Solve complex physical problems with lightning speed

A calculation so complicated that it takes 20 years to complete on a powerful desktop computer can now be done in an hour on a regular laptop. Physicist Andreas Ekström of Chalmers University of Technology, together with international research colleagues, has developed a new method to calculate the properties of atomic nuclei incredibly quickly.

The new approach is based on a concept called emulation, where an estimated calculation replaces a full and more complex calculation. Although the researchers take a shortcut, the solution turns out almost exactly the same. It is reminiscent of machine learning algorithms, but in the end the researchers developed an entirely new method. It opens even more possibilities in basic research in areas such as nuclear physics.

“Now that we can simulate atomic nuclei with this method, we have a completely new tool to construct and analyze theoretical descriptions of the forces between protons and neutrons in the atomic nucleus,” said study leader Andreas Ekström, associate professor in the physics department. at Chalmers.

Fundamental to understand our existence

The topic may sound niche, but in fact it is fundamental to understanding our existence and the stability and origin of visible matter. Most of the atomic mass is 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 force 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 fundamental research 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. Fundamental research in nuclear physics also provides essential input for astrophysics, atomic physics and particle physics.

Opening doors to completely new possibilities

“I am incredibly excited to be able to make calculations with such 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 advanced statistical perform analyzes of our quantum mechanical models. This emulation method shows that we can achieve results that were previously considered impossible. This certainly opens doors to completely new possibilities, “says Andreas Ekström.

More about the math shortcut

The new emulation method is based on something called eigenvector continuation (EVC). It enables emulation of many quantum mechanical properties of atomic nuclei with incredible speed and accuracy. Rather than directly solving the time-consuming and complex many-body problem over and over again, researchers created a mathematical shortcut, using a transformation to a special subspace. This makes it possible to use some exact solutions and then obtain approximate solutions much faster.

If the emulator is working properly, it will generate solutions that are almost exactly – about 99 percent – comparable to the solutions to the original problem. In many ways, these are the same principles used in machine learning, but it is not a neural network or a Gaussian process – an entirely new method supports it. The EVC method for emulation is not limited to atomic nuclei and the researchers are currently looking further into different types of applications.