19013112
Order of the QCD transition and QCD sum rules.
We propose using the finite-temperature {rho}-meson mass as an order parameter to monitor the QCD transition. This is suggested by the {rho}-meson mass formula that emerges from finite-temperature QCD sum rules in the vector channel, and which encompasses the effects of both quark and gluon condensates. We find that a second-order chiral-restoring transition implies a second-order behavior for the {rho} mass even if the value of the gluon condensate is unaffected by the transition.
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.
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.
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.
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.
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.
19989163
Nucleon scattering from 34S and the relative sign of neutron and proton transition matrix elements for the (0-->22+) transition.
Data obtained by scattering 29.8 MeV protons and 21.7 MeV neutrons from $^{34}\mathrm{S}$ are used in a consistent analysis to obtain values and relative signs for proton (${M}_{\mathrm{p}}$) and neutron (${M}_{\mathrm{n}}$) multiple matrix elements for E2 transitions to the first three ${2}^{+}$ states in $^{34}\mathrm{S}$. The data for the ${0}^{+}$(g.s.)\ensuremath{\rightarrow}${2}_{2}^{+}$(3.30 MeV) transition are consistent only with the assumption of the same relative sign of ${M}_{\mathrm{p}}$ and ${M}_{\mathrm{n}}$. .AE
20082114
Probe of the shell crossing at A=40 via beta decay: Experiment and theory.
The ..beta../sup -/ decays of /sup 35/P, /sup 37/S, /sup 38/S, and /sup 38/Cl were studied both experimentally and via shell-model calculations. The four decaying nuclei were formed by bombardment of 81% enriched /sup 36/S by triton and deuteron beams. Gamma-ray spectroscopy was carried out with Ge detectors, either bare or surrounded by a Compton suppression NaI(Tl) shield. One new Gamow-Teller decay was observed in /sup 35/P decay, and one new first-forbidden decay was observed in /sup 38/S decay. Otherwise ..gamma..-ray measurements of E/sub ..gamma../ and I-/sub ..gamma../ (and limits on I/sub ..gamma../ for unobserved transitions) were improved significantly over previous results. Shell-model studies were undertaken in order to bring these beta decay results to bear on an understanding of the shell structure in the (sd) to (fp) transition region at A = 40. An interaction was constructed in the 1d/sub 5/2/, 1d/sub 3/2/, 2s/sub 1/2/, 1f/sub 7/2/, 1f/sub 5/2/, 1p/sub 3/2/, 1p/sub 1/2/ model space. This interaction started from the Wildenthal ''USD'' (sd) interaction and the van Hees-Glaudemans (fp) interaction, which were connected by the cross-shell Millener-Kurath interaction. Certain important two-body matrix elements and single-particle energies were adjusted to fit experimental binding energies in A = 40, 41, 42.more » This interaction was then used to calculate level spectra for the daughter nuclei /sup 35/S, /sup 37/Cl, /sup 38/Cl, and /sup 38/Ar as well as Gamow-Teller and unique first-forbidden beta decays leading to these nuclei. The techniques used in these relatively large scale calculations are discussed in detail, as are the results.« less
5059193
High-energy reaction cross sections of light nuclei.
The high-energy reaction cross sections of Li and Be isotopes are calculated using a simplified Glauber model and densities constrained by the empirical binding energies. We find excellent agreement with experiment, reproducing the large increase for the most neutron-rich nuclei.
19945972
Corrections to the Fermi matrix element for superallowed beta decay.
Corrections to the Fermi matrix element for superallowed transitions due to isospin nonconservation are reexamined. The sources of theoretical uncertainty and the possibility of a previously neglected correction based on the mismatch between the spectator nucleons are investigated. The consequences to the conserved-vector-current hypothesis and the Kobayashi-Maskawa mixing angles are discussed.
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.