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Statistics of spectral properties of matrix-valued random variables.

16 votes
Accepted

Laws of Iterated Logarithm for Random Matrices and Random Permutation

My initial answer was wrong. Instead of completely deleting it, I left it at the bottom of the post. I use notation now that slightly differ from my original post. As before, I give only a partial a …
ofer zeitouni's user avatar
11 votes
Accepted

Repeated random two-steps in $\mathbb{R}^3$: unbounded?

I assume your random $M_i$s are from $O(3)$, not $SO(3)$. In fact, I suspect that the answer depends on whether $M_1M_2$ has eigenvalue $1$ or eigenvalue $-1$. If I did not make a mistake, when you e …
ofer zeitouni's user avatar
7 votes

Eigenvalue distribution of the sum of two random matrices

You did not specify whether J is assumed symmetric or not. If it is, the limit of empirical values of eigenvalues of J alone is the semicircle, while in the non-symmetric it is the circular law. If …
ofer zeitouni's user avatar
7 votes
Accepted

Concentration of sum of powers of normals

For $p>1$, the random variables you discuss do not possess exponential moments; You are in the regime of large deviations with stretched exponential tails. See for example the following recent paper b …
ofer zeitouni's user avatar
6 votes
Accepted

How to calculate expected value of matrix norms of $A^TA$?

Expanding a bit on Yemon Choi's comment: concentration is indeed the key. First, $\|B\|_F^2$ is simply the sum of the squares of singular values of $A$, and $E\|B\|_F^2=m(m-1)n+mn^2$. On the other ha …
ofer zeitouni's user avatar
6 votes

Distribution of eigenvalues of a Wishart matrix

All you need is that the empirical measure of the $k_i$s converge. Whenever it does, just apply the original Pastur-Marcenko (1967) results to get that the empirical measure associated with your matr …
ofer zeitouni's user avatar
6 votes
Accepted

Marchenko-Pastur Law under general covariance structure

In the Gaussian case, you can rewrite $x_i=R^{1/2}y_i$ where $y_i$ now possess iid entries. This leads you to computing the eigenvalues of $Y^*RY$, this is actually the problem solved by Pastur and Ma …
ofer zeitouni's user avatar
5 votes

Expected value of the spectral radius of a random nonnegative matrix

To amplify on Brendan's answer: You are dealing with a matrix of zero mean iid's plus a rank one perturbation: $M=W+ A$ where $A=c11^T$ and $c=EY$. The spectral norm of $W$ is asymptotically $2\sqrt …
ofer zeitouni's user avatar
4 votes
Accepted

Distribution of entries of a doubly-sorted random matrix

Let $X$ be the array after your operation. The law of $X_{i,j}$ for $(i,j)$ chosen in a deterministic way from $[1,..,n]^2$ converges to the uniform law. The tilting due to your operations is very sma …
ofer zeitouni's user avatar
4 votes

What is the spectral norm of a random projection times a diagonal?

I think the following answers your question (and more): http://www-personal.umich.edu/~romanv/papers/product-random-deterministic.pdf
ofer zeitouni's user avatar
4 votes

Number of permutations with longest increasing subsequences of length at most $n$

An explicit formula is the hook-product formula, due to Schensted I believe. This formula is used in the classical work of Logan and Shepp, as well as in Vershik-Kerov. See for example equation (1.1) …
ofer zeitouni's user avatar
4 votes

Deterministic matrices with random matrix properties

Actually, just to get the semicircle is not hard. Take an $n$-by-$n$ Jacobi matrix whose on diagonal entries are $0$ and $i$th entry on the off diagonal is $\sqrt{i/n}$. The limit ESD will be the semi …
ofer zeitouni's user avatar
3 votes
Accepted

Random matrices: why to distingusish bulk and edge cases?

Intuitively, the fact that the density vanishes at the edge already hints that the spacing at the edge changes (which indeed it does), and that the asymptotics are different; this is confirmed in the …
ofer zeitouni's user avatar
3 votes
Accepted

Determining the asymptotic behavior of random matrices with vanishing ratio dimensions

There are many ways to see that, maybe the simplest is the following: let $W=XX^T/K$. Compute $E Tr W^k$ as $K,N\to\infty$. The combinatorics is easy - essentially, the only terms that survive passag …
ofer zeitouni's user avatar
3 votes

How to calculate eigenvalue density function of $XX^\dagger$ from the density function of X

The relation between singular values and eigenvalues in the invariant case is evaluated in this paper, under some technical conditions: http://arxiv.org/abs/0909.2214 (see http://annals.math.princeton …
ofer zeitouni's user avatar

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