The surface charges associated with the symmetries of asymptotically flat four dimensional spacetimes at null infinity are constructed. They realize the symmetry algebra in general only up to a field-dependent central extension that satisfies a suitably generalized cocycle condition. This extension vanishes when using the globally well defined BMS algebra. For the Kerr black hole and the enlarged BMS algebra with both supertranslations and superrotations, some of the supertranslation charges diverge whereas there are no divergences for the superrotation charges. The central extension is proportional to the rotation parameter and involves divergent integrals on the sphere.

BMS charge algebra

for mildew. After the rainy season comes the dust, especially in the rural areas where there are no paved roads, and the heat which reaches its peak during April and May. Government employees work only during morning hours in this period. The people are hospitable and family ties are very strong. Orphans, halforphans, and old people are well cared for by their own relatives or families. The team assigned to the Demonstration Area and Training Center works under the supervision of the director of the Institute of Hygiene. It includes a manager, health officer, school physician, dental health officer, health educator and nutritionist, nurse supervisor and a staff of five public health nurses, social worker, sanitary inspector, a clerical staff, and drivers. When the WHO maternal and child health consultant and the nurse-supervisor arrived in Quezon, the other member of the team had already completed a house-to-house survey of 18,000 people living in the demonstration area. The team had learned the conditions under which people live, their attitudes and beliefs and, most necessary of all, their needs. The service given in the health centers was mainly curative. Opportunities for health teaching were seldom utilized and the system of record keeping was very time-consuming. UNICEF had agreed to provide supplies and equipment but the Filipinos had been too modest in their requests and the supplies were far from adequate to meet the needs of the proposed service. A new requisition list was therefore drawn up and the most essential equipment was borrowed from other sources so that work in the centers could be improved. The Quezon City Health Department retained responsibility fore providing public health service to the community, while the Rural Health Demonstration and Training Center assumed responsibility for directing and supervising the training program, and helping to elevate the standards of the public health services. The two organizations agreed to participate jointly in carrying out the training program. In each center, one day was set aside for antepartum clinics and another day was designated for chiId health conferences. Procedures were worked out gradually. A nurse of the demonstration team was assigned to each health center or subcenter, in A health demonstration center with a well-

With WHO in the Philippines.

Ideal observational cosmology

The surface charges associated with the symmetries of asymptotically flat four dimensional spacetimes at null infinity are constructed. They realize the symmetry algebra in general only up to a field-dependent central extension that satisfies a suitably generalized cocycle condition. This extension vanishes when using the globally well defined BMS algebra. For the Kerr black hole and the enlarged BMS algebra with both supertranslations and superrotations, some of the supertranslations charges diverge whereas there are no divergences for the superrotation charges. The central extension is proportional to the rotation parameter and involves divergent integrals on the sphere.

To any space time a boundary is attached on which incomplete geodesics terminate as well as inextensible timelike curves of finite length and bounded acceleration. The construction is free ofad hoc assumptions concerning the topology of the boundary and the identification of curves defining the same boundary point. Moreover it is a direct generalization of the Cauchy completion of positive definite Riemannian spaces.

A new definition of singular points in general relativity

A direct connection between the spin and conformally weighted functions on the sphere and geometric objects in Minkowski space is established through the isomorphism of the conformal group of the sphere to the restricted Lorentz group. It is shown that with the use of these functions one can duplicate all the standard work on the representations of the Lorentz group. It is shown further that these functions can be used to obtain a generalization of the classical equations of motion in which internal degrees of freedom arise naturally.

The Lorentz Group and the Sphere

Motion and structure of singularities in general relativity

This, the second paper in a series on the motion and structure of a class of (elementary) singularities, extends the earlier work on ``free'' singularities to the interaction of these singularities with ``background'' gravitational and electromagnetic fields. The principle result is an unusual derivation of the Lorentz‐Dirac equations of motion for a charged particle. The results do not depend on any ad hoc assumptions nor upon any renormalization, but follow uniquely from the Einstein‐Maxwell equations applied to the elementary singularities. A concomitant result is the time evolution of the structure of the singularity.

Motion and Structure of Singularities in General Relativity. II.

Equations of motion and the structure of singularities.

Roger Posadas is Professor of Physics and Technology Management, Technology Management Centre, University of the Philippines, Diliman, 1101 Quezon City, Philippines. SINCE THE END of World War II, when the decolonisation of the Third World began, and the emergence of newly independent nations ensued, the assimilation of modern science and technology (S&T) in the less developed countries has been increasingly recognised as critically important to national development. Hence, for the past half century, there have arisen various national and international studies and debates on science and technology policies, technology transfers, appropriate technologies, impacts of science and technology on society, and other topics in the area of science, technology and society. Today, more than ever before, science and technology have been affecting the shape and course of society so significantly and pervasively that human civilisation is said to be on the threshold of a ’tech-

R. Posadas

Papers

The Lorentz Group and the Sphere

Motion and structure of singularities in general relativity

Motion and Structure of Singularities in General Relativity. II.

Equations of motion and the structure of singularities.

The Development of Science and Technology in South-East Asia: Status and Prospects: