Resumen de Isometries between matrix algebras
Chi-Kwong Li, Wai-Shun Cheung, Yiu-Tung Poon
As an attempt to understand linear isometries between -algebras without the surjectivity assumption, we study linear isometries between matrix algebras. Denote by the algebra of complex matrices. If and has the form or for some unitary and contractive linear map , then for all . We prove that the converse is true if , and the converse may fail if . Related results and questions involving positive linear maps and the numerical range are discussed.
