Non-perturbative computation of the bubble nucleation rate in the cubic anisotropy model

At first order phase transitions the transition proceeds through droplet nucleation and growth. We discuss a lattice method for calculating the droplet nucleation rate, including the complete dynamical factors. The method is especially suitable for very strongly suppressed droplet nucleation, which is often the case in physically interesting transitions. We apply the method to the 3-dimensional cubic anisotropy model in a parameter range where the model has a radiatively induced strong first order phase transition, and compare the results with analytical approaches

Constraints on self-interacting Q-ball dark matter

We consider different types of Q-balls as self-interacting dark matter. For the Q-balls to act as the dark matter of the universe they should not evaporate, which requires them to carry very large charges; depending on the type, the minimum charge could be as high as Q \sim 10^{33} or the Q-ball coupling to ordinary matter as small as \sim 10^{-35}. The cross-section-to-mass ratio needed for self-interacting dark matter implies a mass scale of m \sim O(1) MeV for the quanta that the Q-balls consist of, which is very difficult to achieve in the MSSM.Comment: 13 pages, 2 figure

Fast Electroweak Symmetry Breaking and Cold Electroweak Baryogenesis

We construct a model for delayed electroweak symmetry breaking that takes place in a cold Universe with T<<100 GeV and which proceeds by a fast quench rather than by a conventional, slow, phase transition. This is achieved by coupling the Standard Model Higgs to an additional scalar field. We show that the quench transition can be made fast enough for successful Cold Electroweak Baryogenesis, while leaving known electroweak physics unchanged.Comment: 13 pages, 5 figures. Section and extra checks added, conclusions unchanged. Published versio

Disparities in physical activity resource availability in six US regions

We conducted an ecologic study to determine physical activity resource availability overall and by sociodemographic groups in parts of six states (CA, IL, MD, MN, NC, NY). Data on parks and recreational facilities were collected from 3 sources in 2009–2012. Three measures characterized park and recreational facility availability at the census tract level: presence of ≥1 resource, number of resources, and resource kernel density. Associations between resource availability and census tract characteristics (predominant racial/ethnic group, median income, and proportion of children and older adults) were estimated using linear, binomial, and zero-inflated negative binomial regression in 2014. Pooled and stratified analyses were conducted. The study included 7,139 census tracts, comprising 9.5% of the 2010 US population. Overall the availability of parks and recreational facilities was lower in predominantly minority relative to non-Hispanic white census tracts. Low-income census tracts and those with a higher proportion of children had an equal or greater availability of park resources but fewer recreational facilities. Stratification revealed substantial variation in resource availability by state. The availability of physical activity resources varied by sociodemographic characteristics and across regions. Improved knowledge of resource distribution can inform strategies to provide equitable access to parks and recreational facilities

Classical Sphaleron Rate on Fine Lattices

We measure the sphaleron rate for hot, classical Yang-Mills theory on the lattice, in order to study its dependence on lattice spacing. By using a topological definition of Chern-Simons number and going to extremely fine lattices (up to beta=32, or lattice spacing a = 1 / (8 g^2 T)) we demonstrate nontrivial scaling. The topological susceptibility, converted to physical units, falls with lattice spacing on fine lattices in a way which is consistent with linear dependence on $a$ (the Arnold-Son-Yaffe scaling relation) and strongly disfavors a nonzero continuum limit. We also explain some unusual behavior of the rate in small volumes, reported by Ambjorn and Krasnitz.Comment: 14 pages, includes 5 figure

Neighborhood Social Resources and Depressive Symptoms: Longitudinal Results from the Multi-Ethnic Study of Atherosclerosis

