Geodesic
Topological manifolds and real algebraic geometry
Bollettino della Unione matematica italiana, Série 8, 6B (2003) no. 3, pp. 545-555.

Voir la notice de l'article provenant de la source Biblioteca Digitale Italiana di Matematica

We study the problem of approximating, up to homotopy, compact topological manifolds by real algebraic varieties. As a consequence, we realize any integral non-degenerate quadratic form as the intersection form of a real algebraic variety. This is related to a well-known result, due to Freedman [F], on the topology of closed simply-connected topological $4$-manifolds.
Si studia il problema di approssimazione, a meno di omotopia, delle varietà topologiche compatte di dimensione $4$ con varietà algebriche. Come conseguenza si prova che ogni forma quadratica intera non degenere è la forma di intersezione di una varietà algebrica reale di dimensione $4$. Questi risultati sono legati ai ben noti lavori di Freedman sulla topologia delle varietà compatte, semplicemente connesse di dimensione 4. 
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Tognoli, Alberto. Topological manifolds and real algebraic geometry. Bollettino della Unione matematica italiana, Série 8, 6B (2003) no. 3, pp. 545-555. http://geodesic.mathdoc.fr/item/BUMI_2003_8_6B_3_a2/

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