A special treat for the students in my course „Introduction to Topological Data Analysis“: Bastian Rieck (@pseudomanifold.topology.rocks) gave a very interesting guest lecture on topological methods in deep learning.
Very nice explanation of one of my favorite theorems in math, the Ham Sandwich theorem, by @manonym025.bsky.social
www.scientificamerican.com/article/the-...
Joseph Dorfer spoke about flipping spanning trees of convex point sets, showing that computing the flip distance is NP-hard. This paper gave him the crucial ideas for his recent breakthrough on NP-hardness of the flip distance of convex triangulations (arxiv.org/abs/2602.22874)
ETH-Alumni Justin Dallant spoke about his new lower bounds for the number of triangulations parametrized by the convex hull size. First time that I heard about the intriguing unimodality conjecture.
Day 3 of #EuroCG26 started with an invited talk by Jean Cardinal on compact representations of graphs, where he particularly focused on biclique covers. An interesting topic I did not know about before.
My students Jette Gutzeit and Kalani Kistler talked about their joint work with Anna Schenfisch and Tim Ophelders on VPHT-reconstructible graphs, a project that started in our course „Projects in TDA“.
Niko Fink presented our joint paper on „garment numbers“ (arxiv.org/abs/2603.05339). Given that we also try to find „bowties“ in point sets, he wore one for this occasion.
Highlights from day 2 of #EuroCG26. The day started again with an invited talk, today by Maike Buchin who took us on a tour of 35 years of Frechét distance. A very interesting talk, and lots of great illustrations of dogs on walks.
The day ended with a long business meeting (2h instead of the scheduled 1h). #EuroCG28 will take place in Passau, and authors will have the option of only publishing a 1-page abstract in the booklet of abstracts.
Another highlight was the talk of Sarita de Berg on the contiguous art gallery problem. While the original art gallery problem is ETR-complete, this variant can be solved in polynomial time, and Sarita and her coauthors have developed an optimal algorithm for this.
Some personal highlights from day 1 of #EuroCG26: the day started with a great invited talk by Marcus Schaefer about penny graphs and the existential theory of the reals. I recently worked quite a bit in ETR, and it was very interesting to hear one of the founding fathers.
I am at #EuroCG26 in Hagen this week. It is once again an amazing conference with lots of interesting talks and discussions. There are also some of my MSc students from ETH here, attending their first ever conference, and it‘s great to see how they are welcomed by the CG community.
Very cool question with an elegant solution that I also discussed last week in my lecture (I‘m not going to say which lecture so as not to give hints about the answer) ☺️
There is also a fun ghost hunt in the castle, I‘m currently at 26 found ghosts.
Spending an interesting week at Schloss Dagstuhl at the workshop „Intractability in Discrete Geometry and Topology“. A very nice venue, some cool open problems, and even cooler participants.
www.dagstuhl.de/seminars/sem...
Last semester, I organised „Projects in Topological Data Analysis“, where students from several universities collaborate on problems in TDA. My Students Jette and Kalani, together with their mentors Anna and Tim have just uploaded their findings from their project to ArXiv:
arxiv.org/abs/2603.07809
We show that this statement is true for other structures on four points, which we give names like pants, skirts or cravates. This motivates the name „garment numbers“ in our title.
Say you are given n points in the plane (no 3 on a line), colored red and blue. It is conjectured that if n is large enough you can always find a quadrilateral spanned by 4 points of the same color whose interior does not contain any other points.
A new paper on the ArXiv. This one is a result of the research week on geometric graphs in Trier in August 2024. Together with my coauthors Oswin, Helena, Niko, Maarten and Pepa we study a variant of the empty monochromatic quadrilateral problem.
arxiv.org/abs/2603.05339
This will be at #EuroCG26
Really cool result by Joseph Dorfer
The list of accepted papers at #SoCG26 is now online:
cgweek26.computational-geometry.org/contribute/
The list of accepted papers at #EuroCG26 is online:
eurocg26.fernuni-hagen.de/accepted-con...
For those on hiring committees: do you push back against this? What do you do?
In case you‘re wondering what‘s going on: the „three kings“ hotel turns into the „three Waggis“ hotel for the duration of the carnival in Basel. Here is a picture of the end product.
The city of Basel is getting ready for its three most beautiful day. I have a very privileged view of this from my office.
For my randomized algorithms course at the University of Basel, the students will have to present some randomized algorithms to their peers. If you know any algorithm that you think would be particularly interesting, let me know and I‘ll add it to the list of suggestions :)
Today I also started my semester in Basel, where I‘m teaching two courses at @dmi.unibas.ch : a BSc course on algorithms and data structures and an MSc course on randomized algorithms.
I just finished the first lecture of my course „Intro to TDA“ at ETH. It‘s great to see interest steadily increasing, this year there are almost 90 people registered.
If you want to know more about what we‘re doing, we have a lecture page with some public material:
ti.inf.ethz.ch/ew/courses/T...