with examples and counterexamples to test the sharpness of the hypotheses involved, including a reaction-diffusion equation, a discontinuous ordinary differential equation, and an irregular form of the heat equation.

On the Theory of Global Attractors and Lyapunov Functionals

From the point of view of longterm dynamics, we study multivalued and single-valued semigroups of operators acting on complete metric spaces. We provide necessary and sufficient conditions for the existence of the global attractor under minimal requirements in terms of continuity of the semigroup. In the case of single-valued semigroups possessing a Lyapunov functional, we exhibit a simple proof of the existence and the characterization of the attractor in terms of the unstable set of stationary points. As an application, we consider the multivalued semigroup generated by the equation ruling the evolution of the specific humidity in a system of moist air, and we prove the existence of a regular global attractor.

Enhanced Dissipation, Hypoellipticity, and Anomalous Small Noise Inviscid Limits in Shear Flows

We analyze the decay and instant regularization properties of the evolution semigroups generated by two-dimensional drift-diffusion equations in which the scalar is advected by a shear flow and dissipated by full or partial diffusion. We consider both the space-periodic

Uniformly attracting limit sets for the critically dissipative SQG equation

{\mathbb{T}^2}

Singular Limits of Voigt Models in Fluid Dynamics

T2 setting and the case of a bounded channel

Steady states of the hinged extensible beam with external load

{\mathbb{T} \times [0,1]}