The Projective Unitary Irreducible Representations of the Poincar\'e Group in 1+2 Dimensions

We give a complete analysis of the projective unitary irreducible representations of the Poincar\'e group in 1+2 dimensions applying Mackey theorem and using an explicit formula for the universal covering group of the Lorentz group in 1+2 dimensions. We provide explicit formulae for all representations.Comment: 22 pages, PLAIN-TE

Toward a theory of music information retrieval queries: System design implications

This paper analyzes a set of 161 music-related information requests posted to the rec.music.country.old-time newsgroup. These postings are categorized by the types of detail used to characterize the poster's information need, the type of music information requested, the intended use for the information, and additional social and contextual elements present in the postings. The results of this analysis suggest that similar studies of 'native' music information requests can be used to inform the design of effective, usable music information retrieval interfaces

Variability in Plio-Pleistocene climates, habitats, and ungulate biomass in southern Africa

Vrba, and deMenocal and Bloemendal have emphasised the importance of climatic change, particularly temperature, in the context of evolution on the African continent within the past 5 million years. There is no doubt that long-term changes in climate would have affected African habitats, which in turn would have affected the distribution and abundance of populations of various mammalian taxa, including ungulates and hominids. In this study we explore relationships between oxygen isotope ratios (as determined from Shackleton's analysis of foraminifera from deep-sea cores), and estimates of ungulate biomass as determined from faunal assemblages from Plio-Pleistocene sites in southern Africa, using an approach outlined previously. We go further to assess temporal variability in ungulate biomass in terms of changes in habitat, gene pools and hominid evolutio

Response of the West African Monsoon to the Madden–Julian Oscillation

Observations show that rainfall over West Africa is influenced by the Madden-Julian Oscillation (MJO). A number of mechanisms have been suggested: 1) forcing by equatorial waves; 2) enhanced monsoon moisture supply; and 3) increased African easterly wave (AEW) activity. However, previous observational studies are not able to unambiguously distinguish between cause and effect. Carefully designed model experiments are used to assess these mechanisms. Intraseasonal convective anomalies over West Africa during the summer monsoon season are simulated in an atmosphere-only global circulation model as a response to imposed sea surface temperature (SST) anomalies associated with the MJO over the equatorial warm pool region. 1) Negative SST anomalies stabilize the atmosphere leading to locally reduced convection. The reduced convection leads to negative midtropospheric latent heating anomalies that force dry equatorial waves. These waves propagate eastward (Kelvin wave) and westward (Rossby wave), reaching Africa approximately 10 days later. The associated negative temperature anomalies act to destabilize the atmosphere, resulting in enhanced monsoon convection over West and central Africa. The Rossby waves are found to be the most important component, with associated westward-propagating convective anomalies over West Africa. The eastward-propagating equatorial Kelvin wave also efficiently triggers convection over the eastern Pacific and Central America, consistent with observations. 2) An increase in boundary layer moisture is found to occur as a result of the forced convective anomalies over West Africa rather than a cause. 3) Increased shear on the African easterly jet, leading to increased AEW activity, is also found to occur as a result of the forced convective anomalies in the model

The Impact of Globalization on Women: Testing Vandana Shiva’s Critique of Development

Vandana Shiva argues that through the masculinization of agriculture globalization has turned nature and women into passive fields for sowing. Shiva’s critique that international trade, and globalization more generally, has undermined the social and economic position of women in less developed countries provides a wealth of testable hypotheses. For example, Shiva’s argument implies that gender earnings inequality is higher in countries that are more integrated into the world economy, ceteris paribus. After summarizing her argument, we test this hypothesis through cross-sectional regression analysis.Gender Earnings Inequality; Vandana Shiva; Kuznets Curve

Identifying Endogenous Peer Effects in the Spread of Obesity

Recent research in the New England Journal of Medicine (NEJM) purports to show the existence of peer effects in the spread of obesity. Using a dataset of 5124 residents from Framingham, Massachusetts spanning the years 1971 to 2003, the authors show correlations between own weight gain and friends’ and relatives’ weight gain over this period. They find, furthermore, that these results are strongest for males and weaker for females. We use the Adolescent Health Survey, a nationally representative dataset of seventh through twelfth graders in 1994 and 1996 to examine the effect of peers on weight gain. Despite the differences in the samples, we are able to replicate the pattern of results in the NEJM study. However the results are not robust to alternative definitions of the outcome variable. Furthermore, due to the various identification issues that are unresolved in both this and the NEJM paper, we conclude that the evidence for contagion effects in the spread of obesity is only suggestive at best.Peer effects, obesity, adolescent health

Bad Apples, Goody Two Shoes and Average Joes: The Role of Peer Group Definitions in Estimation of Peer Effects

The potential influence of peers and social networks on individual outcomes is important to a variety of educational policy debates including school vouchers, special education, middle school grade configurations and tracking. Researchers usually address the identification problems associated with credibly estimating peer effects in these settings but often do not account for ad-hoc definitions of peer-groups. In this paper, we use extensive information on peer groups to demonstrate that accurate definitions of the peer network seriously impact estimation of peer effects. We estimate the effect of peers’ smoking, drinking, sexual behavior and educational achievement on a teen’s propensity to engage in like-minded behavior and address the major identification problems that plague estimation of these effects.Peer Effects, Education, Adolescent Health