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Nero - Satisfy

We give a framework to produce constructible functions from natural functors between categories, without need of a morphism of moduli spaces to model the functor. We show using the Riemann-Hilbert correspondence that any natural (derived) functor on constructible sheaves on smooth complex algebraic varieties can be used to construct a special kind of constructible sets, called absolute sets, generalizing a notion introduced by Simpson in presence of moduli. We conjecture that the absolute sets of local systems satisfy a "special varieties package", among which is an analog of the Manin-Mumford, Mordell-Lang, and Andr\'e-Oort conjectures. The conjecture gives a simple proof of the Decomposition Theorem for all semi-simple perverse sheaves, assuming the Decomposition Theorem for the geometric ones. We prove the conjecture in the rank one case by showing that the closed absolute sets in this case are finite unions of torsion-translated affine tori. This extends a structure result of the authors for cohomology jump loci to any other natural jump loci. For example, to jump loci of intersection cohomology and Leray filtrations. We also show that the Leray spectral sequence for the open embedding in a good compactification degenerates for all rank one local systems at the usual page, not just for unitary local systems.

Nero - Satisfy


Hyperplane arrangements form the geometric counterpart of combinatorial objects such as matroids. The shape of the sequence of Betti numbers of the complement of a hyperplane arrangement is of particular interest in combinatorics, where they are known, up to a sign, as Whitney numbers of the first kind, and appear as the coefficients of chromatic, or characteristic, polynomials. We show that certain combinations, some nonlinear, of these Betti numbers satisfy Schur positivity. At the same time, we study the higher degree resonance varieties of the arrangement. We draw some consequences, using homological algebra results and vector bundles techniques, of the fact that all resonance varieties are determinantal.

"Lands allotted to citizens shall not in any manner whatever or at any time be incumbered, taken, or sold to secure or satisfy any debt or obligation nor be alienated by the allottee or his heirs before the expiration of five years from the date of the approval of this supplemental agreement, except with the approval of the Secretary of the Interior Each citizen shall select from his allotment forty acres of land, or a quarter of a quarter section, as a homestead, which shall be and remain nontaxable, inalienable, and free from any incumbrance whatever for twenty-one years from the date of the deed therefor, and a separate deed shall be issued to each allottee for his homestead, in which this condition shall appear. 041b061a72


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