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4 votes
0 answers
154 views

How many convex or concave subsets are contained in an arbitrary set of $n$ real numbers?

This question is closely related to this post. A set $A=\{a_1<a_2<\dots<a_n\} \subset \mathbb R$ is said to be convex if the consecutive differences are non-decreasing, i.e. if $a_{j+1} - a_j ...
Oliver Roche-Newton's user avatar
12 votes
3 answers
707 views

A "round" lattice with low kissing number?

Historically, the lattices with high density were studied intensively, e.g. E_8 lattice or Leech Lattice. However, there are situations that lattices with low kissing number are required. Specifically,...
Kore Min's user avatar
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