Projects include evolution of ultrarelativistic heavy-ion collisions, studies of dense matter applied to the problem of neutron star interiors, and other problems in astrophysics; correlations between nucleons in nuclei and of subnuclear degrees of freedom, as seen in high-energy lepton scattering; studies of nuclear vibrational modes applied to scattering experiments on nuclear bound states, giant resonances, the quasi-elastic region, and collective motion at finite temperature.

Quantum field theory is the union of quantum mechanics and relativity theory. It provides a framework suitable for the study of the fundamental interactions of nature the strong, the electromagnetic, and the weak interactions of the elementary particles. Research by the group includes (1) predictions of quantum chromodynamics, the natural generalization of electro magnetism for the structure of strongly interacting particles, (2) semiclassical approach, (3) physics at superhigh energies, and (4) other model field theories.

In the theory called quantum chromodynamics, observed particles such as the proton are composed of quarks, held together by forces transmitted by gluons, described by a nonabelian gauge field. To calculate one uses simulation techniques on a space-time lattice. New methods for dealing with fermions in lattice gauge theories have been developed by our group and are now being extensively exploited to study chiral symmetry restoration and quark deconfinement at finite temperatures and to study particle spectra. Quantum electrodynamics and fluctuating surfaces are also under investigation.

In investigations of the inner crust of neutron stars, near the density at which the matter becomes liquid, there may exist exotic solid phases having two- or one-dimensional translational symmetry. Using realistic nuclear Hamiltonians in the Thomas-Fermi approximation, the properties of and transitions among these phases are explored. Inclusion of pair correlations is considered in the related problem of the pinning of superfluid vortices on the exotic nuclei.

Evidence for chaotic motion in nuclear giant resonances is being investigated by considering the damping of these modes into two-particle two-hole excitations. The energy distribution of the latter as well as the statistical distribution of coupling matrix elements and transition strength is consistent with random-matrix theory. This is widely seen as a manifestation of chaotic motion at the quantum level.

The structure of mesons at finite baryon density and high temperature is of considerable interest in understand ing the quark-gluon phase boundary. Starting from a realistic meson-exchange model for hadronic interactions, we study density and the temperature-dependent modifications of resonances. Significant changes in the resonance shapes are observed. Relevance for the expansion of a hot hadronic gas formed in ultrarelativistic heavy-ion collisions is being investigated.

Starting from low-energy effective Lagrangians that incorporate the basic symmetries of QCD as well as its anomaly structure we study solitonic solutions of the classical field equations. Of particular interest is the soliton-soliton interaction and its semiclassical quantization to obtain the nucleon-nucleon potential. For applications in heavy-ion collisions restoration and of chiral symmetry and scale invariance are investigated by considering multisoliton configurations. In connection with the phenomenon of color transparency, the electromagnetic production of small-size ejectile-nucleus interaction are being investigated.

We are studying the mechanism that breaks the electroweak symmetry and generates the masses of the W and Z bosons, as well as the masses of the quarks and leptons. We are also studying the physics of the recently discovered top quark.