Relatore:	Joseph Zaks (University of Haifa , Haifa (Israel))
Titolo:	A few short combinatorial proofs in Geometry.
Sunto:	We will treat the unit-distance graph over the real (or rational) points in Ed, discuss their connectivity and chromatic numbers, and use it in connection with the Beckman-Quarels Theorem (" Every mapping from Ed to itself, d >= 2, that preserves distance one is an isometry"). We will show that every closed curve on the unit sphere in E^d that meets all the d major hyperplanes has length of at least pi.
Luogo:	Aula Seminari del III piano del Dipartimento di Matematica "Francesco Brioschi", Politecnico di Milano, via Bonardi n. 9 (edificio "La Nave")
Data:	Venerd́ 27 Aprile 2007
Ore:	11:00