2,873 research outputs found
On the construction of discrete approximations to linear differential expressions
Algorithm for generating discrete approximations in terms of ordinates for linear differential expression
Entropic uncertainty relations and locking: tight bounds for mutually unbiased bases
We prove tight entropic uncertainty relations for a large number of mutually
unbiased measurements. In particular, we show that a bound derived from the
result by Maassen and Uffink for 2 such measurements can in fact be tight for
up to sqrt{d} measurements in mutually unbiased bases. We then show that using
more mutually unbiased bases does not always lead to a better locking effect.
We prove that the optimal bound for the accessible information using up to
sqrt{d} specific mutually unbiased bases is log d/2, which is the same as can
be achieved by using only two bases. Our result indicates that merely using
mutually unbiased bases is not sufficient to achieve a strong locking effect,
and we need to look for additional properties.Comment: 9 pages, RevTeX, v3: complete rewrite, new title, many new results,
v4: minor changes, published versio
Optimal path for a quantum teleportation protocol in entangled networks
Bellman's optimality principle has been of enormous importance in the
development of whole branches of applied mathematics, computer science, optimal
control theory, economics, decision making, and classical physics. Examples are
numerous: dynamic programming, Markov chains, stochastic dynamics, calculus of
variations, and the brachistochrone problem. Here we show that Bellman's
optimality principle is violated in a teleportation problem on a quantum
network. This implies that finding the optimal fidelity route for teleporting a
quantum state between two distant nodes on a quantum network with bi-partite
entanglement will be a tough problem and will require further investigation.Comment: 4 pages, 1 figure, RevTeX
Prefactorized subgroups in pairwise mutually permutable products
The final publication is available at Springer via http://dx.doi.org/10.1007/s10231-012-0257-yWe continue here our study of pairwise mutually and pairwise totally permutable
products. We are looking for subgroups of the product in which the given factorization
induces a factorization of the subgroup. In the case of soluble groups, it is shown that a prefactorized
Carter subgroup and a prefactorized system normalizer exist.Aless stringent property
have F-residual, F-projector and F-normalizer for any saturated formation F including the
supersoluble groups.The first and fourth authors have been supported by the grant MTM2010-19938-C03-01 from MICINN (Spain).Ballester-Bolinches, A.; Beidleman, J.; Heineken, H.; Pedraza Aguilera, MC. (2013). Prefactorized subgroups in pairwise mutually permutable products. Annali di Matematica Pura ed Applicata. 192(6):1043-1057. https://doi.org/10.1007/s10231-012-0257-yS104310571926Amberg B., Franciosi S., de Giovanni F.: Products of Groups. Clarendon Press, Oxford (1992)Ballester-Bolinches, A., Pedraza-Aguilera, M.C., Pérez-Ramos, M.D.: Totally and Mutually Permutable Products of Finite Groups, Groups St. Andrews 1997 in Bath I. London Math. Soc. Lecture Note Ser. 260, 65–68. Cambridge University Press, Cambridge (1999)Ballester-Bolinches A., Pedraza-Aguilera M.C., Pérez-Ramos M.D.: On finite products of totally permutable groups. Bull. Aust. Math. Soc. 53, 441–445 (1996)Ballester-Bolinches A., Pedraza-Aguilera M.C., Pérez-Ramos M.D.: Finite groups which are products of pairwise totally permutable subgroups. Proc. Edinb. Math. Soc. 41, 567–572 (1998)Ballester-Bolinches A., Beidleman J.C., Heineken H., Pedraza-Aguilera M.C.: On pairwise mutually permutable products. Forum Math. 21, 1081–1090 (2009)Ballester-Bolinches A., Beidleman J.C., Heineken H., Pedraza-Aguilera M.C.: Local classes and pairwise mutually permutable products of finite groups. Documenta Math. 15, 255–265 (2010)Beidleman J.C., Heineken H.: Mutually permutable subgroups and group classes. Arch. Math. 85, 18–30 (2005)Beidleman J.C., Heineken H.: Group classes and mutually permutable products. J. Algebra 297, 409–416 (2006)Carocca A.: p-supersolvability of factorized groups. Hokkaido Math. J. 21, 395–403 (1992)Carocca, A., Maier, R.: Theorems of Kegel-Wielandt Type Groups St. Andrews 1997 in Bath I. London Math. Soc. Lecture Note Ser. 260, 195–201. Cambridge University Press, Cambridge, (1999)Doerk K., Hawkes T.: Finite Soluble Groups. Walter De Gruyter, Berlin (1992)Maier R., Schmid P.: The embedding of quasinormal subgroups in finite groups. Math. Z. 131, 269–272 (1973
Who Contributes to the Knowledge Sharing Economy?
