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for questions involving inequalities, upper and lower bounds.

3 votes
0 answers
243 views

Maximise $L^q$ norm of a vector, for fixed $L^1$ and fixed $L^p$ norms [closed]

Any pointers/related problems/inequalities are very much welcome. …
VSJ's user avatar
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9 votes
3 answers
732 views

Matrix determinant inequality proof without using information theory

(A statement of the inequality may be found here: Rioul - Information-theoretic proofs of entropy power inequalities, Proposition 9, (65c).) … I am interested in knowing if there is an alternate proof of this result that does not rely on entropy inequalities, and uses linear algebraic tools instead. …
VSJ's user avatar
  • 1,024
5 votes

Matrix determinant inequality proof without using information theory

Let $B := A \Lambda^{1/2}$, so that $A\Lambda A^T = BB^T$. Using the Cauchy-Binet formula for the determinant of $BB^T$, we obtain $$|BB^T| = \sum_{1 \leq i_1 < \dots < i_k \leq n} |B_{i_1 i_2 \dots …
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  • 1,024
1 vote
Accepted

Exercise related to log-Sobolev inequalities

By scaling if necessary, we may assume without loss of generality that $a^2p + b^2\bar p = 1$ Substituting $u = a^2p$, we can rewrite the 1-dimensional inequality as \begin{align*} f(u) := u\log \frac …
VSJ's user avatar
  • 1,024
12 votes
2 answers
2k views

Proving a messy inequality

EDIT: After much work I was able to reduce the inequality to a single variable function which I need to show is non-positive. That function is (for $0\leq p\leq\frac{1}{2}$) $$\frac{p^2(\log(p))^2 - ( …
VSJ's user avatar
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5 votes
Accepted

Proving a messy inequality

I think I managed to prove the entire inequality analytically. The whole proof is a bit long to post here (about 7 pages) and involves ugly looking expressions. I'll outline the general strategy I use …
VSJ's user avatar
  • 1,024
11 votes
2 answers
329 views

A (reverse)-Minkowski type inequality for symmetric sums

Let $(u_1, u_2, u_3, u_4)$ and $(v_1, v_2, v_3, v_4)$ be vectors in $\mathbb R_+^4$. Is the following inequality true? \begin{align*} \left(\sum_{{[4] \choose 3}} \sqrt{u_i u_j u_k}\right)^{2/3} + \ …
VSJ's user avatar
  • 1,024
9 votes
2 answers
455 views

Entropy conjecture for distributions over $\mathbb{Z}_n$

Suppose we have two independent random variables $X$ (with distribution $p_X$) and $Y$ (with distribution $p_Y$) which take values in the cyclic group $\mathbb{Z}_n$. Let $Z = X +Y$, where the additio …
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2 votes
Accepted

Entropy conjecture for distributions over $\mathbb{Z}_n$

The conjecture is wrong! It wasn't as complicated as I thought it was. A simple counter example is over $\mathbb{Z}_6$. Consider $H(X) = 1$ and $H(y) = 1 +\epsilon$ where $\epsilon$ is very small. …
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