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A branch of geometry dealing with convex sets and functions. Polytopes, convex bodies, discrete geometry, linear programming, antimatroids, ...

1 vote

Extending a positive linear functional on the vector space of ternary quartics to the integr...

If I'm not mistaken this should be equivalent to the truncated moment problem for (not-necessarily homogeneous) bivariate quartics. Section 3 of "Positivity of Riesz Functionals and Solutions of Quad …
Noah Stein's user avatar
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0 votes

Uniform Sampling Subject to Linear Equalities and Non-Negativity Constraint

The hit-and-run algorithm and variants are popular choices. These are Monte Carlo methods but should be much better than rejection sampling. Unfortunately I don't know of a canonical reference.
Noah Stein's user avatar
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1 vote

How to determine if two rational cones intersect?

As Yoav Kallus suggests you can also view this problem as finding a hyperplane which separates the $r_i$ from the $t_j$. For this you can use any algorithm for computing a linear classifier, such as …
Noah Stein's user avatar
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1 vote

How to determine if two rational cones intersect?

I'm assuming by interior you mean relative interior. If not just check first that both generating sets span the full space -- if not, one cone has empty topological interior and so the topological in …
Noah Stein's user avatar
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2 votes

What is the dual of an semidefinitely representable (SDR) cone?

Edited in response to Alex Monras's correction in the comments: The cone $\mathcal{K}^*$ is always SDR: this is just the conic / homogeneous version of Theorem 5.57 in the new book "Semidefinite Opti …
Noah Stein's user avatar
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2 votes

Finding an axis-aligned ellipsoid of minimal volume which contains a given ellipsoid

For the reasons discussed in the comments to Suvrit's answer, I will assume your friend would like to minimize $\det(\Lambda^{-1})$. The problem in question is a convex optimization problem: \begin{ …
Noah Stein's user avatar
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4 votes
Accepted

Finding a point that lies in a majority of polytopes

This problem is clearly in NP (guess which polytopes) and becomes NP-complete if we replace $2/3$ with $1/2$ and make it a decision problem, dropping the promise that such a $p$ exists. In particular …
Noah Stein's user avatar
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4 votes

a different algebra/representation for convex sets

Of course it's hard to say without any information, but linear matrix inequalities may be what you're looking for. They are to semidefinite programs what linear inequalities are to linear programs. …
Noah Stein's user avatar
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