Visual Insight
http://blogs.ams.org/visualinsight
Mathematics Made VisibleTue, 16 Sep 2014 01:54:48 +0000en-UShourly1http://wordpress.org/?v=3.9.2Prüfer 2-group
http://blogs.ams.org/visualinsight/2014/09/15/prufer-2-group/?utm_source=rss&utm_medium=rss&utm_campaign=prufer-2-group
http://blogs.ams.org/visualinsight/2014/09/15/prufer-2-group/#commentsMon, 15 Sep 2014 01:00:17 +0000http://blogs.ams.org/visualinsight/?p=986This is the Prüfer $2$-group, the subgroup of the unit complex numbers consisting of all $2^n$th roots of unity. It is also called $\mathbb{Z}(2^\infty)$. ]]>http://blogs.ams.org/visualinsight/2014/09/15/prufer-2-group/feed/6{3,3,7} Honeycomb Meets Plane at Infinity
http://blogs.ams.org/visualinsight/2014/09/01/intersection-of-337-honeycomb-and-the-plane-at-infinity/?utm_source=rss&utm_medium=rss&utm_campaign=intersection-of-337-honeycomb-and-the-plane-at-infinity
http://blogs.ams.org/visualinsight/2014/09/01/intersection-of-337-honeycomb-and-the-plane-at-infinity/#commentsMon, 01 Sep 2014 01:00:41 +0000http://blogs.ams.org/visualinsight/?p=917The {3,3,7} honeycomb is a honeycomb in 3d hyperbolic space. It is the dual of the {7,3,3} honeycomb shown last time. This image, drawn by Roice Nelson, shows the 'boundary' of the {3,3,7} honeycomb: that is, the set of points on the 'plane at infinity' that are limits of points in the {3,3,7} honeycomb.
]]>http://blogs.ams.org/visualinsight/2014/09/01/intersection-of-337-honeycomb-and-the-plane-at-infinity/feed/0{7,3,3} Honeycomb Meets Plane at Infinity
http://blogs.ams.org/visualinsight/2014/08/14/733-honeycomb-meets-plane-at-infinity/?utm_source=rss&utm_medium=rss&utm_campaign=733-honeycomb-meets-plane-at-infinity
http://blogs.ams.org/visualinsight/2014/08/14/733-honeycomb-meets-plane-at-infinity/#commentsThu, 14 Aug 2014 01:00:45 +0000http://blogs.ams.org/visualinsight/?p=989This picture by Roice Nelson shows the boundary of the {7,3,3} honeycomb. The black circles are holes, not contained in the boundary of the {7,3,3} honeycomb. There are infinitely many holes, and the actual boundary, shown in white, is a fractal with area zero.]]>http://blogs.ams.org/visualinsight/2014/08/14/733-honeycomb-meets-plane-at-infinity/feed/3{7,3,3} Honeycomb
http://blogs.ams.org/visualinsight/2014/08/01/733-honeycomb/?utm_source=rss&utm_medium=rss&utm_campaign=733-honeycomb
http://blogs.ams.org/visualinsight/2014/08/01/733-honeycomb/#commentsFri, 01 Aug 2014 01:00:40 +0000http://blogs.ams.org/visualinsight/?p=936This is the {7,3,3} honeycomb as drawn by Danny Calegari using his program 'kleinian'. In this image, hyperbolic space has been compressed down to an open ball using the so-called Poincaré ball model. The {7,3,3} honeycomb is built of regular heptagons in hyperbolic space. These heptagons lie on infinite sheets, each of which is a {7,3} tiling of the hyperbolic plane. The 3-dimensional regions bounded by these sheets are unbounded: they go off to infinity. They show up as holes here. ]]>http://blogs.ams.org/visualinsight/2014/08/01/733-honeycomb/feed/0{7,3} Tiling
http://blogs.ams.org/visualinsight/2014/07/15/73-tiling/?utm_source=rss&utm_medium=rss&utm_campaign=73-tiling
http://blogs.ams.org/visualinsight/2014/07/15/73-tiling/#commentsTue, 15 Jul 2014 01:00:22 +0000http://blogs.ams.org/visualinsight/?p=946This picture, drawn by Anton Sherwood, shows the {7,3} tiling: a tiling of the hyperbolic plane by equal-sized regular heptagons, 3 meeting at each vertex. ]]>http://blogs.ams.org/visualinsight/2014/07/15/73-tiling/feed/1Sierpinski Carpet
http://blogs.ams.org/visualinsight/2014/07/01/sierpinski-carpet/?utm_source=rss&utm_medium=rss&utm_campaign=sierpinski-carpet
