Nell’ambito del programma “Visiting Professor 2016” finanziato dalla Regione Autonoma della Sardegna, la Prof.ssa. Irene I. ONNIS (Università di San Paolo, Brasile) terrà le seguenti lezioni

28 Settembre ore 16 Aula B

Title: **Helix surfaces in the Berger sphere and in the special linear group**

Abstract: In recent years much work has been done to understand the geometry of surfaces whose unit normal vector field forms a constant angle with a fixed field of directions of the ambient space. These surfaces are called helix surfaces or constant angle surfaces and they have been studied in most of the three-dimensional geometries. In this talk, we present a characterization of helix surfaces in the Berger sphere. In particular, we prove that a helix surface is invariant by the action of a one-parameter group of isometries of the ambient space. Also, we discuss some recent results about helix surfaces in the special linear group SL(2,R).

4 Ottobre ore 16 Aula B

Title: **Enneper representation of minimal surfaces in the Lorentz-Minkowski 3-space**

Abstract: In the Lorentz-Minkowski 3-space a Weierstrass representation type theorem was proved by Kobayashi (in 1983) for spacelike minimal immersions and by Konderak (in 2005) for the case of timelike minimal surfaces. Recently, these theorems were extended for immersed minimal surfaces in Riemannian and Lorentzian 3-dimensional manifolds by Lira, Melo and Mercuri. In this talk, we prove an Enneper-type representation for spacelike and timelike minimal surfaces in the Lorentz-Minkowski space. Then, we exhibit some examples of minimal surfaces in this space constructed via the Enneper representation formula, that it is equivalent to the Weierstrass representation obtained by Kobayashi and by Konderak, respectively.