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Metric entropy of an ellipsoid

Let $B^d_2$ denote the unit ball of $\ell_2^d$ and let $T$ be an invertible linear map. Consider the function $$ H(T) := \log M(TB_2^d, B_2^d), $$ which is the packing entropy for $TB_2^d$ by $B_2^d$....
Drew Brady's user avatar
6 votes
1 answer
413 views

How many unit cubes are needed to 'hide' a unit cube fully in 3D?

Question: What is the smallest number of nonoverlapping unit cubes that can hide a unit cube C - in the sense that every ray emanating from the boundary of C meets the interior or the boundary of one ...
Nandakumar R's user avatar
  • 5,979
1 vote
1 answer
231 views

For $x_1,...,x_n$ iid random on sphere of radius $\sqrt{d}$ in $R^d$, what is a good upper-bound on min distance of $x_{n}$ from the other $x_i$'s?

Let $n$ and $d$ be large positive integers with $n \le d^\gamma$, for some absolute constant $\gamma>0$; i.e., $n$ is at most polynomial in $d$. Let $x_1,\ldots,x_n,x_{n+1}$ be drawn iid from the ...
dohmatob's user avatar
  • 6,853
1 vote
0 answers
65 views

Covering a simplex efficiently by efficiently describable polytopes?

Take a standard simplex or cube in $\mathbb R^n$. Is there a way to cover it with $O(poly(\log n))$ convex polytopes each describable by only $O(poly(\log n))$ half-plane inequalities? If not what ...
VS.'s user avatar
  • 1,826
1 vote
0 answers
64 views

Polytopes that can be efficiently described and efficiently covered by cubes or simplices?

Is there a bounded convex polytope $\mathcal P\subseteq\mathbb R^n$ with $m$ vertices, whose vertex vectors span $\mathbb R^n$ (so $m$ is $\Omega(n)$) and just $O(poly(\log n))$ half-plane ...
VS.'s user avatar
  • 1,826
8 votes
1 answer
224 views

Translative packing constant strictly larger than lattice packing constant

Simply put, my question is this: what is the smallest dimension, if any, where we can know for sure that a convex body exists whose translative packing constant is strictly larger than its lattice ...
Yoav Kallus's user avatar
  • 5,971