Página 21 dos resultados de 20101 itens digitais encontrados em 0.010 segundos

## ‣ Fermionic entanglement that survives a black hole

Martin-Martinez, E.; Leon, J.
Tipo: Artigo de Revista Científica
Português
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We introduce an arbitrary number of accessible modes when analyzing bipartite entanglement degradation due to Unruh effect between two partners Alice and Rob. Under the single mode approximation (SMA) a fermion field only had a few accessible levels due to Pauli exclusion principle, conversely to bosonic fields which had an infinite number of excitable levels. This was argued to justify entanglement survival in the fermionic case in the SMA infinite acceleration limit. Here we relax SMA. Hence, an infinite number of modes are excited as the observer Rob accelerates, even for a fermion field. We will prove that, despite this analogy with the bosonic case, entanglement loss is limited. We will show that this comes from fermionic statistics through the characteristic structure it imposes on the infinite dimensional density matrix for Rob. Surprisingly, the surviving entanglement is independent of the specific maximally entangled state chosen, the kind of fermionic field analyzed, and the number of accessible modes considered. We shall discuss whether this surviving entanglement goes beyond the purely statistical correlations, giving insight concerning the black hole information paradox.; Comment: 10 pages, 1 figure, revtex4

## ‣ The optimal bound of quantum erasure with limited means

Miatto, Filippo M.; Piché, Kevin; Brougham, Thomas; Boyd, Robert W.
Tipo: Artigo de Revista Científica
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In practical applications of quantum information science, quantum systems can have non-negligible interactions with the environment, and this generally degrades the power of quantum protocols as it introduces noise. Counteracting this by appropriately measuring the environment (and therefore projecting its state) would require access all the necessary degrees of freedom, which in practice can be far too hard to achieve. To better understand one's limitations, we calculate the upper bound of optimal quantum erasure (i.e. the highest recoverable visibility, or "coherence"), when erasure is realistically limited to an accessible subspace of the whole environment. In the particular case of a two-dimensional accessible environment, the bound is given by the sub-fidelity of two particular states of the \emph{inaccessible} environment, which opens a new window into understanding the connection between correlated systems. We also provide an analytical solution for a three-dimensional accessible environment. This result provides also an interesting operational interpretation of sub-fidelity. We end with a statistical analysis of the expected visibility of an optimally erased random state and we find that 1) if one picks a random pure state of 2 qubits...

## ‣ Non-Markovianity through flow of information between a system and an environment

Haseli, S.; Karpat, G.; Salimi, S.; Khorashad, A. S.; Fanchini, F. F.; Çakmak, B.; Aguilar, G. H.; Walborn, S. P.; Ribeiro, P. H. Souto
Tipo: Artigo de Revista Científica
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Exchange of information between a quantum system and its surrounding environment plays a fundamental role in the study of the dynamics of open quantum systems. Here we discuss the role of the information exchange in the non-Markovian behavior of dynamical quantum processes following the decoherence approach, where we consider a quantum system that is initially correlated with its measurement apparatus, which in turn interacts with the environment. We introduce a new way of looking at the information exchange between the system and environment using the quantum loss, which is shown to be closely related to the measure of non-Markovianity based on the quantum mutual information. We also extend the results of [Phys. Rev. Lett. 112, 210402 (2014)] by Fanchini et al. in several directions, providing a more detailed investigation of the use of the accessible information for quantifying the backflow of information from the environment to the system. Moreover, we reveal a clear conceptual relation between the entanglement and mutual information based measures of non-Markovianity in terms of the quantum loss and accessible information. We compare different ways of studying the information flow in two theoretical examples. We also present experimental results on the investigation of the quantum loss and accessible information for a two-level system undergoing a zero temperature amplitude damping process. We use an optical approach that allows full access to the state of the environment.; Comment: 11 pages...

## ‣ Accessibility percolation and first-passage site percolation on the unoriented binary hypercube

Martinsson, Anders
Tipo: Artigo de Revista Científica
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Inspired by biological evolution, we consider the following so-called accessibility percolation problem: The vertices of the unoriented $n$-dimensional binary hypercube are assigned independent $U(0, 1)$ weights, referred to as fitnesses. A path is considered accessible if fitnesses are strictly increasing along it. We prove that the probability that the global fitness maximum is accessible from the all zeroes vertex converges to $1-\frac{1}{2}\ln\left(2+\sqrt{5}\right)$ as $n\rightarrow\infty$. Moreover, we prove that if one conditions on the location of the fitness maximum being $v$, then provided $v$ is not too close to the all zeroes vertex in Hamming distance, the probability that $v$ is accessible converges to a function of this distance divided by $n$ as $n\rightarrow\infty$. This resolves a conjecture by Berestycki, Brunet and Shi in almost full generality. As a second result we show that, for any graph, accessibility percolation can equivalently be formulated in terms of first-passage site percolation. This connection is of particular importance for the study of accessibility percolation on trees.; Comment: 25 pages, 4 figures

