Abstract
We study some geometric properties associated with the t-geometric means A ♯ t B:= A 1/2(A −1/2 BA −1/2)t A 1/2 of two n × n positive definite matrices A and B. Some geodesical convexity results with respect to the Riemannian structure of the n × n positive definite matrices are obtained. Several norm inequalities with geometric mean are obtained. In particular, we generalize a recent result of Audenaert (2015). Numerical counterexamples are given for some inequality questions. A conjecture on the geometric mean inequality regarding m pairs of positive definite matrices is posted.
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In memory of Professor Miroslav Fiedler who passed away on November 20, 2015
The research of the first author is funded by Vietnam National Foundation for Science and Technology Development (NAFOSTED) under the grant number 101.04-2014.40.
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Dinh, T.H., Ahsani, S. & Tam, TY. Geometry and inequalities of geometric mean. Czech Math J 66, 777–792 (2016). https://doi.org/10.1007/s10587-016-0292-8
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DOI: https://doi.org/10.1007/s10587-016-0292-8
Keywords
- geometric mean
- positive definite matrix
- log majorization
- geodesics
- geodesically convex
- geodesic convex hull
- unitarily invariant norm