http://blogs.ams.org/visualinsight/2014/07/01/sierpinski-carpet/#commentsTue, 01 Jul 2014 01:00:12 +0000http://blogs.ams.org/visualinsight/?p=952To build the Sierpinski carpet you take a square, cut it into 9 equal-sized smaller squares, and remove the central smaller square. Then you apply the same procedure to the remaining 8 subsquares, and repeat this ad infinitum. This image by Noon Silk shows the first six stages of the procedure.]]>http://blogs.ams.org/visualinsight/2014/07/01/sierpinski-carpet/feed/4Origami Dodecahedra
http://blogs.ams.org/visualinsight/2014/06/15/origami-dodecahedra/?utm_source=rss&utm_medium=rss&utm_campaign=origami-dodecahedra
http://blogs.ams.org/visualinsight/2014/06/15/origami-dodecahedra/#commentsSun, 15 Jun 2014 07:45:58 +0000http://blogs.ams.org/visualinsight/?p=908There is a nice photograph of some interlocking origami dodecahedra created by Dirk Eisner on the website Mathematical Origami. But it's hard to be sure how many dodecahedra the whole model contains, since some are hidden from view. This raises a puzzle: assuming the configuration is as symmetrical as possible, how many dodecahedra are there? Here you see Greg Egan's answer to this puzzle—and to a much more challenging puzzle.]]>http://blogs.ams.org/visualinsight/2014/06/15/origami-dodecahedra/feed/0Grace–Danielsson Inequality
http://blogs.ams.org/visualinsight/2014/06/01/grace-danielsson-inequality/?utm_source=rss&utm_medium=rss&utm_campaign=grace-danielsson-inequality
http://blogs.ams.org/visualinsight/2014/06/01/grace-danielsson-inequality/#commentsSun, 01 Jun 2014 01:00:57 +0000http://blogs.ams.org/visualinsight/?p=843When can you fit a tetrahedron between two nested spheres? Suppose the radius of the large sphere is $R$ and the radius of the small one is $r$. Suppose the distance between their centers is $d$. Then you can fit a tetrahedron between these spheres if and only if the Grace--Danielsson inequality $ d^2 \le (R + r)(R - 3r) $ holds. This was independently proved by Grace in 1917 and Danielsson in 1949. But Antony Milne has found a new proof of this inequality using quantum information theory!]]>http://blogs.ams.org/visualinsight/2014/06/01/grace-danielsson-inequality/feed/19Pattern-Equivariant Homology of a Penrose Tiling
http://blogs.ams.org/visualinsight/2014/05/15/pattern-equivariant-homology-of-a-penrose-tiling/?utm_source=rss&utm_medium=rss&utm_campaign=pattern-equivariant-homology-of-a-penrose-tiling
http://blogs.ams.org/visualinsight/2014/05/15/pattern-equivariant-homology-of-a-penrose-tiling/#commentsThu, 15 May 2014 01:00:13 +0000http://blogs.ams.org/visualinsight/?p=817The Penrose kite and dart are a pair of tiles that can be used to create aperiodic tilings of the plane. This image illustrates a 'pattern-equivariant 1-chain', a tool used by James J. Walton to study the topology of the kite and dart tiling, and other aperiodic tilings. ]]>http://blogs.ams.org/visualinsight/2014/05/15/pattern-equivariant-homology-of-a-penrose-tiling/feed/0{6,3,6} Honeycomb
http://blogs.ams.org/visualinsight/2014/05/01/636-honeycomb/?utm_source=rss&utm_medium=rss&utm_campaign=636-honeycomb
http://blogs.ams.org/visualinsight/2014/05/01/636-honeycomb/#commentsThu, 01 May 2014 01:00:01 +0000http://blogs.ams.org/visualinsight/?p=801This is the {6,3,6} honeycomb, drawn by Roice Nelson. A 3-dimensional honeycomb is a way of filling 3d space with polyhedra or infinite sheets of polygons. Besides honeycombs in 3d Euclidean space, we can also have honeycombs in 3d hyperbolic space, a non-Euclidean geometry with constant negative curvature. The {6,3,6} honeycomb lives in hyperbolic space... and it's special, because it's self-dual!]]>http://blogs.ams.org/visualinsight/2014/05/01/636-honeycomb/feed/0