13,575 research outputs found
Charge Lattices and Consistency of 6D Supergravity
We extend the known consistency conditions on the low-energy theory of
six-dimensional N = 1 supergravity. We review some facts about the theory of
two-form gauge fields and conclude that the charge lattice Gamma for such a
theory has to be self-dual. The Green-Schwarz anomaly cancellation conditions
in the supergravity theory determine a sublattice of Gamma. The condition that
this sublattice can be extended to a self-dual lattice Gamma leads to a strong
constraint on theories that otherwise appear to be self-consistent.Comment: 15 pages. v2: minor changes; references, additional example added;
v3: minor corrections and clarifications added, JHEP versio
Ambiguous correlation
Many decisions are made in environments where outcomes are determined by the realization of multiple random events. A decision
maker may be uncertain how these events are related. We identify and experimentally substantiate behavior that intuitively reflects a lack of confidence in their joint distribution. Our findings suggest a dimension of ambiguity which is different from that in the classical distinction between risk and "Knightian uncertainty"
Hidden Quantum Group Structure in Einstein's General Relativity
A new formal scheme is presented in which Einstein's classical theory of
General Relativity appears as the common, invariant sector of a one-parameter
family of different theories. This is achieved by replacing the Poincare` group
of the ordinary tetrad formalism with a q-deformed Poincare` group, the usual
theory being recovered at q=1. Although written in terms of noncommuting
vierbein and spin-connection fields, each theory has the same metric sector
leading to the ordinary Einstein-Hilbert action and to the corresponding
equations of motion. The Christoffel symbols and the components of the Riemann
tensor are ordinary commuting numbers and have the usual form in terms of a
metric tensor built as an appropriate bilinear in the vierbeins. Furthermore we
exhibit a one-parameter family of Hamiltonian formalisms for general
relativity, by showing that a canonical formalism a` la Ashtekar can be built
for any value of q. The constraints are still polynomial, but the Poisson
brackets are not skewsymmetric for q different from 1.Comment: LaTex file, 21 pages, no figure
Spinning Particle Dynamics on Six-Dimensional Minkowski Space
Massive spinning particle in -Minkowski space is described as a
mechanical system with the configuration space . The
action functional of the model is unambiguously determined by the requirement
of identical (off-shell) conservation for the phase-space counterparts of three
Casimir operators of Poincar\'e group. The model proves to be completely
solvable. Its generalization to the constant curvature background is presented.
Canonical quantization of the theory leads to the relativistic wave equations
for the irreducible fields.Comment: 21 pages, LaTe
Ontology-based data access with databases: a short course
Ontology-based data access (OBDA) is regarded as a key ingredient of the new generation of information systems. In the OBDA paradigm, an ontology defines a high-level global schema of (already existing) data sources and provides a vocabulary for user queries. An OBDA system rewrites such queries and ontologies into the vocabulary of the data sources and then delegates the actual query evaluation to a suitable query answering system such as a relational database management system or a datalog engine. In this chapter, we mainly focus on OBDA with the ontology language OWL 2QL, one of the three profiles of the W3C standard Web Ontology Language OWL 2, and relational databases, although other possible languages will also be discussed. We consider different types of conjunctive query rewriting and their succinctness, different architectures of OBDA systems, and give an overview of the OBDA system Ontop
Quintessence in a quandary: prior dependence in dark energy models
The archetypal theory of dark energy is quintessence: a minimally coupled
scalar field with a canonical kinetic energy and potential. By studying random
potentials we show that quintessence imposes a restricted set of priors on the
equation of state of dark energy. Focusing on the commonly-used
parametrisation, , we show that there is a natural
scale and direction in the plane that distinguishes quintessence
as a general framework. We calculate the expected information gain for a given
survey and show that, because of the non-trivial prior information, it is a
function of more than just the figure of merit. This allows us to make a
quantitative case for novel survey strategies. We show that the scale of the
prior sets target observational requirements for gaining significant
information. This corresponds to a figure of merit FOM, a
requirement that future galaxy redshift surveys will meet.Comment: 5 pages, 3 figures. For the busy reader, Fig. 1 is the money plot.
v2: Minor changes, matches published version. Code open source at
gitorious.org/random-quintessenc
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