Effects of intermediate scales on renormalization group running of fermion observables in an SO(10) model

In the context of non-supersymmetric SO(10) models, we analyze the renormalization group equations for the fermions (including neutrinos) from the GUT energy scale down to the electroweak energy scale, explicitly taking into account the effects of an intermediate energy scale induced by a Pati--Salam gauge group. To determine the renormalization group running, we use a numerical minimization procedure based on a nested sampling algorithm that randomly generates the values of 19 model parameters at the GUT scale, evolves them, and finally constructs the values of the physical observables and compares them to the existing experimental data at the electroweak scale. We show that the evolved fermion masses and mixings present sizable deviations from the values obtained without including the effects of the intermediate scale.Comment: Comments: 20 pages, 3 figures. Final version published in JHE

New Constraints (and Motivations) for Abelian Gauge Bosons in the MeV-TeV Mass Range

We survey the phenomenological constraints on abelian gauge bosons having masses in the MeV to multi-GeV mass range (using precision electroweak measurements, neutrino-electron and neutrino-nucleon scattering, electron and muon anomalous magnetic moments, upsilon decay, beam dump experiments, atomic parity violation, low-energy neutron scattering and primordial nucleosynthesis). We compute their implications for the three parameters that in general describe the low-energy properties of such bosons: their mass and their two possible types of dimensionless couplings (direct couplings to ordinary fermions and kinetic mixing with Standard Model hypercharge). We argue that gauge bosons with very small couplings to ordinary fermions in this mass range are natural in string compactifications and are likely to be generic in theories for which the gravity scale is systematically smaller than the Planck mass - such as in extra-dimensional models - because of the necessity to suppress proton decay. Furthermore, because its couplings are weak, in the low-energy theory relevant to experiments at and below TeV scales the charge gauged by the new boson can appear to be broken, both by classical effects and by anomalies. In particular, if the new gauge charge appears to be anomalous, anomaly cancellation does not also require the introduction of new light fermions in the low-energy theory. Furthermore, the charge can appear to be conserved in the low-energy theory, despite the corresponding gauge boson having a mass. Our results reduce to those of other authors in the special cases where there is no kinetic mixing or there is no direct coupling to ordinary fermions, such as for recently proposed dark-matter scenarios.Comment: 49 pages + appendix, 21 figures. This is the final version which appears in JHE

Anniversary of the discovery/isolation of the yeast centromere by Clarke and Carbon

ABSTRACT The first centromere was isolated 35 years ago by Louise Clarke and John Car-bon from budding yeast. They embarked on their journey with rudimentary molecular tools (by today’s standards) and little knowledge of the structure of a chromosome, much less the nature of a centromere. Their discovery opened up a new field, as centromeres have now been isolated from fungi and numerous plants and animals, including mammals. Budding yeast and several other fungi have small centromeres with short, well-defined sequences, known as point centromeres, whereas regional centromeres span several kilobases up to megabases and do not seem to have DNA sequence specificity. Centromeres are at the heart of artificial chromosomes, and we have seen the birth of synthetic centromeres in budding and fission yeast and mammals. The diversity in centromeres throughout phylogeny belie conserved functions that are only beginning to be understood. It was ∼35 years ago that centromere DNA was first discovered by Louise Clarke and John Carbon working at the University of California, Santa Barbara (Clarke and Carbon, 1980, 1985). To ap-preciate the pioneering aspect of this work, it is important to con