Academics From France

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April 10, 2026

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April 10, 2026

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"Let us now consider toposes. ... Unlike schemes, toposes generate geometry without points. In fact, nothing prevents us from proposing an axiomatic framework for geometry in which points, lines, and planes would all be on the same footing. Thus we know axiomatic systems for projective geometry (George Birkhoff) in which the primitive notion is that of a plate (a generalization of lines and planes), and in which the fundamental relationship is that of incidence. In mathematics, we consider a class of partially ordered sets called lattices; each of these corresponds to a distinct geometry. ... In the geometry of a topological space, the lattice of open sets plays a starring role, while points are relatively minor. But Grothendieck’s originality was to reprise Riemann’s idea that multivalued functions actually live not on open sets of the complex plane, but on spread-out Riemann surfaces. The spread-out Riemann surfaces project down to each other and thus form the objects of a category. However, a lattice is a special case of a category, since it includes at most one transformation between two given objects. Grothendieck thus proposed replacing the lattice of open sets with the category of spread-out open sets. When adapted to algebraic geometry, this idea solves a fundamental difficulty, since there is no implicit function theorem for algebraic functions. Sheaves can now be considered as special functors on the lattice of open sets (viewed as a category), and can thus be generalized to étale sheaves, which are special functors of the étale topology. Grothendieck would successfully play many variations on this theme in the context of various problems of geometric construction (for example, the problem of modules for algebraic curves). His greatest success in this regard would be the étale “ℓ-adic” cohomology of schemes, the cohomological theory needed to attack the Weil conjectures."

- Pierre Cartier (mathematician)

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"Along the same lines, the antiquities discovered at Quetta in 1985, which are also sometimes connected with intruding Indo-Aryans (i.e., e.g. Allchin 1995), can also simply be viewed as reflecting "the economic dynamism of the area extending from South Central Asia to the Indus Valley." The fact that similar objects are also found in graves and deposits in northern Iran, eastern Iran, northwestern Afghanistan, South Turkmenia, and Baluchistan might simply indicate "a wide distribution of common beliefs and ritual practices" (Jarrige and Hassan (1985) 1989, 162-163). Jarrige and Hassan reject the idea that these finds were associated with invaders related to the Hissar III C complex, since "there is nothing in the Gorgan Plain and at Hissar to prove that northern Iran has been a relay station for invading people. The . . . grey ware can very well be explained within its local context" (163-164). Nor are these scholars partial to the northern steppe Andronov alternatives, since: We leave to the linguists the problem of whether Indo-European languages were introduced into the Middle Asian regions from a still unknown part of the Eurasian steppes in the course of the third millennium or if Indo-Iranian languages have been associated with these regions for a much longer period. As far as archaeology is concerned, we do think that it is increasingly necessary for specialists in Indo-lranian studies to pay attention to the . . . interrelated cultural entities of the late third and early second millennium in the regions between Mesopotamia and the Indus. It is a direction of research that is likely to be more fruitful than are traditional attempts to locate remains left by nomads from "the Steppes," attempts that were in fashion when the Indo-Iranian Borderlands were thought to be a cultural vacuum. (164)"

- Jean-François Jarrige

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