32,110 research outputs found
Struggling to a monumental triumph : Re-assessing the final stages of the smallpox eradication program in India, 1960-1980
The global smallpox program is generally presented as the brainchild of a handful of actors from the WHO headquarters in Geneva and at the agency's regional offices. This article attempts to present a more complex description of the drive to eradicate smallpox. Based on the example of India, a major focus of the campaign, it is argued that historians and public health officials should recognize the varying roles played by a much wider range of participants. Highlighting the significance of both Indian and international field officials, the author shows how bureaucrats and politicians at different levels of administration and society managed to strengthen—yet sometimes weaken—important program components. Centrally dictated strategies developed at WHO offices in Geneva and New Delhi, often in association with Indian federal authorities, were reinterpreted by many actors and sometimes changed beyond recognition
Pieces of nilpotent cones for classical groups
We compare orbits in the nilpotent cone of type , that of type ,
and Kato's exotic nilpotent cone. We prove that the number of \F_q-points in
each nilpotent orbit of type or equals that in a corresponding
union of orbits, called a type- or type- piece, in the exotic nilpotent
cone. This is a finer version of Lusztig's result that corresponding special
pieces in types and have the same number of \F_q-points. The
proof requires studying the case of characteristic 2, where more direct
connections between the three nilpotent cones can be established. We also prove
that the type- and type- pieces of the exotic nilpotent cone are smooth
in any characteristic.Comment: 32 page
Geometric Satake, Springer correspondence, and small representations II
For a split reductive group scheme over a commutative ring with Weyl
group , there is an important functor defined by
taking the zero weight space. We prove that the restriction of this functor to
the subcategory of small representations has an alternative geometric
description, in terms of the affine Grassmannian and the nilpotent cone of the
Langlands dual group to . The translation from representation theory to
geometry is via the Satake equivalence and the Springer correspondence. This
generalizes the result for the case proved by the first two
authors, and also provides a better explanation than in that earlier paper,
since the current proof is uniform across all types.Comment: Version 4: minor revisions; 73 page
Normality of orbit closures in the enhanced nilpotent cone
We continue the study of the closures of -orbits in the enhanced
nilpotent cone V\times\cN begun by the first two authors. We prove that each
closure is an invariant-theoretic quotient of a suitably-defined enhanced
quiver variety. We conjecture, and prove in special cases, that these enhanced
quiver varieties are normal complete intersections, implying that the enhanced
nilpotent orbit closures are also normal.Comment: 30 page
Modular generalized Springer correspondence: an overview
This is an overview of our series of papers on the modular generalized
Springer correspondence. It is an expansion of a lecture given by the second
author in the Fifth Conference of the Tsinghua Sanya International Mathematics
Forum, Sanya, December 2014, as part of the Master Lecture `Algebraic Groups
and their Representations' Workshop honouring G. Lusztig. The material that has
not appeared in print before includes some discussion of the motivating idea of
modular character sheaves, and heuristic remarks about geometric functors of
parabolic induction and restriction.Comment: 19 pages. Version 2 includes more examples and tables in Section
Modular generalized Springer correspondence II: classical groups
We construct a modular generalized Springer correspondence for any classical
group, by generalizing to the modular setting various results of Lusztig in the
case of characteristic- coefficients. We determine the cuspidal pairs in all
classical types, and compute the correspondence explicitly for
with coefficients of arbitrary characteristic and for and
with characteristic- coefficients.Comment: 52 pages. Version 2 corrects a minor mistake in the combinatorics of
the type D case; no numbered statements are affected. Version 3 has minor
additions, mostly in Section 2; final version, to appear in J. Eur. Math. So
Measuring Economic Growth from Outer Space
GDP growth is often measured poorly for countries and rarely measured at all for cities. We propose a readily available proxy: satellite data on lights at night. Our statistical framework uses light growth to supplement existing income growth measures. The framework is applied to countries with the lowest quality income data, resulting in estimates of growth that differ substantially from established estimates. We then consider a longstanding debate: do increases in local agricultural productivity increase city incomes? For African cities, we find that exogenous agricultural productivity shocks (high rainfall years) have substantial effects on local urban economic activity.economic growth; remote sensing; urbanization; income measurement
Modular generalized Springer correspondence III: exceptional groups
We complete the construction of the modular generalized Springer
correspondence for an arbitrary connected reductive group, with a uniform proof
of the disjointness of induction series that avoids the case-by-case arguments
for classical groups used in previous papers in the series. We show that the
induction series containing the trivial local system on the regular nilpotent
orbit is determined by the Sylow subgroups of the Weyl group. Under some
assumptions, we give an algorithm for determining the induction series
associated to the minimal cuspidal datum with a given central character. We
also provide tables and other information on the modular generalized Springer
correspondence for quasi-simple groups of exceptional type, including a
complete classification of cuspidal pairs in the case of good characteristic,
and a full determination of the correspondence in type .Comment: 40 pages. Version 2: added section 7.5, modified Table 5.2 to match
current conventions of GAP3. Version 3 has minor edits suggested by the
referee, including a slight strengthening of Proposition 3.2; final version,
to appear in Math. Annale
Constraints on the Origin of Gold in the Meguma Zone, Ecum Secum area, Nova Scotia
Gold occurs mainly in laminated bedding-parallel quartz veins in the Goldenvllle Formation metawacke-slate sequence. The bedding-parallel veins formed by hydraulic fracturing before the beds were folded. Subsequently, during development of the folds, en echelon quartz veins formed on the fold limbs, and perhaps in the latest stage of folding, saddle reef veins formed along fold hinges. All these vein types are locally auriferous, but gold was first deposited during formation of the bedding-parallel veins. Absence of any through-going system of "feeder" veins as well as the formation of hydraulic fractures indicate that the rocks were not permeable during vein formation, and the quartz and gold were derived locally from the host strata.
RÉSUMÉ
L'or présent dans la suite métawacke-schiste de la Formation Goldenvllle est localisé principalement dans des veines de quartz laminles et parallèls à la stratification. Ces veines parallèls ià stratification furent formées par fracture hydraulique avant le plissement des lits. Par la suite, pendant l'amplification des lits, des veines de quartz en échelon furent formées sur les flancs de plis et peut-être, pendant la phase finale de plisseaent, des veines en "gite de selle" se formèrent à la charnière de plis. Tous ces types de veines sont surifères par endroit mais l'apport initial de l'or date de la formation des veines parallèes à la stratification. L'absence de système de veines nourricières sinsi que la formation de fractures hydrauliques indiquent que les roches n'étalent pas perméables à l'époque de formation de veine et que le quartz et l'or sont de provenance locale.
[Traduit par le journal
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