Existence of ground states for approximately inner two--parameter $C_0$--groups on $C^*$--algebras

Document Type : Research Paper


Department of Mathematics, Mashhad Branch, Islamic Azad University, Mashhad, Iran.


In this paper, we generalize the definitions of approximately inner $C_0$-groups and their ground states to the two- parameter case and study necessary and sufficient conditions for a state to be ground state. Also we prove that any approximately inner two- parameter $C_0$--group must have at least one ground state. Finally some applications are given.


Main Subjects

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