L. Wilets's research while affiliated with University of Washington Seattle and other places

Publications (182)

Conference Paper
In a departure from our previous work modeling antiproton capture on Helium, with it's relatively straightforward, fixed center target, extending the semiclassical approach to molecular hydrogen, i.e. a multi-center target with target masses identical to the projectile, requires that we revisit the fundamental nature of our model, including the mom...
Chapter
The soliton model allows for the dynamical degrees of freedom associated with the confinement mechanism. The soliton model has the flexibility, by choice of the parameters, to reproduce either the MIT or the SLAC bags. With appropriate choice of parameters and inclusion of one gluon exchange, the resulting hadronic spectra is similar to the MIT mod...
Article
In contrast to our previous work modeling antiproton capture on Helium, with its relatively straightforward, fixed center target, extending the semiclassical approach to molecular hydrogen, i.e. a multi‐center target with target masses identical to the projectile, requires that we revisit the fundamental nature of our model, including the momentum‐...
Article
Special bases of orthogonal polynomials are defined, that are suited to expansions of density and potential perturbations under strict particle number conservation. Particle–hole expansions of the density response to an arbitrary perturbation by an external field can be inverted to generate a mapping between density and potential. Information is ob...
Article
The reaction barpp arrowbarLambdaLambda provides a test for models of strangeness production and the barLambdaLambda interaction. Of primary interest is whether the strangeness production mechanism is better described in terms of meson-baryon or quark-gluon degrees of freedom. The reaction is sensitive to both initial and final state interactions a...
Article
Exact solutions to the Schrödinger equation for potentials containing Coulomb (∼1/r) plus harmonic oscillator (∼r2) terms are found, subject to constraints on the ratio of the strengths of the Coulomb and harmonic oscillator terms. The solutions have the simple form of a product of exponential and polynomial functions.
Article
Full-text available
This document is a summary of the physics research carried out by the Nuclear Theory Group at the University of Washington during the last twelve-month period, 1999-2000.
Article
Full-text available
The fusion enhancement factor due to screening in the solar plasma is calculated. We use the finite temperature Green's function method and a self consistent mean field approximation. We reduce this to one center problems, because in the collision of two fusing ions, the turning point where tunneling may occur lies far inside the screening radius....
Article
Extensions to the finite temperature Green’s-function method for the calculation of equilibrium densities within the Kohn-Sham formulation of density functional theory are presented. In particular, an expression for the density in terms of single-particle Green’s-function differences summed over all Matsubara poles is utilized. Numerical methods fo...
Article
The authors have studied the large-N limit of two-dimensional QCD using the axial gauge. First they solved numerically the Schwinger-Dyson equation for the quark propagator. Then the Bethe-Salpeter equation for the meson wavefunctions was solved in the zero-momentum frame of the quark-antiquark pair. The spectrum obtained agrees with that calculate...
Article
A variational method for calculating the correlation structure of atoms is proposed. The full wavefunction is written in the form Psi = Omega Phi where Phi is a sum of determinantal functions. Omega is expanded in terms of one-, two-, three-, etc. body cluster operators. The following approximations are made: (i) the cluster expansion is truncated;...
Article
The soliton bag model is studied at finite temperature and zero baryon density. The authors work in the one-loop approximation, including both quark and sigma loops. A phase transition occurs at a temperature approximately 100 MeV (for three light quark flavours). The dependence of the transition temperature on the model parameters is presented. Th...
Article
In order to resolve the problem of infinite forces and renormalizability of the self-energy of point charges in non-uniform local dielectric media. The authors propose a formalism based on a nonlocal dielectric function. Implications for both solid-state physics and chromodielectric models of QCD are discussed. The formalism to calculate the energi...
Article
The present work is an extension of a previous study of the nucleonnucleon interaction based on the chromo-dielectric soliton model. The former approach was static, leading to an adiabatic potential. Here we perform a dynamical study in the framework of the Generator Coordinate Method. In practice, we derive an approximate Hill-Wheeler differential...
