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Theory and applications of probability and stochastic processes: e.g. central limit theorems, large deviations, stochastic differential equations, models from statistical mechanics, queuing theory.

2 votes
0 answers
166 views

An attempt to define expected value of a Riemannian manifold valued random variable - what'l...

Let $X:\Omega\to (M,g)$ be a random variable taking values in a Riemannian manifold $(M,g)$ with the Riemannian volume form denoted by $dvol_g(x).$ We know that there's no standard way to generalize t …
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0 votes
1 answer
60 views

What can we say about the order of convergence of a critical point of Gaussian mixture densi...

Density of Gaussian mixture with $n$ components is given by: $$f(x):=C \sum_{i=1}^{n}e^{-\frac{1}{2}||\frac{x-x_i}{h}||^2}, x_i \in \mathbb{R}^d, h > 0$$ where $C$ is a normalization constant ensuring …
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4 votes
1 answer
273 views

Local maxima of the sum of Gaussian functions in *multiple dimensions* are always strict loc...

This is a follow up of the question in one dimension, that asked to show that the all the maxima of the sum of Gaussian $$f_n(x):= \sum_{i=1}^{n}e^{-(x-x_i)^2}, x_1 < x_2 < \dots < x_n$$ are strict lo …
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0 votes
1 answer
3k views

In linear regression, we have 0 training error if data dimension is high, but are there simi...

I tried posting this question on Cross Validated (the stack exchange for statistics) but didn't get an answer, so posting here: Let's consider a supervised learning problem where $\{(x_1,y_1) \dots (x …
Learning math's user avatar
0 votes
1 answer
124 views

Question on limit in probability of the ratio of max to min of 2 sequences of non-ive, conti...

For each $ m \ge 1$, let $X_m$ and $Y_m$ be two non-negative iid random variables with the same distribution. (The distributions of $X_m$ may change with different $m$.) **Assume that their support of …
Learning math's user avatar
1 vote
1 answer
144 views

Asymptotics of $\chi_m$-distribution where the degree of freedom $m \to \infty?$

I'm interested to see a result where for large degree of freedom $m,$ the chi distribution $\chi_m$ is increasingly well approximated by a family of normal distributions with parameters depending on $ …
Learning math's user avatar
0 votes
1 answer
407 views

First and last order statistics and their ratio for $\chi^2_{m}$ random samples

Let $X_1, \dots, X_n \sim_{iid} \chi^2_{m}$ be a random sample from a chi-squared distribution with $m$ degrees of freedom (d.f.). I was wondering if there's any known result for the order statistics …
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-1 votes
1 answer
134 views

On the concentration of Lipschitz functions near its expectation, where the vector has ident...

Consider the random vector $X:=(X_1\dots X_1) \in \mathbb{R}^n, X_1 \sim \mathcal{N}(0,1).$ Notice the identical components, they're identically distributed but not independent. Now, I was wondering …
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0 votes
0 answers
243 views

Concentration (or two sided tail bounds around expectations) of maximum and minimum of $n$ i...

I asked this on MSE, but got no answer, hence asking here now. Help appreciated! My question is motivated by this question and this question, where the first was aimed for giving a one sided tail bou …
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0 votes
1 answer
361 views

Concentration of norm of linearly transformed normal random vector as dimension go to infinity

Earlier asked on MSE, but didn't get an answer, so posting here: Let $X=(X_1 \dots X_n) \in \mathbb{R}^n, X_i\sim N(0,1), iid.$ Let $B: \mathbb{R}^n \to \mathbb{R}^n $ be the diagonal linear map: $B …
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0 votes
0 answers
137 views

What is the distribution of the norm of the multivariate $X \sim \mathcal{N}(\mu, \Sigma) \i...

Let $X \sim \mathcal{N}(\mu, \Sigma) \in \mathbb{R}^d$ follow a multivariate normal distribution. Then what's the distribution (PDF, CDF etc.) of $X?$ When $\mu = 0, \Sigma = I_d,$ we know that $||X| …
Learning math's user avatar
2 votes
1 answer
884 views

Asymptotically tight concentration of norms of subgaussian random vectors with independent c...

Let $X=(X_1 \dots X_n)\in \mathbb{R}^n,$ be a subgaussian random vector so that $X_i$'s are independent, $\mathbb{E}X_i = 0, \mathbb{E}X_i^2=1.$ Before we pose our question, let's state the following: …
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4 votes
0 answers
627 views

Comparison of concentrations of different $L^p$-norms of (sub) Gaussian distributions

It's well-known that the Euclidean $2$-norm of subgaussian random vectors concentrates in high dimensions, e.g. when $X \sim \mathcal{N}(0,I_n),$ (or in general $X$ is subgaussian with independent co- …
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2 votes
1 answer
992 views

Bound on eigenvalues of sample covariance matrices in terms of $d, n$, where $n=$ sample siz...

Let $Z=[z_1, \dots z_n]$ be a $d \times n$ matrix, where the $z_i$'s are iid random vactors with mean $\mu \in \mathbb{R}^d$ and $d \times d$ (population) covariance matrix $\Sigma$, but the entries $ …
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1 vote
0 answers
122 views

Law of large numbers and Central Limit Theorem for eigenvalues of perturbed matrices

I'm looking for results where perturbation by iid random entries to a matrix will result in convergence of the eigenvalues to the original eigenvalues. More precisely, Let $ \forall n \in \mathbb{N} …
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