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14 votes
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How many unit balls can be put into a unit cube?

Here a unit ball is a ball of diameter 1, and a unit cube is a cube of edge length 1. A famous counterintuitive fact is that, as the dimension increases, the volume of the unit ball tends to zero whi …
1 vote
0 answers
304 views

Which term is better for the so called "sphere packing"?

I'm working on sphere packings. When I write, I'm confused with basic definitions. I'm hesitating between the terms "sphere", "ball" or "oriented sphere". For example, on the wikipedia page of circle …
Hao Chen's user avatar
  • 2,581
7 votes
1 answer
341 views

For a 3D Apollonian packing, do we really know that the Hausdorff dimension of the complemen...

The fractal dimension of the 3D Apollonian packing is computed in this paper. In the introduction, the authors cite three of Boyd's paper (Ref 2, 5, 6) to support that the fractal dimension (Hausdo …
Hao Chen's user avatar
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1 vote
Accepted

For a 3D Apollonian packing, do we really know that the Hausdorff dimension of the complemen...

OK, I found the reference: For those who care, it's recently proved in a much stronger form by Oh and Shah in The asymptotic distribution of circles in the orbits of Kleinian groups. The paper is ab …
Hao Chen's user avatar
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5 votes

Three-dimensional Apollonian spirals

According to the discussion in Coxeter (1968), the tangent points lie asymptotically on a concho-spiral, so the distribution is not uniform on the sphere, but is uniform on a circle. By the way, the …
Hao Chen's user avatar
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3 votes

Is there a midsphere theorem for 4-polytopes?

I recently showed that: The graph of a stacked $4$-polytope is $3$-ball packable if and only if it does not contain six $4$-cliques sharing a $3$-clique. While Eppstein, Kuperberg and Ziegler 20 …
Hao Chen's user avatar
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5 votes

Is there a midsphere theorem for 4-polytopes?

In a recent paper of Padrol and me, we studied several generalizations of this problem. http://arxiv.org/pdf/1508.03537v1.pdf Regarding Q1, Yoav already mentioned Schulte's work, and Gil mentioned t …
Hao Chen's user avatar
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