5,846 research outputs found

### Secondary Quantum Hamiltonian Reduction

Recently, it has been shown how to perform the quantum hamiltonian reduction
in the case of general $sl(2)$ embeddings into Lie (super)algebras, and in the
case of general $osp(1|2)$ embeddings into Lie superalgebras. In another
development it has been shown that when $H$ and $H'$ are both subalgebras of a
Lie algebra $G$ with $H'\subset H$, then classically the $W(G,H)$ algebra can
be obtained by performing a secondary hamiltonian reduction on $W(G,H')$. In
this paper we show that the corresponding statement is true also for quantum
hamiltonian reduction when the simple roots of $H'$ can be chosen as a subset
of the simple roots of $H$. As an application, we show that the quantum
secondary reductions provide a natural framework to study and explain the
linearization of the $W$ algebras, as well as a great number of new
realizations of $W$ 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 $W$-algebra like composite operators occurring in the commutation
relations, but with generators of conformal dimension 1,$\frac{3}{2}$ 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 $G\oplus sl(2)$. 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

### 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 ($~10^{26}$ g/cm$^4$) 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

### Farm Programs, Price Supports and Iowa Farms - Some Possible Adjustments under Lower Future Prices

What would happen to Iowa farms if farm prices dropped an average of 20 percent? It\u27s not likely to happen, but to find out, economists made projectiosn, then analyzed to see what adjustments could be possible

### Amounts and Costs of Alternative Land Retirement Programs

A study by economists from ISU\u27s Center for Agricultural and Economic Development projects costs and land requirements for various farm programs. Their conclusion: there\u27s no program that\u27s all good nor all bad. The public will have to compare goals and values to select the program they desire

### Electronic structure of the ferromagnetic superconductor UCoGe from first principles

The superconductor UCoGe is analyzed with electronic structure calculations
using Linearized Augmented Plane Wave method based on Density Functional
Theory. Ferromagnetic and antiferromagnetic calculations with and without
correlations (via LDA+U) were done. In this compound the Fermi level is
situated in a region where the main contribution to DOS comes from the U-5f
orbital. The magnetic moment is mainly due to the Co-3d orbital with a small
contribution from the U-5f orbital. The possibility of fully non-collinear
magnetism in this compound seems to be ruled out. These results are compared
with the isostructural compound URhGe, in this case the magnetism comes mostly
from the U-5f orbital

### Chiral phase properties of finite size quark droplets in the Nambu--Jona-Lasinio model

Chiral phase properties of finite size hadronic systems are investigated
within the Nambu--Jona-Lasinio model. Finite size effects are taken into
account by making use of the multiple reflection expansion. We find that, for
droplets with relatively small baryon numbers, chiral symmetry restoration is
enhanced by the finite size effects. However the radius of the stable droplet
does not change much, as compared to that without the multiple reflection
expansion.Comment: RevTex4, 9 pages, 6 figures, to be published in Phys. Rev.

### Strangelet spectra from type II supernovae

We study in this work the fate of strangelets injected as a contamination in
the tail of a "strange matter-driven" supernova shock. A simple model for the
fragmentation and braking of the strangelets when they pass through the
expanding oxygen shell is presented and solved to understand the reprocessing
of this component. We find that the escaping spectrum is a scaled-down version
of the one injected at the base of the oxygen shell. The supernova source is
likely to produce low-energy particles of $A \sim 100-1000$ quite independently
of the initial conditions. However, it is difficult that ultrarrelativistic
strangelets (such as the hypothetical Centauro primaries) can have an origin in
those explosive events.Comment: RevTex file, 5 pp., no figure

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