Form factors in lattice QCD

Lattice simulations of QCD have produced precise estimates for the masses of the lowest-lying hadrons which show excellent agreement with experiment. By contrast, lattice results for the vector and axial vector form factors of the nucleon show significant deviations from their experimental determination. We present results from our ongoing project to compute a variety of form factors with control over all systematic uncertainties. In the case of the pion electromagnetic form factor we employ partially twisted boundary conditions to extract the pion charge radius directly from the linear slope of the form factor near vanishing momentum transfer. In the nucleon sector we focus specifically on the possible contamination from contributions of higher excited states. We argue that summed correlation functions offer the possibility of eliminating this source of systematic error. As an illustration of the method we discuss our results for the axial charge, gA, of the nucleon.Comment: 16 pages, 11 figures, presented at Conclusive Symposium, CRC443, "Many-body structure of strongly interacting systems", 23-25 Feb 2011, Mainz, German

Homeownership as social policy in the U.S.: Risk and responsibility after the subprime crisis

Homeownership in the U.S. has been used as a vehicle to promote a variety of political, economic and social goals. After briefly reviewing how these objectives were expressed during key phases of U.S. history, the paper traces the events and decisions that led up to the subprime crisis and assesses the impacts, particularly as they relate to the social goals of homeownership. The paper argues that the various changes that occurred in the U.S. system of mortgage finance system between the 1970s and 2000s have altered traditional conceptualizations of how risks and responsibilities should be carried by homeowners and lenders. This second section lays the groundwork for understanding the extent to which factors pertaining to risk and responsibility have contributed to unraveling or at least damaging the likelihood of realizing the social objectives of homeownership. The third section further explores events in the 1970s, which foreshadowed the types of problems arising from the new set of financial arrangements in the mortgage market. Fourth, the paper discusses deregulation of financial institutions in the 1980s and the key characteristics of the mortgage finance system that took shape in the 1990s. The fifth section describes the key elements of the contemporary mortgage finance system, which has continued on the path that emerged during the 1970s. Sixth, the paper examines the many causes of the subprime crisis and how they came together in a \u93perfect storm.\u94 In the seventh section the paper returns to a discussion of the multiple goals of homeownership and how they have been undermined by the subprime crisis. The eighth and final section concludes with observations about the types of risks and responsibilities that both lenders and homeowners must assume if mortgage lending transactions are to be successful. In particular, in order to achieve the multiple goals of homeownership, specific interventions and safeguards must be instituted that will counter the depersonalized, risk-shifting nature of our contemporar