28894226
Proton-nucleus scattering and density dependent meson masses in the nucleus.
The influence of density dependent meson masses, proposed in many previous papers, on proton-nucleus scattering in the several hundred MeV region is investigated. Introduction of this density dependence is found to remove the nuclear radius discrepancy which persistently occurred in analyses with the nonrelativistic impulse approximation when empirical nuclear densities obtained from electron scattering were employed. Nonlocality, suggested by earlier derivations of the density dependent masses, had to be introduced. Taking the estimated range of nonlocality from the earlier calculations, agreement with experiment was significantly improved by this introduction. Effects on the spin-orbit interaction and imaginary part of the optical model are qualitatively discussed. The density dependent meson masses aid in increasing the strength of the spin-orbit interaction. Preliminary results calculated in a relativistic impulse approximation (IA2) formalism for the spin observables are shown and discussed.
122541063
Relativistic effects in nuclear physics
Relativistic effects in nuclear physics are discussed. Very important effects stem from the lowering of the nucleon effective mass m* by the attractive scalar mean field. Spontaneous symmetry breaking by this field in the vacuum was originally responsible for the nucleon mass. Implications implied by the quark/gluon phase transition for this scalar mean field is discussed.
120275311
Kaon condensation, black holes, and cosmological natural selection.
It is argued that a well-measured double neutron-star binary in which the two neutron stars are more than 4% different from each other in mass or a massive neutron star with mass M≥ 2M o would put in serious doubt or simply falsify the following chain of predictions: (1) a nearly vanishing vector meson mass at chiral restoration, (2) kaon condensation at a density n ∼ 3n o , (3) the Brown-Bethe maximum neutron-star mass M maX ≈1.5M ⊙ , and (4) Smolin's "cosmological natural selection" hypothesis.
117511063
The Physics of Supernovae and the Equation of State of Dense Nuclear Matter
The collapse of large stars leading to supernova explosions continues until the core reaches supranuclear densities. The large energy of SN(1987)A (Shelton) implies a soft equation of state, which makes it possible to transfer a large amount of energy from the core to the shock wave which carries through the explosion. At nuclear matter density the Landau forward scattering sum rule puts constraints on the Fermi liquid parameters strongly favouring a low-compression modulus. Whereas conventional nuclear physics calculations give a stiffer equation of state than required for supernovae at higher densities, it is pointed out that these do not include meson masses which decrease with increasing nuclear-matter density. This decrease in meson masses is implied by chiral symmetry. With decreasing meson masses the standard mechanism for saturation disappears, and saturation must be obtained from higher-order loops. These give the possibility, at least, of obtaining a low-compression modulus and soft equation of state at higher densities, because of their smooth dependence on density. In any case, this soft EOS seems to be required by the supernova explosion.
15066887
Renormalization group approach to neutron matter: quasiparticle interactions, superfluid gaps and the equation of state
Renormalization group methods can be applied to the nuclear many-body problem using the approach proposed by Shankar. We start with the two-body low momentum interaction Vlowk and use the RG flow from the particle–hole channels to calculate the full scattering amplitude in the vicinity of the Fermi surface. This is a new straightforward approach to the many-body problem which is applicable also to condensed matter systems without long-range interactions, such as liquid 3He. We derive the one-loop renormalization group equations for the quasiparticle interaction and the scattering amplitude at zero temperature. The RG presents an elegant method to maintain all momentum scales and preserve the antisymmetry of the scattering amplitude. As a first application we solve the RG equations for neutron matter. The resulting quasiparticle interaction includes effects due to the polarization of the medium, the so-called induced interaction of Babu and Brown. We present results for the Fermi liquid parameters, the equation of state of neutron matter and the 1S0 superfluid pairing gap.
