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How to visualize the order-type of a set of points (which triples are clockwise, which counterclockwise, and which collinear)?

In "Minimal Representations of Order Types by Geometric Graphs" (arxiv.org/abs/1908.05124), Aichholzer et al consider points without collinear triples, and draw a graph over the points so that as points move the order-type changes only as points cross edges. Their graph's embedding determines the order type and has at most 1/3 as many edges as the complete graph.

Stop using Zip Codes for geospatial analysis: carto.com/blog/zip-codes-spati, via metafilter.com/182600/humans-d

The problem is that they are designed to be convenient for the post office (geographically compact) rather than convenient for demographers (they sometimes combine areas that have quite different groups of people in them). The linked article is by a group selling software for one alternative subdivision that works better, but recommends several others as well.

Anyone know how to remove followers from a dead and defederated mastodon instance, or from an instance that redirects profile pages off-site?

Although freefedifollowers.ga is now defederated from my instance, my profile still lists many followers from there. The only instructions I can find for removing followers say to go to their profile and block them from there. But their profiles used to redirect to youtube and are now deadlinks. So I can't do it that way.

Are there any other ways?

New blog post "Footprints in the snow" (11011110.github.io/blog/2019/0) based on my new arXiv preprint "Tracking paths in planar graphs" (arxiv.org/abs/1908.05445)

Should graduate students be expected to bring refreshments to their doctoral defenses? insidehighered.com/news/2019/0

Con:
- It can be an imposition
- It distracts from preparing from the defense
- Students on graduate fellowships may not easily afford it
- It looks like bribery of the examining committee

Pro:
- A non-hungry committee is a non-hangry committee

Solution:
- Ban it and/or provide refreshments through other means

Duffin–Schaeffer conjecture solved: quantamagazine.org/new-proof-s, arxiv.org/abs/1907.04593

This is about finding rational approximations to irrational numbers, like $\pi\approx 355/113$. Given a criterion for how good an approximation you want, depending only on the denominator (for instance, allowing only prime denominators and seeking an approximation accurate to $\pm 1/p^{3/2}$ for denominator $p$) the new theorem tells you when almost all irrationals have a good-enough approximation.

@christianp My followers list is getting spammed by huge numbers of accounts of the form (random string) at freefedifollowers.ga

The name does not sound promising (implies a way of artificially boosting follower counts) and it is making it impossible for me to see a useful listing of real followers. You think maybe this is worth defederating over? Or is there some way for me to block that whole set on my own?

This is the highest award of the German Computer Science Society, and the first time since its establishment in 1987 that the winner is a woman.

Dorothea's research includes graph drawing, route planning, optimization, and social network analysis; see en.wikipedia.org/wiki/Dorothea

Knots and Narnias, mathenchant.wordpress.com/2018

Riffing on a video of a Bill Thurston lecture, Jim Propp explains that when a portal to another dimension has a knotted boundary, it can actually be a portal to several other dimensions.

The Longest Matrilineal Chain in Math: blogs.scientificamerican.com/r

Evelyn Lamb finds "five advisor-advisee chains of length four containing only women" in the Mathematics Genealogy Project, all starting with Olga Ladyzhenskaya and her student Nina Ivochkina. But her searches were haphazard so there may be longer ones still to find.

A letter from the University of California Academic Council expressing their alarm at "the increasingly racialized ways in which international scholars and students—especially those from China, Iran, and Russia—are being targeted in national conversations about academic espionage" and their support for the open exchange of research: senate.universityofcalifornia.

New blog post: Report from CCCG (the Canadian Conference on Computational Geometry), 11011110.github.io/blog/2019/0

The WADS excursion was to the University of Alberta's botanic gardens. Here are a few photos I took there: 11011110.github.io/blog/2019/0

The University of California's fight with Elsevier spills over to editorships: 30 UC editors of Elsevier journals "will no longer provide editorial services" to Elsevier unless/until a satisfactory deal with Elsevier is reached. insidehighered.com/quicktakes/

Why modern integer factoring algorithms have the time bounds they do, and what would be needed to improve them: blog.computationalcomplexity.o

Manu suggests reducing our impact on the planet by making conferences virtual: emanueleviola.wordpress.com/20

Or we could, you know, publish our papers in journals instead of conferences like everyone else

(...posted from a conference, my 4th this summer)

Mati y sus mateaventuras, mati.naukas.com/
Blog of popularized mathematics stories by mathematician Clara Grima and illustrator Raquel Gu (in Spanish). The latest one (from a year ago; it hasn't updated much recently) is on Wythoff's game, en.wikipedia.org/wiki/Wythoff%

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Reading this fantastic graphic novel called "Prime Suspects". It's all about analytic number theory in metaphors.

It has amazing one-liners like:

A Mastodon instance for maths people. The kind of people who make $\pi z^2 \times a$ jokes.
Use $ and $ for inline LaTeX, and $ and $ for display mode.