Article
Classical dynamics, often called 'molecular dynamics' when applied to atoms and molecules, is much easier than solving the many-body Schrodinger equation for a number of reasons. In particular, correlation and rearrangement are simple in classical dynamics. Fermion molecular dynamics (FMD) is a quasi-classical method for treating quantum-mechanical...
Article
A quark model which includes both scalar and vector contributions to the reaction mechanism is used in a DWBA calculation of total and differential cross-sections, polarizations, and spin correlation coefficients for the reaction bar p p arrow bar Lambda Lambda, bar Lambda Sigma, bar Sigma Lambda, and bar Sigma Sigma at laboratory momenta from thre...
Article
Complex mass poles, or ghost poles, are present in the Hartree-Fock solution of the Schwinger-Dyson equation for the nucleon propagator in renormalizable models with Yukawa-type meson-nucleon couplings, as shown many years ago by Brown, Puff and Wilets (BPW). These ghosts violate basic theorems of quantum field theory and their origin is related to...
Article
In recent years there has been renewed interest in semiclassical methods of modeling atomic structure and collision dynamics. A class of many-body models applied to these problems are descendants of the original work by Kirschbaum and Wilets [Phys. Rev. A 21, 834 (1980)], who used momentum dependent pseudopotentials to exclude particles from quantu...
Article
Full-text available
We present a study of the 4He charge distribution based on realistic nucleonic wave functions and incorporation of quark substructure. Any central depression of the proton point density seen in modern four-body calculations is too small by itself to lead to a correct description of the charge distribution of 4He if folded with a fixed proton size p...
Article
Full-text available
We solve the Schwinger-Dyson equation for the nucleon propagator in the vacuum using $\pi$, $\sigma$, and $\omega$ mesons. For bare interaction vertices (Hartree-Fock approximation) we obtain a pair of complex-conjugated poles (ghost poles) and for vertices dressed by phenomenological form-factors these ghosts disappeared. We use these two differen...
Article
Full-text available
The chromodielectric soliton model is Lorentz and chirally invariant. It has been demonstrated to exhibit dynamical chiral symmetry breaking and spatial confinement in the locally uniform approximation. We here study the full nonlocal quark self-energy in a color-dielectric medium modeled by a two-parameter Fermi function. Here color confinement is...
Article
Full-text available
The measurement and analysis of electron scattering from He-3 and He-4 by Sick and collaborators reported 20 years ago remains a matter of current interest. By unfolding the measured free-proton charge distribution, they deduced a depression in the central point nucleon density, which is not found in few-body calculations based on realistic potenti...
Article
Full-text available
The present work is an extension of a previous study of the nucleon-nucleon interaction based on the chromodielectric soliton model. The former approach was static, leading to an adiabatic potential. Here we perform a dynamical study in the framework of the generator coordinate method. In practice we derive an approximate Hill-Wheeler differential...
Article
We employ a relativistic quark bag picture, the chromo-dielectric soliton model, to discuss the quarks' symmetry structure and momentum distribution in the $N$-$N$ system. Six-quark clusters are constructed in a constrained mean-field calculation. The corresponding Hamiltonian contains not only an effective interaction between the quarks and a scal...
Chapter
The scope of nuclear many-body problems of current interest is staggering. It covers the range in A from 1 to (say) 300 and infinity (nuclear matter); isotopic compositions N and Z near and far from the stable valley, and the equation of state of nuclear matter as a function of T and p. A speculative phase diagram (reproduced from Nagamiya and Gyul...
Article
Atomic,PNC experiments on heavy elements have reached sufficiently high precision to allow for the determination of sin2 0~ to such a level as to make a significant con-tribution to tests of the Standard Model at the level of one loop radiative corrections. In order to extract the weak coupling parameters in experiments on single isotopes, it is ne...
Article
Full-text available
A quark model which includes both scalar and vector contributions to the reaction mechanism is used in a DWBA calculation of total and differential cross-sections, polarizations, and spin correlation coefficients for the reaction $\bar pp \to \bar \Lambda \Lambda $ at laboratory momenta from threshold to 1.92GeV/c. The free parameters of the calc...
