Research

Atomic nuclei are among nature’s most fascinating objects. They exhibit a variety of quantum phenomena, especially if the number of protons and neutrons they consist of are unbalanced. Through numerical simulations of nuclei and their confrontation with the wealth of new experimental data that FRIB and other facilities like it will produce, my group seeks to deepen our understanding of nuclear interactions and the quantum mechanics of strongly correlated many-body systems. This will help nuclear scientists answer important scientific questions that range from understanding the symmetries of nature at the smallest scales to the life and death of stars and the origin of elements in the cosmos. By pursuing a systematic, first-principles approach, we can assess uncertainties in our theoretical models and numerical simulations, maximizing our predictive power. In this way, our simulations provide important guidance for designing experiments, including efforts at the interface of nuclear, atomic and particle physics that test the fundamental symmetries of nature.

On a practical level, our simulations heavily rely on high-performance computing, as well as applied mathematical techniques for data reduction and uncertainty quantification that are also highly relevant to modern data science and machine learning. Our applications to the physics of nuclei are a challenging testing ground for these methods and prompt the development of new extensions and improvements that can be useful more broadly for applications that involve large amounts of complex data.

A new generation of calculations of the nuclear matrix element of 76Ge, a key nuclear structure input for understanding its (so far unobserved) neutrinoless double decay. The systematic understanding of uncertainties in our results (central and right panels) significantly narrows the previously determined range of values (green box). For details, see A. Belley et al., PRL 132, 182502 (2024).

Biography

I grew up on a farm in a small town in the German state of Hesse, but my interest in science led me to pursue a career in research. In 2008, I received my doctoral degree from the Technical University in Darmstadt, Germany, specializing in nuclear many-body theory. After postdoctoral stays at MSU’s National Superconducting Cyclotron Laboratory (the predecessor of FRIB) and The Ohio State University, I returned to Lansing as an FRIB Theory Fellow in 2014 and joined the faculty in the following year. In addition to computational nuclear physics, I also have research interests and collaborations in general topics of applied mathematics and scientific computing, like model reduction, machine learning or quantum computing.

How students can contribute as part of my research team

My group’s work focuses on the development of new methods for simulating nuclei (or general strongly correlated quantum systems), as well as simulation software for computers ranging from small workstations to massively parallel supercomputers. Students will receive training in state-of-the-art methods of quantum many-body theory, high-performance computing, and applied mathematics, in particular model reduction and uncertainty quantification. Our projects typically focus on the development of new extensions to our methods and their application, often in close collaboration with experimental researchers at FRIB and other facilities. This offers prospective students a broad perspective of nuclear science and adjacent fields, and a chance to be immersed in community efforts like the FRIB Theory Alliance, the NUCLEI SciDAC project, the DOE Topical Collaboration “Nuclear Theory for New Physics”, or the new NSF Focused Research Hub on Neutrinoless Double Beta Decay. 

Scientific publications

• Ab initio uncertainty quantification of neutrinoless double-beta decay in 76Ge, A. Belley, J. M. Yao, B. Bally, J. Pitcher, J. Engel, H. Hergert, J. D. Holt, T. Miyagi, T. R. Rodriguez, A. M. Romero, S. R. Stroberg, X. Zhang, Phys. Rev. Lett. 132, 182502 (2024)
• A Guided Tour of Ab Initio Nuclear Many-Body Theory, H. Hergert, Front. Phys. 8, 379 (2020)
• Non-Empirical Interactions for the Nuclear Shell Model: An Update, S. R. Stroberg, H. Hergert, S. K. Bogner, and J.D. Holt, Ann. Rev. Nucl. Part. Sci. 69, 307 (2019)
• In-Medium Similarity Renormalization Group Approach to the Nuclear Many-Body Problem, in “An Advanced Course in Computational Nuclear Physics’’ (eds.~M. Hjorth-Jensen, M. P. Lombardo, U. van Kolck), Springer Lecture Notes in Physics 936 (2017)