Francesco Di Plinio, Brown University Mathematics Department, Pointwise convergence of Fourier series and a Calderon-Zygmund decomposition for modulation invariant singular integrals, Friday, June 19, 2015, time 14:00 o'clock, Aula seminari III piano
Abstract:Abstract:
The Calderon-Zygmund decomposition is a fundamental tool in the analysis of singular integral operators, prime examples of which are the Hilbert and Riesz transforms occurring, for instance, in elliptic PDEs. Its prime purpose is the extension of L^2 boundedness results for operators of this type to (all) other L^p spaces. The exploited mechanism is the extra cancellation occurring when the singular integral operator is applied to functions with mean zero. On the other hand, pointwise convergence of Fourier series of L^p functions is governed by L^p bounds for maximally modulated versions of singular integrals, for which the single zero frequency of f plays no particular role. In this talk, we describe a novel Calderon-Zygmund decomposition adapted to the maximally modulated setting and its applications to both pointwise convergence of Fourier series of functions near L^1 and sharp bounds for the bilinear Hilbert transform near the critical exponent L^{2/3}. The presentation will be non-technical and suitable for an advanced undergraduate audience. Partly joint work with Ciprian Demeter (IU), Christoph Thiele (Bonn), Andrei Lerner (Bar-Ilan U, Israel) and Yumeng Ou (Brown U).

Filippo Dell' Oro, Institute of Mathematics of the Academy of Sciences of the Czech Republic, Exponential stability for thermoelastic Bresse systems with nonclassical heat conduction, Friday, March 06, 2015, time 14:00, Aula seminari III piano
Abstract:Abstract:
We provide a comprehensive stability analysis of the thermoelastic Bresse system (also known as the circular arch problem). In particular, assuming a temperature evolution of Gurtin-Pipkin type, we establish a necessary and sufficient condition for exponential stability in terms of the structural parameters of the problem. As a byproduct, a complete characterization of the longtime behavior of Bresse-type systems with Fourier, Maxwell-Cattaneo and Coleman-Gurtin thermal laws is obtained.

Francesco Tulone, Università di Palermo, HK-type integral and application, Tuesday, Febraury 17, 2015, time 11:00 o'clock, Aula seminari MOX, VI piano
Abstract:Abstract:
Durante il seminario si enunceranno le principali proprietà di integrali non-assolutamente convergenti e le loro applicazioni nella ricostruzione dei coefficienti di Fourier per sistemi di Walh e di Vilenkin

Marisa Toschi, Instituto de Matematica Aplicada del Litoral, Departamento de Matematica, Santa Fe, Argentina , Elliptic operators and Muckenhoupt weights, Thursday, December 04, 2014, time 14:30 o'clock, Aula Seminari III piano
Abstract:Abstract:
Under different conditions on a domain $\Omega$, we prove some weighted a priori estimates for solutions to the Dirichlet problem when the weight is in the Muckenhoupt class $A_p(R^n)$. In particular, we are interested in the case of weights which are powers of the distance to the boundary of $\Omega$ and we study for which powers these weights belongs to $A_p(R^n)$. These results can be extended to a metric measure space $(X;d;\mu)$ satisfying the so called Ahlfors condition, which is a particular case of space of homogeneous type. We also obtain a new family of weights in the class $A_p(X;d;\mu)$ for a general metric measure space. This seminar is organized within the PRIN 2012 Research project «Equazioni alle derivate parziali di tipo ellittico e parabolico: aspetti geometrici, disuguaglianze collegate, e applicazioni - Partial Differential Equations and Related Analytic-Geometric Inequalities» Grant Registration number 2012TC7588_003, funded by MIUR – Project coordinator Prof. Filippo Gazzola

DEBDIP GANGULY, POLITECNICO DI TORINO, PARTIAL DIFFERENTIAL EQUATIONS ON HYPERBOLIC SPACE , Friday, November 28, 2014, time 14:30 o'clock, Aula Seminari III piano
Abstract:Abstract:
In this talk, semilinear elliptic partial differential equations(PDEs) on hy-perbolic space and related problems will be presented. Several geometric problems lead to the study of the equation: $$- \Delta _{B ^N} u - \lambda u = |u| ^ {p-2} u , u \in H ^ 1 (B ^N)$$ where $\lambda$ is a real parameter and $H^1(B^N)$ denotes the Sobolev space on the conformal ball model of the hyperbolic space. Some existence, non existence and qualitative properties of solutions of above equation will be pointed out.

Daniele Castorina, Università di Padova, Ground States for Diffusion Dominated Free Energies with Logarithmic Interaction, Thursday, November 27, 2014, time 12:00 o'clock, Aula seminari III piano
Abstract:Abstract:
Replacing linear diffusion by a degenerate diffusion of porous medium type is known to regularize the classical two-dimensional parabolic-elliptic Keller-Segel model as in Calvez-Carrillo JMPA2006. The implications of nonlinear diffusion are that solutions exist globally and are uniformly bounded in time. We analyse the stationary case showing the existence of a unique, up to translation, global minimizer of the associated free energy. Furthermore, we prove that this global minimizer is a radially decreasing compactly supported continuous density function which is smooth inside its support, and it is characterized as the unique compactly supported stationary state of the evolution model. This unique profile is the clear candidate to describe the long time asymptotics of the diffusion dominated classical Keller-Segel model for general initial data. This is a joint work with Josè Antonio Carrillo and Bruno Volzone.