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Statistics of spectral properties of matrix-valued random variables.

1 vote
Accepted

LDP for Marchenko Pastur with k/n tending to 0

For standard Gaussians, and with the matrix $W/n$, the proof of the LDP given by Ben Arous-Guionnet adapts to the Wishart setup. However, you will have different scalings and so the non-commutative en …
ofer zeitouni's user avatar
1 vote
Accepted

Sum of Square of the Eigenvalues of Wishart Matrix

I will assume $m=\alpha_d d$ with $\alpha_d\to \alpha \in [1,\infty)$ independent of $d$. The case $\alpha\to\infty$ is actually easier. Define $Z=d^{-1} m^{-2} \sum_{i=1}^d \lambda_i^2$. Then $Z$ con …
ofer zeitouni's user avatar
2 votes

Expectation of product of random matrices

This falls within the domain of free probability, at least when the dimension is large. That is, if the matrices are say unitarily invariant and independent, and if we denote by $tr_N$ the trace divid …
ofer zeitouni's user avatar
3 votes

$\ell^1$-norm of eigenvectors of Erdős-Renyi Graphs

The following does not decide on whether the infimum is $0$, but it does give a rough bound. Let $v$ be a normalized eigenvector. Suppose $\|v\|_1<n^{\alpha}$ for some $\alpha<1/2$. Let $I=\{i: |v_i| …
ofer zeitouni's user avatar
1 vote

Expectation of the determinant of the inverse of non-central Wishart matrix

You did not specify whether you have a relation between $n$ and $k$ and whether you care about asymptotics. I will assume that $k/n\to 1$ and that $n\to\infty$, and that your scaling is such that the …
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
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
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
1 vote
Accepted

Universality of the top eigenvalue of correlation matrices

In general you need more than second moment - you need fourth moment finite, otherwise the top eigenvalue can run off to infinity in your scaling. For this and more see the book of Bai and Silverstein …
ofer zeitouni's user avatar
2 votes

Marcenko Pastur law when the dimensionality/sample size ratio $p/n \to 0, \infty$? Lack of r...

It is enough to understand the case $p/n\to 0$, as the eigenvalues of $XX^*$ match those of $X^*X$ up to an extra atom at $0$. In that case you can argue as follows, with $\sigma=1$: writing $W=n^{-1} …
ofer zeitouni's user avatar
1 vote

Real matrices with complex eigenvalues of bounded modulus

I do not understand the role of $k$ in your question, so I will just ignore it. If you take your matrix to consist of independent Gaussian entries (normalized by $\sqrt{n}$), this will give a precise …
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
3 votes
Accepted

Largest eigenvalue of the adjacency matrix of weighted random graph

The question is not completely clear. Do you fix a random $G(n,p)$ and then replace the $1$ in the adjacency matrix by a uniform random variable? Or is it as you write at the end, namely you just take …
ofer zeitouni's user avatar
3 votes
Accepted

Bound for largest eigenvalue of symmetric matrices of uniform random variables over $[0,1]$ ...

The diagonal elements just shift the spectrum (and the top eigenvalue) by $1$. So we may assume they are $0$. You are essentially dealing with a symmetric matrix whose entries above the diagonal are …
ofer zeitouni's user avatar
2 votes
Accepted

Necessary and Sufficient Conditions for $L^p$ Convergence of the Largest Eigenvalue of a Wig...

I believe this follows from the standard estimates that show the convergence. For example, look at the proof in Anderson-Guionnet-Zeitouni's book, page 24. Indeed, from the last display there, you get …
ofer zeitouni's user avatar

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