5,742 research outputs found
Jacobi quasi-Nijenhuis Algebroids
In this paper, for a Jacobi algebroid , by introducing the notion of
Jacobi quasi-Nijenhuis algebroids, which is a generalization of Poisson
quasi-Nijenhuis manifolds introduced by Sti\'{e}non and Xu, we study
generalized complex structures on the Courant-Jacobi algebroid ,
which unifies generalized complex (contact) structures on an
even(odd)-dimensional manifold.Comment: 17 pages, no figur
Reduction of Jacobi manifolds via Dirac structures theory
We first recall some basic definitions and facts about Jacobi manifolds,
generalized Lie bialgebroids, generalized Courant algebroids and Dirac
structures. We establish an one-one correspondence between reducible Dirac
structures of the generalized Lie bialgebroid of a Jacobi manifold
for which 1 is an admissible function and Jacobi quotient
manifolds of . We study Jacobi reductions from the point of view of Dirac
structures theory and we present some examples and applications.Comment: 18 page
AV-Courant algebroids and generalized CR structures
We construct a generalization of Courant algebroids which are classified by
the third cohomology group , where is a Lie Algebroid, and is
an -module. We see that both Courant algebroids and
structures are examples of them. Finally we introduce generalized CR structures
on a manifold, which are a generalization of generalized complex structures,
and show that every CR structure and contact structure is an example of a
generalized CR structure.Comment: 18 page
Effect of anisotropy in the underscreened Kondo lattice
We study the effect of crystal field anisotropy in the underscreened
Kondo lattice model. Starting from the two orbital Anderson lattice model and
including a local anisotropy term, we show, through Schrieffer-Wolff
transformation, that local anisotropy is equivalent to an anisotropic Kondo
interaction (). The competition and coexistence
between ferromagnetism and Kondo effect in this effective model is studied
within a generalized mean-field approximation. Several regimes are obtained,
depending on the parameters, exhibiting or not coexistence of magnetic order
and Kondo effect. Particularly, we show that a re-entrant Kondo phase at low
temperature can be obtained. We are also able to describe phases where the
Kondo temperature is smaller than the Curie temperature (). We propose
that some aspects of uranium and neptunium compounds that present coexistence
of Kondo effect and ferromagnetism, can be understood within this model.Comment: 7 pages, 3 figure
From Environmental Education to Social Education and vice versa
Aquesta reflexió parteix de la idea bàsica: els límits entre els diferents àmbits acadèmics i/o professionals els que regulen i distribueixen el coneixement i la pràctica educativa, es tracen de forma convencional pero no arbitrària. Així, els arguments per delimitar la singularitat de cada camp de l'acció educativa són el producte de conjuntures històriques i de tensions professionals o acadèmiques que s'activen per intentar donar resposta sistemàtica a noves demandes i necessitats educatives derivades de l'evolució de la societat.Esta refexión parte de una idea básica: los límites entre los distintos ámbitos académicos y/o profesionales, los que regulan y distribuyen el conocimiento y la práctica educativa, se trazan de forma convencional pero no arbitraria. Así, los argumentos para delimitar la singularidad de cada campo de la acción educativa son el producto de coyunturas históricas y de tensiones profesionales o académicas que se activan para intentar dar respuesta sistemática a nuevas demandas y necesidades educativas derivadas de la evolución de la sociedad.This reflection starts from the basic premise that the boundaries between the various academic and7or professional fields, those which regulate and disseminate knowledge and educational practice, follow conventional, but not arbitrary, lines the arguments for defining the unique aspect of each field of education are the product of historical circumstances and professional
or academic rivalries arising from the attempt to provide a sistematic response to new demands and needs in education triggered by social evolution
On Jacobi quasi-Nijenhuis algebroids and Courant-Jacobi algebroid morphisms
We propose a definition of Jacobi quasi-Nijenhuis algebroid and show that any
such Jacobi algebroid has an associated quasi-Jacobi bialgebroid. Therefore,
also an associated Courant-Jacobi algebroid is obtained. We introduce the
notions of quasi-Jacobi bialgebroid morphism and Courant-Jacobi algebroid
morphism providing also some examples of Courant-Jacobi algebroid morphisms.Comment: 14 pages, to appear in Journal of Geometry and Physic
Jacobi-Nijenhuis algebroids and their modular classes
Jacobi-Nijenhuis algebroids are defined as a natural generalization of
Poisson-Nijenhuis algebroids, in the case where there exists a Nijenhuis
operator on a Jacobi algebroid which is compatible with it. We study modular
classes of Jacobi and Jacobi-Nijenhuis algebroids
On quasi-Jacobi and Jacobi-quasi bialgebroids
We study quasi-Jacobi and Jacobi-quasi bialgebroids and their relationships
with twisted Jacobi and quasi Jacobi manifolds. We show that we can construct
quasi-Lie bialgebroids from quasi-Jacobi bialgebroids, and conversely, and also
that the structures induced on their base manifolds are related via a quasi
Poissonization
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