We study the structure of generalized parton distributions (GPDs) in spin 0 nuclei within a microscopic approach for nuclear dynamics. GPDs can be used on one side as tools to unravel the deep inelastic transverse structure of nuclei in terms of both transverse spatial and transverse momentum degrees of freedom. On the other, one can obtain information on GPDs themselves by observing how they become modified in the nuclear environment. We derive the structure of the nuclear deeply virtual Compton scattering tensor and generalized parton distributions at leading order in Q in a field-theoretical framework. The nuclear generalized parton distributions are calculated using a two-step process—the convolution approach—where the scattering process happens from a quark inside a nucleon, itself inside a nucleus, disregarding final state interactions with both the nuclear and nucleon debris. We point out that details of the nuclear long-range interactions, such as two-body currents, can be disregarded compared to the deep inelastic induced modifications of the bound GPDs. We show how the pattern of nuclear modifications predicted, and in particular the deviations of off-shell effects from the longitudinal convolution provide clear signals to be sought in experimental measurements. Finally, we find interesting relationships by studying Mellin moments in nuclei: in particular we predict the A dependence for the D term of GPDs within a microscopic approach and the behavior with t of the total momentum carried by quarks in a nucleus. The latter provides an important element for the evaluation of nuclear hadronization phenomena that are vital for interpreting current and future data at RHIC, HERMES, and Jefferson Lab.

The pion-nucleon-scattering amplitudes are calculated in tree approximation with the use of the extended linear sigma model (ELSM) as well as heavy-baryon chiral perturbation theory (HBχPT), and the nonrelativistic forms of the ELSM results are compared with those of HBχPT. We find that the amplitudes obtained in ELSM do not agree with those derived from the more fundamental effective approach, HBχPT.

We employ the unitary correlation operator method (UCOM) to construct correlated, low-momentum matrix elements of realistic nucleon-nucleon interactions. The dominant short-range central and tensor correlations induced by the interaction are included explicitly by an unitary transformation. Using correlated momentum-space matrix elements of the Argonne V18 potential, we show that the unitary transformation eliminates the strong off-diagonal contributions caused by the short-range repulsion and the tensor interaction and leaves a correlated interaction dominated by low-momentum contributions. We use correlated harmonic oscillator matrix elements as input for no-core shell model calculations for few-nucleon systems. Compared to the bare interaction, the convergence properties are dramatically improved. The bulk of the binding energy can already be obtained in very small model spaces or even with a single Slater determinant. Residual long-range correlations, not treated explicitly by the unitary transformation, can easily be described in model spaces of moderate size allowing for fast convergence. By varying the range of the tensor correlator we are able to map out the Tjon line and can in turn constrain the optimal correlator ranges.

We develop a Lorentz- and gauge-invariant dynamical model for pion electroproduction in the resonance region. The model is based on solving the Salpeter (instantaneous) equation for the pion-nucleon interaction with a hadron-exchange potential. We find that the one-particle-exchange kernel of the Salpeter equation for pion electroproduction develops an unphysical singularity for a finite value of $Q^2$. We analyze two methods of dealing with this problem. Results of our model are compared with recent single-polarization data for pion electroproduction.

The induced polarization, $P_y^{\text{'}}$, of the neutron in the deuteron photodisintegration from threshold up to 30 MeV is calculated using a variety of different, latest generation potentials—Argonne $v_{18}$, Bonn 2000, and Nijmegen I—and a realistic model for the nuclear electromagnetic current operator, including one- and two-body terms. The model dependence of the theoretical predictions is found to be very small. These predictions are systematically larger in magnitude than the measured $P_y^{\text{'}}$ values and corroborate the conclusions of an earlier, and much older, study. There is considerable scatter in the available experimental data. New and more accurate measurements of the induced polarization in the ${}^2\mathrm{H}$($\gamma ,\overrightarrow{n}$)${}^1\mathrm{H}$ reaction are needed to establish unequivocally whether there is a discrepancy between theory and experiment.

By differentiating the dressed quark propagator with respect to a constant external field, the linear response of the nonperturbative dressed quark propagator in the presence of the constant external field can be obtained. From this general method, taking the vector vacuum susceptibility as an illustration, we one extract a model-independent expression for the vacuum susceptibility in the quantum chromodynamical (QCD) sum rule two-point external field formula. This expression for the vacuum susceptibility is quite different from that given in the previous literature. The numerical values of the vector vacuum susceptibility are calculated within the framework of the rainbow-ladder approximation of the Dyson-Schwinger approach. A comparison with the results of the previous approaches is given.

A recursion formula for the number of states with a given value of total spin J of n identical fermions in a j orbit, $N(J,j,n)$, is derived. That number is expressed in terms of the number of states with some values of J, of $n,n-1$, and $n-2$ fermions in a ($j-1$) orbit. This formula may be used in calculating $N(J,j,n)$. In this paper the formula is used to prove some interesting results that were found empirically by Zhao and Arima [1].

We have searched for particle-bound ${}^{26}\mathrm{O}$ and ${}^{28}\mathrm{F}$ isotopes in the reaction products of secondary ${}^{27}\mathrm{F}$ and ${}^{29}\mathrm{Ne}$ beams, respectively. No events have been observed. Upper limits of 3.3 mb and 1.2 mb for the respective production cross sections of ${}^{26}\mathrm{O}$ and ${}^{28}\mathrm{F}$ by one p-stripping reactions are established. Since in the case of ${}^{28}\mathrm{F}$, this upper limit is sufficiently small compared to common estimates, we conclude that ${}^{28}\mathrm{F}$ is most likely unbound. For the case of ${}^{26}\mathrm{O}$, our result is not statistically significant, thus, the question cannot be answered whether ${}^{26}\mathrm{O}$ is a particle-unbound nucleus or not.

The reaction $\gamma$${}^3\mathrm{He}$$\to K^{+}\Lambda d$ has been investigated over the energy range from $E_{\gamma }=1.0$ to $1.8$ GeV in a tree-level effective Lagrangian model that incorporates most of the well-established resonances of spins $\frac{1}{2}$ and $\frac{3}{2}$ below 1.9 GeV. Results for the cross-section and two single polarization observables have been obtained within the impulse approximation using four different sets of resonance coupling products, each of which has been fitted to cross-section data for the photoproduction of kaons from the proton. Final-state interactions are incorporated by means of a nonrelativistic overlap integral in momentum space. The required final-state wave function is obtained by solving the momentum space Schrodinger equation using a nonlocal $\Lambda d$ potential that has been fitted to a sum of separable terms. We find that the cross-section normalization and both the sizes and angle dependences of the polarization parameters are sensitive to the inclusion of the final-state interaction. Conversely, only the polarization magnitudes depend much on the particular resonance coupling fit employed and only at the lowest photon energy considered. Neither the cross section normalizations nor the polarization angle dependences are sensitive to the resonance coupling fit.

The semileptonic decays of ${\Lambda }_c$ and ${\Lambda }_b$ are treated in the framework of a constituent quark model. Both nonrelativistic and semirelativistic Hamiltonians are used to obtain the baryon wave functions from a fit to the spectra, and the wave functions are expanded in both the harmonic-oscillator and the Sturmian bases. The latter basis leads to form factors in which the kinematic dependence on $q^2$ is in the form of multipoles, and the resulting form factors fall faster as a function of $q^2$ in the available kinematic ranges. As a result, decay rates obtained in the two models with the Sturmian basis are significantly smaller than those obtained with the harmonic-oscillator basis. In the case of the ${\Lambda }_c$, decay rates calculated with the Sturmian basis are closer to the experimentally reported rates. However, we find a semileptonic branching fraction for the ${\Lambda }_c$ to decay to excited ${\Lambda }^{*}$ states of 11 to 19%, in contradiction to what is assumed in available experimental analyses. Our prediction for the ${\Lambda }_b$ semileptonic decays is that decays to the ground state ${\Lambda }_c$ provide a little less than 70% of the total semileptonic decay rate. For the decays ${\Lambda }_b\to {\Lambda }_c$, the analytic form factors we obtain satisfy the relations expected from heavy-quark effective theory at the nonrecoil point, at leading and next-to-leading orders in the heavy-quark expansion. In addition, some features of the heavy-quark limit are shown to naturally persist as the mass of the heavy quark in the daughter baryon is decreased.

Exact numerical results of the interacting boson model Hamiltonian along the integrable line from U(5) to O(6) are obtained by diagonalization within boson seniority subspaces. The matrix Hamiltonian reduces to a block tridiagonal form that can be diagonalized for large number of bosons. We present results for the low-energy spectrum and the transition probabilities for systems up to 10,000 bosons, which confirm that at the critical point the system is equally well described by the Bohr Hamiltonian with a ${\beta }^4$ potential.

We present a theoretical formulation for the description of nuclear excitations within the framework of a relativistic random-phase approximation whereby the vacuum polarization arising from nucleon-antinucleon fields is duly accounted for. The vacuum contribution to the Lagrangian is explicitly described as extra new terms of interacting mesons by means of the derivative expansion of the effective action. It is shown that the self-consistent calculation yields zero eigenvalue for the spurious isoscalar-dipole state and also conserves the vector-current density.

Based on the rainbow approximation of Dyson-Schwinger equation and the assumption that the inverse dressed quark propagator at finite chemical potential is analytic in the neighborhood of $\mu =0$, a new method for obtaining the dressed quark propagator at finite chemical potential μ from the one at zero chemical potential is developed. Using this method the dressed quark propagator at finite chemical potential can be obtained directly from the one at zero chemical potential without the necessity of numerically solving the corresponding coupled integral equations by iteration methods. A comparison with previous results is given.

The nuclear pasta—a novel state of matter having nucleons arranged in a variety of complex shapes—is expected to be found in the crust of neutron stars and in core-collapse supernovae at subnuclear densities of about ${10}^{14}$ g/cm${}^3$. Owing to frustration, a phenomenon that emerges from the competition between short-range nuclear attraction and long-range Coulomb repulsion, the nuclear pasta displays a preponderance of unique low-energy excitations. These excitations could have a strong impact on many transport properties, such as neutrino propagation through stellar environments. The excitation spectrum of the nuclear pasta is computed via a molecular-dynamics simulation involving up to 100,000 nucleons. The dynamic response of the pasta displays a classical plasma oscillation in the 1- to 2-MeV region. In addition, substantial strength is found at low energies. Yet this low-energy strength is missing from a simple ion model containing a single-representative heavy nucleus. The low-energy strength observed in the dynamic response of the pasta is likely to be a density wave involving the internal degrees of freedom of the clusters.

The properties of neutron stars, consisting of a crust of hadrons and an internal part of hadrons and kaon condensate, are calculated within the quark-meson-coupling model. We considered stars with nucleons only in the hadron phase and also stars with hyperons as well. The results are compared with the ones obtained from the nonlinear Walecka model for the hadronic phase.

We compute the polarized quark distribution function of a bound nucleon. The chiral quark-soliton model provides the quark and antiquark substructure of the nucleon embedded in nuclear matter. Nuclear effects cause significant modifications to the polarized distributions, including an enhancement of the axial coupling constant.

We present a partial-wave analysis of the polarization data for the reaction $\overrightarrow{p}\overrightarrow{p}\to \mathit{pp}{\pi }^0$, based solely on the recent measurements at the Indiana University Cyclotron Facility for this channel. Methods for an improved analysis are discussed. We compare the extracted values to those from a meson exchange model. The fit leads to a ${\chi }^2$ per degree of freedom of 1.7.

Proton-proton bremsstrahlung cross sections and analyzing powers have been calculated at 190 MeV by using a one-boson-exchange model. The results are compared with the recently published high-precision Kernfysisch-Versneller-Instituut (KVI) data. Satisfactory agreement between theory and experiment has been found.

We study neutron matter by combining pionless effective field theory with nonperturbative lattice methods. The neutron contact interaction is determined by zero-temperature scattering data. We simulate neutron matter on the lattice at temperatures of 4 and 8 MeV and densities below one-fifth normal nuclear matter density. Our results at different lattice spacings agree with one another and match bubble-chain calculations at low densities. The equation of state of pure neutron matter obtained from our simulations agrees quantitatively with variational calculations based on realistic potentials.