Solving complex physics problems at lightning speed

A calculation that is so complicated that it takes 20 years to complete on a powerful desktop computer can now be done within one hour on a regular laptop. Physicist Andreas Ekström from Chalmers University of Technology, together with international research colleagues, has designed a new method for calculating the properties of atomic nuclei incredibly fast.

The new approach is based on a concept called emulation, where an approximate calculation replaces a complete and more complex calculation. Although the researchers take a shortcut, the solution ends up almost exactly the same. It is reminiscent of machine learning algorithms, but eventually the researchers devised a completely new method. It offers even more possibilities in fundamental research in areas such as nuclear physics.

“Now that we can use this method to mimic atomic nuclei, we have a completely new tool to construct and analyze theoretical descriptions of the forces between protons and neutrons in the atomic nucleus,” says research leader Andreas Ekström, associate professor at the Department of Physics. by Chalmers.

Fundamental to understanding our existence

The subject may sound niche, but it is fundamental to understand our existence and the stability and origin of visible matter. Most of the atomic mass is located in the center of the atom, in a dense area called the atomic nucleus. The constituent particles of the nucleus, the protons and neutrons, are held together by something called the strong force. Although this power is so central to our existence, no one knows exactly how it works. To increase our knowledge and unravel the fundamental properties of visible matter, researchers must be able to model the properties of atomic nuclei with great accuracy.

The basic research that Andreas Ekström and his colleagues are working on sheds new light on topics ranging from neutron stars and their properties, to the inner structure and decay of nuclei. Basic research in nuclear physics also provides essential inputs to astrophysics, atomic physics and particle physics.

Open doors for completely new possibilities

“I am incredibly excited to be able to make calculations with so much accuracy and efficiency. Compared to our previous methods, it feels like we are now calculating at lightning speed. In our ongoing work here at Chalmers, we hope to further improve the emulation method., And perform “advanced statistical analyzes of our quantum mechanical models. With this emulation method, it seems that we can achieve results that were previously considered impossible. It certainly opens doors for completely new possibilities,” says Andreas Ekström.

More about the mathematical shortcut

The new emulation method is based on something called eigenvector continuation (EVC). It allows for the emulation of many quantum mechanical properties of atomic nuclei with incredible speed and accuracy. Instead of directly solving the time-consuming and complex problem of many body parts, researchers have created a mathematical shortcut by making a transformation into a special subspace. This makes it possible to use some precise solutions to then get much faster approximate solutions.

If the emulator works well, it generates solutions that are almost exactly – about 99 percent – similar to the solutions to the original problem. These are in many respects the same principles used in machine learning, but they are not a neural network or a Gaussian process – a completely new method supports them. The EVC method of emulation is not limited to atomic nuclei, and researchers are currently investigating different types of applications.