Inclusion of Diffraction Effects in the Gutzwiller Trace Formula

The Gutzwiller trace formula is extended to include diffraction effects. The new trace formula involves periodic rays which have non-geometrical segments as a result of diffraction on the surfaces and edges of the scatter.Comment: 4 pages, LaTeX, 1 ps figur

Wave Chaos in Elastodynamic Cavity Scattering

The exact elastodynamic scattering theory is constructed to describe the spectral properties of two- and more-cylindrical cavity systems, and compared to an elastodynamic generalization of the semi-classical Gutzwiller unstable periodic orbits formulas. In contrast to quantum mechanics, complex periodic orbits associated with the surface Rayleigh waves dominate the low-frequency spectrum, and already the two-cavity system displays chaotic features.Comment: 7 pages, 5 eps figures, latex (with epl.cls

Model-independent approach to eta -> pi+ pi- gamma and eta' -> pi+ pi- gamma

We present a new, model-independent method to analyze radiative decays of mesons to a vector, isovector pair of pions of invariant mass square below the first significant pion-pion threshold in the vector channel. It is based on a combination of chiral perturbation theory and dispersion theory. This allows for a controlled inclusion of resonance physics without the necessity to involve vector meson dominance explicitly. As an example, the method is applied to an analysis of the reactions eta -> pi+ pi- gamma and eta'->pi+ pi- gamma.Comment: 16 pages, 4 figure

Unexpected goings-on in the structure of a neutron star crust

We present a brief account of two phenomena taking place in a neutron star crust: the Fermionic Casimir effect and the major density depletion of the cores of the superfluid neutron vortices.Comment: 6 pages, invited talk presented by AB at Tours 2003 Symposium on Nuclear Physics, August 26-29,Tours, Franc

Deriving the quark condensate within a finite Fermi system from the generating functional of chiral perturbation theory

The generating functional of heavy baryon chiral perturbation theory at order {\cal O}(Q^2) in the mean field approximation (with a pseudoscalar source coupling which is consistent with the PCAC-Ward identities on the current quark level) has been exploited to derive Migdal's in--medium pion propagator. It is shown that the prediction for the density dependence of the quark condensate obtained on the composite hadron level by embedding PCAC within the framework of Migdal's approach to finite Fermi systems is identical to that resulting from QCD

In-Medium Pion Properties from Chiral Perturbation Theory

Two--point functions related to the pion weak decay constant $f_\pi$ are calculated from the generating functional of chiral perturbation theory in the mean field approximation and the heavy--baryon limit. The aim is to demonstrate that Lorentz invariance is violated in the presence of background matter. This fact manifests itself in the splitting of both $f_\pi$ and the pion mass into uncorrelated time-- and space--like parts. We emphasize the different in--medium renormalizations of the correlation functions, show the inequivalence between the in--medium values of $f_\pi$ deduced from Walecka--type models, on the one hand, and QCD sum rules, on the other hand, and elaborate on the importance for some nuclear physics observables

Neutron-Proton Mass Difference in Nuclear Matter and in Finite Nuclei and the Nolen-Schiffer Anomaly

The neutron-proton mass difference in (isospin asymmetric) nuclear matter and finite nuclei is studied in the framework of a medium-modified Skyrme model. The proposed effective Lagrangian incorporates both the medium influence of the surrounding nuclear environment on the single nucleon properties and an explicit isospin-breaking effect in the mesonic sector. Energy-dependent charged and neutral pion optical potentials in the s- and p-wave channels are included as well. The present approach predicts that the neutron-proton mass difference is mainly dictated by its strong part and that it markedly decreases in neutron matter. Furthermore, the possible interplay between the effective nucleon mass in finite nuclei and the Nolen-Schiffer anomaly is discussed. In particular, we find that a correct description of the properties of mirror nuclei leads to a stringent restriction of possible modifications of the nucleon's effective mass in nuclei.Comment: 10 pages, 8 figures, presentation at the 19th Int. IUPAP Conf. on Few-Body Problems in Physics (Aug.31-Sep.5, 2009, Univ.of Bonn, Germany

Quantum energies with worldline numerics

We present new results for Casimir forces between rigid bodies which impose Dirichlet boundary conditions on a fluctuating scalar field. As a universal computational tool, we employ worldline numerics which builds on a combination of the string-inspired worldline approach with Monte-Carlo techniques. Worldline numerics is not only particularly powerful for inhomogeneous background configurations such as involved Casimir geometries, it also provides for an intuitive picture of quantum-fluctuation-induced phenomena. Results for the Casimir geometries of a sphere above a plate and a new perpendicular-plates configuration are presented.Comment: 8 pages, 2 figures, Submitted to the Proceedings of the Seventh Workshop QFEXT'05 (Barcelona, September 5-9, 2005), Refs updated, version to appear in JPhys

Instantons As Unitary Spin Maker

The instanton-induced determinantal 't Hooft interaction is built into a three-flavor linear sigma model which is considered in the OZI-rule-respecting basis. The mixing of the strange and non-strange quarkonia, which is due to the presence of instantons in combination with the spontaneous breaking of chiral symmetry, is shown to be ideal thus leading to the formation of an octet-flavor state. We study the impact of 't Hooft's interaction on the eta NN coupling finding the usual SU(3) results for this coupling, however, with possible generalizations to non-ideal mixing angles and different values of the meson decay constants in the strange and non-strange sectors, respectively