Combinatorial Differential Forms

We extend to a scheme-theoretic context the notion of a combinatorial differential form, due to A.Kock in the framework of synthetic differential geometry. We show that group-valued combinatorial forms on a scheme may be identified, under very general hypotheses, with traditional Lie algebra-valued differential forms, and that their Lie algebra structure can be recovered from first principles. Some basic results from differential geometry (Maurer-Cartan equation, Bianchi identity), as well as a higher analogue, are obtained by exploiting this identification.Comment: LaTeX, 49 pages, uses xy-Pi

Current flight test experience related to structural divergence of forward-swept wings

Flight testing the X-29A forward-swept wing aircraft has required development of new flight test techniques to accomplish subcritical extrapolations to the actual structural divergence dynamic pressure of the aircraft. This paper provides current experience related to applying these techniques to analysis of flight data from the forward-swept wing in order to assess the applicability of these techniques to flight test data. The measurements required, maneuvers flown, and flight test conditions are described. Supporting analytical predictions for the techniques are described and the results using flight data are compared to these predictions. Use of the results during envelope expansion and the resulting modifications to the techniques are discussed. Some of the analysis challenges that occurred are addressed and some preliminary conclusions and recommendations are made relative to the usefulness of these techniques in the flight test environment

The Economics of Climate Change

Global climate change poses a threat to the well-being of humans and other living things through impacts on ecosystem functioning, biodiversity, capital productivity, and human health. Climate change economics attends to this issue by offering theoretical insights and empirical findings relevant to the design of policies to reduce, avoid, or adapt to climate change. This economic analysis has yielded new estimates of mitigation benefits, improved understanding of costs in the presence of various market distortions or imperfections, better tools for making policy choices under uncertainty, and alternate mechanisms for allowing flexibility in policy responses. These contributions have influenced the formulation and implementation of a range of climate change policies at the domestic and international levels.climate change, global warming, energy

Inter-Industry Wage Differences and Theories of Wage Determination

Numerous studies have shown large differences in wages for apparently similar workers across industries. These findings pose a challenge to standard model s of labor market behavior. A problem with past studies of industry wage differences is that they have failed to distinguish between union and nonunion workers. Many economists may expect union workers wages to be set in a noncompetitive fashion but would be surprised if nonunion wages were. We examine the differences in wages across industries for both union and nonunion workers. We find that even after controlling for a wide range of personal characteristics and geographic location large wage differences persist for both union and nonunion workers. Furthermore the premiums of union and nonunion workers are highly correlated. We review past studies which demonstrate that industry wage premiums are also highly correlated across countries and have been very similar over many decades. We present new evidence that the wages of different occupations are highly correlated across industries -- that is if any occupation in an industry is highly paid all occupations are. We also review the evidence which suggests that people who move from low to high paying industries receive a large fraction of the industry wage premium and that those who move from high to low paying industries lose the premium. Finally, we review the evidence on the correlates of industry wage differences. Quit rates, human capital variables, capital labor ratios and market power measures are all positively correlated with industry wage differences individually though the data are not adequate to determine their independent contributions in multiple regression. On the basis of all the evidence we conclude that standard labor market clearing models can not easily explain all the facts. Several alternative models are discussed including efficiency wage and collective action threat mode1 s. These are found to be more consistent with the facts though some troubling problems remain.

The Economics of Climate Change

Global climate change poses a threat to the well-being of humans and other living things through impacts on ecosystem functioning, biodiversity, capital productivity, and human health. This paper briefly surveys recent research on the economics of climate change, including theoretical insights and empirical findings that offer guidance to policy makers. Section 1 frames the climate change problem and indicates the ways that economic research can address it. Section 2 describes approaches to measuring the benefits and costs associated with reducing greenhouse gas emissions. In Section 3 we discuss the implications of uncertainty for the timing and stringency of policies to address possible climate change. We then present issues related to policy design, including instrument choice (Section 4), flexibility (Section 5), and international coordination (Section 6). The final section offers general conclusions.