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Recently developed nuclear many-body techniques provide novel results when applied to constituent quark models and to light-front scalar field theory. We show how spontaneous symmetry breaking arises and is consistent with a coherent state ansatz in a variational treatment. The kink and the kink-antikink topological features are identified and the onset of symmetry restoration is demonstrated.

We solve the ab initio no-core shell model (NCSM) in the complete Nmax = 8 basis for A = 7 and A = 8 nuclei with two-nucleon and three-nucleon interactions derived within chiral effective field theory (EFT). We find that including the chiral EFT three-nucleon interaction in the Hamiltonian improves overall good agreement with experimental binding energies, excitation spectra, transitions and electromagnetic moments. We predict states that exhibit sensitivity to including the chiral EFT three-nucleon interaction but are not yet known experimentally., 10 pages, 6 figures, updated references and corrected a typo

We report the microscopic origins of the anomalously suppressed beta decay of ¹⁴C to ¹⁴N using the ab initio no-core shell model with the Hamiltonian from the chiral effective field theory including three-nucleon force terms. The three-nucleon force induces unexpectedly large cancellations within the p shell between contributions to beta decay, which reduce the traditionally large contributions from the nucleon-nucleon interactions by an order of magnitude, leading to the long lifetime of ¹⁴C.

Ab initio no‐core shell‐model solutions for the structure of light nuclei are shown to be dominated by low‐spin and high‐deformation configurations. This implies that only a small fraction of the full model space is important for a description of bound‐state properties of light nuclei. It further points to the fact that the coupling scheme of choice for carrying out calculations for light nuclear systems is an algebraic‐based, no‐core shell‐model scheme that builds upon an LS coupling [SO(3)⊗SU(2)] foundation with the spatial part of the model space further organized into its symplectic [SO(3)⊂SU(3)⊂Sp(3, R)] structure. Results for 12C and 16O are presented with the cluster nature of the excited 0+ states in 16O analyzed within this framework. The results of the analysis encourages the development of a no‐core shell model code that takes advantage of algebraic methods as well as modern computational techniques. Indeed, although it is often a very challenging task to cast complex algebraic constructs into ...

Understanding the origin, structure, and phases of hadronic matter is a forefront research area in physics. An integral part of this challenge is to achieve realistic modeling of the complex dynamics of atomic nuclei, which is key to comprehending the evolution of the universe from a fundamental quark/gluon level. We recently demonstrated the potential power of an innovative concept, the ab initio symplectic no‐core shell model (Sp‐NCSM), based on expanding the conventional harmonic oscillator basis in terms of the symmetry‐adapted and physically relevant symplectic basis, to reach new domains of nuclear structure. Using realistic interactions tied to Quantum Chromo‐dynamics (QCD), the Sp‐NCSM approach holds promise to build the bridge from QCD to measured properties of light nuclei, predict diverse features of unstable nuclei crucial for astrophysical processes, and provide nuclear structure information essential for cosmology and probing physics beyond the standard model.

Recent advances in ab initio quantum many-body methods and growth in computer power now enable highly precise calculations of nuclear structure. The precision has attained a level sufficient to make clear statements on the nature of 3-body forces in nuclear physics. Total binding energies, spin-dependent structure effects, and electroweak properties of light nuclei play major roles in pinpointing properties of the underlying strong interaction. Eventually, we anticipate a theory bridge with immense predictive power from QCD through nuclear forces to nuclear structure and nuclear reactions. Light front Hamiltonian quantum field theory offers an attractive pathway and we outline key elements.

We present a simple model for the heavy ion optical potential based on the convolution of target and projectile densities with a suitably chosen nucleon-nucleon effective interaction. This model is shown to be appropriate for a number of low energy peripheral processes, such as elastic scattering and one and two particle transfer reactions. Application of the method to cluster states in light nuclei and relativistic heavy ion interactions is also considered.

We construct the many-body effective Hamiltonian for pf-shell by carrying out 2h Omega NCSM calculations at the 2-body cluster level. We demonstrate how the effective Hamiltonian derived from realistic nucleon-nucleon (NN) potentials for the 2h Omega NCSM space should be modified to properly account for the many-body correlations produced by truncating to the major pf-shell. We obtain two-body effective interactions for the pf-shell by using direct projection and use them to reproduce the results of large scale NCSM for other light Ca isotopes.

We have searched for cold fusion produced in an electrolytic cell with Pd cathode and Pt anode. The electrolyte was 0.1 molar LiOD in 99.8% D2O. A 2-mm rod of polycrystalline Pd and a 4-mm rod of single crystal Pd were used. No radiation was detected above background by a BF3 neutron and Ge γ-X detector. The D2 loading of the Pd was 0.8 D per Pd atom reaching saturation after 4 hours. We also attempted to duplicate the work of Scaramuzzi and co-workers on the Ti-D2 system. Both powder and pieces of Ti were used. The material was cycled several times between 1100 K and 77 K. No neutron, γ- or x-ray emission above background was observed. The results of a barrier penetration calculation for H-like atoms are presented. The high fusion rates reported for PdDx. are much larger than those expected from theoretical calculations on these systems.

Properties of finite nuclei are evaluated with two-nucleon (NN) and three-nucleon (NNN) interactions derived within chiral effective field theory. The nuclear Hamiltonian is fixed by properties of the A=2 system, except for two low-energy constants (LECs) that parametrize the short range NNN interaction, which we constrain with the A=3 binding energies. We investigate the sensitivity of 4He, 6Li, 10,11B, and 12,13C properties to the variation of the constrained LECs. We identify observables that are sensitive to this variation and find preferred values that give the best overall description. We demonstrate that the NNN interaction terms significantly improve the binding energies and spectra of mid-p-shell nuclei not just with the preferred choice of the LECs but even within a wide range of the constrained LECs. We find that a very high quality description of these nuclei requires further improvements to the chiral Hamiltonian.

We reproduce Chang's duality condition in a regularized $\phi^4_{1+1}$ theory quantized on a light front. The regularization involves higher derivatives in the Lagrangian, renders the model finite in the ultraviolet, and does not require introduction of a finite size of the system. It is demonstrated that the light-front quantization is a natural way to treat systems with higher derivatives. The phase transition is related to the presence of tachyons in the regularized theory. Prospects for computing the critical coupling in this formulation are briefly discussed.

We investigate cross sections for neutrino-12C exclusive scattering and for muon capture on 12C using wave functions obtained in the ab initio no-core shell model. In our parameter-free calculations with basis spaces up to the 6 variant Planck's over 2pi Omega we show that realistic nucleon-nucleon interactions, like, e.g., the CD-Bonn, underpredict the experimental cross sections by more than a factor of 2. By including a realistic three-body interaction, Tucson-Melbourne TM'(99), the cross sections are enhanced significantly and a much better agreement with experiment is achieved. At the same time, the TM'(99) interaction improves the calculated level ordering in 12C. The comparison between the CD-Bonn and the three-body calculations provides strong confirmation for the need to include a realistic three-body interaction to account for the spin-orbit strength in p-shell nuclei.

We make predictions for the exclusive semileptonic and the non-leptonic decay widths of the B_c meson. We evaluate the B_c semileptonic form factors for different decay channels in a relativistic model, and use factorization to obtain the non-leptonic decay widths., Comment: 11 Pages, 1 Postscript figure

Starting from the QCD Lagrangian, we present the QCD Hamiltonian for near light cone coordinates. We study the dynamics of the gluonic zero modes of this Hamiltonian. The strong coupling solutions serve as a basis for the complete problem. We discuss the importance of zero modes for the confinement mechanism., 32 pages, ReVTeX, 2 Encapsulated PostScript figures

Singular integral equations for meson spectra are obtained by making a Fock space expansion of the quantum chromodynamics (QCD). The expansions are truncated and approximate equations for the mass eigenvalues and eigenvectors are derived variationally using an expansion in cubic B‐splines. In these initial variational calculations we restrict ourselves to configurations having a maximum of one qq pair and twenty gluons. However these variational results compare favorably with the results of the phenomenological two‐constituent quark model and with experiment.

