Cosmoparticle Initiative


Five years on, the first Cosmoparticle PhD Student and her two supervisors reflect on the experience

19 May 2021

In 2016 Constance Mahony was the first PhD student to be accepted onto the Cosmoparticle Initiative’s innovative PhD programme, which offers the student two joint supervisors from different fields.


The supervisors reflect on the experience

Constance Mahony’s PhD project From camera to cosmology with LSST weak lensing magnification embraced the disciplines of Astrophysics and High Energy Physics, a prospect that excited both her supervisors. As Andreas Korn (HEP) explained, “Trying methods from one field in another has led to important advances in physics. For example, the Higgs mechanism in particle physics has some origins in the description of superconductivity. Hence, we went into this new multi-disciplinary endeavour with some excitement.”

The plan for the PhD changed from the original direction, as Benjamin Joachimi (Astrophysics) explains: “We originally planned to split the PhD between cosmological analysis and work on the detector, close to my and Andreas’ expertise. That was too wide a gap to bridge in the end, and there were also external factors that drove us more towards the cosmology route. However, under the cosmology umbrella, Constance worked on large-scale structure as well as neutrino physics.”

Reflecting on the PhD direction change, Benjamin says “Constance’s PhD was truly interdisciplinary, albeit in a completely different way than originally anticipated”, and Andreas comments that the reason for its success was because, “with Constance we appointed an open-minded student with broad interests, who even embarked on a project on the periphery of both of her main supervisors’ expertise!”

There were challenges, and Andreas reflects that there was “also a bit of naivety on how difficult it would be. I always instil into my students that at the end of their study they will be the experts in their specific subject. The constellation of one student with two supervisors from different fields, did pose some unique challenges. Not only from a physics point of view, but also reconciling different cultures and expectations.” Echoing this view, Benjamin says “Pioneering joint supervision of a PhD student in two quite different areas of physics proved to be a challenge, but turned out beneficial for everyone involved.”

And how do the supervisors feel about the experience looking back? “We learned a lot from each other. I certainly learned a great deal about cosmology and methodology in astrophysics from Benjamin and Constance and found the experience rather enjoyable”, says Andreas. Benjamin adds: “We evidently enjoyed the experience as we have jointly since taken on another PhD student!”

Constance reflects on her PhD

As the first PhD student, you were filmed for the video ‘About the Cosmoparticle Initiative’ where you talk about the opportunities to explore new research areas and to learn from people in different disciplines. 

Q. Looking back, was this what attracted you to applying for a CPI PhD?

I actually never applied for a CPI PhD as when I was applying it didn’t exist! I did my masters project in the High Energy Physics group at Imperial, but had also undertaken a couple of summer projects in the Imperial Astrophysics group. I was interested in both areas so I applied to a mix of PhD positions, with more of an Astrophysics skew. I applied to the UCL Astrophysics group and it was at the interview day that I learnt about the possibility of a joint position. It seemed like the perfect fit.

Q. How did it work out having two first supervisors?

It was great. Having two first supervisors gives you two people to learn from and since they come from different disciplines you are exposed to different ways of working. My two supervisors had different strengths and I learnt a huge amount from both of them. It also means there is always someone around to answer your questions.

Q. Did you encounter any challenges?

Yes of course! Being exposed to such a range of research was great at the start of my PhD but became more difficult as my PhD progressed, as it was hard to stay focussed on completing specific projects. The other challenge was that the projects I worked on in my PhD were more varied than many other PhD students. That made switching between them difficult as they didn’t easily relate to one another.

Q. How did you overcome these challenges?

Towards the end of my PhD I had to block out all the exciting work that was going on and focus on my own projects. This meant I became more disconnected from the High Energy Physics group, which was a necessary evil. I also ended up prioritising one project at a time, so that I didn’t waste so much time switching between them.

Q. Were there any unexpected outcomes or benefits? Did the PhD turn out as you’d hoped?

The main benefit of a CPI PhD is getting to know both research groups. Most PhD students tend to interact within their own research group, whereas I was able to meet two great groups of people. I learnt about such a large range of research just from attending both groups’ events. 

I would have liked to work on more projects in my PhD, but I think this is a common issue for all PhDs. It is easy to forget how much you have learned, and how opaque things seemed at the start of a project.

 Q. How has undertaking the CPI PhD enabled to you to develop your research interests and direction? 

Undertaking a CPI PhD got me really interested in neutrinos, since they kept popping up in both cosmology and particle physics talks. Neutrino physics is a truly interdisciplinary area where astrophysics, cosmology and particle physics all come together. My own work has come from a cosmology angle but I am always interested in learning about developments in other areas.

Q. Where are you now, and what is your research area?


I am now a fellow at the German Centre for Cosmological Lensing based at the Ruhr-Universität Bochum. My current research focuses on using galaxy surveys such as the Kilo-Degree Survey and the Vera C. Rubin Observatory Legacy Survey of Space and Time to learn about the structure and evolution of the Universe.

Q. What would you say to someone considering applying for a CPI PHD?

Apply! I very nearly did not apply for any PhDs at all because I did not think I was good enough. It took the encouragement of a lovely personal tutor for me to even put in an application, and I can’t thank him enough. If a CPI PhD sounds remotely interesting to you, just take the first step and submit an application!