Article
Full-text available
The short and medium range parts of the nucleon-nucleon interaction are being studied in the framework of the chromodielectric soliton model. The model consists of current quarks, gluons in the abelian approximation, and a scalar sigma field which simulates the nonabelian interactions of the gluons and governs the medium through the dielectric func...
Article
A quark model that includes both scalar and vector contributions to the reaction mechanism (SV quark model) is used in a DWBA calculation of the {bar {Lambda}}{Lambda} production in {bar p}p interactions. Total and differential cross sections, polarizations, depolarizations, and spin-correlation coefficients are computed for laboratory momenta from...
Article
The dynamics of an idealized, infinite, MIT-type flux tube is followed in time as the interior evolves from a pure gluon field to a $\overline q \ q$ plasma. We work in color U(1). $\overline q\ q$ pair formation is evaluated according to the Schwinger mechanism using the results of Brink and Pavel. The motion of the quarks toward the tube endcaps...
Article
Full-text available
We study the N-N interaction in the framework of the chromo-dielectric soliton model. Here, the long-range parts of the nonabelian gluon self-interactions are assumed to give rise to a color-dielectric function which is parameterized in terms of an effective scalar background field. The six-quark system is confined in a deformed mean field through...
Article
Full-text available
A quark model which includes both scalar and vector contributions to the reaction mechanism (SV quark model) is used in a DWBA calculation of $\bar \Lambda \Lambda$ production in $\bar p p$ interractions. Total and differential cross-sections, polarizations, depolarizations, and spin-correlattion coefficients are computed for laboratory momenta fro...
Article
Full-text available
A semiclassical, many-body atomic model incorporating a momentum-dependent Heisenberg core to stabilize atomic electrons is used to study antiproton capture on helium. Details of the antiproton collisions leading to eventual capture are presented, including the energy and angular-momentum states of incident antiprotons which result in capture via s...
Article
The Schwinger-Dyson equations for the nucleon and meson propagators are solved self-consistently in an approximation that goes beyond the Hartree-Fock approximation. The traditional approach consists in solving the nucleon Schwinger-Dyson equation with bare meson propagators and bare meson-nucleon vertices; the corrections to the meson propagators...
Article
Vertex corrections are taken into account in the Schwinger-Dyson equation for the nucleon propagator in a relativistic field theory of fermions and mesons. The usual Hartree-Fock approximation for the nucleon propagator is known to produce the appearance of complex (ghost) poles which violate basic theorems of quantum field theory. In a theory with...
Article
A quark model which includes both scalar and vector contributions to the reaction mechanism is used in a DWBA calculation of total and differential cross-sections, polarizations, and spin correlation coefficients for the reaction $\bar p p \rightarrow \bar \Lambda \Lambda$ at laboratory momenta from threshold to 1.92 GeV/c. The free parameters of t...
Article
Full-text available
There have been suggestions to measure atomic parity nonconservation (PNC) along an isotopic chain, by taking ratios of observables in order to cancel complicated atomic structure effects. Precise atomic PNC measurements could make a significant contribution to tests of the Standard Model at the level of one loop radiative corrections. However, the...
Article
A quark model which includes both scalar and vector contributions to the reaction mechanism (SV quark model) is used in a DWBA calculation of (anti (Lambda))(Lambda) production in (bar p)p interactions. Total and differential cross-sections, polarizations, depolarizations, and spin-correlation coefficients are computed for laboratory momenta from t...
Article
A transport theory with chiral symmetry is developed from the quark level to describe the chiral dynamics in high-energy heavy-ion collisions. The strong interaction is treated effectively by the Nambu--Jona-Lasinio model. A set of generalized Boltzmann equations of constitutent quarks and mesons is derived by using the closed time-path Green's fun...