Using primarily the tool of deep inelastic lepton scattering, I outline some of the major features of our understanding of the quark and gluon structure of nuclei. The natural progression is from nucleons to deuterium to heavier nuclei. Among other topics, I address the quark-parton model, x-scaling, y-scaling, quark cluster model, and the nuclear equation of state at high density and low temperature.

The photoionization cross sections for the hydrogen atom were measured in the wavelength range from 700−920 Angstroms. It was found that the experimental results agree with the theoretical predictions.(AIP)

We demonstrate that a coherent state may be a valid vacuum in light-front field theory. Then by minimizing the sum of the expectation values of the light-front Hamiltonian and the momentum operators in a variational trial state, we evaluate the ground state (vacuum) of two-dimensional ${\ensuremath{\varphi}}^{4}$ field theory. The resulting expectation value in the coherent state is identical with the result of the effective-potential method in the equal-time formulation. Thus we demonstrate how to solve for the ground state of the strong-coupling (${\ensuremath{\varphi}}^{4}$${)}_{2}$ problem on the light front. We also discuss the calculation of excited states.

Total binding energies for nuclei with 14< or =A< or =18 are obtained from a realistic effective no-core Hamiltonian, H/sub eff/, using moment methods. The lowest few moments of H/sub eff/ are evaluated in an oscillator model space of four major shells. These moments are then used to determine a number of continuous and discrete density of states functions, each of which yields an estimate for the H/sub eff/ ground state energy. The adjustable discrete density of states functions which we introduce are based upon realistic single-particle Hamiltonians. With a reasonable selection of moment method ingredients we obtain good agreement between theory and experiment for relative binding energies within each A chain. The most stable isobar is correctly predicted in all cases and Coulomb energy differences are in close agreement with experiment. Thus, the valley of ..beta.. stability is well reproduced in this approach with a simple overall shift in absolute binding energies for each A chain.

We evaluate the effective shell-model interaction v/sub eff/ for the sd shell, through second order as a function of an energy shift between the valence and unoccupied oscillator states. The Brueckner reaction matrix G for the Reid soft-core potential is obtained in a single-particle basis so the Pauli operator is treated exactly. In terms of second order in G, intermediate-state sums and the dependence of energy denominators on passive particles and holes are both treated with care. Significant dependence on the intermediate-state spectrum is found for v/sub eff/ in both the T = 0 and T = 1 components. An energy shift yielding a total gap of about 49 MeV is found to yield A = 18 two-particle spectra in reasonable agreement with experiment in view of the expected role of 4p-2h intruder states. On the other hand, a comparison of the matrix elements of v/sub eff/ with those determined by Chung and Wildenthal from spectra of A = 18 to 22 nuclei indicates a preference for a total gap between 35 and 40 MeV. These empirically determined gaps may be compared with a total gap of about 30 MeV, motivated by a study of the self-consistent particle spectrum bymore » Gambhir and McCarthy.« less

We have calculated nucleus-nucleus cross sections for a variety of projectile and target nuclei and a wide range of energy. Total, reaction and elastic cross sections, as well as the slopes of the elastic diffraction peak, exhibit an approximate factorization property when the nuclei differ by less than 50% in r.m.s. radii. A simple geometrical interpretation is provided for the failure of factorization which occurs when target and projectile differ greatly in size.

The recently proposed discretized light-front quantization (DLFQ) method is applied to ${\ensuremath{\varphi}}^{4}$ field theory in 1+1 dimensions. We start with the normal-ordered Hamiltonian and perform calculations with and without finite-mass renormalization in order to elucidate its role. We find that finite-mass renormalization prevents the phase transition by restricting the theory to the weak-coupling region. Comparison with results obtained without mass renormalization demonstrates that both treatments can yield the same estimate of the critical coupling for which the mass gap vanishes. This DLFQ estimate of the critical coupling may be compared with other estimates. The invariant mass of various states is calculated as a function of bare coupling. In the weak-coupling region where we can easily extrapolate to the continuum limit we find evidence for scattering but there is no two-particle bound state in agreement with the well-known result established for constructive quantum field theory. In addition, we find no multiparticle bound states.