Information sharing dynamics of social networks rely on a small set of
influencers to effectively reach a large audience. Our recent results and
observations demonstrate that the shape and identity of this elite, especially
those contributing \emph{original} content, is difficult to predict.
Information acquisition is often cited as an example of a public good. However,
this emerging and powerful theory has yet to provably offer qualitative
insights on how specialization of users into active and passive participants
occurs.
This paper bridges, for the first time, the theory of public goods and the
analysis of diffusion in social media. We introduce a non-linear model of
\emph{perishable} public goods, leveraging new observations about sharing of
media sources. The primary contribution of this work is to show that
\emph{shelf time}, which characterizes the rate at which content get renewed,
is a critical factor in audience participation. Our model proves a fundamental
\emph{dichotomy} in information diffusion: While short-lived content has simple
and predictable diffusion, long-lived content has complex specialization. This
occurs even when all information seekers are \emph{ex ante} identical and could
be a contributing factor to the difficulty of predicting social network
participation and evolution.Comment: 15 pages in ACM Conference on Online Social Networks 201
Ionic-liquid doped polymeric composite as passive colorimetric sensor for meat freshness as a use case
[EN] A composite membrane containing 1,2-naphthoquinone-4-sulfonic acid sodium salt (NQS) embedded in an ionic liquid (IL)- polydimethylsiloxane (PDMS)- tetraethyl orthosilicate (TEOS)- SiO2 nanoparticles (NPs) polymeric matrix is proposed. The selected IL was 1-methyl-3-octylimidazolium hexafluorophosphate (OMIM PF6). It is demonstrated that ILs chemical additives of PDMS influenced the sol-gel porosity. The sensor analytical performance for ammonia atmospheres has been tested as a function of sampling time (between 0.5 and 312 h), temperature (25 â—¦C and 4 â—¦C) and sampling volume (between 2L and 22 mL) by means of diffuse reflectance
measurements and sensor photos, which can be registered and saved as images by a smartphone, which permit RGB measurements too. Flexible calibration was possible, adapting it to the sampling time, temperature and sampling volume needed for its application. Calibration linear slopes (mA vs ppmv) between 1.7 and 467 ppmv-1 were obtained for ammonia in function of the several studied conditions. Those slopes were between 48 and 91% higher than those achieved with sensors without ILs. The practical application of this sensing device was demonstrated for the analysis of meat packaging environments, being a potential cost-effective candidate for in situ meat freshness analysis. NQS provided selectivity in reference to other family compounds emitted from meat products, such as sulphides. After 10 days at 4 ◦C ammonia liberated by the assayed meat was 20 ± 4 μg/kg and 18 ± 3 μg/kg, quantified by using diffuse reflectance and %R measurements, respectively. Homogeneity of the ammonia atmosphere was tested by using two sensors placed in two different positions inside the packages
Automated data reduction workflows for astronomy
Data from complex modern astronomical instruments often consist of a large
number of different science and calibration files, and their reduction requires
a variety of software tools. The execution chain of the tools represents a
complex workflow that needs to be tuned and supervised, often by individual
researchers that are not necessarily experts for any specific instrument. The
efficiency of data reduction can be improved by using automatic workflows to
organise data and execute the sequence of data reduction steps. To realize such
