53,096 research outputs found
Non-commutative holonomies in 2+1 LQG and Kauffman's brackets
We investigate the canonical quantization of 2+1 gravity with {\Lambda} > 0
in the canonical framework of LQG. A natural regularization of the constraints
of 2+1 gravity can be defined in terms of the holonomies of A\pm = A \PM
\surd{\Lambda}e, where the SU(2) connection A and the triad field e are the
conjugated variables of the theory. As a first step towards the quantization of
these constraints we study the canonical quantization of the holonomy of the
connection A_{\lambda} = A + {\lambda}e acting on spin network links of the
kinematical Hilbert space of LQG. We provide an explicit construction of the
quantum holonomy operator, exhibiting a close relationship between the action
of the quantum holonomy at a crossing and Kauffman's q-deformed crossing
identity. The crucial difference is that the result is completely described in
terms of standard SU(2) spin network states.Comment: 4 pages; Proceedings of Loops'11, Madrid, to appear in Journal of
Physics: Conference Series (JPCS
Optimal Capacity of the Blume-Emery-Griffiths perceptron
A Blume-Emery-Griffiths perceptron model is introduced and its optimal
capacity is calculated within the replica-symmetric Gardner approach, as a
function of the pattern activity and the imbedding stability parameter. The
stability of the replica-symmetric approximation is studied via the analogue of
the Almeida-Thouless line. A comparison is made with other three-state
perceptrons.Comment: 10 pages, 8 figure
Towards Sustainable Development of Small-Scale Fisheries in the Philippines: Experiences and Lessons Learned from Eight Regional Sites
The focus of this paper is on the governance of small-scale or municipal fisheries in the Philippines in light of the critical role they play in the livelihoods of coastal communities and in the nation as a whole. The information and insights presented in this lessons learned brief derive from the project entitled Strengthening Governance and Sustainability of Small-Scale Fisheries Management in the Philippines: An Ecosystem Approach. The project was funded principally by the Department of Agriculture's Bureau of Agricultural Research (DA-BAR), and implemented from 2008 to 2011 by WorldFish in collaboration with the Department of Science and Technology (DOST) and selected partners. The underlying project's goal was to 'strengthen governance and sustainability of small-scale fisheries management in the Philippines.' There were a variety of objectives spread across two project phases but the primary objectives relevant to this brief include: (1) identifying issues at project sites and assessing potential for an ecosystem based approach to fisheries management, and (2) assessing current fisheries management practices at different levels of governance and identifying best practices. The purposes of this paper are twofold. First, it aims to provide brief highlights of the project findings; second, it aims to present the lessons learned in project implementation covering substantive sectoral concerns as well as methodological issues. It wraps up with some strategic directions that need to be undertaken to reverse the deteriorating conditions of small-scale fisheries (SSF) while at the same time promoting their sustainable development
Thermal measurements of microwave transmitter feedhorn window
Thermal measurements of microwave transmitter feedhorn windows were performed using an imaging infrared radiometer. The measurement technique is described and results are presented for windows made of 0.001-in. Kapton (trademark of Dupont Chemical Co.) and 0.1-in. HTP-6 (Space Shuttle tile material). Measured and calculated temperatures agree well
Non-linear metric perturbation enhancement of primordial gravitational waves
We present the evolution of the full set of Einstein equations during
preheating after inflation. We study a generic supersymmetric model of hybrid
inflation, integrating fields and metric fluctuations in a 3-dimensional
lattice. We take initial conditions consistent with Eintein's constraint
equations. The induced preheating of the metric fluctuations is not large
enough to backreact onto the fields, but preheating of the scalar modes does
affect the evolution of vector and tensor modes. In particular, they do enhance
the induced stochastic background of gravitational waves during preheating,
giving an energy density in general an order of magnitude larger than that
obtained by evolving the tensors fluctuations in an homogeneous background
metric. This enhancement can improve the expectations for detection by planned
gravitational waves observatories.Comment: 5 pages, 4 eps figures, matches Phys. Rev. Lett. versio
Unbounded violations of bipartite Bell Inequalities via Operator Space theory
In this work we show that bipartite quantum states with local Hilbert space
dimension n can violate a Bell inequality by a factor of order (up
to a logarithmic factor) when observables with n possible outcomes are used. A
central tool in the analysis is a close relation between this problem and
operator space theory and, in particular, the very recent noncommutative
embedding theory. As a consequence of this result, we obtain better Hilbert
space dimension witnesses and quantum violations of Bell inequalities with
better resistance to noise
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