Geometry of the projective unitary group of a C*-algebra

• Autores: Andruchow, Esteban
• Año de publicación: 2017
• Idioma: inglés
• Tipo de recurso: artículo
• Fuente: Revista de la Unión Matemática Argentina. Jun. 2017; 58(2): 319-329; https://inmabb.criba.edu.ar/revuma/revuma.php?p=toc/vol58
• Materia: C*-Algebra; Projective unitaries
• Institución: Universidad Nacional de General Sarmiento

Fil: Andruchow, Esteban. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina.
Fil: Andruchow, Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto Argentino de Matemática "Alberto P. Calderón"; Argentina.
Let A be a C*-algebra with a faithful state ?. It is proved thatthe projective unitary group P UA of A,P UA = UA/T.1,(UA denotes the unitary group of A) is a C?-submanifold of the Banach spaceBs(A) of bounded operators acting in A, which are symmetric for the ?-innerproduct, and are usually called symmetrizable linear operators in A.A quotient Finsler metric is introduced in P UA, following the theory ofhomogeneous spaces of the unitary group of a C*-algebra. Curves of minimallength with any given initial conditions are exhibited. Also it is proved that ifA is a von Neumann algebra (or more generally, an algebra where the unitarygroup is exponential) two elements in P UA can be joined by a minimal curve.In the case when A is a von Neumann algebra with a finite trace, theseminimality results hold for the quotient of the metric induced by the p-normof the trace (p ? 2), which metrizes the strong operator topology of P UA.