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Statistics of spectral properties of matrix-valued random variables.

4 votes

Random matrix with non-identical variances

Your matrix model can be written as the product of a standard gaussian matrix with a deterministic diagonal matrix. As such, I believe that Theorem 4 of this paper of Bordenave: http://arxiv.org/abs/ …
Terry Tao's user avatar
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9 votes
Accepted

Joint distribution of minor of Wigner Hermitian matrices

There is certainly no asymptotic independence between $\det M_{11}, \det M_{22}$. From the base times height formula for parallelepipeds we see that \begin{align*} \frac{|\det M_{12}|}{|\det M_{22}|} …
Terry Tao's user avatar
  • 114k
43 votes
Accepted

Anti-concentration bound for permanents of Gaussian matrices?

I did a preliminary feasibility analysis of our methods and it appears possible that one may be able to tighten our $n^\epsilon$ loss to something more like $\exp( \sqrt{n} )$ in the Gaussian case, bu …
Terry Tao's user avatar
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3 votes
Accepted

Tail bounds on eigenvalue gaps for GUE

This is studied in Gérard Ben Arous and Paul Bourgade, Extreme gaps between eigenvalues of random matrices, Ann. Probab. 41 (2013), no. 4, 2648--2681. (Ah, so that's how the "insert citation" butto …
Terry Tao's user avatar
  • 114k
21 votes
Accepted

An experiment on random matrices

The distribution of the bulk of the spectrum is an example of the circular law. For the model you selected (where each entry is uniformly chosen at random from an interval), the law was first proven …
Terry Tao's user avatar
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18 votes

Expected determinant of a random NxN matrix

It is a little more convenient to work with random (-1,+1) matrices. A little bit of Gaussian elimination shows that the determinant of a random n x n (-1,+1) matrix is $2^{n-1}$ times the determinan …
Terry Tao's user avatar
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14 votes
Accepted

Intuition behind the spectral density of random matrices

I don't know of a fully intuitive derivation, but there are some informal arguments that give the circular law with a relatively small amount of calculation. Let $M$ be a matrix where the entries are …
Terry Tao's user avatar
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9 votes
Accepted

A question about the paper "The Condition Number of a Randomly Perturbed Matrix"

One does not need to have $n^{-B-3/2}/2$ to be equal to $0.1$, it is enough for it to be less than or equal to $0.1$, which is certainly the case for $n$ large enough. Thanks for pointing out this ty …
Terry Tao's user avatar
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19 votes

Smallest eigenvalue of a tricky random matrix

I think I can get an upper bound of $O(1/n^2)$ by exhibiting a vector $v$ of magnitude comparable to $1$ which gets mapped to a vector of magnitude $O(1/n^2)$. The basic idea is to exploit the birthd …
Terry Tao's user avatar
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3 votes
Accepted

How typical are integer isometries on a hypercube? Littlewood-Offord problem for Bernoulli G...

By the Chernoff bound, we see that for each $1 \leq i < j \leq m$, one has $u_i \cdot u_j = O(\sqrt{n})$ with probability at least $1-\frac{1}{10m^2}$ (say), where implied constants are allowed to dep …
Terry Tao's user avatar
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6 votes

Free probability: A unitary group heuristic for the relationship between additive free convo...

One can get a certain way towards this goal via a sort of "dimensional analysis". This isn't a completely satisfying heuristic argument - in particular, it only partially specifies what compression m …
Terry Tao's user avatar
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24 votes
Accepted

Intuitive understanding of the Stieltjes transform

Firstly, the equation you attribute to Silverstein (and is sometimes known as the "self-consistent equation" for the Stieltjes transform) is not exact, but only asymptotically valid in the limit $n \t …
Terry Tao's user avatar
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11 votes
Accepted

Lower-bound for smallest eigenvalue of random $k \times $k matrix $C(W)$ defined by $C(W)_{i...

We have $$ C(W) = 2 A \circ A + v v^\top$$ where $v$ is the vector with entries $\|w_i\|^2$, $A$ is the Wishart matrix with entries $w_i^\top w_j$, and $\circ$ is the Hadamard product. From the Schur …
Terry Tao's user avatar
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5 votes

Has the technique of "sprinkling" been used in studying random matrices?

The continuous comparison method of Knowles and Yin, Knowles, Antti; Yin, Jun, Anisotropic local laws for random matrices, Probab. Theory Relat. Fields 169, No. 1-2, 257-352 (2017). ZBL1382.15051. fol …
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