John Ellis considers cosmology, colloquiums and new collaborations

On 13 September, physicists from around the world joined John Ellis in a colloquium to celebrate his 65th birthday. In our last issue, we talked to John about the Higgs, the lack of the Higgs and extra dimensions. In this second part of the interview, John speaks about the colloquium and the wide range of topics it covered, all inspired by his career.


John Ellis in his office (July 2011).

How did your birthday colloquium come about?

When physicists here at CERN reach a “certain age” – or reach a transition point in their careers – it is traditional to hold some kind of colloquium. I had previously resisted pressure to hold one of these events. But this year, my official duties for the Organization have come to an end.  While it is unlikely you will see any difference in my working habits, it was a milestone that proved too important to not give into requests for an event.

Rather than a very long sequence of people talking about what they did with me in the dim and distant past, I asked my friends to organise the colloquium around what is going on now. There were discussions of the future of experimental and theoretical particle physics, as well as significant discussion on cosmology.


Two areas of physics that you've been instrumental in bringing together. When do you think the two will finally become a single area of study?

Quite honestly, I regard these fields of particle physics, and high-energy astrophysics or cosmology as already having basically merged. I don't really notice when I am writing a paper, whether I am writing a particle physics paper or a cosmology paper – often it is a combination of the two. There's a symbiotic relationship between the two fields – astrophysics and cosmology feed into particle physics, and vice versa. I am currently writing a paper about the theoretical implications of the non-discovery of supersymmetry so far at the LHC. The key elements of our analysis take what would you expect if supersymmetry were responsible for dark matter in order to explore what would you expect from astrophysical searches and cosmology experiments – all the while taking into account that supersymmetry has not yet been seen in the LHC.


The colloquium also addressed expanding CERN's scientific collaborations outside Europe. What do you think the future will look like for CERN's non-European collaborators?

I acted as non-member state representative for 13 years, and now I really like to think of the E in CERN as meaning “Everywhere”, as opposed to “European”. More and more non-European states are taking steps to formalise their relationship with the Organization. The first non-European nation, Israel, signed on September 16th to become an Associate Member State of the Organisation, on the way to becoming a full Member State. Other non-European countries – like Brazil and India – are actively considering at least becoming Associate Members.

In some sense, these new collaborations are merely formalising existing relationships. Many of these countries have had physicists working at CERN for a long time; they've been part of the CERN community for decades.

I think this global quality is intrinsic to particle physics, as it deals with subjects that are of interest to everybody. Whether you live in Africa, Latin America, Australia – anywhere – you are interested in the fundamental questions explored at CERN. What is dark matter? How did the universe evolve? What is matter made of? These are universal questions undefined by geography, and it is only natural that people from across the globe are interested in working on them.

On the other side of the coin, it has become clear that this type of research requires massive resources. We are at a stage where, as a scientific community, there are very few centres in the world where this research is done at the cutting edge. We're evolving toward a situation where we will have a limited number of laboratories around the world, and each will be the “world centre” for a particular type of fundamental physics. While CERN might be the world centre for doing collider physics at high energies, another laboratory may be the world centre for precision physics at lower energies, another for neutrino physics, and so on.

When we are planning our future projects we need to think of them as global projects, with stakeholders around the world. Some of them may already be members of the Organisation, while others may be outside the Organisation but could join on an ad-hoc basis for that particular project. This might be the case for the LHC upgrade, CLIC or the ILC. The world is becoming a ‘subnuclear family’.

by Katarina Anthony