Joseph O'Rourke
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Registered User
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Professor of Computer Science; Professor of Mathematics.
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2d |
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Term for “Directed acyclic graph with exactly one sink and one source” The term st-graph is well-established in the literature for over twenty years (e.g., Tamassia's "Drawing algorithms for planar st-graphs," 1990). Maybe because I'm accustomed to it, I find "st-graph" natural. |
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2d |
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Expanding disks lead to what packing of the plane? @Brendan: I worry about that myself. It is well defined for points distributed in a finite region, and then that region could be enlarged without bound. But it is not entirely clear that such a limit of larger and larger regions is the same as the infinite plane, leading to infinite components, as you say. So: I don't know. |
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Jun 15 |
revised |
Expanding disks lead to what packing of the plane? added 255 characters in body |
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Jun 15 |
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Expanding disks lead to what packing of the plane? Interesting hypothesis, jc, that this will essentially end up in jammed-disk configurations. I thought that the gradual growth of the radii would lead to something different, but you may be right... |
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Jun 14 |
asked | Expanding disks lead to what packing of the plane? |
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Jun 13 |
answered | Covering the convex body with its smaller homothetic copies |
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Jun 13 |
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Quasicrystals and the Riemann Hypothesis Tangentially, "Nick S" left some critical comments on Dyson's 1D quasicrystal idea at an earlier MO question, "Approaches to Riemann hypothesis using methods outside number theory," comments that I cannot evaluate myself: mathoverflow.net/questions/34699/… |
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Jun 13 |
revised |
Rope simulation with Position Based Dynamics added 189 characters in body |
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Jun 12 |
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Random metrics on compact orientable surfaces The earlier MO question, "Random manifolds," contains some related information and references: mathoverflow.net/questions/70714/random-manifolds |
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Jun 11 |
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Cutting a subset in many pieces with controlled perimeter See also the MO question, "Cutting convex sets": mathoverflow.net/questions/24352/… |
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Jun 9 |
revised |
Can the unsolvability of quintics be seen in the geometry of the icosahedron? added 235 characters in body |
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Jun 9 |
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Can the unsolvability of quintics be seen in the geometry of the icosahedron? @John: Oh, how disappointing! I just ordered it. But Shurman's book is illustrated. |
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Jun 9 |
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Can the unsolvability of quintics be seen in the geometry of the icosahedron? added 342 characters in body |
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Jun 9 |
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Can the unsolvability of quintics be seen in the geometry of the icosahedron? Thanks, Barry & Gerald! I will retrieve that book. (And pardon my ignorance!) |
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Jun 9 |
asked | Can the unsolvability of quintics be seen in the geometry of the icosahedron? |
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Jun 9 |
revised |
Visual pictures of rotation and torsion Added creation details and links. |
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Jun 8 |
answered | Visual pictures of rotation and torsion |
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Jun 5 |
accepted | easter problem - egg shapes |
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Jun 3 |
answered | Algorithms for covering a rectilinear polygon using the same multiple rectangles |
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Jun 3 |
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Algorithms for covering a rectilinear polygon using the same multiple rectangles @hujia06: Do you require that the rectangles be oriented the same way? That is, if they are $a \times b$, is the $a$-side always horizontal? |
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Jun 3 |
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Algorithms for covering a rectilinear polygon using the same multiple rectangles Added tags. |
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Jun 1 |
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Measures of entangledness of an open curve This is an intriguing idea, Qfwfq! |
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Jun 1 |
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Measures of entangledness of an open curve Thanks, Daniel. I too am attracted to not artificially closing the path. |
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Jun 1 |
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Measures of entangledness of an open curve Thanks, jc, it does make sense to use statistical properties of all possible closures. In their case, they connect each endpoint by a segment to a point on a large surrounding sphere. |
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Jun 1 |
asked | Measures of entangledness of an open curve |
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May 31 |
answered | famous papers/results by non professional mathematicians |
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May 31 |
awarded | ● Popular Question |
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May 30 |
accepted | convex polyhedron in the unit cube |
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May 30 |
revised |
convex polyhedron in the unit cube added 102 characters in body |
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May 30 |
revised |
Needle probing for a convex body added 278 characters in body; edited tags; added 24 characters in body |
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May 30 |
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Needle probing for a convex body @Douglas: Very clever to consider the volume-preserving action of changing signs! |
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May 30 |
answered | convex polyhedron in the unit cube |
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May 29 |
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Can one recover a metric from geodesics? A question related in spirit: "Probing a manifold with geodesics" mathoverflow.net/questions/81622/… |
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May 29 |
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An “inchworm-like” random walk on an integer interval Added a guess. |
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May 28 |
answered | An “inchworm-like” random walk on an integer interval |
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May 28 |
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Needle probing for a convex body @Benjamin: Great paper reference, new to me---Thanks! Although I do not doubt that $V=\frac{1}{4}$ is the largest convex volume avoiding those three orthogonal needles, I do not see a proof. |
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May 28 |
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Needle probing for a convex body Very nice, Benjamin! |
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May 27 |
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Needle probing for a convex body @Benjamin: Certainly with the three axes as rays, $V < \frac{1}{4}$ can remain undetected. But is already difficult to see how $V \ge \frac{1}{4}$ can fit around those axes... |
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May 27 |
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Biggest ball included in an intersection of balls Crossposted to MSE: math.stackexchange.com/questions/404006/… |
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May 27 |
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Needle probing for a convex body Yoav Kallus example. |
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May 27 |
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Needle probing for a convex body Apologies for the overlap with earlier questions (including my own!). At least this one asks very specific questions... |
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May 27 |
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Needle probing for a convex body @Douglas: Excellent point! It does seem superfluous... |
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May 27 |
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Needle probing for a convex body @fedja: I am, in fact, more interested in relatively large $V$, but the connection to discrepancy is very useful. Thanks! |
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May 27 |
asked | Needle probing for a convex body |
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May 26 |
revised |
A conjecture on intersection of some intervals. Incorporated the image. |
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May 26 |
revised |
Anything special (historical?) about surface $x\cdot y\cdot z\ +\ x+y+z=0$? added 55 characters in body |
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May 25 |
awarded | ● Nice Question |
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May 25 |
answered | Anything special (historical?) about surface $x\cdot y\cdot z\ +\ x+y+z=0$? |
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May 24 |
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A curious sequence of rationals: finite or infinite? @SuspiciousMinds: Actually, I made a mental error in a cockamamie investigation on binary operators that led to $ab/(a+b)$, which has rather uninteresting behavior. So I subtracted 1 from the denominator, and then it became interesting. By now, it is merely a curiosity. |
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May 24 |
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A curious sequence of rationals: finite or infinite? @Dietrich: Thanks, corrected the typo! |
