90,022 research outputs found
Crossed products by twisted partial actions and graded algebras
For a twisted partial action \Theta of a group G on an (associative
non-necessarily unital) algebra A over a commutative unital ring k, the crossed
product A X_\Theta G is proved to be associative. Given a G-graded k-algebra B
= \oplus_{g\in G}\B_g with the mild restriction of homogeneous non-degeneracy,
a criteria is established for B to be isomorphic to the crossed product B_1
X_\Theta G for some twisted partial action of G on B_1. The equality
B_g\B_{g^{-1}}B_g = \B_g for all g\in G is one of the ingredients of the
criteria, and if it holds and, moreover, B has enough local units, then it is
shown that B is stably isomorphic to a crossed product by a twisted partial
action of G.Comment: 38 pages, no figure
Formal ontology for biomedical knowledge systems integration
The central hypothesis of the collaboration between Language and Computing (L&C) and the Institute for Formal Ontology and Medical Information Science (IFOMIS) is that the methodology and conceptual rigor of a philosophically inspired formal ontology will greatly benefit software application ontologies. To this end LinKBase®, L&C’s ontology, which is designed to integrate and reason across various external databases simultaneously, has been submitted to the conceptual demands of IFOMIS’s Basic Formal Ontology (BFO). With this, we aim to move beyond the level of controlled vocabularies to yield an ontology with the ability to support reasoning applications
The one-loop effective potential of the Wess-Zumino model revisited
The full one-loop supersymmetric effective potential for the Wess-Zumino
model is calculated using superfield techniques. This includes the K\"ahler
potential and the auxiliary field potential, of which the former was originally
computed in 1993 while the latter is derived for the first time. In the purely
bosonic sector our results match those of older component field calculations.
In light of prior contradictory results found in the literature, the
calculation of the leading term in the auxiliary field potential is approached
in a variety of ways. Issues related to conditional convergence that occur
during these calculations and their possible consequences are discussed.Comment: 32 page
Radio observations of the massive stellar cluster Westerlund 1
High-dynamic range radio observations of Westerlund 1 are presented that
detect a total of 21 stars in the young massive stellar cluster, the richest
population of radio emitting stars known for any young massive galactic cluster
in the Galaxy. We will discuss some of the more remarkable objects, including
the highly radio luminous supergiant B[e] star W9, with an estimated mass-loss
rate ~10^{-3} solarmass/yr, comparable to that of eta Carina, along with the
somewhat unusual detection of thermal emission from almost all the cool red
supergiants and yellow hypergiants. There is strong supporting evidence from
X-ray observations that each of the WR stars with radio emission are likely to
be colliding-wind binariesComment: To appear in the proceedings of "Massive Stars: Fundamental
Parameters and Circumstellar Interactions". 2 pages, 1 figur
Relaxed Three-Algebras: Their Matrix Representations and Implications for Multi M2-brane Theory
We argue that one can relax the requirements of the non-associative
three-algebras recently used in constructing D=3, N=8 superconformal field
theories, and introduce the notion of ``relaxed three-algebras''. We present a
specific realization of the relaxed three-algebras in terms of classical Lie
algebras with a matrix representation, endowed with a non-associative
four-bracket structure which is prescribed to replace the three-brackets of the
three-algebras. We show that both the so(4)-based solutions as well as the
cases with non-positive definite metric find a uniform description in our
setting. We discuss the implications of our four-bracket representation for the
D=3, N=8 and multi M2-brane theory and show that our setup can shed light on
the problem of negative kinetic energy degrees of freedom of the Lorentzian
case.Comment: 31 pages, no figure
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