Article
We present the results of distorted-wave calculations for differential cross-sections, polarizations and spin correlation coefficients for the reactions pp-->ΛΛ and pp-->Λ∑0+c.c.. Our model includes both scalar and vector contributions (3P0 and 3S1) to qq annihilation and creation. We obtain good fits to experimental data for scalar and vector stre...
Article
It has been suggested to measure ratios of atomic parity-nonconservation observables in strings of isotopes to cancel atomic-structure effects. Nuclear-structure-effects nevertheless play a significant role in extracting weak-interaction parameters. Uncertainties in nuclear structure, especially in the neutron distribution, severely limit the preci...
Article
The chromodielectric model is a chirally symmetric effective model of quantum chromodynamics, where the long-range parts of the (nonabelian) gluon self-interactions are assumed to give rise to a color-dielectric function. We study dynamical chiral symmetry breaking in this model using a local approximation, where the Goldstone pion is assumed to be...
Article
We have calculated upper bounds for {ital p}-{ital d} and {ital d}-{ital d} fusion rates at octahedral and tetrahedral sites in saturated PdH. Our molecular potentials include Thomas-Fermi screening for two centers and realistic Pd crystal potentials. Accurate numerical techniques were used to solve for radial wave functions down to {ital r}=0. Fro...
Article
In an inhomogeneous medium with μ=κ−1, the linearized gauge field propagator is presented in terms of spherical harmonics for the Coulomb gauge. Explicit expressions for the propagator are given in the case of the MIT bag for both the Coulomb and Lorentz gauges. Gauge invariance is shown explicitly for the one gluon interaction in the MIT bag. This...
Article
We present accurate numerical methods for calculating the one boson and the one fermion loop energy in a static, spherically symmetric background field for a simple theory of fermions interacting with bosons through Yukawa coupling. Various FORTRAN codes have been developed and tested for the calculations. The methods presented here should be usefu...
Article
Quark basis states constructed from molecular-type orbitals were shown previously to be more convenient to use than cluster model states for {ital N}-{ital N} processes. The usual cluster model representation omits configurations which emerge naturally in a molecular basis which contains the same number of spatial functions. The importance of the o...
Article
We present an analysis of six-quark basis states constructed from molecular-type single-particle orbitals. In the present work, we employ a nonrelativistic constituent quark model with one-gluon exchange approximated by a spin-spin interaction. The orbitals are constructed from appropriate combinations of two-center Gaussians. The calculations are...
Article
A number of recent papers have compared the ³Pâ and ³S⁠models for N-barN annihilation. We argue that a more consistent approach is to use both models together because they represent different aspects of quantum chromodynamics. In the approximation of the paper on which this Comment is based, our approach gives better agreement with data.
Article
We study a chirally symmetric effective model of quantum chromodynamics, where the long-range parts of the (non-abelian) gluon self-interactions are assumed to give rise to a color-dielectric field. In particular we show how in this model confinement and the Goldstone pion arise naturally and simultaneously from dynamical chiral symmetry breaking....
Article
A number of recent papers have compared the /sup 3/P/sub 0/ and /sup 3/S/sub 1/ models for N-barN annihilation. We argue that a more consistent approach is to use both models together because they represent different aspects of quantum chromodynamics. In the approximation of the paper on which this Comment is based, our approach gives better agreem...
Article
A number of recent papers have compared the 3P0 and 3S1 models for N¯N annihilation. We argue that a more consistent approach is to use both models together because they represent different aspects of quantum chromodynamics. In the approximation of the paper on which this Comment is based, our approach gives better agreement with data.
Article
The nuclear equation of state is calculated using the soliton bag model and the Wigner-Seitz approximation for baglike states on a lattice. Since the Wigner-Seitz treatment averages over lattice structure, it is more realistic for a fluid like nuclear matter than is a periodic crystal model. A crucial feature of the model presented here is the mann...
Article
A two-component Pauli equation for a composite model of the nucleon is derived using a relativistically covariant quark model. Scalar-isoscalar, vector-isoscalar, vector-isovector, and electromagnetic external potentials are considered. For the vector fields we find anomalous ``magnetic moments,'' which are simply related to the corresponding elect...
