0xDE

I'm a computer scientist at the University of California, Irvine, interested in algorithms, data structures, discrete geometry, and graph theory.

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Last Notes

2026-06-06 23:13:42 UTC

The American Diabetes Association has ejected from its annual meeting the editor-in-chief of its journal Diabetes Care, its former president, and three other scientists, for handing out reprints of an editorial published in the journal and critical of the US government's attacks on science: https://arstechnica.com/science/2026/06/scientists-ejected-from-diabetes-conference-for-distributing-journal-reprints/ . According to video evidence the ejected scientists "were not disruptive or disorderly in their conduct". Nevertheless, the ADA claims that this behavior constituted a violation of the association's code of conduct.
The editorial in question: "Misguided Brushes of a Pen Continue to Dismantle and Destroy Biomedical Research in the United States: We Can No Longer Afford Complacency and Fear. We Must All Act Now!", _Diabetes Care_, http://dx.doi.org/10.2337/dci26-0068
The _Ars Technica_ link also has links to threads on bluesky about this incident.

2026-03-28 19:47:58 UTC

ICML'26 had two groups of reviewers, one for which LLM use was forbidden and another for which it was not. Reviewers could state their preference and only those who claimed to be ok with forbidding LLM use were assigned to that group. But then, ~500 of the reviewers in the LLM-forbidden group were caught using LLMs through hidden watermarks in the papers they reviewed. As a consequence, ~400 of those reviewers had their submissions desk-rejected (~500 rejections). https://blog.icml.cc/2026/03/18/on-violations-of-llm-review-policies/ via https://retractionwatch.com/2026/03/28/weekend-reads-illicit-ai-use-peer-reviews-commentary-talc-retracted-coauthorship-traded-commodity/

2026-03-08 19:43:00 UTC

It's that time of the year when the plum blossoms in the alley behind my office catch the late afternoon sunlight
https://media.mathstodon.xyz/media_attachments/files/116/195/251/855/894/140/original/6fefcd5d609dec0e.jpg

2026-02-18 01:21:30 UTC

The circle packing theorem (https://en.wikipedia.org/wiki/Circle_packing_theorem): every planar graph can be represented by the tangencies of a system of non-overlapping circles.
This theorem was proved by Koebe in 1936, and popularized in the 1980s by Fields medalist William Thurston as a discrete analogue to conformal mapping and uniformization. Its Wikipedia article was created by Oded Schramm in 2008, not long before his untimely mountaineering death. In his own research, Schramm found deep analogies between random walks on circle packings and Brownian motion. My interests in circle packing relate to its use in drawing graphs, constructing polyhedra for given graphs, modeling soap bubble foams, and finding planar separators. And others have found even more varied applications from the study of discrete symmetry groups of hyperbolic space to methods for visualizing the functional areas of the human brain, spread out into a flattened map.
Now a Good Article on Wikipedia.

2026-02-06 21:31:43 UTC

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@nprofile…g0zc The entire government, maybe, but there have been any number of insane MPs.

2026-02-06 19:04:29 UTC

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@nprofile…g0zc Not sure if serious?

2026-01-30 23:23:43 UTC

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@nprofile…g0zc grudging respect?

2026-01-26 08:30:31 UTC

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@nprofile…a3ey This is a big issue for academic conference planning in general, and not just for the ICM. My European friends are telling me that nobody they know there is currently willing to travel to the US and that for some of them there are institutional barriers in place (including issues of the security of institution-owned electronics) that prevent them from doing so. I have also talked to Canadians who have stopped attending conferences they would otherwise travel to in the US. Meanwhile there are also many people within the US who are unable to leave for fear of not being allowed to return.

2026-01-24 22:34:22 UTC

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@nprofile…zl3j This raises the question: which combinatorial types of convex polyhedron can have the property that for each primal-dual edge pair the lengths in the primal and dual are equal? That seems to be the main requirement for a construction like this to work.

2026-01-20 23:02:19 UTC

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@nprofile…vhdw To me this was doubly surprising: the idea that a self-duality might not be an involution did not occur to me, and then even after seeing the statement it took some effort to convince myself it was possible.

2026-01-12 20:27:58 UTC

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@nprofile…t6k2 A strategy I've seen but not used to cut down on irrelevant exam answers is to give a student a checkbox that gives them partial credit for recognizing that they don't have an answer (and when checked prevents the rest of the answer from scoring anything). That way they have less incentive to babble bullshit in the vague hope that something they say hits the mark. I don't have any good suggestions for how to implement such a scheme in social media or whether we would want to, though.

2026-01-07 06:56:07 UTC

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@nprofile…a3ey How do you even get a precise count of that many papers? There are so many edge cases of which things count as papers at all, what to do when papers are merged and split, etc.

2025-12-16 00:48:28 UTC

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@nprofile…8eua @nprofile…pmx6 Sadly, they are definitely not the same. The SF author is Michael Victor Capobianco; the mathematician is Michael F. Capobianco.

