I got to present our results on black hole shadows at the 15. Marcel Grossmann Meeting in Rome. This years meeting was very heavy on the physics side and little mathematical relativity. It was interesting to get an update on recent progresses in observations. It was evident on the theoretical side of the event, that the recent dramatic progress in observations, particularly towards the strong field regime of gravity, enables the test of modified theories. It seems to be the biggest fashion at the moment to modify gravity in any possible way, doing some basic checks and throwing it out as a new model (possibly fitting some observations here and there a little better). The interesting points I picked up:
When people talk about “raw data” it is in fact often highly contaminated by \Lambda CDM and constructive gravity provides an interesting link between the dynamics of the matter models and the dynamics of the geometry it couples to.

On the down side there were some questionable talks admitted to the meeting, which I think is inappropriate for one of the flagship conferences of the field of gravitation.

ETH Zurich

On my visit back home I managed to insert a quick academic visit to my Alma Mater. Had interesting discussions with Tom Ilmanen about spacetime and entropy.
Further I had the  to talk with Thanu Padmanabhan and Hamsa Padmanabhan about their recent paper that links the value of the cosmological constant to the
amplitude of the fluctuations  in the CMB. An nice explanation of their idea, accessible to laymen can be found in Nautilus. Given the claimed perfect match up of the observed values with their prediction it is certainly worth investigating further.
The second picture shows the Drei-Grazien -Brunnen in the entrance of ETH. When I was a student there it used to be the running gag that this is probably the place at ETH with the most women. Unfortunately the numbers haven’t changed too much since then. We need to get more women in STEM!

Home Sweet Home

Part 1

Back at the Albert Einstein Institute. It was great to see everybody again.  Right now it was just two days. But I will be back for more :).
Enjoy one of my favorite songs.

Part 2

So I finally defended my thesis back to back with Siyuan Ma, my academic brother and probably the person I spent the most time with during my PhD. Yay to academic twins.

Part 3

I was invited to give a Journal Club on Causal Fermion Systems. Trying to convince the quantum gravity folks that it is actually an approach worth investigating. (Moral of the story: I still have a lot to learn until I understand the formalism on a deep enough level that I can explain it in a convincing way)


March for Science, Melbourne

Welp I finally arrived in Melbourne and as every good guest arriving in a new country, the first thing I did was going to a protest. (Yay for science)
The turn out was unfortunately not quite as strong as last year (but we will blame the weather given there was actually hail that day).

Institute for Astronomy, Hawaii

My last stop on the way was at the Institute for Astronomy in Hawaii. Now that was an environment completely different from what I am used to. It was really interesting to get a glimps into what is really going on in the universe (or what we can observe there of). Good not to loose touch with physics completely when trying to solve physics related problems in mathematics.
I learned about the fact that when using the typical energy density of the universe to calculate the expansion rate instead of the average density one can obtain an evolution history without dark energy that closely traces a solution with dark energy where the average energy density is considered.
I had the opportunity to speak in the IfA Colloquium about the central problems in mathematical relativity and recent advances in the field.

Perimeter Institute, Waterloo

Next Stop on the way was at the Perimeter Institute in Waterloo, Canada. Such a lovely place. Though kind of a black hole. I think if I would ever get the chance to work there I wouldn’t make many friends in the surroundings as I d spend all the time at the Institute ^^. Great and truly inspiring place and great people. Had again the opportunity to present the findings of our paper this time in the Stong Gravity Group seminar thanks to the kind invitation by Angelika.

Black Hole Initiative, Harvard, Boston

Finally I had to leave Berlin. My first stop on the way over to Melbourne was at the Black Hole Initiative at Harvard in Boston. Besides the fact that i had one of the most interesting accommodation i got to experience so far i ended up discussing more about the philosophy of science within these 7 days then I did within the 4 years of my PhD. I learned (ignorance is bliss) that apparently there is still no satisfactory resolution to the measurement problem in Quantum Mechanics… guess “shut up and calculate” is a valid strategy as long as it gives answers that match experimental results. Martin Lesourd explained to me that apparently evaporating black hole space times are causally fucked up. Further I had the chance to follow an interesting talk by Beatrice Bonga about a common mistake made in the calculation of angular momentum carried by radiating fields in GR.
Last but not least i had the opportunity to present our paper on the information content of a black holes shadow in the group meeting of  Ramesh Narayan’s group.

The Black Hole Initiative is a really interesting Institution as it brings together people from various branches of Physics working on topics related to black holes ranging from observations to pure mathematics and philosophy. (In the light of the fact that the Albert Einstein Institute seems to be moving towards being mono-thematical on  Gravitational Waves the Black Hole Initiative fills an important role)

Field Equations on Lorentzian Space-Times, Hamburg

Next stop on my list this year was Hamburg. Unfortunately I was only able to stay half the time.
Apparently (if i understood the talk by Shadi Tahvildar-Zadeh correct) the pilot wave interpretation of quantum mechanics can be made mathematically consistent after all.  Interesting as well the talk by Lydia Bieri on the different behaviour of gravitational waves in cosmological space times in the near field and far field regime.

“Spring” School on Causal Fermion Systems, Regensburg

Next on the list of this years travels: Spring School on Causal Fermion Systems
Well there sure wasn’t much spring in this (took one hour to warm up again after the hike on Wednesday afternoon at -10 C)
The spring school was really interesting. Helped a lot to get a vague understanding of the mathematical structures involved in the Causal Fermion System framework. Given the claims made at the time it is certainly an approach that deserves a deeper, critical investigation.
Check out the CFS section of my brain farts and conjectures  page
Check out the introductory papers:

For Physicists:
More Mathematical:
The whole thing:

PS: Regensburg is a beautiful little town. (except the University is rather ugly)

Back home for Fasnacht

Trips back home are a rare occasion these days. Before going to the other side of the world I had to visit Basel for Fasnacht (first time in 4 years). If you ever plan on visiting this beautiful city: Fasnacht is the best time to do so.