148 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
Three dimensional loop quantum gravity: coupling to point particles
We consider the coupling between three dimensional gravity with zero
cosmological constant and massive spinning point particles. First, we study the
classical canonical analysis of the coupled system. Then, we go to the
Hamiltonian quantization generalizing loop quantum gravity techniques. We give
a complete description of the kinematical Hilbert space of the coupled system.
Finally, we define the physical Hilbert space of the system of self-gravitating
massive spinning point particles using Rovelli's generalized projection
operator which can be represented as a sum over spin foam amplitudes. In
addition we provide an explicit expression of the (physical) distance operator
between two particles which is defined as a Dirac observable.Comment: Typos corrected and references adde
A Note on B-observables in Ponzano-Regge 3d Quantum Gravity
We study the insertion and value of metric observables in the (discrete) path
integral formulation of the Ponzano-Regge spinfoam model for 3d quantum
gravity. In particular, we discuss the length spectrum and the relation between
insertion of such B-observables and gauge fixing in the path integral.Comment: 17 page
Cosmological Plebanski theory
We consider the cosmological symmetry reduction of the Plebanski action as a
toy-model to explore, in this simple framework, some issues related to loop
quantum gravity and spin-foam models. We make the classical analysis of the
model and perform both path integral and canonical quantizations. As for the
full theory, the reduced model admits two types of classical solutions:
topological and gravitational ones. The quantization mixes these two solutions,
which prevents the model to be equivalent to standard quantum cosmology.
Furthermore, the topological solution dominates at the classical limit. We also
study the effect of an Immirzi parameter in the model.Comment: 20 page
Activité antioxydante des composés phénoliques d’huile d’olive extraite par méthode traditionnelle
L'objectif de cette etude est de determiner la teneur en composes phenoliques totaux de lfhuile dfolive de la variete Chemlal obtenue par extraction artisanale et dfen tester leur pouvoir antioxydant. La teneur phenolique a ete determinee par la methode universelle Folin-Ciocalteu, alors que lfactivite antioxydante a ete evaluee par deux methodes complementaires: le test du radical libre 2,2-diphenyl-1-picrylhydrazyl et le test du β-carotene/acide linoleique. Cette huile dfolive a montre une teneur en composes phenoliques totaux de 167,29 ± 2,71mg EAG/kg et une valeur dfIC50 egale a 25, 38 ± 0,64mg/kg par le test DPPH et une activite antioxydante relative par le test β-carotene/acide linoleique de lfordre de 67,40 ± 1,02%. Le controle positif hydroxy toluene butyle (BHT) a devoile respectivement 23,86 ± 0,14mg/kg et 95,88 ± 0,85%. Ces resultats revelent une possible utilisation de cette huile dans la lutte contre les maladies lies au stress oxydant.Mot cles : Oleaeuropea, β-carotene/acide linoleique, DPPH, variete Chemlal, regime mediterraneen
On the Physical Hilbert Space of Loop Quantum Cosmology
In this paper we present a model of Riemannian loop quantum cosmology with a
self-adjoint quantum scalar constraint. The physical Hilbert space is
constructed using refined algebraic quantization. When matter is included in
the form of a cosmological constant, the model is exactly solvable and we show
explicitly that the physical Hilbert space is separable consisting of a single
physical state. We extend the model to the Lorentzian sector and discuss
important implications for standard loop quantum cosmology
Phenotypic, molecular and technological characterization of autochthonous lactobacilli strains isolated from cow’s milk and goat of Algerian populations
The raw milk is an important reservoir of microbial diversity can have important biotechnological applications, in particular to improve the unique characteristics of dairy products. For this effect, eight strains of autochthonus Lactobacilli have been isolated from goat and cow raw milk of the local Algerian populations (Setifian and Kabyle). The strains were then identified by phenotypic and molecular approaches by amplification and sequencing of 16S rDNA as Lb.casei (C4, C5, V2 and V5), Lb. paracasei (C6) and Lb.plantarum (C7, C8, C10). Virtually all the strains studied, from a technological point of view, produced lactic acid concentrations at or above 0.89g.100 mL<sup>-1</sup>. Most strains exhibit a high capacity and are actively producing proteolytic proteases in the stationary phase between 24 and 30 hours. The strains studied can be used in the starter cultures or co-cultures for making cheese.Keywords: Lactobacillus, identification, acidification, proteolysis
Black hole entropy from an SU(2)-invariant formulation of Type I isolated horizons
A detailed analysis of the spherically symmetric isolated horizon system is
performed in terms of the connection formulation of general relativity. The
system is shown to admit a manifestly SU(2) invariant formulation where the
(effective) horizon degrees of freedom are described by an SU(2) Chern-Simons
theory. This leads to a more transparent description of the quantum theory in
the context of loop quantum gravity and modifications of the form of the
horizon entropy.Comment: 30 pages, 1 figur
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