Localisation and colocalisation of KK-theory at sets of primes

Given a set of prime numbers S, we localise equivariant bivariant Kasparov theory at S and compare this localisation with Kasparov theory by an exact sequence. More precisely, we define the localisation at S to be KK^G(A,B) tensored with the ring of S-integers Z[S^-1]. We study the properties of the resulting variants of Kasparov theory.Comment: 16 page

Using Administrative Data to Explore the Effect of Survey Nonresponse in the UK Employment Retention and Advancement Demonstration

Background: Even a well-designed randomized control trial (RCT) study can produce ambiguous results. This paper highlights a case in which full-sample results from a large-scale RCT in the United Kingdom (UK) differ from results for a sub-sample of survey respondents. Objectives: Our objective is to ascertain the source of the discrepancy in inferences across data sources and, in doing so, to highlight important threats to the reliability of the causal conclusions derived from even the strongest research designs. Research design: The study analyzes administrative data to shed light on the source of the differences between the estimates. We explore the extent to which heterogeneous treatment impacts and survey non-response might explain these differences. We suggest checks which assess the external validity of survey measured impacts, which in turn provides an opportunity to test the effectiveness of different weighting schemes to remove bias. The Subjects included 6,787 individuals who participated in a large-scale social policy experiment. Results: Our results were not definitive but suggest non-response bias is the main source of the inconsistent findings. Conclusions. The results caution against overconfidence in drawing conclusions from RCTs and highlight the need for great care to be taken in data collection and analysis. Particularly, given the modest size of impacts expected in most RCTs, small discrepancies in data sources can alter the results. Survey data remain important as a source of information on outcomes not recorded in administrative data. However, linking survey and administrative data is strongly recommended whenever possible

Vanishing Viscosity Limits and Boundary Layers for Circularly Symmetric 2D Flows

We continue the work of Lopes Filho, Mazzucato and Nussenzveig Lopes [LMN], on the vanishing viscosity limit of circularly symmetric viscous flow in a disk with rotating boundary, shown there to converge to the inviscid limit in $L^2$-norm as long as the prescribed angular velocity $\alpha(t)$ of the boundary has bounded total variation. Here we establish convergence in stronger $L^2$ and $L^p$-Sobolev spaces, allow for more singular angular velocities $\alpha$, and address the issue of analyzing the behavior of the boundary layer. This includes an analysis of concentration of vorticity in the vanishing viscosity limit. We also consider such flows on an annulus, whose two boundary components rotate independently. [LMN] Lopes Filho, M. C., Mazzucato, A. L. and Nussenzveig Lopes, H. J., Vanishing viscosity limit for incompressible flow inside a rotating circle, preprint 2006

The Baum-Connes Conjecture via Localisation of Categories

We redefine the Baum-Connes assembly map using simplicial approximation in the equivariant Kasparov category. This new interpretation is ideal for studying functorial properties and gives analogues of the assembly maps for all equivariant homology theories, not just for the K-theory of the crossed product. We extend many of the known techniques for proving the Baum-Connes conjecture to this more general setting

Desingularization of vortices for the Euler equation

We study the existence of stationary classical solutions of the incompressible Euler equation in the plane that approximate singular stationnary solutions of this equation. The construction is performed by studying the asymptotics of equation -\eps^2 \Delta u^\eps=(u^\eps-q-\frac{\kappa}{2\pi} \log \frac{1}{\eps})_+^p with Dirichlet boundary conditions and $q$ a given function. We also study the desingularization of pairs of vortices by minimal energy nodal solutions and the desingularization of rotating vortices.Comment: 40 page

Finitely-Generated Projective Modules over the Theta-deformed 4-sphere

We investigate the "theta-deformed spheres" C(S^{3}_{theta}) and C(S^{4}_{theta}), where theta is any real number. We show that all finitely-generated projective modules over C(S^{3}_{theta}) are free, and that C(S^{4}_{theta}) has the cancellation property. We classify and construct all finitely-generated projective modules over C(S^{4}_{\theta}) up to isomorphism. An interesting feature is that if theta is irrational then there are nontrivial "rank-1" modules over C(S^{4}_{\theta}). In that case, every finitely-generated projective module over C(S^{4}_{\theta}) is a sum of a rank-1 module and a free module. If theta is rational, the situation mirrors that for the commutative case theta=0.Comment: 34 page

