Theoretical Nuclear Physics

The nuclear theory group carries out research into the structure and behavior of strongly interacting matter in terms of its basic constituents -- quarks and gluons -- over a wide range of conditions: from nucleons and nuclear matter to the cores of stars, and from the Big Bang that was the birth of the universe to the heavy-ion collisions in present-day experiments. We use our expertise to explore new paths to achieve civilian use of nuclear fusion and to understand the evolution of particles and plasmas in primordial Universe.

Our main strength is the creation of novel ideas and tools for unraveling the non-perturbative properties of strongly interacting particles, and we apply them to interdisciplinary problems at the interface with particle, atomic, laser, condensed-matter, and astrophysics and employ artificial intelligence in exploration of frontier challenges in the field. Examples of our interdisciplinary interests include the production of top quarks at LHC, nuclear fusion and fission, strong fields, trapped atoms near Feschbach resonances, and supernovae neutrinos.

Areas studied by the Theoretical Nuclear Physics Group

Our group is internationally recognized for leading the study of nuclear physics from the perspective of quantum chromodynamics (QCD). We have invented Soft Collinear Effective Theory to describe high-energy quarks and gluons, and Nuclear Effective Field Theories to deduce the force among nucleons. We have formulated the innovative No-Core Shell Model to predict the properties of nuclei from fundamental nucleon interactions, and have investigated equilibrium and non-equilibrium properties of nuclear matter. We have also done pioneering work on applications of perturbative QCD to nuclear collisions at the highest attainable energies, and discovered that heavy quarks provide a revolutionary tool for the investigation of a new state of matter recreated in these collisions: the quark-gluon plasma that existed 20 microseconds after the Big-Bang.

The group publishes extensively in professional journals -- three of our papers have been chosen as "50th Anniversary Milestones" by Physical Review C & D because they "announce major discoveries or open up new avenues of research" -- and members of our group have received numerous awards, including two Sloan Fellowships, two DOE Outstanding Junior Investigator Awards, a Humboldt Senior Scientist Award and a DFG-Excellence Professorship, the UA Koffler Prize, the APS Feshbach Prize, APS Fellowships, and membership in the Academia Europaea.

Theoretical Nuclear Physics Faculty

The Fleming group conducts theoretical research in nuclear and particle physics, with a primary focus on effective field theory methods. Fleming was one of the inventors of soft collinear effective theory (SCET), which has become a central framework with broad applications across nuclear and particle physics. Current research applies SCET to a range of problems, with particular emphasis on physics relevant to the future Electron-Ion Collider as well as collaborations with van Kolck on related effective theories such as X-EFT, for molecular bound states of mesons. Fleming also integrates undergraduate researchers into his research program through projects at the interface of nuclear physics and quantum computing. His contributions have had lasting impact on the field, as reflected in the wide adoption and citation of SCET.

The Siwach group studies the nuclear many-body problem using concepts and tools from quantum information science. The group develops quantum algorithms for simulating nuclear systems and investigates computational complexity through measures such as entanglement and quantum magic in nuclear and neutrino physics. This work bridges traditional nuclear structure theory with emerging quantum computing platforms and strengthens the department’s profile in quantum science. Notable contributions include efficient encoding schemes for mapping nuclear systems onto quantum hardware and entanglement-based diagnostics for collective neutrino dynamics in supernova environments, positioning the group at the forefront of an area of growing strategic national interest.

Van Kolck has pioneered the development and application of nuclear effective field theories, which underpin modern research on nuclear structure and reactions. Van Kolck and collaborators have derived nuclear forces and currents that incorporate the symmetries of the Standard Model of particle physics and explain a plethora of observed nuclear properties. They have uncovered the unifying role of discrete scale invariance in systems near two-body unitarity, demonstrating that diverse systems such as atomic helium clusters and light nuclei are governed by a single three-body parameter, with details amenable to perturbation theory. Van Kolck also uses effective field theory methods to explore nuclear signals of physics beyond the Standard Model, such as violations of time-reversal, baryon number, and lepton number --- highlighted, for example, by the discovery of a new leading mechanism for neutrinoless double-beta decay. Van Kolck's research has received numerous international honors, including the Prix Paul Langevin of the Societe Francaise de Physique, University of Arizona’s Koffler Award in Research, Scholarship and Creativity, the APS Herman Feshbach Prize in Theoretical Nuclear Physics, and election to the Academia Europaea. Van Kolck has a long record of service to the nuclear physics community, for example serving as the director of the European Center for Theoretical Studies in Nuclear Physics and Related Areas (ECT*).