Former Nikhef PhD student Melissa van Beekveld is the 2020 winner of the Kluyver Prize for the best summary of a thesis. In September she obtained her doctorate in theoretical physics in Nijmegen.
Melissa van Beekveld’s thesis (Oss, 1992) is about the computational techniques used by theorists to predict outcomes of measurements from particle theory, the Standard Model. Van Beekveld shows how these can be made more precise without making the computation impossible, by means of so-called ‘resummation’.
She also re-examines the chances of extending the Standard Model to include so-called supersymmetry. This SUSY would better explain a number of coincidences in the current theory and possibly also tell what dark matter consists of.
So far the extra particles that SUSY predicts have not been found in experiments. But the PhD student shows that the theory is still far from excluded, the experiments are not yet able to give a definite answer.
Two theses
Two subjects about which you could easily have written two dissertations, and I found it difficult to choose’, Van Beekveld said earlier in the Nikhef magazine Dimensies. ‘But I’m stubborn, so I just did both’. Her promotion was assessed cum laude.
The jury of the Kluyver Prize praised Van Beekveld’s summary of her thesis, which is in both English and Dutch in her book. It is extremely accessible, yet precise and relevant, according to chairman and former Nikhef director Jos Engelen.
Van Beekveld, now a post-doc in Oxford, has worked long and hard on it, she confesses. I absolutely wanted my parents to be able to read it. I come from a family where science isn’t taken for granted at all. I wanted to explain clearly to them what I had been doing during those four years. And that succeeded, I believe, after a number of iterations with my partner and some friends as co-readers. My father and mother were very happy with it. My father immediately started reminiscing about the old days’.
Bats and cows
The summary therefore begins on an August evening in her youth, when she looks outside at the stars and sees bats hunting moths. Why don’t they catch mosquitoes, she wonders. Because the sonar of the bat is not high-frequency enough to follow such small objects, the answer is. And that is the prelude to a story about experiments in particle physics, where higher energy is needed to observe the smallest particles.
Her explanation of brain summation methods is also exemplary. Van Beekveld starts with a story about the simplest description of a cow (“Is round, has a head, ears and a nose”) which only after more details about the tail (“fluffy”) prevents us from seeing a pig instead of a cow.
In the same way, theorists make calculations: first coarse and then step by step with more detail, so called perturbation calculations. Van Beekveld patiently explains how this approach leads to problems if an extra term turns out to be not a detail at all, and how this can be anticipated and tackled.
To be inviting
This is an abstract mathematical subject, and the analogies have their limitations, she acknowledges. These are things you have to study for ten years, we don’t have to be secretive about that. But I think that as a scientist you should at least be inviting to the outside world: if you want, I’ll do my best to explain it to you’.
The Kluyver Prize consists of a cheque of 2,500 euros for the winner, which is presented at Nikhef’s scientific annual meeting, the so-called Jamboree. This year, the Jamboree will be fully online on 14 and 15 December, due to corona.
The prize money will be well spent, Van Beekveld assures. ‘I’m currently looking at how I can give it to my sister, who works on an animal petting zoo where they don’t have a lot of money and a lot has to be done.’