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17 votes
1 answer
458 views

The sparsest planar net that captures every unit segment

Let $\cal C = \lbrace C_i \rbrace$ be a collection of rectifiable curves in the plane with the property that every unit-length segment meets at least one curve in at least one point. Call such a ...
Joseph O'Rourke's user avatar
16 votes
2 answers
1k views

Are Penrose tilings universal? Do aperiodic universal tilings exist?

Consider a tiling of the plane using tiles of at least two types (e.g, a Penrose tiling such as that shown at the bottom of this question, which tiles the plane with two types of tiles). List the tile ...
Louigi Addario-Berry's user avatar
12 votes
1 answer
373 views

A claim on partitioning a convex planar region into congruent pieces

Let us define a perfect congruent partition of a planar region $R$ as a partition of it with no portion left over into some finite number n of pieces that are all mutually congruent (ie any piece can ...
Nandakumar R's user avatar
  • 5,979
11 votes
1 answer
499 views

Tiling with incommensurate triangles

Say that two triangles are incommensurate if they do not share an edge length or a vertex angle, and their areas differ. Suppose you'd like to tile the plane with pairwise incommensurate triangles. I ...
Joseph O'Rourke's user avatar
7 votes
1 answer
186 views

Decidability of convex rearrangements of polygons

Triggered by the MO question, "How many convex shapes can be made with the pieces of the Stomachion?," I would like to pose this question: Q. Given $n$ polygons in a set $S$, say each with integer ...
Joseph O'Rourke's user avatar
6 votes
1 answer
435 views

On the aperiodic monotile

One of the more mind-boggling aspects of the Penrose tiles is that there are uncountably many distinct tilings of the plane, but every tiling contains every finite region that appears in another ...
Jim Conant's user avatar
  • 4,898
4 votes
1 answer
1k views

What Islamic tiling patterns are constructible?

Eric Broug in his book Islamic Geometric Patterns gives straightedge and compass construction of some simpler patterns. It is clear his techniques will provide constructions for many Islamic patterns. ...
Brian Wichmann's user avatar
3 votes
1 answer
152 views

Triangles that can be cut into mutually congruent and non-convex polygons

It is easy to note that an equilateral triangle can be cut into 3 mutually congruent and non-convex polygons (replace the 3 lines meeting at centroid and separating out the 3 congruent quadrilaterals ...
Nandakumar R's user avatar
  • 5,979
2 votes
1 answer
235 views

Tiling with one of each shape

Q. Is there a tiling of the plane by one each of simple polygons of $n$ vertices: one triangle, one quadrilateral, one pentagon, $\ldots$ , one simple polygon of $n$ vertices, $\ldots$ ? Here a ...
Joseph O'Rourke's user avatar
2 votes
1 answer
84 views

What is the average component size of a coloring?

Supose each cell of a big (or infinite) grid is colored at random by one of $k$ colors. Then the connected monochromatic components (here components are not supposed to contain "wasp waists",...
Wolfgang's user avatar
  • 13.4k
1 vote
0 answers
97 views

Tiling the plane with pair-wise non-congruent and mutually similar triangles

Question: Is it possible to tile the plane with triangles that are (1) mutually similar, (2) pairwise non-congruent and (3)non-right? No other constraints. Note 1: Reg requirement 3 above: since any ...
Nandakumar R's user avatar
  • 5,979
0 votes
0 answers
36 views

Vertex configuration to tile repeat unit

I am working with elongated triangular tiling which has a vertex configuration of 3.3.3.4.4 and noticed that the representative symmetry is not the repeat unit. Is there a general formula to convert ...
Jim Z's user avatar
  • 1