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Let $n,m \geq 1$. We fix $n$ distinct vectors $x_1, ... , x_n \in \mathbb{R}^m$. We define $A \in \mathbb{R}^{n\times n}$ as \begin{equation} A_{ij} = x_i^T \left(n x_j - \sum_{1 \leq k \leq n} x_k \...

Let $A_n$ be the matrix whose rows and columns are indexed by pairs $(i,j)$ with $1\leq i,j\leq n$ and $i\neq j$ (so $A$ is an $n(n-1)\times n(n-1)$ matrix), whose $((i,j),(k,l))$-entry is 0 if $i=k$ ...

Let $p_1$ and $p_2$ be a complete system of orthogonal projections on $R^n$, $n\geq 2$ (i.e., $p^2_i=p_i=p^*_i$ and $p_1+p_2=\bf{1}$) and $S_1,S_2$ be two commuting hermitian operators on $R^n$ (i.e., ...

Let $n\ge 2$. Let $p$ be a prime and $\mathbb{Z}_p$ denote the finite field with $p$ elements. I want to know about the presentation for the group $GL(n,\mathbb{Z}_p)$ consisting of its generators and ...

Let $\mathcal C$ denote the commuting variety of pairs of matrices in $M_n(\mathbb{C})$, defined as: $$ \mathcal C = \{ (A, B) \in M_n(\mathbb{C})^2 \mid [A, B] = 0 \}. $$ It is well known that $\...