Yukawa's Pion, Low-Energy QCD and Nuclear Chiral Dynamics

A survey is given of the evolution from Yukawa's early work, via the understanding of the pion as a Nambu-Goldstone boson of spontaneously broken chiral symmetry in QCD, to modern developments in the theory of the nucleus based on the chiral effective field theory representing QCD in its low-energy limit.Comment: 21 pages, 13 figures. Proc. Yukawa-Tomonaga Symposium, Kyoto, Dec.06; to be publ. in Progr. Theor. Phys. Suppl. (Kyoto

Dense Baryonic Matter and Strangeness in Neutron Stars

Recent developments of chiral effective field theory (ChEFT) applications to nuclear and neutron matter are summarized, with special emphasis on a (non-perturbative) extension using functional renormalisation group methods. Topics include: nuclear thermodynamics, extrapolations to dense baryonic matter and constraints from neutron star observables. Hyperon-nuclear interactions derived from SU(3) will be discussed with reference to the "hyperon puzzle" in neutron star matter.Comment: 17 pages, 7 figures; invited talk at the Int. Conf. on Quarks and Nuclear Physics (QNP 2018), Tsukuba, Japan; to appear in JPS Conf. Pro

Baryons 2002: Outlook

Summary and outlook presented at the 9th International Conference on the Structure of Baryons (BARYONS 2002), Jefferson Lab, March 3-8, 2002Comment: 10 pages, to be publ.in: Proceedings Int. Conf. BARYONS 2002, Jefferson Lab., March 200

Chiral Dynamics in Nuclear Systems

A survey is given on selected topics concerning the role of spontaneous chiral symmetry breaking in low-energy QCD, and its dynamical implications for nuclear systems. This includes aspects of chiral thermodynamics (the temperature and density dependence of the chiral condensate). It also includes an update on the theory of low-energy (s-wave) pion-nuclear interactions relevant for deeply-bound states of pionic atoms and the quest for possible fingerprints of chiral symmetry restoration in nuclear systems.Comment: 16 pages, 5 figures, Proceedings CHIRAL 02, Kyoto, Japa

Shear viscosity from Kubo formalism: NJL-model study

A large-$N_{\rm c}$ expansion is combined with the Kubo formalism to study the shear viscosity $\eta$ of strongly interacting matter in the two-flavor NJL model. We discuss analytical and numerical approaches to $\eta$ and investigate systematically its strong dependence on the spectral width and the momentum-space cutoff. Thermal effects on the constituent quark mass from spontaneous chiral symmetry breaking are included. The ratio $\eta/s$ and its thermal dependence are derived for different parameterizations of the spectral width and for an explicit one-loop calculation including mesonic modes within the NJL model.Comment: 14 pages, 11 figures. Revision includes additionally the spectral width at one-loop level (chapter V) and Appendix A. Matches published versio

Functional renormalization group approach to neutron matter

The chiral nucleon-meson model, previously applied to systems with equal number of neutrons and protons, is extended to asymmetric nuclear matter. Fluctuations are included in the framework of the functional renormalization group. The equation of state for pure neutron matter is studied and compared to recent advanced many-body calculations. The chiral condensate in neutron matter is computed as a function of baryon density. It is found that, once fluctuations are incorporated, the chiral restoration transition for pure neutron matter is shifted to high densities, much beyond three times the density of normal nuclear matter.Comment: 5 pages, 4 figures, to appear in Phys. Lett.