The generation of gravitational waves. 2: The post-linear formalism revisited

Two different versions of the Green's function for the scalar wave equation in weakly curved spacetime (one due to DeWitt and DeWitt, the other to Thorne and Kovacs) are compared and contrasted; and their mathematical equivalence is demonstrated. The DeWitt-DeWitt Green's function is used to construct several alternative versions of the Thorne-Kovacs post-linear formalism for gravitational-wave generation. Finally it is shown that, in calculations of gravitational bremsstrahlung radiation, some of our versions of the post-linear formalism allow one to treat the interacting bodies as point masses, while others do not

Principal Bundles and the Dixmier Douady Class

A systematic consideration of the problem of the reduction and extension of the structure group of a principal bundle is made and a variety of techniques in each case are explored and related to one another. We apply these to the study of the Dixmier-Douady class in various contexts including string structures, U-res bundles and other examples motivated by considerations from quantum field theory.Comment: 28 pages, latex, no figures, uses amsmath, amsthm, amsfonts. Revised version - only change a lot of irritating typos remove

Curbing the HIV Epidemic by Supporting Effective Engagement in HIV Care: Recommendations for Health Plans and Health Care Purchasers

The United States is poised to dramatically reduce the scope of its HIV epidemic, but this demands increased leadership and attention from health plans and health care purchasers (including Medicaid, Medicare, marketplaces, and other private purchasers). This new amfAR report identifies changes in policy and practice in clinics, communities, and health care programs to reduce unnecessary health spending, increase the effectiveness of services, and increase the integration of services. Done right, the same steps that lead to appropriate management of care by health plans and purchasers also will help to achieve national public health goals