Why Are Neutrinos Light? -- An Alternative

We review the recent proposal that neutrinos are light because their masses are proportional to a low scale, f, of lepton flavor symmetry breaking. This mechanism is testable because the resulting pseudo-Goldstone bosons, of mass m_G, couple strongly with the neutrinos, affecting the acoustic oscillations during the eV era of the early universe that generate the peaks in the CMB radiation. Characteristic signals result over a very wide range of (f, m_G) because of a change in the total relativistic energy density and because the neutrinos scatter rather than free-stream. Thermodynamics allows a precise calculation of the signal, so that observations would not only confirm the late-time neutrino mass mechanism, but could also determine whether the neutrino spectrum is degenerate, inverted or hierarchical and whether the neutrinos are Dirac or Majorana. The flavor symmetries could also give light sterile states. If the masses of the sterile neutrinos turn on after the MeV era, the LSND oscillations can be explained without upsetting big bang nucleosynthesis, and, since the sterile states decay to lighter neutrinos and pseudo-Goldstones, without giving too much hot dark matter.Comment: Talk given by LJH at the Fujihara Seminar on Neutrino Mass and Seesaw Mechanism held at KEK, Japan, February 2004. 11 pages, 1 figure, 3 table

Late Time Neutrino Masses, the LSND Experiment and the Cosmic Microwave Background

Models with low-scale breaking of global symmetries in the neutrino sector provide an alternative to the seesaw mechanism for understanding why neutrinos are light. Such models can easily incorporate light sterile neutrinos required by the LSND experiment. Furthermore, the constraints on the sterile neutrino properties from nucleosynthesis and large scale structure can be removed due to the non-conventional cosmological evolution of neutrino masses and densities. We present explicit, fully realistic supersymmetric models, and discuss the characteristic signatures predicted in the angular distributions of the cosmic microwave background.Comment: 4 pages, revtex

Bounded gaps between primes in number fields and function fields

The Hardy--Littlewood prime $k$-tuples conjecture has long been thought to be completely unapproachable with current methods. While this sadly remains true, startling breakthroughs of Zhang, Maynard, and Tao have nevertheless made significant progress toward this problem. In this work, we extend the Maynard-Tao method to both number fields and the function field $\mathbb{F}_q(t)$

Ensemble asteroseismology and hierarchical bayesian models: new inferences of astrophysics with oscillating stars

Asteroseismology – the study of stellar oscillations – is one of the key tools used to study stars in modern astronomy. This thesis focuses on asteroseismology of solar-like oscillators, which exhibit variability driven by the same mechanism as the Sun. By studying variations in the brightness of stars on their surface, asteroseismology probes the full stellar interior, giving insight into stars’ internal processes and fundamental properties. In this thesis, I provide an introduction to asteroseismology and the state of the field. This is followed by a description of asteroseismic analysis tools I developed for the open source Python package ‘Lightkurve’, and a presentation of two studies that use asteroseismology to probe different aspects of astrophysics. The first study uses an asteroseismic ensemble of 5576 evolved Red Clump stars to calibrate data from the Gaia mission, and quantify systematic differences in asteroseismic modelling techniques. The second focuses on 91 main sequence stars like the Sun, using asteroseismology to measure their rotation rates. Along with asteroseismic ages, these new rotation rates are used to quantitatively state that stars experience a change in how they lose angular momentum half-way through their main sequence lifetimes. A common thread throughout both these studies is the use of Bayesian statistics, which allows us to leverage large asteroseismic ensembles to make inferences about adjacent fields of astronomy

Dark Energy and Right-Handed Neutrinos

We explore the possibility that a CP violating phase of the neutrino mass matrix is promoted to a pseudo-Goldstone-boson field and is identified as the quintessence field for Dark Energy. By requiring that the quintessence potential be calculable from a Lagrangian, and that the extreme flatness of the potential be stable under radiative corrections, we are led to an essentially unique model. Lepton number is violated only by Majorana masses of light, right-handed neutrinos, comparable to the Dirac masses that mix right- with left-handed neutrinos. We outline the rich and constrained neutrino phenomenology that results from this proposal.Comment: 10 pages, 2 figure

A four year prospective study of age-related cognitive change in adults with Down's syndrome

Background. While neuropathological studies indicate a high risk for Alzheimer's disease in adults with Down's syndrome, neuropsychological studies suggest a lower prevalence of dementia. In this study, cognitive deterioration in adults with Down's syndrome was examined prospectively over 4 years to establish rates and profiles of cognitive deterioration.Methods. Fifty-seven people with Down's syndrome aged 30 years or older were assessed using a battery of neuropsychological tests on five occasions across 50 months. Assessments of domains of cognitive function known to change with the onset of Alzheimer related dementia were employed. These included tests of learning, memory, orientation, agnosia, apraxia and aphasia. The individual growth trajectory methodology was used to analyse change over time.Results. Severe cognitive deterioration, such as acquired, apraxia and agnosia, was evident in 28·3% of those aged over 30 and a higher prevalence of these impairments was associated with older age. The rate of cognitive deterioration also increased with age and degree of pre-existing cognitive impairment. Additionally, deterioration in memory, learning and orientation preceded the acquisition of aphasia, agnosia and apraxia.Conclusions. The prevalence of cognitive impairments consistent with the presence of Alzheimer's disease is lower than that suggested by neuropathological studies. The pattern of the acquisition of cognitive impairments in adults with Down's syndrome is similar to that seen in individuals with Alzheimer's disease who do not have Down's syndrome.</jats:p