Christian Shell is a PhD student at the Max-Planck Institute for Gravitational Physics /Einstein Institute/ and the Berlin School of Mathematics. He is researching in the field of numerical mathematical relativity and is among the first PaperHive ambassadors!

**What sparked your interest in numerical mathematical relativity?
Is there or was there an alternative to your career path?**

I guess in some sense I already had a tendency towards physics and math in high school but that doesn’t necessarily imply to study those subjects. Back then when starting as an undergraduate, I was rather easy-going and just interested in finding some study program I like to carry out but wasn’t really fixed on anything particular. Somehow I got caught by physics and mathematics. And I am into it ever since. Maybe one could interpret it as a chain of fortunate coincidences. For me, it is of importance to some extend to take things as they come. I’m not saying that I’m not trying to plan ahead, on the contrary, but it is not possible to take all circumstances into account. In this sense there are always alternatives on the road. Stay tuned.

**Please share a piece of advice for young researchers
and **

**another one for more experienced ones.**

Most probably there is no advice that can be applied universally to everybody. But talking about myself I recommend to try to follow always your individual tendencies and interests. At least I have good experience with it. Usually, it doesn’t pay off to force yourself into something which doesn’t fit. No doubt, there are always subprojects that are tackled with some kind of reluctance but I claim that, at least considering the big picture, you should try to find something that you can carry out with joy. Usually, that comes along with some intrinsic motivation for what you do and that is of significant importance.

**Which are your favourite sources for articles?**

ArXiv is probably the most important paper collection for me. Unfortunately, in most cases I don’t go to the library and search and copy papers anymore. I have to admit that I might be kind of lazy and appreciate the online version. In addition to the easy access you have the advantage of cross references, hyperlinks, supplementary material and there like. In recent years these add-ons and facilities were largely growing. One example is indeed the PaperHive project, offering the possibility to discuss and annotate papers in the community. Usually, that is considerably harder in the offline version, if possible at all. A further project, also of great value for me and colleagues in my field and interesting in that respect, is the living reviews journal (e.g. http://relativity.

**Who are the contemporary researchers
that have influenced you the most?**

If you want me to pick a particular scientist I would probably go for Stephen Hawking. Besides outstanding scientific achievements, he has an interesting personality as well. Nowadays I highly appreciate that one has the chance to actually meet some of the distinguished authorities in the area by yourself. At the end of the day, my field of research (mathematical relativity/numerical relativity) is a small world. Of course, direct contact helps to become influenced by them. Personally, I like that a lot of these persons are quite some character and also distinguished from that perspective.

**How would you explain the broader significance of your**

** work to non-researchers or academics from other disciplines?**

I specify my field of research as numerical mathematical relativity. Thus I consider myself as doing fundamental research. The aim is more an epistemological extension of our knowledge so to say. More specifically I am after a deeper understanding of Einstein’s field equations which are at the heart of the general relativistic theory of gravity. To achieve it I make extensive use of numerical computations. That requires that I have to develop new tools for the numerical analysis and code and test them. To give an example a deeper understanding of the axisymmetrical wave equation in spherical coordinates including the development of new techniques for dealing with the singularity at the origin turned out to be key for my progress with respect to Einstein’s theory. That is actually quite typical for our field. For example the current knowledge about nonlinear hyperbolic differential equations is in large parts motivated by the need to understand problems in general relativity. Advantages for the broad field come usually indirectly.

**How can you and other researchers in numerical **

**mathematical relativity benefit from using PaperHive?**

Important is to make papers accessible for other researchers. New in PaperHive is the possibility to discuss and annotate papers. The printed and published version is final and hence static in some sense. Amendments and corrections are possible in principle but usually slightly involved and therefore not necessarily common. PaperHive offers the possibility in a comparably easy way. Furthermore it seems to be appealing to add information, corrections, discussions etc, both as an author and reader. The paper becomes dynamical in that way.