## ‣ An approach to NLO QCD analysis of the semi-inclusive DIS data with modified Jacobi polynomial expansion method

Sissakian, A. N.; Shevchenko, O. Yu.; Ivanov, O. N.
Tipo: Artigo de Revista Científica
Português
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It is proposed the modification of the Jacobi polynomial expansion method (MJEM) which is based on the application of the truncated moments instead of the full ones. This allows to reconstruct with a high precision the local quark helicity distributions even for the narrow accessible for measurement Bjorken $x$ region using as an input only four first moments extracted from the data in NLO QCD. It is also proposed the variational (extrapolation) procedure allowing to reconstruct the distributions outside the accessible Bjorken $x$ region using the distributions obtained with MJEM in the accessible region. The numerical calculations encourage one that the proposed variational (extrapolation) procedure could be applied to estimate the full first (especially important) quark moments.

## ‣ Cryptocat: Adopting Accessibility and Ease of Use as Security Properties

Tipo: Artigo de Revista Científica
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Cryptocat is a Free and Open Source Software (FL/OSS) browser extension that makes use of web technologies in order to provide easy to use, accessible, encrypted instant messaging to the general public. We aim to investigate how to best leverage the accessibility and portability offered by web technologies in order to allow encrypted instant messaging an opportunity to better permeate on a social level. We have found that encrypted communications, while in many cases technically well-implemented, suffer from a lack of usage due to their being unappealing and inaccessible to the "average end-user". Our position is that accessibility and ease of use must be treated as security properties. Even if a cryptographic system is technically highly qualified, securing user privacy is not achieved without addressing the problem of accessibility. Our goal is to investigate the feasibility of implementing cryptographic systems in highly accessible mediums, and to address the technical and social challenges of making encrypted instant messaging accessible and portable.; Comment: Working Draft

## ‣ Evolutionary accessibility of mutational pathways

Franke, Jasper; Klözer, Alexander; de Visser, J. Arjan G. M.; Krug, Joachim
Tipo: Artigo de Revista Científica
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Functional effects of different mutations are known to combine to the total effect in highly nontrivial ways. For the trait under evolutionary selection (fitness'), measured values over all possible combinations of a set of mutations yield a fitness landscape that determines which mutational states can be reached from a given initial genotype. Understanding the accessibility properties of fitness landscapes is conceptually important in answering questions about the predictability and repeatability of evolutionary adaptation. Here we theoretically investigate accessibility of the globally optimal state on a wide variety of model landscapes, including landscapes with tunable ruggedness as well as neutral holey' landscapes. We define a mutational pathway to be accessible if it contains the minimal number of mutations required to reach the target genotype, and if fitness increases in each mutational step. Under this definition accessibility is high, in the sense that at least one accessible pathwayexists with a substantial probability that approaches unity as the dimensionality of the fitness landscape (set by the number of mutational loci) becomes large. At the same time the number of alternative accessible pathways grows without bound. We test the model predictions against an empirical 8-locus fitness landscape obtained for the filamentous fungus \textit{Aspergillus niger}. By analyzing subgraphs of the full landscape containing different subsets of mutations...

## ‣ Alignment of reference frames and an operational interpretation for the G-asymmetry

Tipo: Artigo de Revista Científica
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We determine the quantum states and measurements that optimize the accessible information in a reference frame alignment protocol associated with the groups U(1), corresponding to a phase reference, and $\mathbb{Z}_M$, the cyclic group of $M$ elements. Our result provides an operational interpretation for the $G$-asymmetry which is information-theoretic and which was thus far lacking. In particular, we show that in the limit of many copies of the bounded-size quantum reference frame, the accessible information approaches the Holevo bound. This implies that the rate of alignment of reference frames, measured by the (linearized) accessible information per system, is equal to the regularized, linearized $G$-asymmetry. The latter quantity is equal to the number variance in the case where $G=U(1)$. Quite surprisingly, for the case where $G=\mathbb{Z}_{M}$ and $M\geq 4$, it is equal to a quantity that is not additive in general, but instead can be superadditive under tensor product of two distinct bounded-size reference frames. This remarkable phenomenon is purely quantum and has no classical analog.; Comment: 12pages, no figures. Title has been changed to match teh published version

