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4 votes
2 answers
890 views

Partitioning an orthogonal matrix into full rank square submatrices

Let $U$ be an $n \times n$ orthogonal matrix. Given an arbitrary partition ${\mathcal P}_c=\{y_1,y_2,\ldots,y_k\}$ of the columns of $U$, does there always exist a corresponding partition ${\mathcal ...
David Shuman's user avatar
7 votes
3 answers
221 views

What is special in dimension $2$ (When characterizing isometries using the cofactor matrix)?

Let $A$ be a real $n \times n$ matrix. Denote by $\operatorname{cof} A$ The cofactor matrix of $A$. By definition, $A (\operatorname{cof} A)^T=\det A \cdot I$. Thus, it is immediate that $A \in \...
Asaf Shachar's user avatar
  • 6,741
5 votes
1 answer
214 views

When does isometric projection respect multiplication?

Every $A \in \text{GL}_n(\mathbb{R})$ has a unique orthogonal polar factor $O_A=A(\sqrt{A^TA})^{-1}$, ( $A=O_AP_A$, $O \in \operatorname{O}_n, P \in \operatorname{Psym}_n$see Polar decomposition). ...
Asaf Shachar's user avatar
  • 6,741
4 votes
4 answers
2k views

I want a smooth orthogonalization process

The following question is related to research I am doing on reinforcement learning on manifolds. I have a set of basis vectors $\boldsymbol{B} = \{\boldsymbol{b}_1,\dots,\boldsymbol{b}_k\}$ that span ...
Jabby's user avatar
  • 155