12,119 research outputs found
Geometric mutual information at classical critical points
A practical use of the entanglement entropy in a 1d quantum system is to
identify the conformal field theory describing its critical behavior. It is
exactly for an interval of length in an infinite system,
where is the central charge of the conformal field theory. Here we define
the geometric mutual information, an analogous quantity for classical critical
points. We compute this for 2d conformal field theories in an arbitrary
geometry, and show in particular that for a rectangle cut into two rectangles,
it is proportional to . This makes it possible to extract in classical
simulations, which we demonstrate for the critical Ising and 3-state Potts
models.Comment: 5 pages. v3: published versio
Advanced Coordinated Beamforming for the Downlink of Future LTE Cellular Networks
Modern cellular networks in traditional frequency bands are notoriously
interference-limited especially in urban areas, where base stations are
deployed in close proximity to one another. The latest releases of Long Term
Evolution (LTE) incorporate features for coordinating downlink transmissions as
an efficient means of managing interference. Recent field trial results and
theoretical studies of the performance of joint transmission (JT) coordinated
multi-point (CoMP) schemes revealed, however, that their gains are not as high
as initially expected, despite the large coordination overhead. These schemes
are known to be very sensitive to defects in synchronization or information
exchange between coordinating bases stations as well as uncoordinated
interference. In this article, we review recent advanced coordinated
beamforming (CB) schemes as alternatives, requiring less overhead than JT CoMP
while achieving good performance in realistic conditions. By stipulating that,
in certain LTE scenarios of increasing interest, uncoordinated interference
constitutes a major factor in the performance of CoMP techniques at large, we
hereby assess the resilience of the state-of-the-art CB to uncoordinated
interference. We also describe how these techniques can leverage the latest
specifications of current cellular networks, and how they may perform when we
consider standardized feedback and coordination. This allows us to identify
some key roadblocks and research directions to address as LTE evolves towards
the future of mobile communications.Comment: 16 pages, 6 figures, accepted to IEEE Communications Magazin
Domestic competition and export performance of manufacturing firms in Côte d’Ivoire
Because of transportation costs, African manufacturing firms benefit from some market power on their domestic market, where they can charge a higher price than the export price, net of transportation cost. We present a simple theoretical model of an exporting firm that discriminates between the export and the domestic markets, where firms engage in Cournot competition. It is then shown that the impact of increased competition on export performance by the firms is ambiguous, and may be negative for a non trivial range of parameter values. Using survey data on Ivoirian firms, our empirical analysis gives some support to this prediction, showing that the probability of a firm exporting decreases with increased competition.
Approche par les principes, approche par les cas : les limites philosophiques d'une opposition
International audienceAnalyse de l'articulation entre cas et principe en éthique clinique, à partir du modèle élaboré par le Centre d'éthique clinique de l'hôpital Cochi
Guayaquil (1900-1940): agro-exportation et structuration de l'espace urbain
L'analyse des dynamiques urbaines de Guayaquil de 1900 à 1940 permet de mettre en valeur quatre structures élémentaires pour composer un modèle spécifique des structures spatiales du port principal de l'Équateur
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