PhD defence

Solving the Gravitational N-body Problem with Machine Learning

• V. Saz Ulibarrena

Date

Tuesday 7 October 2025

Time

11:30 - 12:30 hour

Address

Lokhorstkerk
Pieterskerkstraat 1
2311 SV Leiden

Supervisor(s)

• Prof.dr. S.F. Portegies Zwart
• Prof.dr. B. Koren (TU Eindhoven)
• dr. E. Sellentin

Summary

In my research I explore the creation of new methods that optimize simulations of the gravitational N-body problem. Specifically, I take advantage of the recent popularity of Machine Learning methods to find tools that can suit this problem.

First of all, running simulations with large numbers of bodies can become extremely computationally expensive. By replacing these expensive parts with neural networks, the total time it takes to run a simulation can be reduced by orders of magnitude. We take advantage of a specific type of neural networks that include physical knowledge into their structure: physics-aware neural networks.  

Secondly, setting up a simulation requires the selection of multiple simulation parameters. In most cases, expert knowledge is required to make the right choice for each specific system. A wrong choice can lead to the simulation being incorrect, and therefore unusable for scientific discovery. I create a reinforcement learning method that automatically chooses one of the most important parameters: the time-step size. With my method, this value is chosen to balance accuracy and speed in the simulation, leading to optimum results without the need of expert knowledge.

My work presents an initial exploration of the capabilities of Machine Learning techniques for a complex problem: the simulation of multiple bodies moving under their mutual gravity. I identify the challenges of this problem and present innovative solutions.

PhD dissertations

Approximately one week after the defence, PhD dissertations by Leiden PhD students are available digitally through the Leiden Repository, that offers free access to these PhD dissertations. Please note that in some cases a dissertation may be under embargo temporarily and access to its full-text version will only be granted later.

Press enquiries (journalists only)

[phone]
[e-mail]

General information

Beadle's Office
[e-mail]
[phone]