Teaching and Commuting

I haven’t gotten around to writing much here recently as my live has gotten much more busy since I started teaching in Regensburg last October. I do enjoy teaching quite a lot. It is actually a great opportunity to revise in my basic math, given that in my BSc and MSc I was trained as a physicist and only moved towards math during my PhD. Nevertheless this does take quite some time out of my week, especially in combination that I commute weekly between Berlin and Regensburg. Hence writing updates here has become a lower priority in recent times also since the pandemic travelling has reduced significantly as a lot happens via Zoom these days and it isn’t quite as exciting to write an update about an interesting Zoom conversation as it is about in person visits involving travelling and all that comes with it.

Home office

My home office.

The past three month were a strange time for everyone. As everyone else who can, I have been working from home. Sometimes I found it hard to focus without the usual daily and weekly structures of going to the office, doing sports and so on and so forth. I don’t think I have ever spent such a long time in a row in Berlin since I started my PhD. Luckily I just moved into a new flat at the beginning of the pandemic, so setting up everything provided some welcome distraction. Having four awesome flatmates made the lockdown time less isolating than it would have been otherwise. Academically the lack of alternative things to do proved quite productive and I finally got a whole bunch of projects finished, and others that have started to gather dust restarted. In particular we finally finished the Causal Fermion Systems website providing an accessible introduction to the theory and serving as a hub for the community.
Virtual seminars are a great thing I believe, as they allow people across the world to access events that would otherwise take place in a closed room at a particular location. I hope that they will become the norm and more open to interested outsiders. However I truly miss the face to face interactions and the opportunity to visit people for discussions. There are aspects to the direct exchange that just don’t transfer to the digital setting all that well. (Read here about our attempt at replacing our annual Challenge reunion with a social distancing compatible alternative.) We will have to restrict ourselves for quite some time into the future however I am really glad that things begin to normalize now.


My last trip before the Corona lock down took me to Vienna. I finally had the chance to take David Fajman up on an invitation, which was extended quite a while back (being back in Europe makes these sort of visits so much easier), to give a talk in the Seminar of the Gravitation group of the University of Vienna.
I also took the chance to pop over to the Math department for a quick chat with Roland Donninger about Strichartz estimates and results in my upcoming paper with Felix.
As you can see, for once, I forgot to bring my beloved proton and hence it is missing from my pictures :).


After Stockholm I went straight home to celebrate my grandpa’s 95. birthday and to spend Christmas with my family. The wee before Christmas I spent in Zurich where I met with Jürg Fröhlich and Tom Ilmanen to learn more about Jürg Fröhlich’s Events, Trees Histories (ETH) approach to quantum mechanics. In a lecture at UZH Jürg Fröhlich presented a model based on the ETH approach that interpolates between stochastic and unitary evolution based on the coupling strength between the system and electro-magnetic fields. This leaves unitary evolution as a short time approximation for quantum mechanical systems that are weakly coupled to electro-magnetic fields. There exist some vague ideas how to test this.

Mittag Leffler

From mid October to mid December I got to visit the Institut Mittag-Leffler in Stockholm for the research program: “General Relativity, Geometry and Analysis: beyond the first 100 years after Einstein “.
Given the number of people attending, I can’t list everyone but it was easily one of the best research events I have ever been to. The setting in the old villa feels like Hogwarts for mathematicians and it provides a unique environment. At almost any time of the day you’d hear people discuss in every cozy corner of the house (of which there are many). I’ve never before been working on mathematics in such a lively atmosphere.

I was able to give an informal lecture on Kerr uniqueness and T-orthogonal trapping and held the inaugural Gösta Guerilla lecture giving an introduction to the theory of Causal Fermion Systems. Following the informal lecture, Carla Cederbaum, OliverLindblad Petersen, Klaus Kröncke, Eric Ling and myself had several meetings where we had time to discuss the various obstacles in the way of a uniqueness proof for stationary black hole space times in the non-analytical setting. Some new ideas came out of this, but as I’ve already had too many ideas on this problem (which ultimately turned out not to work ) I’m not too optimistic on that one.


