Physicists have developed a new method with which complex calculations can be emulated at lightning speed. This could provide new insights into the quantum properties of highly interacting matter, such as atomic nuclei and neutron stars. Illustration: Andreas Ekström and Yen Strandqvist / Chalmers University of Technology. Credit: Andreas Ekström and Yen Strandqvist / Chalmers University of Technology
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 with research intensive university in Gothenburg, Sweden, founded in 1829 after a donation from William Chalmers, a director of the Swedish East India Company. It focuses on technology, science, architecture and shipping. “Class =” glossaryLink “> Chalmers University of Technologyhas worked with international research colleagues to develop 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 it is in fact 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. In order to increase our knowledge and unravel the fundamental properties of visible matter, researchers must investigate the properties of atomic nuclei with large accuracy.
Andreas Ekström, Associate Professor, Department of Physics, Chalmers University of Technology Photo: Anna-Lena Lundqvist / Chalmers University of Technology. Credit: Anna-Lena Lundqvist / Chalmers University of Technology
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 so accurately and efficiently. 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 analysis of our quantum mechanical models. With this emulation method, it turns out 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.
Plot of the energy and radius of the oxygen isotope 16-O for 100,000 different parametrisations of the strong nuclear interaction. Using the new method, the results were generated on a standard laptop within minutes. The dashed lines indicate the values of experimental data. Illustration: Andreas Ekström and Yen Strandqvist / Chalmers University of Technology. Credit: Andreas Ekström and Yen Strandqvist / Chalmers University of Technology
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’s not a neural network or a Gaussian process – a completely new method supports it. The EVC method of emulation is not limited to nuclear nuclei, and the researchers are currently investigating different types of applications.
References:
“Eigenvector continuation as an efficient and accurate emulator for uncertainty quantification” by S. König, A. Ekström, K. Hebeler, D. Lee and A. Schwenk, September 30, 2020, Physics Letters B.
DOI: 10.1016 / j.physletb.2020.135814
“Global Sensitivity Analysis of Bulk Properties of an Atomic Nucleus” by Andreas Ekström and Gaute Hagen, December 20, 2019, Physical Review Letters.
DOI: 10.1103 / PhysRevLett.123.252501