Albert Einstein Institute – Reebhu Bhattacharyya

936 Views, Posted on: June 17, 2017

Falling Under The Attraction of Gravity
DAAD WISE Scholar at Albert Einstein Institute, Potsdam, Germany



How did I get here?

As I sit and ponder upon conformal Killing Yano tensors  (no, you are not expected to know what that is) I realize that almost a month has passed since I started my research internship here at Albert Einstein Institute (Max-Planck-Institut für Gravitationphysik) in Potsdam, Germany.

The whole process started way back in September 2016 when I began looking for professors willing to host me for the summers. I was aware of the DAAD(Deutscher Akademischer Austauschdienst) WISE (Working Internships in Science and Engineering) program which funds students from select institutes for a short period (~3 months) for training or research in Germany. One caveat was that I had to find a professor willing to host you before applying, and the deadline being October end meant I didn’t have much time on my hands to apply.

Being interested in Mathematical Physics and Mathematics meant that it was not easy to find willing professors since you need a whole lot of background even for the most basic projects. It was then that I realized how useful the whole bunch of extra theoretical courses I had done would be – they helped me to gain credibility and potential for understanding advanced stuff, it was these points I highlighted in my emails to the professors. I knew of two seniors who had previously secured internships at the Max Planck Institute for Gravitational Physics and I decided to start from there. The research areas of this institute aligning strongly with my interests. I had to send about 25 emails before getting two favorable replies, one from MPI Potsdam and one from University of Heidelberg. I decided to go with the former if only because of my bias towards the institute, and with only six days left for deadline set out to complete the formalities. I managed completed the procedure by the skin of my teeth, and dispatched the applications to the DAAD office in Delhi. And then began the wait.

Towards the end of December, I received confirmation of the scholarship. The award letter arrived by January end, it was time I began preparations for my first international trip. I managed to get reservations at the institute guesthouse and did not face as much trouble about accommodation as did some of my fellow WISE scholars. I was to depart from Mumbai on 4th May, arriving at Frankfurt in the afternoon and then proceed to take an overnight train to Potsdam(with three changes) to arrive at my destination on the morning of the 5th. The prospect of an almost 48 hour journey in unknown lands with little rest had me anxious.

The Journey

The flight landed on time at 14:20 localreebhu3 time, however ground crew operations were halted due to heavy rains so that when I finally exited the airport, it was almost 17:00. My train was at 21:30 and I had a test of patience before me already being exhausted. The station is adjacent to the airport and so I didn’t have any trouble in reaching the platform.  Now, for the first time, I began to appreciate the extremely chilly weather ( I learnt later it was around 4℃) and hastily reached for the jacket from my suitcase. I took this time to observe the people around me and it struck me how organized the whole situation was quite unlike that in India (especially Mumbai).  Two things struck me, the impeccable cleanliness and the discipline followed by each and every one, as hard as you might try, you wouldn’t be able to find either a single scrap of paper on the platform or a person shoving past others to get onto a train.

A few more differences became apparent to me even before I reached my destination. The days here are very long, during the summers, the sun rises at around five a.m. and sets around ten p.m. which took me by surprise although in hindsight, I should have expected it. Another thing is how punctual and organized the public transport system is, I will elaborate on this further below. And one thing that you cannot even expect in India but is taken to be the standard in Germany is honesty. People actually leave their bags in a rack (unchained) and go to sleep on the train (albeit uncomfortably, since there are only chairs and no berths) without a worry. I was a bit apprehensive at first and got up to check up on the luggage several times,but later realized it was quite unnecessary.

At six a.m of 5th May, I finally arrived at the Max-Planck campus tired, hungry, and cold. It took me quite a bit of time to find the reception since not  a single living soul was out on the streets so early on a cold morning and the reception was in the main building of the Max Planck campus which is set further inside hidden behind other buildings and there are no apparent directions for where to go. Finally, having located it, I was handed keys to my room and identity pass for the institute. Seeing a bed for the first time in 48 hours made me almost cry with joy and you can expect what I did next, freshen up and promptly go to sleep!

Intermingling of Maths and Physics: Gravity and Geometry

True to its name, the Albert Einstein Institute deals solely with gravity, both Einsteinian general relativity and modifications of it. It is bliss for someone like me who finds the interplay of maths and physics to be fascinating and awe-inspiring.

I was introduced to models of f(R) gravity, some whose action differs from the canonical Einstein-Hilbert action, another which on varying the action, gives second order quasilinear differential equation like the original Einstein field equations. While the first model supports bound orbits in spacetimes of dimension greater than 4, whereas Einsteinian gravity only supports bound orbits in spacetime dimension 4. Are we really living in a world with Einstein gravity with 4 spacetime dimensions or are we living in a world with higher dimensions with a different model of Gravity?

Symmetries in Classical Field Theory, Quantum Interpretation and Maxwellian Nature of Gravitational Waves

Therein, I was introduced to the topics I would be dealing with for the rest of my stay. I had considered myself to be familiar with Maxwell’s equations in electrodynamics, every first year students sees them (PH 108 in IIT Bombay) and I had recently done a course in advanced electrodynamics (PH 308). But I was in for a surprise. I came to know of the duplex symmetry of the free Maxwell equations (i.e., in vacuum): one can rotate E and B fields into each other continuously without changing the equations.

Enter Gauge Theory and Gravitational Instantons

Another topic of interest was gravitational instantons, which require a deep understanding of differential geometry (principal bundles and connections on principal bundles), spinor and twistor formalisms and spin geometry. I am in the process of acquainting  myselfwith these topics (maybe the relevance of the first line becomes more transparent now). Let’s get back to fun stuff.reebhu1

Life in Potsdam

As I remarked before, I was amazed at how pollution free and clean the city is. My residence is in Golm, on the outskirts of Potsdam and here life is quiet and peaceful. Compared to hustle and bustle of Mumbai crowds, it seems as if I am living in isolation, very few people can be seen on the streets at any time. The local supermarket has been my saviour: it has everything you could possibly need, all under one roof. It has saved me from making trips to the city too often. One of the upsides (or downside?) of living here is that I have had to learn to cook, the cafeteria and restaurants are way too costly for me to afford on a tight budget. Cooking my own food, I manage to get by on about 5€ per day otherwise I would only afford one meal for the same 5€ (or more). It does not hurt that the kitchenette at the guest house is first class, equipped with everything I could possibly need.

Public transportation is efficient and punctual, albeit a bit costly. The whole system is based on trust and honesty, you are expected to have a ticket or take one from the machine inside buses and trams and get it stamped as you begin the journey, there is nobody to ask or check the same (there may be surprise checks by officials, and the fine if caught is large enough to deter any dishonesty). The cost of getting from one point to another (in the same city) is the same regardless of whether you travel by bus, tram or train or switch in between – the ticket is valid for all. There are indicators at major stops indicating when the next bus/tram will arrive and  they are punctual to the minute, quite unexpected for someone from India where delays are the norm.

The presence of directions and street names at every turn and corner makes it easy to navigate, even for someone not familiar with the place. Here, cycles are quite popular with dedicated lanes for cycles at many places. One thing to keep in mind though is many of the locals speak only German and asking for directions can prove to be quite a task.

I am enjoying every moment of my stay here and the learning experience has been great. I still have a month and half to go, but already have fallen under the attraction of Potsdam and gravity!

Before I go, here is something that I regretted overlooking:

Tip: Always carry a travel adapter for the place you are going to, they are cheaper in India .

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