## ‣ Random Oracles in a Quantum World

Boneh, Dan; Dagdelen, Özgür; Fischlin, Marc; Lehmann, Anja; Schaffner, Christian; Zhandry, Mark
Tipo: Artigo de Revista Científica
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The interest in post-quantum cryptography - classical systems that remain secure in the presence of a quantum adversary - has generated elegant proposals for new cryptosystems. Some of these systems are set in the random oracle model and are proven secure relative to adversaries that have classical access to the random oracle. We argue that to prove post-quantum security one needs to prove security in the quantum-accessible random oracle model where the adversary can query the random oracle with quantum states. We begin by separating the classical and quantum-accessible random oracle models by presenting a scheme that is secure when the adversary is given classical access to the random oracle, but is insecure when the adversary can make quantum oracle queries. We then set out to develop generic conditions under which a classical random oracle proof implies security in the quantum-accessible random oracle model. We introduce the concept of a history-free reduction which is a category of classical random oracle reductions that basically determine oracle answers independently of the history of previous queries, and we prove that such reductions imply security in the quantum model. We then show that certain post-quantum proposals, including ones based on lattices...

## ‣ A Reflection on the Structure and Process of the Web of Data

Rodriguez, Marko A.
Tipo: Artigo de Revista Científica
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The Web community has introduced a set of standards and technologies for representing, querying, and manipulating a globally distributed data structure known as the Web of Data. The proponents of the Web of Data envision much of the world's data being interrelated and openly accessible to the general public. This vision is analogous in many ways to the Web of Documents of common knowledge, but instead of making documents and media openly accessible, the focus is on making data openly accessible. In providing data for public use, there has been a stimulated interest in a movement dubbed Open Data. Open Data is analogous in many ways to the Open Source movement. However, instead of focusing on software, Open Data is focused on the legal and licensing issues around publicly exposed data. Together, various technological and legal tools are laying the groundwork for the future of global-scale data management on the Web. As of today, in its early form, the Web of Data hosts a variety of data sets that include encyclopedic facts, drug and protein data, metadata on music, books and scholarly articles, social network representations, geospatial information, and many other types of information. The size and diversity of the Web of Data is a demonstration of the flexibility of the underlying standards and the overall feasibility of the project as a whole. The purpose of this article is to provide a review of the technological underpinnings of the Web of Data as well as some of the hurdles that need to be overcome if the Web of Data is to emerge as the defacto medium for data representation...

## ‣ WILI - Web Interface for people with Lowvision Issues

Kuppusamy, K. S.; Francis, Leena Mary; Aghila, G.
Tipo: Artigo de Revista Científica
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Though World Wide Web is the single largest source of information, it is ill-equipped to serve the people with vision related problems. With the prolific increase in the interest to make the web accessible to all sections of the society, solving this accessibility problem becomes mandatory. This paper presents a technique for making web pages accessible for people with low vision issues. A model for making web pages accessible, WILI (Web Interface for people with Low-vision Issues) has been proposed. The approach followed in this work is to automatically replace the existing display style of a web page with a new skin following the guidelines given by Clear Print Booklet provided by Royal National Institute of Blind. "Single Click Solution" is one of the primary advantages provided by WILI. A prototype using the WILI model is implemented and various experiments are conducted. The results of experiments conducted on WILI indicate 82% effective conversion rate.; Comment: 8 Pages; 6 Figures, International Journal on Computational Sciences & Applications (IJCSA) Vo2, No.2, April 2012, ISSN: 2200-0011

## ‣ Evryscope science: exploring the potential of all-sky gigapixel-scale telescopes

Law, Nicholas M.; Fors, Octavi; Ratzloff, Jeffrey; Wulfken, Philip; Kavanaugh, Dustin; Sitar, David J.; Pruett, Zachary; Birchart, Mariah; Barlow, Brad; Cannon, Kipp; Cenko, S. Bradley; Dunlap, Bart; Kraus, Adam; Maccarone, Thomas J.
Tipo: Artigo de Revista Científica
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Low-cost mass-produced sensors and optics have recently made it feasible to build telescope arrays which observe the entire accessible sky simultaneously. In this article we discuss the scientific motivation for these telescopes, including exoplanets, stellar variability and extragalactic transients. To provide a concrete example we detail the goals and expectations for the Evryscope, an under-construction 780 MPix telescope which covers 8,660 square degrees in each two-minute exposure; each night, 18,400 square degrees will be continuously observed for an average of approximately 6 hours. Despite its small 61mm aperture, the system's large field of view provides an etendue which is ~10% of LSST. The Evryscope, which places 27 separate individual telescopes into a common mount which tracks the entire accessible sky with only one moving part, will return 1%-precision, many-year-length, high-cadence light curves for every accessible star brighter than mV=16.5, with brighter stars having few-millimagnitude photometric precision in long-term light curves. It will be capable of searching for transiting giant planets around the brightest and most nearby stars, where the planets are much easier to characterize; it will also search for small planets nearby M-dwarfs...