2025-11-29 22:33:26 UTC

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@nprofile…dand Yes, but they're not basing decisions on its reviews. I didn't submit anything to STOC so I didn't try it, but I heard anecdotally from another author that it was actually very helpful: it provided a lot of bullshit comments but among them was a discovery of a significant but fixable bug, in time to fix it before the final submission deadline.

2025-11-29 21:34:43 UTC

It's not a good time to be a program chair of a major conference:
21% of the peer reviews at ICLR (a major annual machine learning conference) were discovered to be entirely written by AI, and "more than half contained signs of AI use". This appears to be in violation of ICLR's terms of conduct, which "prohibited AI use that would have breached the confidentiality of manuscripts". The ICLR chairs write that they are planning to penalize reviewers who did this by desk-rejecting the reviewers' submissions but they say nothing about what they are doing for authors whose submissions received these reviews.
Report in Nature, https://www.nature.com/articles/d41586-025-03506-6, https://archive.is/1cmjJ; details of analysis by Pangram, https://www.pangram.com/blog/pangram-predicts-21-of-iclr-reviews-are-ai-generated; response from ICLR program chairs, https://blog.iclr.cc/2025/11/19/iclr-2026-response-to-llm-generated-papers-and-reviews/; via https://lobste.rs/s/ww6cfs/major_ai_conference_flooded_with_peer

2025-11-26 04:29:18 UTC

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@nprofile…ztfm That might work but I'd rather not annoy whichever staffer has to answer it

2025-11-26 01:37:06 UTC

It is graduate-school application season and that means filling out lots of web forms to submit recommendation letters to lots of schools. One thing I am noticing is that a significant fraction of these forms require a phone number from the recommender. It has been years since my university automatically provided and paid for an office phone number for all faculty members; we could still have a number if we paid for it using our own funds but I do not. I am not going to put my personal cell phone number on these forms (fortunately they tend to allow any nonblank alphanumeric input) and if anyone I didn't know called on it I would probably not answer. Nobody ever calls to verify graduate-school recommendation letters anyway. So what is the point?

2025-11-25 02:42:27 UTC

Peter Cameron, as a retired professor still active in research, finds himself locked out of unfree-open-access publication because his university won't use their publication-fee funding for emeriti despite continuing to count his publications towards its research productivity metrics: https://cameroncounts.wordpress.com/2025/11/22/old-age-and-open-access/

2025-11-22 23:35:02 UTC

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@nprofile…8eua @nprofile…puw0 In general Overleaf seems to have a setup with high resilience to problematic LaTeX sources, so that things work there that would not work elsewhere. It can cause problems of interoperability with other LaTeX systems because the Overleaf users learn to ignore any errors and warnings and write code that works only on Overleaf.

2025-11-19 20:26:03 UTC

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@nprofile…fhty @nprofile…l4xy Fixed; I hope it sticks

2025-11-19 06:36:36 UTC

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@nprofile…8eua @nprofile…puw0 Faces may be irrelevant for this example but they're just as easy to describe, as bitstrings with wildcards. Vertices (0-faces) are strings of five bits. Edges (1-faces) are strings with one of the bits replaced by a *. Squares (2-faces) are strings with two of the bits replaced by *s, etc. The vertices in a face are all ways of expanding each * into a 0 or 1.

2025-11-18 06:03:19 UTC

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@nprofile…ztfm @nprofile…hcpk The new CS review policy appears to have been misreported as stronger than it is. Judging from both the actual press release from arXiv, and what I have seen behind the scenes as a moderator, the new policy is that CS review/survey articles on arXiv are not actually forbidden, but they need to be published elsewhere first. Thurston's "On proof and progress", for instance, was published in the Bulletin of the AMS, so it would pass this policy (even disregarding its applicability to mathematics).

2025-11-12 17:17:12 UTC

Quanta on the smoothness of high-dimensional minimal surfaces: https://www.quantamagazine.org/new-proofs-probe-soap-film-singularities-20251112/

2025-11-11 22:02:14 UTC

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@nprofile…u6hy So pre-printing illuminated manuscript pages don't count? https://commons.wikimedia.org/wiki/File:Woman_teaching_geometry.jpg

2025-11-11 20:37:21 UTC

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@nprofile…l4xy @nprofile…u6hy I think the Zelena Hora tiling has a similar structure to the one in Amagertorv, Copenhagen (https://11011110.github.io/blog/2018/06/26/copenhagen-non-penrose.html), which also involves regular pentagons. They are not quite the same: the Zelena Hora one has dihedral symmetry (with center of symmetry at the top center of the linked image) but the Copenhagen one has chiral cyclic symmetry.

