- When I was eight years of age or so I had a relative who always asked me tricky mathematical questions, one was about the weight of a chicken...

The deep interest in mathematics developed from the first years in school all the way through to becoming a professor in mathematical physics in 1996. When Bengt describes books he read, demanding teachers, a particle physics project in high school, it all adds up to the picture of someone who has had a very straight career path focused on mathematics and later mathematical physics.

When he entered university he was part of a large expansion of the Swedish higher educational system where most students came from families without an academic tradition. Bengt, like many other students, was compensated by coming from a background of entrepreneurship and highly developed work ethics. He brings with him a zeal for equality, justice and the possibility of lively discussions to this very day.

- It is an integral part of who I am.

No wonder John Cleese’s Argument Clinic is one of his favorites and it explains his keen interest in reaching the public.

- The public has to be more educated in physics and related topics, or at least get a better understanding and appreciation of the importance of rational arguments. To develop this requires a lot on behalf of us scientists.

What does it take to make a good scientist, science?

- Doing science has a resemblance to being a sportsperson – you need a strong drive and definite goals. You also want to make an impact and to be acknowledged for your achievements.

He has given many contributions to his field of science and has been acknowledged for it. Most physicists would be happy to have an h-index around 30 before retiring. Bengt has at least one more PhD generation before he formally retires and is already approaching h=40. His most cited paper, a Physics Reports on Kaluza-Klein supergravity, has been quoted by others nearly a thousand times.

After his exam in physics at Gothenburg University he did a year in teachers’ college and another one in the military service before he started a PhD with Lars Brink in the department of Theoretical Physics. With a thesis in the field of supergravity he started a long journey into the mathematical framework of the smallest structures of our universe:

- I’m most proud that we managed to show the ultra-violet finiteness of the N=4 Yang-Mills theory and that I introduced Cartan’s pure spinors into our field of research. It is also nice to have played a role in the early development of compactifications of the eleven-dimensional string/M-theory in the 1980s that you can read about in the Physics Reports I mentioned before.

This is technical jargon, however, we don’t have to know what it means in detail. The sheer importance of this shows up in a well-deserved reputation among his peers for contributing these tools for dealing with the ever more complicated mathematical frameworks describing the deepest workings of our universe.

Why is mathematical physics so important to you?

- The main method I use, conformal field theory, both classical and quantum, is so general and has so many applications. It is a key ingredient in string/M-theory but it turns out to be extremely important also in condensed matter physics where graphene is the buzzword of the day.

Bengt gets even more determined when he gets stuck and has to find out new ways to push the research frontier forward.

- The results coming out can be really fascinating in themselves – like pieces of the jigsaw puzzle of nature falling into the right places.

It strikes me that Bengt has an unusual balance in his life; you really feel like you are talking to someone who knows what life is all about and someone you can trust and rely on. He plucks his strings in the same cool way as J J Cale, a favorite of his. He values good food, extensive travel and his family. Just imagine a Sunday dinner discussion with his life companion, a Montessori teacher, and their three boys who are into film, consulting and finance with past elite efforts in floorball and football.

As many of his colleagues he has taken turns in administrative positions such as head of department. This is the first time I notice something he has had mixed feelings about. Why have you still been doing this on repeated occasions?

- We need to strengthen our internal discussions and have a more lively involvement of our faculty in the decision making at our university which more and more starts to look like a company.

Company?

- The values of openness, discussions based on rational arguments and an atmosphere in which research always is our main focus are all ingredients we must foster in an academy. Not only do we come up with what you don’t know that you need to know but we also address the major human challenges of today and the ones we’ve been thinking about for thousands of years.

What worries him and many others is the current trend of external financing dominating our universities, largely defining the future direction of research. Areas like basic science with its long-term interest in human development are constantly running into financial trouble when the universities often refuse to provide any kind of reasonable long-term funding.

- We need time to think, and we need time and resources to develop the stuff that may seem to have no immediate use but could be crucial to some future technology. The history of science is flooded by examples like this.

We finish our pastry, Bengt is a pastry freak like myself, and I look forward to hearing more about his worldview in the book he nourishes an idea to write.

**Text:**Peter Apell

**Photo:**Henrik Sandsjö