1,329 research outputs found
Assumindo novas identidades: resistĂȘncia indĂgena no litoral sul do EspĂrito Santo (sĂ©culo XVIII).
Na primeira metade do sĂ©culo XVI, a resistĂȘncia indĂgena nesta e em outras capitanias deixou claro aos portugueses quĂŁo difĂcil seria a colonização dessas ĂĄreas. Diante desses desafios a Coroa Portuguesa adotou uma nova polĂtica, da qual fazia parte o envio de jesuĂtas para a AmĂ©rica. Nesse contexto foram criadas no sul do EspĂrito Santo as missĂ”es de Guaraparim e Iriritiba. Nesta Ășltima, local de moradia do padre JosĂ© de Anchieta em seus derradeiros anos de vida, a gravidade e amplitude de uma sĂ©rie de levantes iniciados no ano de 1742 deixaram sobressaltadas autoridades civis e religiosas. A notoriedade desta localidade e desses eventos, no entanto, nĂŁo se refletiu na academia. Buscando contribuir para a mudança nesse panorama, começamos um processo de releitura de obras sobre a histĂłria do EspĂrito Santo e de correspondĂȘncias oficiais sobre as revoltas utilizando conceitos como circularidade cultural, hibridismo, mestiçagem e etnogĂȘnese impressos nos textos de autores como Carlo Ginzburg, Guillaume Boccara, John Manuel Monteiro, Ronaldo Vainfas, Eduardo Viveiros de Castro, Manuela Carneiro da Cunha, Michel de Certeau e Maria Regina Celestino de Almeida. A princĂpio constatamos que apesar do esforço daqueles autores em apresentarem uma narrativa dual, que acondicionava colonizados e colonizadores em compartimentos estanques, seus textos traziam indĂcios que contrariavam essa representação simplista. Pensamento consolidado com a publicação do Auto da Devassa de 1761, ação organizada pelo Santo OfĂcio para apurar supostas irregularidades cometidas pelos inacianos durante sua permanĂȘncia nesta capitania. Ao reproduzir o depoimento de Ăndios que viviam em Guaraparim, Iriritiba e no OrobĂł, o documento nos apresentou indivĂduos com trajetĂłrias impensĂĄveis para os modelos dicotĂŽmicos anteriores. Pessoas que para sobreviverem a todas aquelas transformaçÔes reinventaram-se repetidas vezes, criando e assumindo diferentes identidades. Uma parte deles, uma vez alijada dos cargos de administração da aldeia, migrou para o vale do OrobĂł fundando uma aldeia onde viveram, como sugeria o nome por eles escolhido, Ă eles, para eles, com a exclusĂŁo deles
Surgery and the Spectrum of the Dirac Operator
We show that for generic Riemannian metrics on a simply-connected closed spin
manifold of dimension at least 5 the dimension of the space of harmonic spinors
is no larger than it must be by the index theorem. The same result holds for
periodic fundamental groups of odd order.
The proof is based on a surgery theorem for the Dirac spectrum which says
that if one performs surgery of codimension at least 3 on a closed Riemannian
spin manifold, then the Dirac spectrum changes arbitrarily little provided the
metric on the manifold after surgery is chosen properly.Comment: 23 pages, 4 figures, to appear in J. Reine Angew. Mat
Generic metrics and the mass endomorphism on spin three-manifolds
Let be a closed Riemannian spin manifold. The constant term in the
expansion of the Green function for the Dirac operator at a fixed point is called the mass endomorphism in associated to the metric due to
an analogy to the mass in the Yamabe problem. We show that the mass
endomorphism of a generic metric on a three-dimensional spin manifold is
nonzero. This implies a strict inequality which can be used to avoid
bubbling-off phenomena in conformal spin geometry.Comment: 8 page
The Dirac operator on generalized Taub-NUT spaces
We find sufficient conditions for the absence of harmonic spinors on
spin manifolds constructed as cone bundles over a compact K\"ahler base. These
conditions are fulfilled for certain perturbations of the Euclidean metric, and
also for the generalized Taub-NUT metrics of Iwai-Katayama, thus proving a
conjecture of Vi\csinescu and the second author.Comment: Final version, 16 page
A Reilly formula and eigenvalue estimates for differential forms
We derive a Reilly-type formula for differential p-forms on a compact
manifold with boundary and apply it to give a sharp lower bound of the spectrum
of the Hodge Laplacian acting on differential forms of an embedded hypersurface
of a Riemannian manifold. The equality case of our inequality gives rise to a
number of rigidity results, when the geometry of the boundary has special
properties and the domain is non-negatively curved. Finally we also obtain, as
a by-product of our calculations, an upper bound of the first eigenvalue of the
Hodge Laplacian when the ambient manifold supports non-trivial parallel forms.Comment: 22 page
On a spin conformal invariant on manifolds with boundary
