Sopra un teorema di R. Sturm

Ohne Zusammenfassung     

Sopra un problema di interazione di onde elettromagnetiche in un plasma non lineare a geometria sferica

We consider the problem of the approximate determination of the electromagnetic field generated by two oscillating electric dipoles in the center of a spherical cavity imbedded in a nonlinear plasma. The influence of the nonlinearities of the plasma upon the field are investigated by means of a perturbative solution of the relevant equations, deduced from the ‘quasi-hydrodynamic’ approach. Analytical and numerical results, which illustrate several nonlinear effects, as well as the influence of the rarefaction and ionization of the gas, are included. The main result of the paper is the prediction of an observable second harmonic field.     

A proposito di un teorema di rotocontrazione

Sunto. In questo lavoro viene indicato, per certi autoomeomorfismi delle corone circolari, un teorema circa la presenza di curve libere che uniscano o separino le due circonferenze estreme della corona.