Some Convexity Results for the Cartan Decomposition

2003 ◽  
Vol 55 (5) ◽  
pp. 1000-1018 ◽  
Author(s):  
P. Graczyk ◽  
P. Sawyer

AbstractIn this paper, we consider the set = a(eXKeY) where a(g) is the abelian part in the Cartan decomposition of g. This is exactly the support of the measure intervening in the product formula for the spherical functions on symmetric spaces of noncompact type. We give a simple description of that support in the case of SL(3; F) where F= R, Cor H. In particular, we show that is convex.We also give an application of our result to the description of singular values of a product of two arbitrary matrices with prescribed singular values.

2014 ◽  
Vol 98 (2) ◽  
pp. 232-256 ◽  
Author(s):  
P. GRACZYK ◽  
P. SAWYER

AbstractWe study the absolute continuity of the convolution ${\it\delta}_{e^{X}}^{\natural }\star {\it\delta}_{e^{Y}}^{\natural }$ of two orbital measures on the symmetric spaces $\mathbf{SO}_{0}(p,p)/\mathbf{SO}(p)\times \mathbf{SO}(p)$, $\mathbf{SU}(p,p)/\mathbf{S}(\mathbf{U}(p)\times \mathbf{U}(p))$ and $\mathbf{Sp}(p,p)/\mathbf{Sp}(p)\times \mathbf{Sp}(p)$. We prove sharp conditions on $X$, $Y\in \mathfrak{a}$ for the existence of the density of the convolution measure. This measure intervenes in the product formula for the spherical functions.


1993 ◽  
Vol 72 (1) ◽  
pp. 1-29 ◽  
Author(s):  
Ralph S. Phillips ◽  
Mehrdad M. Shahshahani

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