Mirror Symmetry and Other Miracles in Superstring Theory

The dominance of string theory in the research landscape of quantum gravity physics (despite any direct experimental evidence) can, I think, be justified in a variety of ways. Here I focus on an argument from mathematical fertility, broadly similar to Hilary Putnam's 'no miracles argument' that, I argue, many string theorists in fact espouse. String theory leads to many surprising, useful, and well-confirmed mathematical 'predictions' - here I focus on mirror symmetry. These predictions are made on the basis of general physical principles entering into string theory. The success of the mathematical predictions are then seen as evidence for framework that generated them. I attempt to defend this argument, but there are nonetheless some serious objections to be faced. These objections can only be evaded at a high (philosophical) price.Comment: For submission to a Foundations of Physics special issue on "Forty Years Of String Theory: Reflecting On the Foundations" (edited by G. `t Hooft, E. Verlinde, D. Dieks and S. de Haro)

Health outcomes of Experience Corps®: A high-commitment volunteer program

10.1016/j.socscimed.2010.04.009Social Science and Medicine712414-420SSMD

Health outcomes of Experience Corps®: A high-commitment volunteer program

Experience Corps® (EC) is a high-commitment US volunteer program that brings older adults into public elementary schools to improve academic achievement of students. It is viewed as a health promotion program for the older volunteers. We evaluated the effects of the EC program on older adults' health, using a quasi-experimental design. We included volunteers from 17 EC sites across the US. They were pre-tested before beginning their volunteer work and post-tested after two years of service. We compared changes over time between the EC participants (n = 167) and a matched comparison group of people from the US Health and Retirement Study (2004, 2006). We developed the comparison group by using the nearest available Mahalanobis metric matching within calipers combined with the boosted propensity scores of those participating in the EC. We corrected for clustering effects via survey regression analyses with robust standard errors and calculated adjusted post-test means of health outcomes, controlling for all covariates and the boosted propensity score of EC participants. We found that compared to the comparison group, the EC group reported fewer depressive symptoms and functional limitations after two years of participation in the program, and there was a statistical trend toward the EC group reporting less decline in self-rated health. Results of this study add to the evidence supporting high-intensity volunteering as a social model of health promotion for older adults.Older people Community-based health promotion Propensity score matching method Volunteer program effect USA Experience Corps