5,454 research outputs found
Branes at angles and calibrated geometry
In a recent paper, Ohta and Townsend studied the conditions which must be
satisfied for a configuration of two intersecting M5-branes at angles to be
supersymmetric. In this paper we extend this result to any number of M5-branes
or any number of M2-branes. This is accomplished by interpreting their results
in terms of calibrated geometry, which is of independent interest.Comment: 16 pages, LaTeX2e (Minor correction in next to last paragraph of
section 5.2
Planes, branes and automorphisms: I. Static branes
This is the first of a series of papers devoted to the group-theoretical
analysis of the conditions which must be satisfied for a configuration of
intersecting M5-branes to be supersymmetric. In this paper we treat the case of
static branes. We start by associating (a maximal torus of) a different
subgroup of Spin(10) with each of the equivalence classes of supersymmetric
configurations of two M5-branes at angles found by Ohta & Townsend. We then
consider configurations of more than two intersecting branes. Such a
configuration will be supersymmetric if and only if the branes are G-related,
where G is a subgroup of Spin(10) contained in the isotropy of a spinor. For
each such group we determine (a lower bound for) the fraction of the
supersymmetry which is preserved. We give examples of configurations consisting
of an arbitrary number of non-coincident intersecting fivebranes with
fractions: 1/32, 1/16, 3/32, 1/8, 5/32, 3/16 and 1/4, and we determine the
resulting (calibrated) geometry.Comment: 26 pages (Added a reference and modified one table slightly.
Pattern for Re-engineering a Classification Scheme, which Follows the Adjacency List Data Model, to a Taxonomy
This pattern for re-engineering non-ontological resources (pr-nor) fits in the schema re-engineering category proposed by [3]. The pattern defines a procedure that transforms the classification scheme components into ontology representational primitives. This pattern comes from the experience of ontology engineers in developing ontologies using classification schemes in several projects (seemp 1 , neon 2 , and knowledge web 3 ). The pattern is included in a pool of patterns, which is a key element of our method for re-engineering non-ontological resources into ontologies [2]. The patterns generate the ontologies at a conceptualization level, independent of the ontology implementation language
Supersymmetric Yang-Mills, octonionic instantons and triholomorphic curves
In four-dimensional gauge theory there exists a well-known correspondence
between instantons and holomorphic curves, and a similar correspondence exists
between certain octonionic instantons and triholomorphic curves. We prove that
this latter correspondence stems from the dynamics of various dimensional
reductions of ten-dimensional supersymmetric Yang-Mills theory. More precisely
we show that the dimensional reduction of the (5+1)-dimensional supersymmetric
sigma model with hyperkaehler (but otherwise arbitrary) target X to a
four-dimensional hyperkaehler manifold M is a topological sigma model
localising on the space of triholomorphic maps M -> X (or hyperinstantons).
When X is the moduli space M_K of instantons on a four-dimensional hyperkaehler
manifold K, this theory has an interpretation in terms of supersymmetric gauge
theory. In this case, the topological sigma model can be understood as an
adiabatic limit of the dimensional reduction of ten-dimensional supersymmetric
Yang-Mills on the eight-dimensional manifold M x K of holonomy Sp(1) x Sp(1) in
Spin(7), which is a cohomological theory localising on the moduli space of
octonionic instantons.Comment: 26 pages, LaTeX2e (A comment and a corresponding acknowledgement
added and a reference ammended
On The Removal of Agricultural Price Bands in Chile: A General Equilibrium Analysis
Chile has supported its agriculture with the use of price bands on selected commodities namely wheat, vegetable oils and fats, and sugar. In this paper we consider agricultural reform and how urban unemployment, and rural-urban migration, may alter the expected welfare effects of agricultural reform. We utilize a new CGE model of the Chilean economy based on the Harris-Todaro ramework, incorporating imperfect labor mobility, and consider both price band removal and more extensive agricultural reform that eliminates all tariffs on agricultural and food commodities in Chile. Results show that if trade reforms damage the rural economy in Chile, potential gains in welfare from lower agricultural prices are offset by increased urban unemployment and lower rural wages resulting in net welfare loss from trade reform.
The uses of Connes and Kreimer's algebraic formulation of renormalization theory
We show how, modulo the distinction between the antipode and the "twisted" or
"renormalized" antipode, Connes and Kreimer's algebraic paradigm trivializes
the proofs of equivalence of the (corrected) Dyson-Salam,
Bogoliubov-Parasiuk-Hepp and Zimmermann procedures for renormalizing Feynman
amplitudes. We discuss the outlook for a parallel simplification of
computations in quantum field theory, stemming from the same algebraic
approach.Comment: 15 pages, Latex. Minor changes, typos fixed, 2 references adde
A Pattern Based Approach for Re-engineering Non-Ontological Resources into Ontologies
With the goal of speeding up the ontology development process, ontology engineers are starting to reuse as much as possible available ontologies and non-ontological resources such as classification schemes, thesauri, lexicons and folksonomies, that already have some degree of consensus. The reuse of such non-ontological resources necessarily involves their re-engineering into ontologies. Non-ontological resources are highly heterogeneous in their data model and contents: they encode different types of knowledge, and they can be modeled and implemented in different ways. In this paper we present (1) a typology for non-ontological resources, (2) a pattern based approach for re-engineering non-ontological resources into ontologies, and (3) a use case of the proposed approach
Supersymmetry and homogeneity of M-theory backgrounds
We describe the construction of a Lie superalgebra associated to an arbitrary
supersymmetric M-theory background, and discuss some examples. We prove that
for backgrounds with more than 24 supercharges, the bosonic subalgebra acts
locally transitively. In particular, we prove that backgrounds with more than
24 supersymmetries are necessarily (locally) homogeneous.Comment: 19 pages (Erroneous Section 6.3 removed from the paper.
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