The ways in which a neighborhood environment may affect depression and depressive symptoms have not been thoroughly explored. This study used longitudinal data from 5475 adults in the Multi-Ethnic Study of Atherosclerosis to investigate associations of time-varying depressive symptoms between 2000 and 2012 (measured using the 20-item Center for Epidemiologic Studies Depression Scale (CES-D)) with survey-based measures of neighborhood safety and social cohesion (both individual-level perceptions and neighborhood-level aggregates) and densities of social engagement destinations. Linear mixed models were used to examine associations of baseline cross-sectional associations and cumulative exposures with changes over time in CES-D. Econometric fixed effects models were utilized to investigate associations of within-person changes in neighborhood exposures with within-person changes in CES-D. Adjusting for relevant covariates, higher safety and social cohesion and greater density of social engagement destinations were associated with lower CES-D at baseline. Greater cumulative exposure to these features was not associated with progression of CES-D over 10 years. Within-person increases in safety and in social cohesion were associated with decreases in CES-D, although associations with cohesion were not statistically significant. Social elements of neighborhoods should be considered by community planners and public health practitioners to achieve optimal mental health

Walkability and cardiometabolic risk factors: Cross-sectional and longitudinal associations from the Multi-Ethnic Study of Atherosclerosis

We used data from 3,227 older adults in the Multi-Ethnic Study of Atherosclerosis (2004–2012) to explore cross-sectional and longitudinal associations between walkability and cardiometabolic risk factors. In cross-sectional analyses, linear regression was used to estimate associations of Street Smart Walk Score® with glucose, triglycerides, HDL and LDL cholesterol, systolic and diastolic blood pressure, and waist circumference, while logistic regression was used to estimate associations with odds of metabolic syndrome. Econometric fixed effects models were used to estimate longitudinal associations of changes in walkability with changes in each risk factor among participants who moved residential locations between 2004 and 2012 (n=583). Most cross-sectional and longitudinal associations were small and statistically non-significant. We found limited evidence that higher walkability was cross-sectionally associated with lower blood pressure but that increases in walkability were associated with increases in triglycerides and blood pressure over time. Further research over longer time periods is needed to understand the potential for built environment interventions to improve cardiometabolic health

Built environment change and change in BMI and waist circumference: Multi‐ethnic S tudy of A therosclerosis

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109571/1/oby20873.pd

A truncation allele in vascular endothelial growth factor c reveals distinct modes of signaling during lymphatic and vascular development

Vascular endothelial growth factor C (Vegfc) is a secreted protein that guides lymphatic development in vertebrate embryos. However, its role during developmental angiogenesis is not well characterized. Here, we identify a mutation in zebrafish vegfc that severely affects lymphatic development and leads to angiogenesis defects on sensitized genetic backgrounds. The um18 mutation prematurely truncated Vegfc, blocking its secretion and paracrine activity but not its ability to activate its receptor Flt4. When expressed in endothelial cells, vegfc(um18) could not rescue lymphatic defects in mutant embryos, but induced ectopic blood vessel branching. Furthermore, vegfc-deficient endothelial cells did not efficiently contribute to tip cell positions in developing sprouts. Computational modeling together with assessment of endothelial cell dynamics by time-lapse analysis suggested that an autocrine Vegfc/Flt4 loop plays an important role in migratory persistence and filopodia stability during sprouting. Our results suggest that Vegfc acts in two distinct modes during development: as a paracrine factor secreted from arteries to guide closely associated lymphatic vasculature and as an autocrine factor to drive migratory persistence during angiogenesis

Electroweak Bubble Nucleation, Nonperturbatively

We present a lattice method to compute bubble nucleation rates at radiatively induced first order phase transitions, in high temperature, weakly coupled field theories, nonperturbatively. A generalization of Langer's approach, it makes no recourse to saddle point expansions and includes completely the dynamical prefactor. We test the technique by applying it to the electroweak phase transition in the minimal standard model, at an unphysically small Higgs mass which gives a reasonably strong phase transition (lambda/g^2 =0.036, which corresponds to m(Higgs)/m(W) = 0.54 at tree level but does not correspond to a positive physical Higgs mass when radiative effects of the top quark are included), and compare the results to older perturbative and other estimates. While two loop perturbation theory slightly under-estimates the strength of the transition measured by the latent heat, it over-estimates the amount of supercooling by a factor of 2.Comment: 48 pages, including 16 figures. Minor revisions and typo fixes, nothing substantial, conclusions essentially unchange