efficiency gains, we designed a system that allows intuitive representation,
execution and modification of the data reduction workflow, and has facilities
for inspection and interaction with the data. The European Southern Observatory
(ESO) has developed Reflex, an environment to automate data reduction
workflows. Reflex is implemented as a package of customized components for the
Kepler workflow engine. Kepler provides the graphical user interface to create
an executable flowchart-like representation of the data reduction process. Key
features of Reflex are a rule-based data organiser, infrastructure to re-use
results, thorough book-keeping, data progeny tracking, interactive user
interfaces, and a novel concept to exploit information created during data
organisation for the workflow execution. Reflex includes novel concepts to
increase the efficiency of astronomical data processing. While Reflex is a
specific implementation of astronomical scientific workflows within the Kepler
workflow engine, the overall design choices and methods can also be applied to
other environments for running automated science workflows.Comment: 12 pages, 7 figure
Multiphase Plasma in Sub-Damped Lyman Alpha Systems: A Hidden Metal Reservoir
We present a VLT/UVES spectrum of a proximate sub-damped Lyman-alpha
(sub-DLA) system at z=2.65618 toward the quasar Q0331-4505
(z_qso=2.6785+/-0.0030). Absorption lines of O I, Si II, Si III, Si IV, C II, C
III, C IV, Fe II, Al II, and O VI are seen in the sub-DLA, which has a neutral
hydrogen column density log N(H I)=19.82+/-0.05. The absorber is at a velocity
of 1820+/-250 km/s from the quasar; however, its low metallicity
[O/H]=-1.64+/-0.07, lack of partial coverage, lack of temporal variations
between observations taken in 2003 and 2006, and non-detection of N V imply the
absorber is not a genuine intrinsic system. By measuring the O VI column
density and assuming equal metallicities in the neutral and ionized gas, we
determine the column density of hot ionized hydrogen in this sub-DLA, and in
two other sub-DLAs with O VI drawn from the literature. Coupling this with
determinations of the typical amount of warm ionized hydrogen in sub-DLAs, we
confirm that sub-DLAs are a more important metal reservoir than DLAs, in total
comprising at least 6-22% of the metal budget at z~2.5.Comment: 5 pages, 3 color figures, accepted for publication in ApJ
On a theorem of Kang and Liu on factorised groups
[EN] Kang and Liu ['On supersolvability of factorized finite groups', Bull. Math. Sci. 3 (2013), 205-210] investigate the structure of finite groups that are products of two supersoluble groups. The goal of this note is to give a correct proof of their main theorem.The first author was supported by the grant MTM2014-54707-C3-1-P from the Ministerio de Economia y Competitividad, Spain, and FEDER, European Union, and a project of Natural Science Foundation of Guangdong Province (No. 2015A030313791).Ballester-Bolinches, A.; Pedraza Aguilera, MC. (2018). On a theorem of Kang and Liu on factorised groups. Bulletin of the Australian Mathematical Society. 97(1):54-56. https://doi.org/10.1017/S0004972717000363S5456971Ezquerro, L. M., & Soler-EscrivĂ , X. (2003). On MutuallyM-Permutable Products of Finite Groups. Communications in Algebra, 31(4), 1949-1960. doi:10.1081/agb-120018515Kang, P., & Liu, Q. (2013). On supersolvability of fatorized finite groups. Bulletin of Mathematical Sciences, 3(2), 205-210. doi:10.1007/s13373-013-0032-4Ballester-Bolinches, A., Esteban-Romero, R., & Asaad, M. (2010). Products of Finite Groups. de Gruyter Expositions in Mathematics. doi:10.1515/9783110220612Ballester-Bolinches, A., Cossey, J., & Pedraza-Aguilera, M. C. (2001). ON PRODUCTS OF FINITE SUPERSOLUBLE GROUPS. Communications in Algebra, 29(7), 3145-3152. doi:10.1081/agb-501
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