Microscopic Theory of Quantum Fluids and Nuclear Systems

Washington University, Saint Louis MO

Investigators

Abstract

PHY-0140316 Clark This award supports research on a broad spectrum of quantum many-body problems. The primary objective is prediction, from first principles,of the properties of strongly correlated systems of fundamental and technological importance, assuming realistic interactions and dealingwith realistic conditions of density and temperature. The main focus is on outstanding questions in the theory of nuclei and nuclear matter. However, the research also crosses disciplinary boundaries into many-body problems in neutron-star matter, helium and other quantum liquids, strongly correlated electron systems, spin-lattice models, and lattice-gauge systems. Much of the work involves application of two highly developed semi-analytic methods, namely the self-consistent Green's function approach and correlated-basis theory. In addition to their quantitative accuracy and ab initio character, these methods are capable of providing information on important system properties associated with quantum coherence that are not yet accessible to brute-force computer simulation. Two themes of current and enduring interest will be emphasized during the period of the grant, namely the contrasting roles of short- and long-range correlations in nuclear systems and the occurrence of quantum phase transitions in a rich variety of physical settings. Within the latter theme, pairing phenomena are being studied with new techniques that promise unique insights into superfluidity in neutron stars, exotic nuclei, and liquid Helium-3 as well as high-temperature superconductivity. The selection of problems and goals is motivated by the potential for impact facilities and observations of compact astrophysical objects from orbiting observatories. Specific highlights of the project include (i) a comparison of pionic long-range excitations in nuclear matter and in finite nuclei to determine whether such correlations should be excluded in the calculation of nuclear saturation properties, (ii) an improved description of collective features of Oxygen-16 that will permit quantitative evaluation of spectroscopic factors for single-nucleon knockout and cross sections for two-nucleon removal, (iii) analysis ofexperimental data to deduce the properties of the highest-momentum protons in the nucleus (the "last missing protons"), (iv) application of incisive new methods of analysis and computation in pairing theoryto elucidate the superfluid phase diagrams of neutron matter, symmetrical nuclear matter, liquid Helium-3, and quantum chromodynamics, (v)exploration of the breakdown of Fermi-liquid theory, as manifested in fermion condensation and other rearrangements of single-particle degrees of freedom in strongly correlated systems, and (vi) investigation of mathematical and many-body aspects of quantum control relevant to laser control of chemical reactions and to quantum computation. Continuing a long tradition, the preparation of graduate students for productive careers in teaching and research plays a central role in the program, essential to its success.