6,914 research outputs found
Secondary Quantum Hamiltonian Reduction
Recently, it has been shown how to perform the quantum hamiltonian reduction
in the case of general embeddings into Lie (super)algebras, and in the
case of general embeddings into Lie superalgebras. In another
development it has been shown that when and are both subalgebras of a
Lie algebra with , then classically the algebra can
be obtained by performing a secondary hamiltonian reduction on . In
this paper we show that the corresponding statement is true also for quantum
hamiltonian reduction when the simple roots of can be chosen as a subset
of the simple roots of . As an application, we show that the quantum
secondary reductions provide a natural framework to study and explain the
linearization of the algebras, as well as a great number of new
realizations of algebras.Comment: 33 pages, LATEX. Final version, including proof of conjecture.
Accepted for publication in Comm. Math. Phy
Extended Superconformal Algebras from Classical and Quantum Hamiltonian Reduction
We consider the extended superconformal algebras of the Knizhnik-Bershadsky
type with -algebra like composite operators occurring in the commutation
relations, but with generators of conformal dimension 1, and 2,
only. These have recently been neatly classified by several groups, and we
emphasize the classification based on hamiltonian reduction of affine Lie
superalgebras with even subalgebras . We reveiw the situation
and improve on previous formulations by presenting generic and very compact
expressions valid for all algebras, classical and quantum. Similarly generic
and compact free field realizations are presented as are corresponding
screening charges. Based on these a discussion of singular vectors is
presented. (Based on talk by J.L. Petersen at the Int. Workshop on "String
Theory, Quantum Gravity and the Unification of the Fundamental Interactions",
Rome Sep. 21-26, 1992)Comment: 30 pages, NBI-HE-92-8
Immunohistochemical staining for S-lOO and GFAP proteins of spontaneous brain tumours in Wistar rats
The occurrence of spontaneous brain tumours in rats is relatively rare. The need for a histological correct classification of rat brain tumours is of great importance in evaluation of chemical induced brain neoplasms in long term carcinogenicity studies.The value of additional immunohistochemical staining for GFAP and S-100 proteins were investigated in a long term carcinogenicity study. Astrocytomas were positive for the GFAP protein but no tumours had a clear positive reaction for the S-100 protein. The most common tumour type was granular cell tumour which did not stain for the GFAP and S-100 proteins. However one tumour of this type had a subpopulation of cells that stained for GFAP protein. In the light of the relatively few astrocytomas in the material, no firm conclusion on the value of staining for GFAP protein can be drawn. However the investigation suggests that staining for GFAP protein is of value in the diagnosis ofastrocytomas. Staining for S-100 protein did not show a positive reaction in any ofthe tumours. In conclusion staining for S-100 protein in this study did not have any diagnostic value
The Strange Star Surface: A Crust with Nuggets
We reexamine the surface composition of strange stars. Strange quark stars
are hypothetical compact stars which could exist if strange quark matter was
absolutely stable. It is widely accepted that they are characterized by an
enormous density gradient ( g/cm) and large electric fields at
surface. By investigating the possibility of realizing a heterogeneous crust,
comprised of nuggets of strange quark matter embedded in an uniform electron
background, we find that the strange star surface has a much reduced density
gradient and negligible electric field. We comment on how our findings will
impact various proposed observable signatures for strange stars.Comment: 4 pages, 2 figure
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