La croissance de la gestion indicielle: la fin du marché ?

La gestion indicielle consiste à répliquer, physiquement ou synthétiquement, un indice de marché et de laisser évoluer ce panier sans modifier les pondérations. Il existe de nombreuses méthodes de pondération, mais les indices actuels ont pour critère le flottant des capitalisations boursières des actifs le composant. Dès lors, les fonds de réplication, simple de construction, ont les mêmes biais que les indices sous-jacents. La théorie de l’efficience des marchés est à la base de la gestion indicielle. Elle montre que dans un marché efficient, il est impossible de surperformer l’indice de référence sur le long terme, et ce encore moins après frais. Cette théorie s’avère vérifiée empiriquement par de nombreuses études sur certains marchés comme aux États-Unis. L’analyse comparative confirme que les rendements perçus activement sont souvent inférieurs à ceux de la gestion passive. Elle montre aussi que l’efficience n’est pas au même stade selon les régions et les secteurs. Ces études expliquent la croissance des actifs sous gestion des promoteurs de fonds indiciels. Les ETFs ont accéléré cette croissance en rendant encore plus accessibles les fonds passifs. Ces véhicules négociables en bourse offrent une liquidité permanente pour les investisseurs. Néanmoins, ils font l’objet de plusieurs critiques comme le fait qu’ils gonflent les prix des actions sous-jacentes et déforment les marchés. Lorsqu’un investisseur choisit un ETF passif, il ne tient pas compte des fondamentaux des entreprises. Il achètera au même titre une firme saine qu’une entreprise en ralentissement, toutes deux composantes de l’indice. Potentiellement, cette méthodologie va à l’encontre du schéma de découverte du prix équilibrant l’offre et la demande en cas d’excès d’utilisation de ces produits. Toutefois, ces instruments financiers complètent l’offre de produits et contribuent à l’efficience des marchés. L’environnement actuel est favorable au développement de ces fonds passifs. Le cadre réglementaire joue un rôle significatif car il est de plus en plus strict. Ainsi, les gérants actifs ont de moins en moins de liberté, ce qui réduit ainsi leur marge pour créer de la performance et augmentant leurs coûts notamment celui de la compliance. L’émergence des robots advisors contribue également à la croissance de la gestion passive, car elle donne accès à une grande diversification à coût faible. Finalement, les fonds indiciels n’ont pas encore atteint un seuil critique. Il est difficile de dire quelles seront les conséquences d’une telle masse sous gestion dans ce type de fonds dans le futur

A telecom band single-photon source using a grafted carbon nanotube coupled to a fiber Fabry-Perot cavity in the Purcell regime

We report on the coupling of a reconfigurable high Q fiber micro-cavity to an organic color center grafted to a carbon nanotube for telecom wavelength emission of single photons in the Purcell regime. Using three complementary approaches we assess various figures of merit of this tunable single photon source and of the cavity quantum electrodynamical effects : the brightening of the emitter is obtained by comparison of the count rates of the very same emitter in free-space and cavity coupled regimes. We demonstrate a fiber coupled single-photon output rate up to 20 MHz at 1275~nm. Using time-resolved and saturation measurements, we determine independently the radiative quantum yield and the Purcell factor of the system with values up to 30 for the smallest mode volumes. Finally, we take advantage of the tuning capability of the cavity to measure the spectral profile of the brightness of the source which gives access to the vacuum Rabi splitting $g$ with values up to $25 \; \mu$eV

Impact on construction project planning council of aqueduct Fruticas Chipaque

En los últimos años Colombia ha tenido un papel destacado en el escenario internacional por ser un país emergente económicamente, fortaleciendo significativamente los aspectos más relevantes para el desarrollo de un país. Dentro de estos factores relevantes se encuentra la construcción de infraestructurapública, que aporta grandes beneficios y brinda bienestar a la comunidad en general. Sin embargo muchas de estas obras se han visto afectadas por la mala planeación con la que se programan, incurriendo en sobrecostos que han llevado en el mejor de los casos a tiempos más largos de ejecución y en los casos más críticos al abandono de los proyectos, causando un notorio detrimento en el patrimonio de la nación y de los colombianos. Una vez revisada la información concerniente a la construcción del acueducto Fruticas del municipio de Chipaque se pudo determinar que son varios los factores que intervinieron para que su ejecución no se realizara dentro de los tiempos establecidos, siendo los más relevantes una pésima planeación de la obra dentro de su parte inicial y una gestión del riesgo inadecuada e inoportuna. El propósito fundamental de este artículo es hacer un análisis de un caso específico de un mal proyecto de construcción de infraestructura pública en Colombia, con el fin emitir algunas conclusiones, que de ser tenidas en cuenta, contribuyan a evitar que nuevos casos similares a este se presenten, afectando directamente a la economía del país y al mejoramiento de la calidad de vida de todos los colombianos.In recent years Colombia has had a prominent role on the international stage for being an economically emerging country, significantly strengthening the most important for a country's development issues. These relevant factors are the construction of public infrastructure, which provides great benefits and provides welfare to the community. However many of these works have been affected by the poor planning that are programmed with, incurring cost overruns that led to the best at longer runtimes and the most critical project abandonment cases causing a noticeable detriment to the heritage of the nation and Colombians. After reviewing the information concerning the construction of Fruticas aqueduct Township Chipaque it was determined that several factors intervened to your execution is not carried out within the established time, the most important being a lousy planning of the work within part of their initial management and inadequate and inappropriate risk. The main purpose of this paper is to analyze a specific case of a bad project to build public infrastructure in Colombia, to issue some conclusions, which if taken into account, help prevent new cases similar to this one submit, directly affecting the economy and improving the quality of life for all Colombians

