Anna Lisa Varri

Dr Anna Lisa Varri is as much a mathematician as she is a physicist. Since the very beginning of her studies, she has been torn between the two disciplines. Even though her time in school had been dominated by humanities and she had taken “very few scientific core subjects”, she was determined to pursue a career in a mathematics-related field. Initially, she went with an undergraduate degree in physics because she felt it might be more accessible, especially for someone like her who didn’t have the luxury of a strong foundational knowledge in science. Her desire to deal with the most interesting problems at the interface between the two subjects then led her to a master’s degree and a PhD in Theoretical Astrophysics at Università degli Studi di Milano and thereby to the research she is doing today.

Stellar dynamics

Nowadays, Dr Varri’s field of research is stellar dynamics, a very specific part of theoretical astrophysics which deals with collections of stars and their behaviour due to their own gravity. This is related to the gravitational n-body problem. Unfortunately, no one has been able to find a general solution to this for any cases where three or more bodies are involved. Since analysing star clusters or even galaxies sometimes requires keeping track of more than a million individual masses, the search for an exact analytical solution is unfeasible, to say the least. That’s why the calculations involve approximations.

While there is a way to come up with a single equation that describes the collective motion of all the stars within a cluster, most good approximations cannot be worked out with only pen and paper. High-performance computing is required, but even the most powerful computers we have today would not be of any use without good models. This is where Dr Varri’s everyday work comes in. She tries to come up with such models and then tests them against real-world data.

This means that she is very reliant on the most up-to-date datasets. Unfortunately, it is impossible to make any impactful observations anywhere in Scotland. In fact, there are few locations on the surface of the Earth that have the right conditions to allow for measurements with sufficient precision.

Most of the data is collected by satellites like Gaia. Due to being unaffected by the atmospheric limitations, it is able to conduct much more accurate measurements. However, before any of the resulting values can be used by the scientific community, a lot of pre-processing is required to ensure the expected quality standards are met. This very important work is done by groups of dedicated researchers around the world, some of whom are based in Edinburgh. So even though we are not able to record any data, a lot of data-related work is still being done at the University.

Globular clusters

Dr Varri is particularly interested in globular clusters, i.e. clusters of stars that are very dense and almost spherical in shape. There are a multitude of good reasons for their relevance to scientists around the world. For one, globular clusters are amongst the oldest structures in the entire universe. This makes them similar to fossils, in the sense that understanding them may yield insights into the origins of our galaxy and, by extension, the Solar System and Earth itself.

Another reason has to do with one of the questions Dr Varri wants to help answer in the future. At the moment, we know about two distinct groups of black holes: solar mass black holes which are small and can be found at the centre of globular clusters, and supermassive black holes, typically found at the centre of galaxies like our own Milky Way. This begs the question of why we have only been able to locate representatives of these two extreme classes. Some researchers theorise that intermediate-mass, i.e. medium-sized, black holes may too be found within globular clusters. Coming up with constraints on the presence of intermediate-mass black holes would be a significant step towards understanding our own galaxy.

Dark matter and energy

Another big issue is our lack of understanding of dark matter and dark energy. While our assessment of the energy balance in the universe tells us about their theoretical existence, we have very little understanding of either of them. While Dr Varri’s research is not directly related to this, she would be delighted if she could make a small contribution to accelerate the vast amounts of research that are going into it.

Advice to future students

If you yourself are interested in starting a career in mathematics, physics or a related field, perhaps to tackle some of the big outstanding questions we have covered, Dr Varri has some important advice for you. If you feel like you don’t have the right background because you have not learned enough about the subjects in school, you should not let that stop you.