A quantitative technique for studying the localization of heavy-ion reactions in both coordinate (r) and angular momentum (L) space has been developed. A comparison of the degree of localization in elastic, inelastic, and one-particle transfer reactions is presented. For elastic scattering, the localization is studied as a function of the angular range of the data. A fully quantum mechanical relationship between L and r is demonstrated. (AIP)

We present a simple model for three and four particle cluster states in light nuclei. These states are considered as bound states and single particle resonances of a cluster-core potential, which is obtained by folding the cluster and core mass densities. We calculate some properties of these states in $^{16}\mathrm{O}$ and $^{20}\mathrm{Ne}$, such as the rms radii, $B(E2)$ values, $\ensuremath{\alpha}$-decay widths, and energy spectra. Good agreement with available data is obtained and some predictions are made for $B(E2)$ values in the ${K}^{\ensuremath{\pi}}={0}^{\ensuremath{-}}$ bands in $^{16}\mathrm{O}$ and $^{20}\mathrm{Ne}$. This model is also used to interpret recent heavy ion three particle transfer data. Dynamical support is offered for high spin assignments in $^{15}\mathrm{N}$ and $^{15}\mathrm{O}$ previously based on kinematical considerations.NUCLEAR STRUCTURE $^{15}\mathrm{N}$, $^{16}\mathrm{O}$, $^{20}\mathrm{Ne}$; calculated energies, $J$, $\ensuremath{\pi}$, $B(E2)$ values, $\ensuremath{\alpha}$ widths, radii in cluster model with folded potential.

Fluctuations of selected observables and their dependence on the size of the system are studied within the framework of an exactly solvable model that mimics the interplay between pairing and long range forces. It is found that thermal mean-field results for fluctuations can yield an adequate estimate of the true fluctuations provided one evaluates those fluctuations in a particular manner.

The multipolarity (L) dependence of the inelastic form factor for heavy- ion-induced excitations predicted by the folding model is confirmed in the analysis of the scattering of $sup 14$N from $sup 12$C and $sup 16$O at 155 MeV. Agreement between the target deformation lengths ($beta$/subL/R/subt/) of these measurements and those from electromagnetic and proton experiments is found when the strongly L-dependent folding-model form factor is employed.

Heavy ion inelastic scattering cross sections to low-lying collective states have been calculated in the framework of a folding model for the optical potential. The inelastic transition form factor is generated by deforming the target density directly, rather than the potential. Good agreement with experimental data for 58Ni(16O,16O′)58Ni∗(2+) is obtained at 50, 60, and 70 MeV. A value of the deformation length β2RT is obtained which is consistent with that extracted from measured B(E2) values.

Finite Temperature Hartree Fock (FTHF) calculations have been performed in 4He in a quasiparticle basis which contains nucleons as well as Δ(1232) isobars. For temperatures less than 10 MeV, the isobar admixture probabilities are negligibly small.

Motivated by the need to test the adequacy of realistic nucleon-nucleon potentials for yielding the dynamics of many-nucleon systems we develop effective Iiamiltonians for large-space moment method studies. These Hamiltonians consist of the relative kinetic energy operator and an exact Brueckner G-matrix acting between all pairs of nucleons in the nucleus. That is, there is no core and the nuclear properties are obtained through moment methods as a function of the size of the model space. The primary initial emphasis is to obtain the binding energy and comparisons are made with results of the coupled-cluster or exp(s) calculations. We find a systematic but slow decrease in the importance of three and higher body effective forces as the model space is increased. The results with the Reid soft core interaction for the binding energy of 160 appear to be converging close to the exp(s) results. Further tests of the moment methods themselves are indicated as well as the desirability of increasing still further the model space for the no-core studies.

Recently, the shell model in the complex k-plane (the so-called Gamow shell model) has been formulated using a complex Berggren ensemble representing bound single-particle states, single-particle resonances and non-resonant continuum states. The single-particle basis used is that of the Hartree-Fock potential generated self-consistently by a finite-range residual interaction. In this framework, we shall discuss the numerical aspects of the Gamow shell model related to the optimization of the shell-model basis.