32185846
Scaling effective Lagrangians in a dense medium.
By using effective chiral Lagrangians with a suitable incorporation of the scaling property of QCD, we establish the approximate {ital in}{minus}{ital medium} scaling law, {ital m}{sub {sigma}}{sup *}/{ital m}{sub {sigma}}{approx}{ital m}{sub N}{sup *}/{ital m}{sub N} {approx}{ital m}{sub {rho}}{sup *}/{ital m}{sub {rho}}{approx}{ital m}{sub {omega}}{sup *}/{ital m}{sub {omega}}{approx}{ital f}{sub {pi}}{sup *}/{ital f}{sub {pi}}. This has a highly nontrivial implication for nuclear processes at and above nuclear-matter density. Some concrete cases are cited in this paper.
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.
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.
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.
46635156
Isovector M1 transitions in 28Si and the role of meson exchange currents.
At the newly installed 180{degree} Darmstadt electron scattering facility we have measured the isovector {ital M}1 transition strengths in {sup 28}Si in the excitation energy range from 10 to 18 MeV. Overall agreement with a shell-model calculation using the unified {ital sd}-shell interaction and effective {ital g} factors is obtained. Comparison with Gamow-Teller strength deduced from ({ital p},{ital n}) data reveals the presence of meson exchange current contributions of the order of 25{percent} to the summed {ital M}1 transition strength. {copyright} {ital 1996 The American Physical Society.}
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
13068301
Temperature, energy, and heat capacity of asymptotically anti-de Sitter black holes.
We investigate the thermodynamical properties of black holes in (3+1)- and (2+1)-dimensional Einstein gravity with a negative cosmological constant. In each case, ther thermodynamic internal energy is computed for a finite spatial region that contains the black hole. The temperature at the boundary of this regoin is defined by differentiating the energy with respect to entropy, and is equal to the product of the surface gravity (divided by 2\ensuremath{\pi}) and the Tolman redshift factor for temperature in a stationary gravitational field. We also compute the thermodynamic surface pressure and, in the case of the 2+1 black hole, show that the chemical potential conjugate to angular momentum is equal to the proper angular velocity of the black hole with respect to observers who are at rest in the stationary time slices. In 3+1 dimensions, a calculation of the heat capacity reveals the existence of a thermodynamically stable black hole solution and a negative heat capacity instanton. This result holds in the limit that the spatial boundary tends to infinity only if the cosmological constant is negative; if the cosmological constant vanishes, the stable black hole solution is lost. In 2+1 dimensions, a calculation of the heat capacity reveals the existence of a thermodynamically stable black hole solution, but no negative heat capacity instanton.
115714674
BaBar results on sin(2beta) and B0 oscillations
8977451
Isospin-mixing corrections for fp-shell Fermi transitions.
Isospin-mixing corrections for superallowed Fermi transitions in {ital fp}-shell nuclei are computed within the framework of the shell model. The study includes three nuclei that are part of the set of nine accurately measured transitions as well as five cases that are expected to be measured in the future at radioactive-beam facilities. We also include some new calculations for {sup 10}C. With the isospin-mixing corrections applied to the nine accurately measured {ital ft} values, the conserved-vector-current hypothesis and the unitarity condition of the Cabbibo-Kobayashi-Maskawa matrix are tested.