2025-11-11 20:25:32 UTC

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@nprofile…u6hy Do sangaku count as publications? Many of them used color. Here's one of Soddy's hexlet, I think the one from 1822 (predating Soddy's 1937 publication): https://commons.wikimedia.org/wiki/File:Sangaku_of_Soddy%27s_hexlet_in_Samukawa_Shrine.jpg

2025-11-07 07:35:56 UTC

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@nprofile…ztfm https://en.wikipedia.org/w/index.php?title=Mapping_class_group&diff=1320874735&oldid=1309685705

2025-10-29 00:21:53 UTC

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@nprofile…ztfm It probably depends on what your input looks like. If it's a proof formalized in Lean or the like, it's almost code already and probably can be handled in the same way. And there should be less need of cycle-breaking because a cyclic dependence in a proof is probably bad. The question is whether it's more important to preserve the sequential order of dependencies (we use this lemma first, etc.) and whether doing so might help make the layout more stable.

2025-10-28 23:43:10 UTC

SpiderMonkey replaces GraphViz by a custom graph layout algorithm specialized for visualizing the block structure of computer programs: https://spidermonkey.dev/blog/2025/10/28/iongraph-web.html via https://lobste.rs/s/rhi0ud/new_graph_layout_algorithm_for
They cite as reasons for the change two problems with GraphViz-based layout: First, because GraphViz is based purely on the graph structure of the code blocks and not on the logical structure of the code, its placement of nodes makes it hard to understand the nesting, sequential ordering, and loop structure of code blocks. And second, because it allows big rearrangements in order to try to optimize the layout, small changes to the code can cause big changes to its layout.
The resulting algorithm sticks to a Sugiyama-style layered graph drawing framework, using its understanding of code structure to break cycles (because this layout needs its graph to be a DAG) and to assign blocks to layers, and skipping the part of the framework that permutes blocks within each layer (as counterproductive for understandability and stability).

2025-10-25 04:50:32 UTC

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@nprofile…00p2 valid point

2025-10-14 16:32:01 UTC

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@nprofile…yg3j Now I want to know if the tiles of a single color would flex or are rigid as a hinged assembly

2025-09-04 06:59:12 UTC

New Good Article on Wikipedia: Pythagorean addition, https://en.wikipedia.org/wiki/Pythagorean_addition
This is the operation of computing the hypotenuse of a right triangle from its two sides. Because this is commutative and associative, it defines a commutative monoid, and Knuth defined it as a built-in binary operation in metafont, writing that it could likely replace most uses of square roots in software.
Back when people used slide rules instead of computers, some slide rules had special scales (positioning numbers by their square roots rather than their logs) that would allow them to perform this calculation, for instance in converting from Cartesian to polar coordinates: see "Find absolute value" on p.3 of slide-rule instruction guide https://sliderulemuseum.com/Manuals/ISRM_M325_SunHemmi_153_SpecialScalesInst_GiftOfEdwardWright.pdf
Nowadays most programming language libraries provide this operation as hypot.

2025-04-07 16:52:36 UTC

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@nprofile…fa4k Small correction: the journal is called "Zeitschrift für Mathematische Logik und Grundlagen der Mathematik". Still easier to abbreviate as ZML. The "Deutsche Vereinigung für Mathematische Logik und für Grundlagenforschung der Exakten Wissenschaften" is not the name of the journal, but the name of the society that sponsored the old journal and cancelled their sponsorship.

2025-03-04 03:35:50 UTC

If not all rounded triangles are Reuleaux triangles, it stands to reason that not all rounded tetrahedra are Reuleaux tetrahedra (the intersections of four spheres each centered at a point where the other three cross). Here's another one: the elliptope, the space of positive semi-definite matrices with unit diagonal, https://franknielsen.github.io/elliptope/index.html — for 3x3 matrices, there are three off-diagonal terms and you get a three-dimensional curved tetrahedron sitting inside a unit cube. It's a special case of a spectrahedron (https://en.wikipedia.org/wiki/Spectrahedron).
Via https://web-cdn.bsky.app/profile/bbolker.bsky.social/post/3lakemxuvf22z where the image makes clear that it is has a quite different geometry than the Reuleaux tetrahedron: the four tetrahedral faces meet at the straight line-segment edges of a regular tetrahedron, and pillow outward from there. Instead the Reuleaux tetrahedron's edges are circular arcs where two spheres meet.

2025-02-10 17:53:03 UTC

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@nprofile…yu7x Colorless green quarks sleep furiously (in a composite with their red and blue quarks).

2024-11-24 08:39:43 UTC

For-profit academic publishers love LLM garbage: Kevin Munger on Crooked Timber, https://crookedtimber.org/2024/11/08/for-profit-academic-publishers-love-llm-garbage/
Munger argues that under current open-access pay-to-publish standards, they make a profit on each LLM-produced paper, are motivated primarily by profit, and have little short-term incentive to make their journal content meaningful to subscribers. Therefore, if we want to continue to be able to find meaningful scholarly content, we need to look elsewhere than these publishers. Munger advocates diamond open-access instead, cutting out the profit motive.