Deckungsbeiträge

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The Problem of Matter Stability in the Nambu--Jona-Lasinio Model

We reinvestigate the conditions for stable matter solutions in the Nambu--Jona-Lasinio (NJL) model. In mean field approximation the NJL model can be regarded as an extension of the Walecka mean field model to include negative energy fermion states. While this extension is necessary to allow for a chiral phase transition, it was found some time ago that at the same time it destroys the wanted saturation properties of the Walecka model. We reformulate this problem in terms of the thermodynamic potential and find that there is indeed a connection between these two features. We show that the minimum of the thermodynamic potential which corresponds to stable nuclear matter in the Walecka model is shifted from a finite to zero effective fermion mass in the chiral NJL model. This shift is closely related to the chiral phase transition. Under certain conditions the shifted minima may still lead to stable matter solutions but only in the chirally restored phase. We discuss a possible interpretation of these solutions as a schematic bag model description.Comment: 21 pages, LaTeX, 5 postscript figures, Nucl. Phys. A, in pres

Nucleons or diquarks? Competition between clustering and color superconductivity in quark matter

We study the instabilities of quark matter in the framework of a generalized Nambu--Jona-Lasinio model, in order to explore possible competition between three-quark clustering to form nucleons and diquark formation leading to color superconductivity. Nucleon and $\Delta$ solutions are obtained for the relativistic Faddeev equation at finite density and their binding energies are compared with those for the scalar and axial-vector diquarks found from the Bethe-Salpeter equation. In a model with interactions in both scalar and axial diquark channels, bound nucleons exist up to nuclear matter density. However, except at densities below about a quarter of that of nuclear matter, we find that scalar diquark formation is energetically favored. This raises the question of whether a realistic phase diagram of baryonic matter can be obtained from any model which does not incorporate color confinement.Comment: 23 pages (RevTeX), 5 figures (epsf

REVIEW OF PARTICLE PHYSICS

The Review summarizes much of particle physics and cosmology. Using data from previous editions, plus 3,324 new measurements from 878 papers, we list, evaluate, and average measured properties of gauge bosons and the recently discovered Higgs boson, leptons, quarks, mesons, and baryons. We summarize searches for hypothetical particles such as supersymmetric particles, heavy bosons, axions, dark photons, etc. Particle properties and search limits are listed in Summary Tables. We give numerous tables, figures, formulae, and reviews of topics such as Higgs Boson Physics, Supersymmetry, Grand Unified Theories, Neutrino Mixing, Dark Energy, Dark Matter, Cosmology, Particle Detectors, Colliders, Probability and Statistics. Among the 120 reviews are many that are new or heavily revised, including a new review on High Energy Soft QCD and Diffraction and one on the Determination of CKM Angles from B Hadrons. The Review is divided into two volumes. Volume 1 includes the Summary Tables and 98 review articles. Volume 2 consists of the Particle Listings and contains also 22 reviews that address specific aspects of the data presented in the Listings. The complete Review (both volumes) is published online on the website of the Particle Data Group (pdg.lbl.gov) and in a journal. Volume 1 is available in print as the PDG Book. A Particle Physics Booklet with the Summary Tables and essential tables, figures, and equations from selected review articles is available in print and as a web version optimized for use on phones as well as an Android app.Peer reviewe

Glueballs, Hybrids, Multiquarks. Experimental facts versus QCD inspired concepts

The spectroscopy of light and heavy mesons is reviewed with emphasis on glueballs, hybrids, and tetraquarks.Comment: 266 pages, 117 figures, 39 tables. to be published in Physics Report

Personal narrative of a pilgrimage to El-Medinah and Meccah /

Illustrations by Hanhart; after R. Burton and J. Brandard.V. 2 has four appendices: 1. A Murshid's diploma -- 2. The navigation ... of Ludovicus -- 3. The pilgrimage of Joseph Pitts -- 4. Giovanni Finati."List of plates" appears in v. 3 only.Printed by A. And G.A. Spottiswoode, New Street Square.Vol. I. El-Misr -- v. II. El-Medinah -- v. III. Meccah.Penzrt, N. An annotated bibliography of Sir Richard Francis Burton,Abbey, J.R. TravelMode of access: Internet.BAC: Binding label reads: Bound by Edmonds & Remnants, London.BAC: British Art Center copy bound in blue publishers cloth.BAC: British Art Center copy is the Abbey copy