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8 votes
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Geometric mean of three or more positive definite matrices

The geometric mean of two positive definite (Hermitian) matrices of same size is defined by $$A\natural B := A^{1/2}(A^{-1/2}BA^{-1/2})^{1/2}A^{1/2},$$equivalently, $$A\natural B =(BA^{-1})^{1/2}A=A(A^...
Wolfgang's user avatar
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2 votes
0 answers
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Constructing an $n$-simplex at the border of a $n$-ball by orthogonal hyperplanes

I want to construct an $n$-simplex the following way: Choose $n$ vectors in the boundary of an $n$ dimensional ball, which are forming an $(n-1)$-simplex together. Place the orthogonal affine $n-1$-...
weierstrass181's user avatar
1 vote
2 answers
1k views

Möbius transformation by 3 points in the Minkowski model

Goal I'm interested in describing Möbius transformations in the plane, and I'd like to define them in terms of three points and their images. What I have tried I know that a projective ...
MvG's user avatar
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1 vote
1 answer
319 views

Are there any applications of linear algebra over the complex numbers, where the role of complex conjugation is replaced with the trivial involution?

The complex inner product $\langle u, v \rangle$ is a special case of a sesquilinear form over a field. Its definition is $\langle u, v \rangle = \sum_{i} u_i \overline{v_i}$. There is clearly the ...
wlad's user avatar
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