Search results for " Matematica"

$PT$-symmetric graphene under a magnetic field

2016

We propose a $PT$-symmetrically deformed version of the graphene tight-binding model under a magnetic field. We analyze the structure of the spectra and the eigenvectors of the Hamiltonians around the $K$ and $K'$ points, both in the $PT$-symmetric and $PT$-broken regions. In particular we show that the presence of the deformation parameter $V$ produces several interesting consequences, including the asymmetry of the zero-energy states of the Hamiltonians and the breakdown of the completeness of the eigenvector sets. We also discuss the biorthogonality of the eigenvectors, which {turns out to be} different in the $PT$-symmetric and $PT$-broken regions.

A version of Hake’s theorem for Kurzweil–Henstock integral in terms of variational measure

2019

Abstract We introduce the notion of variational measure with respect to a derivation basis in a topological measure space and consider a Kurzweil–Henstock-type integral related to this basis. We prove a version of Hake’s theorem in terms of a variational measure.

Un’esperienza educativa di trasposizione culturale nella scuola primaria

2015

La nostra ricerca vuole mostrare come lo studio di approcci sviluppati in diversi contesti culturali può essere importante per riflettere sulle nostre pratiche didattiche e per progettare nuove sperimentazioni nelle classi. In particolare abbiamo studiato le rappresentazioni grafiche usate per descrivere e risolvere problemi additivi nella scuola primaria in Russia e Cina. In questo articolo introdurremo l’idea di trasposizione culturale che sarà anche esemplificata attraverso la descrizione e analisi di due percorsi didattici realizzati in una II e in una V primaria italiane.

Approfondimenti di Didattica della Matematica. Le abilità logico matematiche nei bambini. Una ricerca con alunni da tre ad undici anni” – Terza Parte

2006

Un modello per il riempimento delle reti di distribuzione idrica in presenza di turnazione del servizio

2010

Stieltjes Differential Inclusions with Periodic Boundary Conditions without Upper Semicontinuity

2021

We are studying first order differential inclusions with periodic boundary conditions where the Stieltjes derivative with respect to a left-continuous non-decreasing function replaces the classical derivative. The involved set-valued mapping is not assumed to have compact and convex values, nor to be upper semicontinuous concerning the second argument everywhere, as in other related works. A condition involving the contingent derivative relative to the non-decreasing function (recently introduced and applied to initial value problems by R.L. Pouso, I.M. Marquez Albes, and J. Rodriguez-Lopez) is imposed on the set where the upper semicontinuity and the assumption to have compact convex value…

Multi-phase epidemic model and its numerical simulation

2008

A note on the existence of an invariant measure for a stochastic model with periodic coefficients

2012

We consider a stochastic model of malaria which concern the infected population and the vector population and whose coefficients are periodic functions. Under a suitable condition the existence of an invariant measure is proved.

SIRV epidemic model with stochastic perturbation

2014

We propose a stochastic disease model where vaccination is included and such that the immunity is permanent. The existence, uniqueness and positivity of the solution and the stability of the disease free-equilibrium are studied

Compactness in Groups of Group-Valued Mappings

2022

We introduce the concepts of extended equimeasurability and extended uniform quasiboundedness in groups of group-valued mappings endowed with a topology that generalizes the topology of convergence in measure. Quantitative characteristics modeled on these concepts allow us to estimate the Hausdorff measure of noncompactness in such a contest. Our results extend and encompass some generalizations of Fréchet–Šmulian and Ascoli–Arzelà compactness criteria found in the literature.