Flipped Angles and Phases: A Systematic Study

We discuss systematically the fermion mass and mixing matrices in a generic \linebreak field-theoretical flipped $SU(5)$ model, with particular applications to neutrino and baryon number-changing physics. We demonstrate that the different quark flavour branching ratios in proton decay are related to the Cabibbo-Kobayashi-Maskawa angles, whereas the lepton flavour branching ratios are undetermined. The light neutrino mixing angles observable via oscillation effects are related to the heavy conjugate (right-handed) neutrino mass matrix, which also plays a key role in cosmological baryogenesis. The ratios of neutrino and charged lepton decay modes in baryon decay may also be related to neutrino oscillation parameters. Plausible Ans\"atze for the generation structure of coupling matrices motivate additional relations between physical observables, and yield a satisfactory baryon asymmetry.Comment: 13 pages, no figures, latex (twice), CERN-TH.6842/93, UMN-TH-1130/93, CTP-TAMU-11/9

N=2 Supermultiplet of Currents and Anomalous Transformations in Supersymmetric Gauge Theory

We examine some properties of supermultiplet consisting of the U(1)_{J} current, extended supercurrents, energy-momentum tensor and the central charge in N=2 supersymmetric Yang-Mills theory. The superconformal improvement requires adding another supermultiplet beginning with the U(1)_{R} current. We determine the anomalous (quantum mechanical) supersymmetry transformation associated with the central charge and the energy-momentum tensor to one-loop order.Comment: 8 pages, LaTe

Dual models

The author presents a review of dual models; formulations of the theory; string approach; operator formalism; dual fermions; and ends with a brief discussion of unsolved problems. (52 refs)

Cosmic Chemical Evolution with an Early Population of Intermediate Mass Stars

We explore the consequences of an early population of intermediate mass stars in the 2 - 8 M\odot range on cosmic chemical evolution. We discuss the implications of this population as it pertains to several cosmological and astrophysical observables. For example, some very metal-poor galactic stars show large enhancements of carbon, typical of the C-rich ejecta of low-mass stars but not of supernovae; moreover, halo star carbon and oxygen abundances show wide scatter, which imply a wide range of star-formation and nucleosynthetic histories contributed to the first generations of stars. Also, recent analyses of the 4He abundance in metal-poor extragalactic H II regions suggest an elevated abundance Yp \simeq 0.256 by mass, higher than the predicted result from big bang nucleosynthesis assuming the baryon density determined by WMAP, Yp = 0.249. Although there are large uncertainties in the observational determination of 4He, this offset may suggest a prompt initial enrichment of 4He in early metal-poor structures. We also discuss the effect of intermediate mass stars on global cosmic evolution, the reionization of the Universe, the density of white dwarfs, as well as SNII and SNIa rates at high redshift. We also comment on the early astration of D and 7Li. We conclude that if intermediate mass stars are to be associated with Population III stars, their relevance is limited (primarily from observed abundance patterns) to low mass structures involving a limited fraction of the total baryon content of the Universe.Comment: Submitted to MNRA