Geometry » Polytopes

Extension complexity of (convex) polygons ★★

Author(s):

The extension complexity of a polytope $ P $ is the minimum number $ q $ for which there exists a polytope $ Q $ with $ q $ facets and an affine mapping $ \pi $ with $ \pi(Q) = P $.

Question   Does there exists, for infinitely many integers $ n $, a convex polygon on $ n $ vertices whose extension complexity is $ \Omega(n) $?

Keywords: polytope, projection, extension complexity, convex polygon

Posted by DOT
updated August 13th, 2011
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Topology

Strict inequalities for products of filters ★

Author(s): Porton

Conjecture   $ \mathcal{A} \times^{\mathsf{\ensuremath{\operatorname{RLD}}}}_F \mathcal{B} \subset \mathcal{A} \ltimes \mathcal{B} \subset \mathcal{A} \times^{\mathsf{\ensuremath{\operatorname{RLD}}}} \mathcal{B} $ for some filter objects $ \mathcal{A} $, $ \mathcal{B} $. Particularly, is this formula true for $ \mathcal{A} = \mathcal{B} = \Delta \cap \uparrow^{\mathbb{R}} \left( 0 ; + \infty \right) $?

A weaker conjecture:

Conjecture   $ \mathcal{A} \times^{\mathsf{\ensuremath{\operatorname{RLD}}}}_F \mathcal{B} \subset \mathcal{A} \ltimes \mathcal{B} $ for some filter objects $ \mathcal{A} $, $ \mathcal{B} $.

Keywords: filter products

Posted by porton
updated August 9th, 2011
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Topology

Join of oblique products ★★

Author(s): Porton

Conjecture   $ \left( \mathcal{A} \ltimes \mathcal{B} \right) \cup \left( \mathcal{A} \rtimes \mathcal{B} \right) = \mathcal{A} \times^{\mathsf{\ensuremath{\operatorname{RLD}}}} \mathcal{B} $ for every filter objects $ \mathcal{A} $, $ \mathcal{B} $.

Keywords: filter; oblique product; reloidal product

Posted by porton
updated August 9th, 2011
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