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dohmatob
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Given a large random matrix, how to prove that every large submatrix whose range contains a large ball?

Context. Studing a problem in machine-learning, I'm led to consider the following problem in RMT...


Fix $\delta \in (0, 1)$ once and for all.

Q: Is it possible to find universal constants $c_1 > 0$ and $c_2 > 0$ (depending only on $\delta$) such that the following phenomenon holds ?

Phenomenon. Let $m$ and $n$ be large positive integers with $m \le \delta n$, and let $k \ge c_1 m$. Let $X$ an $m$-by-$n$ random real matrix with iid $N(0,1)$ entries. Finally, denote by $c_2\mathbb B^k$ the ball of radius $c_2$ in $\mathbb R^k$.

With high probability $p(n,m)$, every $k$-by-$n$ submatrix $Z$ of $X$ verifies $$ c_2\mathbb B^k \subseteq Z\mathbb B^{n}:= \{Zv \mid v \in \mathbb B^n\}. $$

Also, how large can the $p(n,m)$ probability be as a function of $n$, $m$, $m/n$, etc. ?

dohmatob
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