An infinite genus mapping class group and stable cohomology

We exhibit a finitely generated group \M whose rational homology is isomorphic to the rational stable homology of the mapping class group. It is defined as a mapping class group associated to a surface \su of infinite genus, and contains all the pure mapping class groups of compact surfaces of genus $g$ with $n$ boundary components, for any $g\geq 0$ and $n>0$. We construct a representation of \M into the restricted symplectic group ${\rm Sp_{res}}({\cal H}_r)$ of the real Hilbert space generated by the homology classes of non-separating circles on \su, which generalizes the classical symplectic representation of the mapping class groups. Moreover, we show that the first universal Chern class in H^2(\M,\Z) is the pull-back of the Pressley-Segal class on the restricted linear group ${\rm GL_{res}}({\cal H})$ via the inclusion ${\rm Sp_{res}}({\cal H}_r)\subset {\rm GL_{res}}({\cal H})$.Comment: 14p., 8 figures, to appear in Commun.Math.Phy

Habitat and Seasonality Affect Mosquito Community Composition in the West Region of Cameroon.

To identify potential sylvatic, urban and bridge-vectors that can be involved in current or future virus spillover from wild to more urbanised areas, entomological field surveys were conducted in rural, peri-urban and urban areas spanning the rainy and dry seasons in western Cameroon. A total of 2650 mosquitoes belonging to 37 species and eight genera were collected. Mosquito species richness was significantly influenced by the specific combination of the habitat type and the season. The highest species richness was found in the peri-urban area (S = 30, Chao1 = 121 ± 50.63, ACE = 51.97 ± 3.88) during the dry season (S = 28, Chao1 = 64 ± 25.7, ACE = 38.33 ± 3.1). Aedes (Ae.) africanus and Culex (Cx.) moucheti were only found in the rural and peri-urban areas, while Cx. pipiens s.l. and Ae. aegypti were only found in the urban area. Cx. (Culiciomyia) spp., Cx. duttoni and Ae. albopictus were caught in the three habitat types. Importantly, approximately 52% of the mosquito species collected in this study have been implicated in the transmission of diverse arboviruses. This entomological survey provides a catalogue of the different mosquito species that may be involved in the transmission of arboviruses. Further investigations are needed to study the vectorial capacity of each mosquito species in arbovirus transmission

Sturmian morphisms, the braid group B_4, Christoffel words and bases of F_2

We give a presentation by generators and relations of a certain monoid generating a subgroup of index two in the group Aut(F_2) of automorphisms of the rank two free group F_2 and show that it can be realized as a monoid in the group B_4 of braids on four strings. In the second part we use Christoffel words to construct an explicit basis of F_2 lifting any given basis of the free abelian group Z^2. We further give an algorithm allowing to decide whether two elements of F_2 form a basis or not. We also show that, under suitable conditions, a basis has a unique conjugate consisting of two palindromes.Comment: 25 pages, 4 figure

Diagnostic value of cone beam computed tomography (CBCT) in occult scaphoid and wrist fractures

OBJECTIVE: Evaluate the diagnostic value of cone beam computed tomography (CBCT) for scaphoid and wrist fractures that are missed on standard radiographs. MATERIALS AND METHODS: Between September 2014 and October 2015, we prospectively enrolled 49 patients with a clinically suspected scaphoid fracture following an acute injury but had normal radiographs. Each patients underwent radiographs, CBCT and (magnetic resonance imaging) MRI within 7days of the initial injury event. Both exam were evaluated independently by two radiologists. RESULTS: For scaphoid cortical fractures CBCT sensitivity is 100% (95% CI: 75%-100%), specificity 97% (95% CI: 83%-100%). CBCT diagnosed all 24 corticals wrist fractures, corresponding to a sensitivity of 100% (95% CI: 83%-100%), specificity of 95% (95% CI: 75%-100%). Kappa agreement rate between the two radiologists was K=0.95 (95% CI: 0.85-1) for scaphoid fractures and K=0.87 (95% CI: 0.73-1) for wrist fractures. CONCLUSIONS: CBCT is superior to radiographs for diagnosing occult cortical fractures. Because of its low radiation dose, we believe that CBCT can be used in current practice as a replacement or supplement to radiographs to detect these fractures and optimize the cost-effectiveness ratio by limiting the number of needless immobilizations