The Theoretical Physics Group performs world-leading research in nuclear physics and astrophysics that is of critical importance to the mission of the DOE Office of Nuclear Physics and is fully aligned with the latest Nuclear Science Long Range Plan. Their state-of-the-art 3D simulations of supernovae are redefining our understanding of the catastrophic stellar events that create and disperse the elements of life; their supercomputer simulations of subatomic nuclei have mapped out the limits of nuclear existence and probed properties of nuclei that cannot yet be made in the laboratory; and their software techniques have applications ranging from quantum computing to hydrodynamic flows.
One major research focus is to understand the mechanism of, and element synthesis in, Core Collapse (Type II) and Thermonuclear (Type Ia) Supernovae. Our approach is to develop state-of-the-art Exaflop Supercomputer applications containing the latest advances in the physics of nuclei, neutrinos, and astrophysics. Some of these codes take months to run on the worlds fastest supercomputers. A recent success story is the largest ever collection (160) of three-dimensional core collapse supernova simulations that undermine the paradigm that there is a “critical luminosity” that sharply separates systems that explode from those that do not explode. Another focus for the Group is to understand the structure of exotic nuclei via coupled cluster theory and energy density functional approaches. These calculations of the nuclear many-body problem also require extreme computational power. A recent notable accomplishment is the first realistic calculation of the structure of nickel-78 and its isotopic neighbors from first principles, which confirmed that Nickel-78 is a doubly magic nucleus. Their approach included three-nucleon forces, coupling to the continuum, and correlations that all impact our understanding of how neutron-rich matter is bound together.