4,082 research outputs found
Reduction and approximation in gyrokinetics
The gyrokinetics formulation of plasmas in strong magnetic fields aims at the
elimination of the angle associated with the Larmor rotation of charged
particles around the magnetic field lines. In a perturbative treatment or as a
time-averaging procedure, gyrokinetics is in general an approximation to the
true dynamics. Here we discuss the conditions under which gyrokinetics is
either an approximation or an exact operation in the framework of reduction of
dynamical systems with symmetryComment: 15 pages late
A lattice in more than two Kac--Moody groups is arithmetic
Let be an irreducible lattice in a product of n infinite irreducible
complete Kac-Moody groups of simply laced type over finite fields. We show that
if n is at least 3, then each Kac-Moody groups is in fact a simple algebraic
group over a local field and is an arithmetic lattice. This relies on
the following alternative which is satisfied by any irreducible lattice
provided n is at least 2: either is an S-arithmetic (hence linear)
group, or it is not residually finite. In that case, it is even virtually
simple when the ground field is large enough.
More general CAT(0) groups are also considered throughout.Comment: Subsection 2.B was modified and an example was added ther
Conjugacy theorems for loop reductive group schemes and Lie algebras
The conjugacy of split Cartan subalgebras in the finite dimensional simple
case (Chevalley) and in the symmetrizable Kac-Moody case (Peterson-Kac) are
fundamental results of the theory of Lie algebras. Among the Kac-Moody Lie
algebras the affine algebras stand out. This paper deals with the problem of
conjugacy for a class of algebras --extended affine Lie algebras-- that are in
a precise sense higher nullity analogues of the affine algebras. Unlike the
methods used by Peterson-Kac, our approach is entirely cohomological and
geometric. It is deeply rooted on the theory of reductive group schemes
developed by Demazure and Grothendieck, and on the work of J. Tits on buildingsComment: Publi\'e dans Bulletin of Mathematical Sciences 4 (2014), 281-32
On Motives Associated to Graph Polynomials
The appearance of multiple zeta values in anomalous dimensions and
-functions of renormalizable quantum field theories has given evidence
towards a motivic interpretation of these renormalization group functions. In
this paper we start to hunt the motive, restricting our attention to a subclass
of graphs in four dimensional scalar field theory which give scheme independent
contributions to the above functions.Comment: 54
Representations and -theory of Discrete Groups
Let be a discrete group of finite virtual cohomological dimension
with certain finiteness conditions of the type satisfied by arithmetic groups.
We define a representation ring for , determined on its elements of
finite order, which is of finite type. Then we determine the contribution of
this ring to the topological -theory , obtaining an exact
formula for the difference in terms of the cohomology of the centralizers of
elements of finite order in .Comment: 4 page
Componentes da variância genética no cruzamento de feijões andinos e mesoamericanos.
Quando os cruzamentos são viáveis, frequentemente a população obtida apresenta desempenho abaixo da média dos pais para produtividade de grãos. Entretanto a partir do cruzamento entre as linhagens ESAL 686 (Andina) e Carioca MG (Mesoamericana) foram obtidas linhagens com bom desempenho (BRUZI et al., 2007). Seria importante estimar os componentes da variância genética e fenotÃpica desse cruzamento a fim de verificar se a variabilidade obtida é diferente do que é normalmente observado em outros cruzamentos de feijoeiro do mesmo conjunto gênico.CONAFE
Análise genética do inÃcio do florescimento em feijoeiro pelo "Triple Test Cross".
objetivo deste trabalho foi detectar a presença de epistasia e estimar os componentes da variância genética para o caráter inÃcio do florescimento em populações de feijoeiro (Phaseolus vulgaris L.) oriundas de genitores de diferentes conjuntos gênicos (pools gênicos)
Twisting algebras using non-commutative torsors
Non-commutative torsors (equivalently, two-cocycles) for a Hopf algebra can
be used to twist comodule algebras. After surveying and extending the
literature on the subject, we prove a theorem that affords a presentation by
generators and relations for the algebras obtained by such twisting. We give a
number of examples, including new constructions of the quantum affine spaces
and the quantum tori.Comment: 27 pages. Masuoka is a new coauthor. Introduction was revised.
Sections 1 and 2 were thoroughly restructured. The presentation theorem in
Section 3 is now put in a more general framework and has a more general
formulation. Section 4 was shortened. All examples (quantum affine spaces and
tori, twisting of SL(2), twisting of the enveloping algebra of sl(2)) are
left unchange
- …