Article
The chromo-dielectric mechanism of absolute confinement is studied in the nontopological soliton model. The model lagrangian is chirally invariant, since it contains no direct coupling between the quarks and the scalar field. The static chromo-electric gluon propagator is calculated in medium in the one-loop approximation, and the ultraviolet diver...
Article
A new quark model forN [`(N)]\bar N annihilation is proposed. It is argued that a linear superposition of the so-called3P0 and3S1 models is more consistent with QCD and the inclusion of quark degrees of freedom inNN scattering, and is also suggested by the data. A comparison is made, in Born approximation, with the angular distribution for p[`(p)]...
Article
Six-quark configurations relevant to N-N scattering and bound states are constructed from parity eigenfunctions which can be obtained from any static independent particle model. The two lowest, one even and one odd, parity orbitals are considered. In the (TS)=(10) and (01) sectors, there are 16 orthogonal color-singlet configurations of various orb...
Article
We have investigated quantum corrections to topological and nontopological solitons in several two-dimensional theories at the one-loop level utilizing a numerical Green’s-function method. For the φ4 kink and sine-Gordon soliton, as well as the kink coupled to fermions, we reproduce the masses of static solitons obtained analytically in the cases f...
Article
In a previous paper we presented a method for calculating center-of-mass corrections to hadron properties in soliton models. Here we apply this method to the soliton bag model. We construct quantum bag solutions of quarks interacting with a scalar sigma field and color gauge fields in the one-gluon-exchange approximation. The sigma part of Hilbert...
Article
In the context of the soliton bag model, the quarks, soliton field and the gluon propagator are calculated self-consistently in the mean-field, one-gluon exchange approximation. The use of a confined propagator, as compared with a free propagator, is primarily to change the effective quark-gluon coupling constant by a factor of approximately two in...
Conference Paper
An essential feature of quantum chromcodynamics is the confinement of quarks and gluons in localized, color-singlet states. This has been effected by models through the introduction of a color function kappa and magnetic permittivity ..mu.. = kappa/sup -1/. In regions of confinement, such as the interior of a ''bag,'' kappa approx. = 1, while in th...
Conference Paper
The work presented is to classify and construct six-quark states as totally antisymmetric states of six fermions, each described by orbital, spin, isospin, and color degrees of freedom. A classification scheme is proposed based on parity eigenfunctions. The single-particle hamiltonian is assumed to be reflectionally and axially symmetric and can be...
Article
The pion cloud surrounding the nucleon and the $\Delta${} is studied in the soliton bag model. The quark-antiquark substructure of the pion is fully taken into account using generator-coordinate techniques. The one-gluon-exchange piece of the model Hamiltonian is responsible for creating the qq\ifmmode\bar\else\textasciimacron\fi{} pair. The result...
Article
The soliton bag model introduced by Friedberg and Lee is applied to nucleon-nucleon scattering. The dynamics of six quarks and their confining soliton field is treated in the generator coordinate method. The potential obtained in an effective Schrödinger equation substantially differs from the results of adiabatic calculations.
Article
The effects of strong, short-range attraction in exotic atoms are considered in a simplified model. The model consists of a spherical box of radius b which contains a strong, short-range, real potential well of radius a. Its eigenvalue spectrum has two parts: negative energy, strongly bound ``nuclear'' states, and positive energy ``atomic'' states....
Article
The method of projection is applied to a relativistic field theory of fermions interacting with a nonlinear scalar field, specifically the Friedberg-Lee soliton model. Projection is effected by operating on a localized bag state with the translation operator exp (iPZ), and integrating overZ. The resulting state is an eigenstate of zero momentum. Th...
Article
We present a method for calculating center-of-mass corrections to hadron properties in soliton models and we apply the method to the soliton bag model. A coherent state is used to provide a quantum wave function corresponding to the mean-field approximation. This state is projected onto a zero-momentum eigenstate. States of nonzero momentum can be...
