91 research outputs found
Unifying W-Algebras
We show that quantum Casimir W-algebras truncate at degenerate values of the
central charge c to a smaller algebra if the rank is high enough: Choosing a
suitable parametrization of the central charge in terms of the rank of the
underlying simple Lie algebra, the field content does not change with the rank
of the Casimir algebra any more. This leads to identifications between the
Casimir algebras themselves but also gives rise to new, `unifying' W-algebras.
For example, the kth unitary minimal model of WA_n has a unifying W-algebra of
type W(2,3,...,k^2 + 3 k + 1). These unifying W-algebras are non-freely
generated on the quantum level and belong to a recently discovered class of
W-algebras with infinitely, non-freely generated classical counterparts. Some
of the identifications are indicated by level-rank-duality leading to a coset
realization of these unifying W-algebras. Other unifying W-algebras are new,
including e.g. algebras of type WD_{-n}. We point out that all unifying quantum
W-algebras are finitely, but non-freely generated.Comment: 13 pages (plain TeX); BONN-TH-94-01, DFTT-15/9
Infinite Symmetry in the Fractional Quantum Hall Effect
We have generalized recent results of Cappelli, Trugenberger and Zemba on the
integer quantum Hall effect constructing explicitly a for
the fractional quantum Hall effect such that the negative modes annihilate the
Laughlin wave functions. This generalization has a nice interpretation in
Jain's composite fermion theory. Furthermore, for these models we have
calculated the wave functions of the edge excitations viewing them as area
preserving deformations of an incompressible quantum droplet, and have shown
that the is the underlying symmetry of the edge
excitations in the fractional quantum Hall effect. Finally, we have applied
this method to more general wave functions.Comment: 15pp. LaTeX, BONN-HE-93-2
Steps towards Lattice Virasoro Algebras: su(1,1)
An explicit construction is presented for the action of the su(1,1)
subalgebra of the Virasoro algebra on path spaces for the c(2,q) minimal
models. In the case of the Lee-Yang edge singularity, we show how this action
already fixes the central charge of the full Virasoro algebra. For this case,
we additionally construct a representation in terms of generators of the
corresponding Temperley-Lieb algebra.Comment: 15 pages, plain TeX, 4 typos correcte
Algebraic Quantization, Good Operators and Fractional Quantum Numbers
The problems arising when quantizing systems with periodic boundary
conditions are analysed, in an algebraic (group-) quantization scheme, and the
``failure" of the Ehrenfest theorem is clarified in terms of the already
defined notion of {\it good} (and {\it bad}) operators. The analysis of
``constrained" Heisenberg-Weyl groups according to this quantization scheme
reveals the possibility for new quantum (fractional) numbers extending those
allowed for Chern classes in traditional Geometric Quantization. This study is
illustrated with the examples of the free particle on the circumference and the
charged particle in a homogeneous magnetic field on the torus, both examples
featuring ``anomalous" operators, non-equivalent quantization and the latter,
fractional quantum numbers. These provide the rationale behind flux
quantization in superconducting rings and Fractional Quantum Hall Effect,
respectively.Comment: 29 pages, latex, 1 figure included with EPSF. Revised version with
minor changes intended to clarify notation. Acepted for publication in Comm.
Math. Phy
Verbal short-term memory deficits in Down syndrome: phonological, semantic, or both?
The current study examined the phonological and semantic contributions to the verbal short-term memory (VSTM) deficit in Down syndrome (DS) by experimentally manipulating the phonological and semantic demands of VSTM tasks. The performance of 18 individuals with DS (ages 11–25) and 18 typically developing children (ages 3–10) matched pairwise on receptive vocabulary and gender was compared on four VSTM tasks, two tapping phonological VSTM (phonological similarity, nonword discrimination) and two tapping semantic VSTM (semantic category, semantic proactive interference). Group by condition interactions were found on the two phonological VSTM tasks (suggesting less sensitivity to the phonological qualities of words in DS), but not on the two semantic VSTM tasks. These findings suggest that a phonological weakness contributes to the VSTM deficit in DS. These results are discussed in relation to the DS neuropsychological and neuroanatomical phenotype
Enobrecimento, trajetórias sociais e remuneração de serviços no império português: a carreira de Gaspar de Sousa, governador geral do Estado do Brasil
Carreira e trajetória social na monarquia e no império ultramarino português, governadores gerais do Estado do Brasil (1640-1702)
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