119072699
Nuclear matter with Brown–Rho-scaled Fermi liquid interactions
Abstract We present a description of symmetric nuclear matter within the framework of Landau Fermi liquid theory. The low momentum nucleon–nucleon interaction V low - k is used to calculate the effective interaction between quasiparticles on the Fermi surface, from which we extract the quasiparticle effective mass, the nuclear compression modulus, the symmetry energy, and the anomalous orbital gyromagnetic ratio. The exchange of density, spin, and isospin collective excitations is included through the Babu–Brown induced interaction, and it is found that in the absence of three-body forces the self-consistent solution to the Babu–Brown equations is in poor agreement with the empirical values for the nuclear observables. This is improved by lowering the nucleon and meson masses according to Brown–Rho scaling, essentially by including a scalar tadpole contribution to the meson and nucleon masses, as well as by scaling g A . We suggest that modifying the masses of the exchanged mesons is equivalent to introducing a short-range three-body force, and the net result is that the Brown–Rho double decimation [G.E. Brown, M. Rho, Phys. Rep. 396 (2004) 1] is accomplished all at once.
36469643
Lorentzian path integral for minisuperspace cosmology.
The path integral for minisuperspace models of cosmology is defined as a sum over Lorentzian geometries, and is a Green function for the Wheeler-DeWitt operator. It is shown to be a symmetric function of the initial and final configurations, and its real part is a solution to the Wheeler-DeWitt equation. The Lorentzian path integral is computed explicitly for the de Sitter minisuper-space model and is convergent. The resulting Green function is then related to the solutions of the Wheeler-DeWitt equation known as the Hartle-Hawking and tunneling wave functions of the Universe. The real part of this Green function is a product of Hartle-Hawking wave functions.
8824086
Isovector and isoscalar spin-flip excitations in even-even s-d shell nuclei excited by inelastic proton scattering.
Forward-angle cross sections for 1/sup +/ states have been measured in /sup 24,26/Mg, /sup 28/Si, and /sup 32/S by 201 MeV proton inelastic scattering. Comparisons are made with (..gamma..,..gamma..'), (e,e'), and (p,n) results. The measured strength is compared with microscopic distorted-wave Born approximation calculations using large-scale shell-model wave functions. Ratios of experimental to theoretical 1/sup +/ strengths are given. Almost no quenching is observed.
29372740
Strength functions and spreading widths of simple shell model configurations.
The exact solution of the many-body problem in the framework of the nuclear shell model with a realistic residual Hamiltonian makes it possible to study the fragmentation of simple configurations as a function of excitation energy and interaction strength. The analysis is performed for 839 states with quantum numbers {ital J}{sup {pi}}{ital T}=0{sup +}0 in a system of 12 valence particles within the {ital sd} shell. Our statistics allow us to establish the generic shape of the strength function in the region of strong mixing. For the realistic interaction, the strength function is close to Gaussian in the central part and has exponential wings. The spreading width is larger than predicted by the standard golden rule. At the artificially suppressed interaction strength, we recover the Breit-Wigner shape and the golden rule for the spreading width. The transition between these regimes agrees with theoretical considerations based on the idea of chaotic dynamics. {copyright} {ital 1996 The American Physical Society.}
13491513
Shell-model analysis of high-resolution data for elastic and inelastic electron scattering on 19F.
A comprehensive theoretical and experimental investigation of electron scattering on /sup 19/F is presented. Theoretical procedures for calculating the various components of electron scattering form factors from multiparticle shell-model wave functions are summarized. These procedures are used to compare shell-model predictions with data from electron scattering on /sup 19/F. For the positive-parity states of /sup 19/F we use 1s0d shell-model wave functions obtained with a new ''universal'' Hamiltonian and for the negative-parity states we use 0p-1s0d shell-model wave functions based on the cross-shell Hamiltonian of Millener and Kurath. The comparisons are made with measured longitudinal and transverse form factors for momentum transfers up to 2.4 fm/sup -1/ which are extracted from experimental data obtained with electron energies from 78 to 340 MeV, and angles of 45/sup 0/, 90/sup 0/, and 160/sup 0/. The energy resolution was 25--50 keV and most of the known levels below 8 MeV in excitation were resolved and compared with theory.
26272900
Limits on the presence of scalar and induced-scalar currents in superallowed beta decay.
Limits on the scalar and induced-scalar coupling constants are established from experimental {ital ft} values of superallowed Fermi transitions. The role of the uncertainties in the {ital ft} values is discussed, leading to minimal coupling strengths that can be extracted from {ital ft} values. The implications for the Kobayashi-Maskawa mixing angles are also discussed.