Conference Paper
The Friedberg-Lee soliton model, which effects confinement by a quantal scalar field, is discussed. The Lagrangian for the non-topological soliton model is the usual QCD Lagrangian supplemented by a non-linear scalar sigma field term. Static solutions to the field equations are considered in the mean field approximation. Small amplitude oscillation...
Article
A summary of recent and current research on the Soliton Bag Model is presented. The unique feature of the model, namely dynamics, is emphasized, since this permits calculation of reactions within the frame-work of the covariant effective Lagrangian. One gluon exchange effects are included.
Article
A model for nuclear matter is introduced as consisting of an infinite number of bags placed on a spatial cubic lattice. Using the soliton bag model of Friedberg and Lee in the self-consistent mean-field approximation we study the properties of the system as a function of the lattice constant. At low densities the hadronic matter is well described b...
Article
Gluonic effects are included to lowest order in calculations using the soliton bag model. The N-Δ splitting is calculated in the one-gluon-exchange approximation, using a gluon propagator which is confined by the σ field. The string constant is obtained, in the Abelian approximation, from a self-consistent calculation for a cylindrical system of σ...
Article
The gauge field propagator is calculated in configuration space using an expansion in spherical harmonics for the scalar Green function and in vector spherical harmonics for the tensor Green function. We work in the Coulomb gauge where the scalar Green function is instantaneous and the frequency-dependent tensor Green function is transverse. Explic...
Conference Paper
The soliton bag model introduced by Friedberg and Lee is applied to S-wave nucleon-nucleon scattering. The dynamics of six quarks and their confining soliton field is treated in the generator co-ordinate method. We find an attraction of 120 MeV at a NN separation of 2.5 fm, but no attraction in the vicinity of the spherically symmetric shape of the...
Article
The solitons studied are localized, static solutions to classical (or semiclassical) nonlinear field equations. Being localized, they do not correspond to momentum eigenstates, even though the field theories solved are translationally invariant. In order to construct states of good momentum, an explicity quantum wave function is needed and not just...
Article
We formulate a three-dimensional quantum-mechanical model for the study of nucleon transfer in heavy ion collisions. This model describes the independent particle motion of nucleons initially separated in two adjacent cubic boxes and brought into contact through a window created in the separating wall. We calculate the one-sided flux and the spread...
Article
Variational electron correlation techniques described earlier (by Wilets, Henley and Martensson, 1980) are developed and generalised to four-electron (i.e. Be-like) atoms. Both spin-dependent and momentum-dependent two-body correlations are considered; the latter prove to be the more significant and it is found that, with a very few parameters, it...
Conference Paper
The soliton bag model of interacting quarks and gluons, introduced by Friedberg and Lee, provides a framework for dynamical calculations of hadrons and hadronic processes. The model contains five parameters which must be fit to data in order to test the consistency of the model and to allow prediction. A considerable number of calculations have bee...
Article
The static classical gauge potentials generated by a shell source of SU(2) color are examined. This is done within an ansatz for the gauge potentials which incorporates not only the Abelian, or Coulomb, solution but also spans the space of static fluctuations which have been shown by Magg to lower the energy from its Coulomb value. We find that, fo...
Article
We construct a three-dimensional quantum mechanical model relevant for nucleon transfer in heavy ion collisions. It consists of two adjacent cubic boxes with a rectangular window in the wall which separates them. We calculate the one-sided flux as a function of the window size and compare it with previous results.
Conference Paper
The soliton model of interacting quarks and gluons, introduced by Friedberg and Lee, effects both spatial and color confinement of the constituents. The properties of the static bag have been reported previously. Because the model is described by a complete Hamiltonian, the dynamics of the system can be followed unambiguously. For this purpose, we...
Article
The recoil corrections to bag models are considered using a definition of the center-of-energy operator analogous to the Newtonian concept of center of mass. This definition is used to calculate corrections to bag energy, charge radius, and other properties within the framework of the soliton bag model. Some of our results also apply directly to th...
Article
The energy levels of massless quarks conf