This year I got lucky to receive an invitation to SciFoo. The concept is kinda hard to describe, but the outcome is pretty awesome. The main point is: you take a bunch of interesting people from all walks of life (scientists, entrepreneurs, policy makers, artists), put them in a box, shake it, and see what happens.
From my point of view the result is simply an awesome event. The curation of participants tends to skew attendance towards the extroverted end of the spectrum and I truly enjoyed that. As side effect the quality of talks and pitches where extraordinarily high, especially compared to regular conferences (unfortunately many brilliant scientists are terrible presenters).

The interdisciplinary mix was awesome for me to get some feedback on my various side projects (there are always plenty of those, as I unfortunately have about the attention span of a goldfish).
Also I particularly liked the discussion about the inner working of science and academic institutions. But the best take-home message from SciFoo was definitely the fact that I met so many enthusiastic people (and my little proton made some friends as well as you can see from the pictures.

Big thanks also here at Cat Allman and the whole organizing team. It was a truly amazing event and if you ever get an invitation you should move hell and earth to be able to make it.


This time over in Europe I had a month of intense travelling and work. In Berlin I visited Marius Oancea, Jeremie Joudioux and Lars Andersson to finish up our review on the current state of research concerning the gravitational spin Hall effect of light (online soon). We also talked about a strategy to tackle some of the open questions discussed in the review.

The visit in Regensburg with Felix Finster was mostly dedicated to prepare the meeting with Jürg Fröhlich and Tom Ilmanen at ETH Zürich the following week. The meeting in Zürich was aimed to understand whether and how the Causal Fermion System Framework and the ETH approach to Quantum Mechanics can fit together.
After three days of intense discussion, we had to come to the conclusion that at present it is not possible to establish a solid link between the two.
The discussion gave me a clear picture where further work is needed to further develop Felix’ CFS framework. However it was great to see that the CFS framework held up to a three day intensive scrutiny by Jürg and Tom even if we were not able to fully convince them of the framework.

At ETH I also found time for a quick coffee with Christoph Niedermann whom I used to be in close contact with during my time on the board of VSETH. Besides catching up, we discussed how PhD programs are structured in different academic institutions.

ANZAMP -Merimbula

This years annual meeting of the Australian and New Zealand Association of Mathematical Physics took place in Merimbula. Probably the smallest airport I’ve ever flown from.
It was interesting to see what is going on in other fields of mathematical physics and to meet the people around here, as well as this little birdy in the picture.
Before the conference I had two days to explore the beautiful surroundings of Merimbula. Which I can really recommend.


My last trip in this crazy year lead me to Brisbane, where the weather in this time of the year can best be described by “blue sky with occasional sprinkles of holy shit what a storm”. 

I had the pleasure to give an introductionary talk to Causal Fermion Systems at the Physics Department of the University of Queensland. There I also had a chance to discuss with Magdalena Zych her recent results on the implications for causality when the center of mass of an object is in superposition at two different locations. 

Further I had the chance to go on a dive with my friend from school back home, Cedric van den Berg who is studying the role of visual information in marine ecosystems for his PhD. 

Science Communication in Berlin and Talk in Regensburg

I started my trip in Berlin with a visit back at the AEI admitting defeat on a bet with Marius Oancea (I promised him a first draft for our paper to the end of the trip, which I failed, so he gets to choose a costume for my next talk in Berlin). 
Then on Saturday I took part in the second edition of Kieznerds. Kieznerds is a follow up initiative of the Berlin March for Science crew. The idea is to bring science into the neighborhoods where people live. To initiate eye level conversations and make people aware that most science is done by absolutely normal people and not some crazy genius superstars. 

Next I went for a quick vacation back in Switzerland and on the way back I stopped in Regensburg. There I talked with Felix Finster about the possibilities of a compatibility of Jürg Fröhlich’s ETH interpretation of Quantum Mechanics with the Causal Fermion System Framework. 

My visit in Regensburg ended with a talk about my resent ideas around cosmology based on mechanisms provided by the Causal Fermion System Framework. A preprint should be ready soon, stay tuned. 

I finished my trip with a stop at The Bear. A storytelling event in Berlin. I will link my story in the Science Communication section as soon as it is available online.