Berry Phase Effects on Electronic Properties

Ever since its discovery, the Berry phase has permeated through all branches of physics. Over the last three decades, it was gradually realized that the Berry phase of the electronic wave function can have a profound effect on material properties and is responsible for a spectrum of phenomena, such as ferroelectricity, orbital magnetism, various (quantum/anomalous/spin) Hall effects, and quantum charge pumping. This progress is summarized in a pedagogical manner in this review. We start with a brief summary of necessary background, followed by a detailed discussion of the Berry phase effect in a variety of solid state applications. A common thread of the review is the semiclassical formulation of electron dynamics, which is a versatile tool in the study of electron dynamics in the presence of electromagnetic fields and more general perturbations. Finally, we demonstrate a re-quantization method that converts a semiclassical theory to an effective quantum theory. It is clear that the Berry phase should be added as a basic ingredient to our understanding of basic material properties.Comment: 48 pages, 16 figures, submitted to RM

δ\delta meson effects on neutron stars in the modified quark-meson coupling model

The properties of neutron stars are investigated by including $\delta$ meson field in the Lagrangian density of modified quark-meson coupling model. The $\Sigma^-$ population with $\delta$ meson is larger than that without $\delta$ meson at the beginning, but it becomes smaller than that without $\delta$ meson as the appearance of $\Xi^-$. The $\delta$ meson has opposite effects on hadronic matter with or without hyperons: it softens the EOSes of hadronic matter with hyperons, while it stiffens the EOSes of pure nucleonic matter. Furthermore, the leptons and the hyperons have the similar influence on $\delta$ meson effects. The $\delta$ meson increases the maximum masses of neutron stars. The influence of $(\sigma^*,\phi)$ on the $\delta$ meson effects are also investigated.Comment: 10 pages, 6 figures, 4 table

Clinical Features of Ehlers-Danlos Syndrome

Background/PurposeEhlers-Danlos syndrome (EDS) is a clinically and genetically heterogeneous connective tissue disorder characterized by hyperextensibility of the skin, hypermobility of joints, and tissue fragility. This retrospective study analyzed the characteristics of patients with EDS.MethodsReview of medical records identified 16 cases of EDS during the study period from November 1997 to October 2002. Data on these patients, including clinical presentation, physical examinations, Beighton score, echocardiogram, bone mineral density findings and clinical classification, were analyzed.ResultsThe age of the patients ranged from 13 months to 36 years. All patients had skin hyperextensibility, joint hypermobility (Beighton score > 5 points), and tissue fragility. Complete bone mineral density study was performed in 11 patients and revealed that all had osteoporosis. Echocardiographic study was performed in 14 patients and showed aortic root dilatation/valve prolapse in 6/14 (43%). Other common features of EDS had the following prevalence: premature rupture of membranes in 3/16 (19%); prematurity in 3/16 (19%); neonatal hypotonia in 5/16 (31%); congenital hip dislocation in 3/16 (19%); unstable gait in 7/16 (44%); bone fracture(s) in 3/16 (19%); motor delay in 3/16 (19%); scoliosis in 3/16 (19%); short stature in 7/16 (44%); and positive family history in 8/16 (50%). All patients had a Beighton score of more than 5 points.ConclusionThe results of this study emphasize the importance of echocardiographic monitoring of aortic size and valvular condition, and assessment of bone mineral density in patients with EDS. Clinical evaluation and counseling should be undertaken prior to pregnancy in patients with EDS because of the risk from labor and vaginal delivery in patients with type IV and the inability to distinguish EDS subtypes in Taiwan due to the unavailability of biochemical assay or molecular mutation analysis as part of standard care