On a n-dimensional connected compact manifold with non-empty boundary
equipped with a Riemannian metric, a spin structure and a chirality operator,
we study some properties of a spin conformal invariant defined from the first
eigenvalue of the Dirac operator under the chiral bag boundary condition. More
precisely, we show that we can derive a spinorial analogue of Aubin's
inequality.Comment: 26 page
Vacuum Spacetimes with Future Trapped Surfaces
In this article we show that one can construct initial data for the Einstein
equations which satisfy the vacuum constraints. This initial data is defined on
a manifold with topology with a regular center and is asymptotically
flat. Further, this initial data will contain an annular region which is
foliated by two-surfaces of topology . These two-surfaces are future
trapped in the language of Penrose. The Penrose singularity theorem guarantees
that the vacuum spacetime which evolves from this initial data is future null
incomplete.Comment: 19 page
Vanishing Viscous Limits for 3D Navier-Stokes Equations with A Navier-Slip Boundary Condition
In this paper, we investigate the vanishing viscosity limit for solutions to
the Navier-Stokes equations with a Navier slip boundary condition on general
compact and smooth domains in . We first obtain the higher order
regularity estimates for the solutions to Prandtl's equation boundary layers.
Furthermore, we prove that the strong solution to Navier-Stokes equations
converges to the Eulerian one in and
L^\infty((0,T)\times\o), where is independent of the viscosity, provided
that initial velocity is regular enough. Furthermore, rates of convergence are
obtained also.Comment: 45page
Changes in electrophysiological static and dynamic human brain functional architecture from childhood to late adulthood
Published: 04 November 2020This magnetoencephalography study aimed at characterizing age-related changes in resting-state functional brain organization from mid-childhood to late adulthood. We investigated neuromagnetic brain activity at rest in 105 participants divided into three age groups: children (6â9 years), young adults (18â34 years) and healthy elders (53â78 years). The effects of age on static resting-state functional brain integration were assessed using band-limited power envelope correlation, whereas those on transient functional brain dynamics were disclosed using hidden Markov modeling of power envelope activity. Brain development from childhood to adulthood came with (1) a strengthening of functional integration within and between resting-state networks and (2) an increased temporal stability of transient (100â300 ms lifetime) and recurrent states of network activation or deactivation mainly encompassing lateral or medial associative neocortical areas. Healthy aging was characterized by decreased static resting-state functional integration and dynamic stability within the primary visual network. These results based on electrophysiological measurements free of neurovascular biases suggest that functional brain integration mainly evolves during brain development, with limited changes in healthy aging. These novel electrophysiological insights into human brain functional architecture across the lifespan pave the way for future clinical studies investigating how brain disorders affect brain development or healthy aging.This study was supported by the Action de Recherche ConcertĂ©e Consolidation (ARCC, âCharacterizing the spatio-temporal dynamics and the electrophysiological bases of resting state networksâ, ULB, Brussels, Belgium), the Fonds Erasme (Research Convention âLes Voies du Savoirâ,Brussels, Belgium) and the Fonds de la Recherche Scientifique (Research Convention: T.0109.13, FRS-FNRS, Brussels, Belgium). Nicolas Coquelet has been supported by the ARCC, by the Fonds Erasme (Research Convention âLes Voies du Savoirâ, Brussels, Belgium) and is supported by the FRS-FNRS (Research Convention: Excellence of Science EOS âMEMODYNâ). Alison Mary is Postdoctoral Researcher at the FRS-FNRS. Maxime Niesen and Marc Vander Ghinst have been supported by the Fonds Erasme. Mariagrazia Ranzini is supported by the Marie Sklodowska-Curie European Unionâs Horizon 2020 research and innovation program (Research Grant: 839394). Mathieu Bourguignon is supported by the program Attract of Innoviris (Research Grant 2015-BB2B-10, Brussels, Belgium), the Marie Sklodowska-Curie Action of the European Commission (Research Grant: 743562) and by the Spanish Ministery of Economy and Competitiveness (Research Grant: PSI2016-77175-P). Xavier De TiĂšge is Postdoctorate Clinical Master Specialist at the FRS-FNRS. The MEG project at the CUB HĂŽpital Erasme is financially supported by the Fonds Erasme
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