Inflating with Large Effective Fields

We re-examine large scalar fields within effective field theory, in particular focussing on the issues raised by their use in inflationary models (as suggested by BICEP2 to obtain primordial tensor modes). We argue that when the large-field and low-energy regimes coincide the scalar dynamics is most effectively described in terms of an asymptotic large-field expansion whose form can be dictated by approximate symmetries, which also help control the size of quantum corrections. We discuss several possible symmetries that can achieve this, including pseudo-Goldstone inflatons characterized by a coset $G/H$ (based on abelian and non-abelian, compact and non-compact symmetries), as well as symmetries that are intrinsically higher dimensional. Besides the usual trigonometric potentials of Natural Inflation we also find in this way simple {\em large-field} power laws (like $V \propto \phi^2$) and exponential potentials, $V(\phi) = \sum_{k} V_k \; e^{-k \phi/M}$. Both of these can describe the data well and give slow-roll inflation for large fields without the need for a precise balancing of terms in the potential. The exponential potentials achieve large $r$ through the limit $|\eta| \ll \epsilon$ and so predict $r \simeq \frac83(1-n_s)$; consequently $n_s \simeq 0.96$ gives $r \simeq 0.11$ but not much larger (and so could be ruled out as measurements on $r$ and $n_s$ improve). We examine the naturalness issues for these models and give simple examples where symmetries protect these forms, using both pseudo-Goldstone inflatons (with non-abelian non-compact shift symmetries following familiar techniques from chiral perturbation theory) and extra-dimensional models.Comment: 21 pages + appendices, 3 figure

Diverse Aging and Health Inequality by Race and Ethnicity

Although gerontologists have long embraced the concept of heterogeneity in theories and models of aging, recent research reveals the importance of racial and ethnic diversity on life course processes leading to health inequality. This article examines research on health inequality by race and ethnicity and identifies theoretical and methodological innovations that are transforming the study of health disparities. Drawing from cumulative inequality theory, we propose greater use of life course analysis, more attention to variability within racial and ethnic groups, and better integration of environmental context into the study of accumulation processes leading to health disparities

Evidence of magnetic field quenching of phosphorous-doped silicon quantum dots

We present data on the electrical transport properties of highly-doped silicon-on-insulator quantum dots under the effect of pulsed magnetic fields up to 48 T. At low field intensities, B<7 T, we observe a strong modification of the conductance due to the destruction of weak localization whereas at higher fields, where the magnetic field length becomes comparable to the effective Bohr radius of phosphorous in silicon, a strong decrease in conductance is demonstrated. Data in the high and low electric field bias regimes are then compared to show that close to the Coulomb blockade edge magnetically-induced quenching to single donors in the quantum dot is achieved at about 40 T.Comment: accepted for publication at Current Applied Physic

Effect of external conditions on the structure of scrolled graphene edges

Characteristic dimensions of carbon nanoscrolls - "buckyrolls" - are calculated by analyzing the competition between elastic, van der Waals, and electrostatic energies for representative models of suspended and substrate-deposited graphene samples. The results are consistent with both atomistic simulations and experimental observations of scrolled graphene edges. Electrostatic control of the wrapping is shown to be practically feasible and its possible device applications are indicated.Comment: 4 pages, 3 figure

The Dust Properties of Eight Debris Disk Candidates as Determined by Submillimeter Photometry

The nature of far-infrared dust emission toward main sequence stars, whether interstellar or circumstellar, can be deduced from submillimeter photometry. We present JCMT/SCUBA flux measurements at 850 microns toward 8 stars with large photospheric excesses at 60-100 microns. 5 sources were detected at 3-sigma or greater significance and one was marginally detected at 2.5-sigma. The inferred dust masses and temperatures range from 0.033 to 0.24 Earth masses and 43-65 K respectively. The frequency behavior of the opacity, tau_nu ~ nu^beta, is relatively shallow, beta < 1. These dust properties are characteristic of circumstellar material, most likely the debris from planetesimal collisions. The 2 non-detections have lower temperatures, 35-38 K and steeper opacity indices, beta > 1.5, that are more typical of interstellar cirrus. The confirmed disks all have inferred diameters > 2'', most lie near the upper envelope of the debris disk mass distribution, and 4 are bright enough to be feasible for high resolution imaging.Comment: accepted by Ap