Viewpoint: Estimating the causal effects of policies and programs

Estimation, inference and interpretation of the causal effects of programs and policies have all advanced dramatically over the past 25 years. We highlight three particularly important intellectual trends: an improved appreciation of the substantive importance of heterogeneous responses and of their methodological implications, a stronger focus on internal validity brought about by the “credibility revolution,” and the scientific value that follows from grounding estimation and interpretation in economic theory. We discuss a menu of commonly employed partial equilibrium approaches to the identification of causal effects, emphasizing that the researcher’s central intellectual contribution always consists of making an explicit case for a specific causal interpretation given the relevant economic theory, the data, the institutional context and the economic question of interest. We also touch on the importance of general equilibrium effects and full cost–benefit analyses.RésuméPoint de vue: Sur l’estimation des effets causatifs des politiques et programmes. Dans le monde de l’estimation, l’inférence et l’interprétation des effets causatifs des programmes et des politiques, il y a eu des progrès dramatiques au cours des derniers 25 ans. Les auteurs soulignent trois tendances intellectuelles particulièrement importantes : une appréciation améliorée de l’importance substantielle des réponses hétérogènes et de leur importance méthodologique, une focalisation plus robuste sur la validité interne engendrée par la « révolution de la crédibilité », et la valeur scientifique qui découle d’un ancrage de l’estimation et de l’interprétation dans la théorie économique. On discute un éventail d’approches d’équilibre partiel à l’identification des effets causatifs, mettant au premier plan que la contribution intellectuelle centrale du chercheur consiste à bâtir un argumentaire explicite pour une interprétation causale spécifique compte tenu de la théorie économique pertinente, des données, du contexte institutionnel, et de la question économique d’intérêt. On mentionne aussi l’importance des effets d’équilibre général et des analyses de tous les coûts et avantages.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134884/1/caje12217.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134884/2/caje12217_am.pd

The geometry of a vorticity model equation

We provide rigorous evidence of the fact that the modified Constantin-Lax-Majda equation modeling vortex and quasi-geostrophic dynamics describes the geodesic flow on the subgroup of orientation-preserving diffeomorphisms fixing one point, with respect to right-invariant metric induced by the homogeneous Sobolev norm $H^{1/2}$ and show the local existence of the geodesics in the extended group of diffeomorphisms of Sobolev class $H^{k}$ with $k\ge 2$.Comment: 24 page

Gorenstein homological algebra and universal coefficient theorems

We study criteria for a ring—or more generally, for a small category—to be Gorenstein and for a module over it to be of finite projective dimension. The goal is to unify the universal coefficient theorems found in the literature and to develop machinery for proving new ones. Among the universal coefficient theorems covered by our methods we find, besides all the classic examples, several exotic examples arising from the KK-theory of C*-algebras and also Neeman’s Brown–Adams representability theorem for compactly generated categories

Boys are victims, too: the influence of perpetrators’ age and gender in sexual coercion against boys

Sexual coercion among adolescent boys in South Africa is an underresearched topic despite the frequency of such events. Although quantitative research has illuminated the prevalence of sexual coercion toward boys, it has provided little understanding of the context of sexual coercion for adolescent boys. Given the often severe consequences of sexual coercion, it is important to further understand these experiences to inform prevention efforts. The current study aims to provide a more nuanced understanding of the context of sexual coercion. Data come from the baseline assessment for a translational research evaluation of a school-based intervention. The current study focuses on a subset of early and middle adolescent boys who reported experiencing sexual coercion (n = 223). Analyses examine boys’ reports of their perpetrators’ characteristics and details about the sexual coercion encounter. Logistic regression is used to examine how coercion tactics used by the perpetrator differs depending on the perpetrator’s age and gender. Eighth-grade boys were most likely to report that their perpetrator was a similar-aged female and that perpetrator’s age played a particularly important role in what tactics were used. Adult perpetrators were more likely to use physical force, threaten them, harass them electronically, and drink or use drugs at the time. Results provide important insight into boys’ experiences of sexual coercion that have implications for both future research and intervention efforts. Although much research is needed on the topic, intervention programs should recognize that both male and female adolescents can be victim and perpetrator