no. 15-16
Geometry/Calculus of Variations
Geodesics in infinite dimensional Stiefel and Grassmann manifolds
[Géodesiques sur des variétiés de Stiefel et de Grassmann de dimension infinie]

Présenté par : Jean-Pierre Demailly

Harms, Philipp1 ; Mennucci, Andrea C.G.2
1 Harvard Education Innovation Laboratory, Harvard University, 44, Brattle Street, Cambridge, MA 02138, USA
2 Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy
Comptes Rendus. Mathématique, Tome 350 (2012) no. 15-16, pp. 773-776.

Soit V un espace de Hilbert séparable, éventuellement de dimension infinie. Soient St(p,V) lʼensemble des systèmes orthonormés de p vecteurs de V, appelé la variété de Stiefel, et Gr(p,V) lʼensemble des sous-espaces vectoriels de V de dimension p, appelé la variété Grassmannienne. En réduisant le problème en dimension finie, nous montrons que dans ces espaces il existe des géodésiques minimales entre chaque paire de points et nous caractérisons le cut-locus.

Let V be a separable Hilbert space, possibly infinite dimensional. Let St(p,V) be the Stiefel manifold of orthonormal frames of p vectors in V, and let Gr(p,V) be the Grassmann manifold of p-dimensional subspaces of V. We study the distance and the geodesics in these manifolds, by reducing the matter to the finite dimensional case. We then prove that any two points in those manifolds can be connected by a minimal geodesic, and characterize the cut locus.

Reçu le :
Accepté le :
Publié le :
DOI : 10.1016/j.crma.2012.08.010
Harms, Philipp 1 ; Mennucci, Andrea C.G. 2

1 Harvard Education Innovation Laboratory, Harvard University, 44, Brattle Street, Cambridge, MA 02138, USA
2 Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy 
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     title = {Geodesics in infinite dimensional {Stiefel} and {Grassmann} manifolds},
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Harms, Philipp; Mennucci, Andrea C.G. Geodesics in infinite dimensional Stiefel and Grassmann manifolds. Comptes Rendus. Mathématique, Tome 350 (2012) no. 15-16, pp. 773-776. doi : 10.1016/j.crma.2012.08.010. http://www.numdam.org/articles/10.1016/j.crma.2012.08.010/

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☆ This research was funded by SNS09MENNB of the Scuola Normale Superiore, and by the FWF Project 21030.