Branes, U-folds and hyperelliptic fibrations

We construct a class of supersymmetric vacua of type IIB string theory describing systems of three- and seven-branes non-perturbatively completed by brane instantons. The vacua are specified by a set of holomorphic functions defined over a complex plane up to non-trivial U-duality monodromies around the brane locations. In the simplest setting, the solutions can be seen as a generalization of F-theory elliptic fibrations, where the torus fiber is replaced by a genus two Riemann surface with periods encoding the information on the axio-dilaton, the warp factor and the NS-NS and R-R fluxes.Comment: 49 pages, including 22 pages of Appendix, 2 figures. Minor change

Understanding the Role of Social Factors in Farmworker Housing and Health

Differences in social advantage significantly influence health conditions and life expectancy within any population. Such factors reproduce historic class, race, and ethnic disparities in community success. Few populations in the United States face more social and economic disadvantage than farmworkers, and farmworker housing has significant potential to ameliorate or amplify the health impact of those disadvantages. Drawing on the limited direct research on farmworkers, and on additional research about poor, isolated, and immigrant societies, we propose four mechanisms through which housing can be expected to affect farmworker health: quality of social capital within farmworker communities, stress effects of poor housing situations, effects of housing on social support for healthy behaviors, and interactions among these factors, especially effects on children that can last for generations. Policy and planning definitions of adequate farmworker housing should take a more holistic view of housing needs to support specific social and community benefits in design decisions. The Author(s) 2015