Postdoc/student positions

I have several postdoc/student positions available. Just contact me and we can chat about science.

not me

(honestly write to me. If you just apply via some bureaucratic system it can happen that I don’t really see your application unless I already read your paper. Because I get many applications. Sorry) (plus it is just cooler to talk about science directly)

me (in the standard representation of S_3, French notation)

Also check out the job posting at Renyi which was brought to my attention by my very best in the world friend Janos Pach.

Jewish Poker

For quite a while the two of us sat at our table, wordlessly stirring our coffee. Ervinke was bared. All right, he said. Let’s play poker.

No, I answered. I hate cards. I always lose.

Who’s talking about cards? thus Ervinke. I was thinking of Jewish poker.

He then briefly explained the rules of the game. Jewish poker is played without cards, in your head, as befits the People of the Book.

You think of a number, I also think of a num­ber, Ervinke said. Whoever thinks of a higher num­ber wins. This sounds easy, but it has a hundred pit­falls. Nu!

All right, I agreed. Let’s try.

We plunked down five piasters each, and, leaning back in our chairs began to think of numbers. After a while Ervinke signaled that he had one. I said I was ready.

All right, thus Ervinke. Let’s hear your number.

Eleven, I said.

Twelve, Ervinke said, and took the money.

I could have’ kicked myself, because originally I had thought of Fourteen, and only at the last moment had I climbed down to Eleven, I really don’t know why. Listen. I turned to Ervinke. What would have happened had I said Fourteen?

What a question! I’d have lost. Now, that is just the charm of poker: you never know how things will turn out. But if your nerves cannot stand a little gam­bling, perhaps we had better call it off.

Jewish Poker by Ephraim Kimshon

What just happened? by Hendrick ter Brugghen
Continue reading

Can animals recognize symmetry? A foolish idea for a few seconds

Here is how stupid thoughts are made: I read a post by my friend Michael Kapovich about succulents that evolution made look like stones to avoid animals that might feed on them.


My first thought was: those are just colorful, beautiful butts.

My second thought: It makes me actually wonder: from a human perspective, we immediately recognize the symmetry and see that this is not a stone. To be evolutionarily effective, that must mean that animals, for the most part, may not recognize symmetry. Antisymmetry must not have an advantage when it comes to camouflage. Which led me to find out that symmetry and its recognition is barely understood in either way, but that I may also be stupid because in real life these plants may look less symmetric. Still, maybe there is something about it.

Continue reading

It just piles up

This is the third in line of three posts about “worldly” problems, with the diplomacy one here and the diversity one here. I will probably also write one on freedom of expression at another point, which is a different topic important to me, but you know, this entire site is an exercise in speaking my mind on whatever I want. Needless to say, this is different from mathematics in that the problems are often trivially solved, but the implementation often comes with resistance. I mean, outside of alphabet agencies, a mathematical theorem rarely endangers your life. Well commutative algebra does. And you know, having both in your life is kind of nice 😉

In a small update to this post, I remember visiting a spring next to Jerusalem, in Lifta, with a dear friend. It is small and beautiful, and close to one of my favorite works of architecture, that impressively greets you once you enter my favorite place in the world.

But of Lifta, I mostly remember one thing: The ungodly amounts of trash that were littered in and around the spring. There is a clear issue in that once it reaches a level of visibility, people tend to loose all morals and just add to it.

Continue reading

Not because it is easy…

and not because it is hard either.

A few years ago there was a heated discussion about diversity statements, initiated by an opinion by my friend Abby. And I felt that either way, either side missed a critical point. A quick overview: Diversity statements are a requirement that some universities, some science foundations and some companies require. Abby argued against them, some people argued for her, some against. All in all, it was kind of ugly.

And what is really the issue, the real culprit, the thief in the night, could just get away.

Because you see, universities, governments, companies etc. can say that they required a diversity statement, and they are done. That they imposed a quota for the organization or attendance of a conference, and they did their duty. Alas, the hard part, to actually enable participation, is usually not given. It is not easy for a parent to juggle childcare and studies, it is not easy for a disadvantaged person to attend a conference or workshop or university in the first place.

Continue reading

What I (also) talk about when I talk about struggling

In reference to some recent posts like this and nightlong discussions with Dasha Poliakova, I wanted to clarify a metapoint of why I actually made the post. And there is a point besides the point of me actually struggling, or me dying to those Rune Bears or difficult exploration projects.

It is that I am aware that I am, even if a questionable person, in a position of power. And as such, people look up to someone like me, whether it is with hate or admiration. I additionally have real power over my employees, what happens in my field etc.

Hence talking about struggling is not actually only talking about struggling. It is also serves a higher objective, in that it shows it is okay to struggle, and it is ok to talk to me about struggling. I think the former is just evidently good, the latter is more subtle. But I have made the experience (on myself and others) that a struggling person is still very capable of hiding, of subterfuge and of distraction, wasting much more of their time on this than on getting better. Hence, you (as a person encountering someone struggling) may not notice anything, or think everything is fine.

I do not make up a struggle, and you should not either. You do not have to emulate the specific struggles of your students. It can be something as simple to admitting you are struggling to understand a paper today, or have trouble figuring out a problem (not that not understanding that paper is entirely your fault). It shows those around you and under your care that you have experience with it.

And again, there is a metapoint to this post: if you are in a position of power, if you have people under your care, this might be something for you to consider. Plus you can do it from bed at 5pm while frustrasted and laying down a paper about analytic torsion (or just still snuggling).

At least two 2-associahedra, QFT and the importance of taking a bird’s eye view

A useful idea to study an object is, it turns out, not to just consider the object but an entire space of objects like it. Consider, for instance, the situation in which you want to simplify an object to one you understand (like in the solution of the Poincaré conjecture) or when the space is naturally evolving over time (like spacetime): in this case, it is often easier to understand the space of spaces, rather than the space itself, as difficulties like singularities can vanish once you have taken a broader, bird’s eye view.

I want to discuss a specific case of this, based on a great talk Daria Poliakova gave in our seminar. If you don’t like it, well…

Continue reading

Angles, gherkins, polytopes and a sociological experiment

Let me start by admitting that this blog is a social experiment to see how long people take to ask me “what the fuck?” (I am kidding)

(seriously though, I am always a bit of chaos. Nothing out of the ordinary, though admittedly a bit sick and depressed at the moment. Thank you and all the love for caring y’all. Love you all 😉 )

Now, on to the other stuff: At some point in my life, I was doing my PhD and being an all around useless student (I spent most of my office computer hours watching Game of Thrones and Gossip Girl; this is not to say I did not work, but I usually cannot sit in an office chair and work. I paced around outside. Honestly I feel most time was wasted because I was anxious about seeming to work and ending up watching series rather than going out and thinking my own way), my advisor PhD Günter Ziegler and I looked at a gherkin and said: this is going to make a fine math paper. Anyway, tonight I was visited by three ghosts, and they told me a tale.

Continue reading