977 research outputs found
Entanglement and correlations in the continuous multi-scale entanglement renormalization ansatz
We investigate the entanglement structure of the continuous multi-scale
entanglement renormalization ansatz (cMERA) [Haegeman et al., Phys. Rev. Lett.,
110, 100402 (2013)] for ground states of quantum field theories (QFTs). The
cMERA, proposed as an extension to QFTs of the lattice MERA, is defined
directly in the continuum but is nevertheless naturally equipped with a
short-distance scale that acts as a UV regulator for quantum
fluctuations. We consider the simplified setting of Gaussian cMERA for free
QFTs, where explicit calculations can be performed. For relativistic free
massless bosonic and fermionic QFTs in both 1+1 and 2+1 spacetime dimensions,
we show that the cMERA state indeed displays no UV divergences in two-point
correlation functions or entanglement entropy, in sharp contrast with the exact
ground states.Comment: 28 pages, 20 figures, 4 appendices. Improved with referee's comment
Single-atom control of the optoelectronic response in sub-nanometric cavities
By means of ab-initio time dependent density functional theory calculations
carried out on an prototypical hybrid plasmonic device (two metallic
nanoparticles bridged by a one-atom junction), we demonstrate the strong
interplay between photoinduced excitation of localized surface plasmons and
electron transport through the single atom. Such an interplay is remarkably
sensitive to the atomic orbitals of the junction. Therefore, we show the
possibility of a twofold tuning (plasmonic response and photoinduced current
across the juntion) just by changing a single atom in the device.Comment: 5 pages, 5 figure
Stochastic resource allocation with a backhaul constraint for the uplink
We propose a novel stochastic radio resource alloca-
tion strategy for the uplink that achieves long-term fairness in
terms of similar bitrates considering backhaul and air-interface
capacity limitations. We focus on a single cell scenario based
on WCDMA technology. We propose to use a maximin criteria
to introduce fairness among the different users’ throughputs.
An stochastic approximation is implemented to obtain an online
algorithm where the Lagrange multipliers are estimated at each
scheduling period. Our results show that the proposed scheme
achieves higher fairness among the users and, in some cases, a
higher sum-rate compared with the well-known proportional fair
scheduler.Postprint (author's final draft
Anderson localization in carbon nanotubes: defect density and temperature effects
The role of irradiation induced defects and temperature in the conducting
properties of single-walled (10,10) carbon nanotubes has been analyzed by means
of a first-principles approach. We find that di-vacancies modify strongly the
energy dependence of the differential conductance, reducing also the number of
contributing channels from two (ideal) to one. A small number of di-vacancies
(5-9) brings up strong Anderson localization effects and a seemly universal
curve for the resistance as a function of the number of defects. It is also
shown that low temperatures, around 15-65 K, are enough to smooth out the
fluctuations of the conductance without destroying the exponential dependence
of the resistivity as a function of the tube length.Comment: 4 pages, 4 figure
Molecular epidemiology of Salmonella Typhimurium and Salmonella 4,5,12:i:- isolated from pig farms in Spain
The genetic diversity of 194 salmonella isolates belonging to different phagetypes of S. Typhimurium and S 4,5, 12:i- isolated from both healthy slaughter (157) and diarrhoea-affected (37) pigs was assessed using molecular typing (plasmid profiling and PFGE). The aim of this study was to elucidate the sources of infection, and to follow the spread of specific clones within the infected farms. In spite of the genetic diversity observed amongst the isolates, some clones were more prevalent and widely distributed in the pig population, being detected in several slaughter batches from the same and different farms. This finding suggests the existence of multiple and recurrent infection sources, as well as mechanisms favouring survival, persistence and spreading of certam clones within and between pig farms
How to assist the students while learning from text? Effects of inserting adjunct questions on text processing
This study analyzes the effect of text-inserted questions and post-text-reading questions, i.e., question timing, on students' processing and learning when studying challenging texts. Seventy-six freshmen read two science texts and answered ten adjunct questions with the text available, being tested on learning 5 days afterwards. Questions were presented either after reading the whole text or inserted in the text after reading the relevant information. Online processing data were recorded while reading and searching the texts, and measures of processing strategies (i.e., paraphrases, elaborations) while answering the questions were collected. Compared to students in the post-reading condition, those in the inserted condition spent more time reading the text initially, were more efficient at searching for information in the text, and produced more accurate elaborations, all of which may explain why answering inserted questions in an available text were more efective in terms of learning than answering post-reading questions. Limitations and educational implications of these results are also discussed
Base station on/off strategies for wireless networks powered with energy harvesting sources
In this paper, we present a procedure for switching on and off base stations (BSs) that are powered with solar panels and have finite batteries. In the scenario under consideration it is considered that the BSs are placed at the same site with fully overlapped coverage areas and using different frequencies. We propose a decision strategy where we assume perfect knowledge of the traffic profile and a second approach where a robust Bayesian strategy is considered in order to account for possible error modeling in the traffic profile information.The research leading to these results has received funding from the European Commission in the framework of the FP7 Network of Excellence in Wireless COMmunications NEWCOM# (Grant agreement no. 318306) and project TUCAN3G (Grant agreement no. ICT-2011-601102), from the Spanish Ministry of Economy and Competitiveness (Ministerio de Economía y Competitividad) through the project TEC2011-29006-C03-02 (GRE3N-LINK-MAC), project TEC2013-41315-R (DISNET), and FPI grant BES-2012-052850, and from the Catalan Government (AGAUR) through the grant 2014 SGR 60.Peer ReviewedPostprint (author's final draft
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