Chiral pion-nucleon dynamics in finite nuclei: spin-isospin excitations

The nuclear density functional framework, based on chiral dynamics and the symmetry breaking pattern of low-energy QCD, is extended to the description of collective nuclear excitations. Starting from the relativistic point-coupling Lagrangian previously introduced [Nucl. Phys. A770 (2006) 1], the proton-neutron (quasiparticle) random phase approximation is formulated and applied to investigate the role of chiral pion-nucleon dynamics in excitation modes involving spin and isospin degrees of freedom, e.g. isobaric analog states and Gamow-Teller resonances.Comment: 17 pages, 6 figures, elsart class. Minor revisions, Nuclear Physics A in prin

An assessment of age determination methods for captured passerine birds

Various methods of determining age of passerine birds, using eye color, shape of flight feathers, plumage color patterns, etc. are presented in handbooks for bird banders, such as Pyle, et al., Identification Guide to North American Passerines (1987). We compared several such methods with the standard, reliable (but time-consuming) method, skulling , in 22 species of passerines captured and banded during Fall 1994, in a general netting operation at the University of Wisconsin-Milwaukee Field Station. In many species these methods were in agreement; however in 10 species there was substantial disagreement, especially involving buffy covert tips in thrushes and shape of rectrices or primary remiges in warblers. Since members of these groups are caught in large numbers, it is important to reevaluate these criteria and find more reliable methods

Latitude dependence of ionospheric electron content

Ionospheric electron content calculation method applied to Faraday fading signal

Nonlocal Polyakov-Nambu-Jona-Lasinio model and imaginary chemical potential

With the aim of setting constraints for the modeling of the QCD phase diagram, the phase structure of the two-flavor Polyakov-loop extended Nambu and Jona-Lasinio (PNJL) model is investigated in the range of imaginary chemical potentials ($\mu_\mathrm{I}$) and compared with available $N_f=2$ lattice QCD results. The calculations are performed using the advanced nonlocal version of the PNJL model with the inclusion of vector-type quasiparticle interactions between quarks, and with wave-function-renormalization corrections. It is demonstrated that the nonlocal PNJL model reproduces important features of QCD at finite $\mu_\mathrm{I}$, such as the Roberge-Weiss (RW) periodicity and the RW transition. Chiral and deconfinement transition temperatures for $N_f=2$ turn out to coincide both at zero chemical potential and at finite $\mu_\mathrm{I}$. Detailed studies are performed concerning the RW endpoint and its neighborhood where a first-order transition occurs.Comment: 26 page, 13 figure, typo corrected, some references added and corrected, one figure updated, version accepted for publication in Phys. Rev.

Hypernuclear single particle spectra based on in-medium chiral SU(3) dynamics

A previously derived relativistic energy density functional for nuclei, based on low-energy in-medium chiral dynamics, is generalized to implement constraints from chiral SU(3) effective field theory and applied to $\Lambda$ hypernuclei. Density-dependent central and spin-orbit mean fields are calculated for a $\Lambda$ hyperon using the SU(3) extension of in-medium chiral perturbation theory to two-loop order. Long range $\Lambda N$ interactions arise from kaon-exchange and from two-pion-exchange with a $\Sigma$ hyperon in the intermediate state. Short-distance dynamics is encoded in contact interactions. They include scalar and vector mean fields reflecting in-medium changes of quark condensates, constrained by QCD sum rules. The $\Lambda$ single particle orbitals are computed for a series of hypernuclei from $^{13}_{\Lambda}$C to $^{208}_{\Lambda}$Pb. The role of a surface (derivative) term is studied. Its strength is found to be compatible with a corresponding estimate from in-medium chiral perturbation theory. Very good agreement with hypernuclear spectroscopic data is achieved. The smallness of the $\Lambda$-nuclear spin-orbit interaction finds a natural explanation in terms of an almost complete cancellation between short-range scalar/vector contributions and longer range terms generated by two-pion exchange.Comment: 30 pages, 5 figures, elsart class, minor corrections, to be published in Nuclear Physics

Quasiparticle Description of Hot QCD at Finite Quark Chemical Potential

We study the extension of a phenomenologically successful quasiparticle model that describes lattice results of the equation of state of the deconfined phase of QCD for Tc <= T < 4 Tc, to finite quark chemical potential mu. The phase boundary line Tc(mu), the pressure difference (p(T,mu)-p(T,mu=0))/T^4 and the quark number density nq(T,mu)/T^3 are calculated and compared to recent lattice results. Good agreement is found up to quark chemical potentials of order mu = Tc.Comment: 12 pages, 7 figures; added reference

Possibility of s-wave pion condensates in neutron stars revisited

We examine possibilities of pion condensation with zero momentum (s-wave condensation) in neutron stars by using the pion-nucleus optical potential U and the relativistic mean field (RMF) models. We use low-density phenomenological optical potentials parameterized to fit deeply bound pionic atoms or pion-nucleus elastic scatterings. Proton fraction (Y_p) and electron chemical potential (mu_e) in neutron star matter are evaluated in RMF models. We find that the s-wave pion condensation hardly takes place in neutron stars and especially has no chance if hyperons appear in neutron star matter and/or b_1 parameter in U has density dependence.Comment: 4 pages, 3 figures, REVTe

Nuclear Many-Body Dynamics constrained by QCD and Chiral Symmetry

We present a novel description of nuclear many-body systems, both for nuclear matter and finite nuclei, emphasizing the connection with the condensate structure of the QCD ground state and spontaneous chiral symmetry breaking. Lorentz scalar and vector mean-fields are introduced in accordance with QCD sum rules. Nuclear binding arises from pionic fluctuations, using in-medium chiral perturbation theory up to three-loop order. Ground state properties of $^{16}$O and $^{40}$Ca are calculated. The built-in QCD constraints reduce the number of input parameters significantly in comparison with purely phenomenological relativistic mean-field approaches.Comment: 6 pages, 3 figures, to be published in European Physical Journal