## ‣ Dark matter and Consequences of SUSY

Arnowitt, R.; Dutta, B.
Tipo: Artigo de Revista Científica
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We examine here the constraints from the amount of relic density of neutralino dark matter and other experiments have on the SUSY parameter space for the mSUGRA model and for models with non-universal soft breaking at the GUT scale. In mSUGRA, the allowed amount of dark matter restricts the SUSY parameter space to a narrow band in m_0 - m_{1/2} (except at very large \tan\beta). The Higgs mass and b-> s\gamma constraints produce a lower bound of m_{1/2}>~{\sim} 300GeV and if the muon magnetic moment anomaly can be interpreted as a 3\sigma deviation from the Standard Model, one also obtains an upper bound of m_{1/2} <~900 GeV, making the SUSY spectrum well accessible to the LHC. The B_s->\mu \mu decay is seen to be accessible to the Tevatron Run2B with 15 fb^{-1} for \tan\beta>~30. However, only parts of the spectrum will be accessible to the NLC if it's energy is below 800GeV. Non-universal soft breaking opens new regions of parameter space. Thus the m_{1/2} lower bound constraint of b->s\gamma and also the Higgs mass can be reduced greatly if the gluino mass is assumed larger at the GUT scale (allowing for a lighter gaugino spectrum), and non-universal Higgs soft breaking masses at the GUT scale can open new allowed regions at relatively low m_{1/2} and high m_0 where dark matter detection cross sections may be increased by a factor of ten or more.; Comment: 11 pages...

## ‣ On High-Contrast Characterization of Nearby, Short-Period Exoplanets with Giant Segmented-Mirror Telescopes

Crossfield, Ian J. M.
Tipo: Artigo de Revista Científica
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Measurements of the frequency with which short-period planets occur around main sequence stars allows a direct prediction of the number and types of such planets that will be amenable to characterization by high-contrast instruments on future giant segmented- mirror telescopes (GSMTs). Adopting conservative assumptions, I predict of order 10 planets with radii R_P=1-8 R_Earth and equilibrium temperatures <400 K should be accessible around stars within 8 pc of the Sun. These numbers are roughly the same for both near-infrared observations of scattered starlight and mid-infrared observations of planetary thermal emission, with the latter observations demonstrating greater relative sensitivity to smaller and cooler planets. Adopting the conservative assumption that planets with R_P=1-2 R_E and 2-4 R_E occur with equal frequency, I predict a 40% chance that a planet with R_P=1-2 R_E and equilibrium temperature 200-250 K will accessible to high-contrast thermal infrared characterization; this would be a compelling object for further study. To validate these predictions, more detailed analyses are needed of the occurrence frequencies of low-mass planets around M dwarfs, both in the Kepler field and in the solar neighborhood. Several planets already discovered by radial velocity surveys will be accessible to near-infrared high-contrast GSMT observations...

## ‣ Designing a cell phone application to alert and report drinking water quality to South Africans

Brown, Deana
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
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Drinking water quality, especially in many parts of South Africa, is far below acceptable standards. With an annual estimate of 43, 000 deaths from diarrheal diseases, 3 million cases of illness and treatment costs of over half a billion US dollars, the impact is critical (Mackintosh & Colvin, 2003). To address this issue the Aquatest project seeks to develop a simplified low-cost water quality test kit and information management solution. This would allow Water Service Providers, especially in rural areas, to monitor water quality and distribute test data to the necessary parties - Water Service Authorities and consumers. This research addresses the challenge of reporting complex and critical water quality information in a way that is accessible to all South Africans as law requires. In a country with high illiteracy rates, 11 official languages and limited-to-no access to technology in many areas, this is no easy feat. We propose that the use of appropriate information and communication technologies (ICT), coupled with culturally appropriate ways of presenting scientific data, would allow water quality information to be accessible to South Africans. With the penetration level of cell phones exceeding 100% of the South African population (ITU...

## ‣ The ethics of web design: ensuring access for everyone

Cook, Jack; Cook, Laura
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Parte de Livro
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Web accessibility is really not a technological issue but rather a cultural problem. A Web site is said to be web accessible if anyone, regardless of capabilities or disabilities, using any kind of Web browsing technology to visit the site has the ability to interact with the site if required. If properly planned from the start, a Web site can be functional, accessible and aesthetically pleasing. This chapter focuses on ensuring access to information available on the Internet. The overall objective is to increase awareness of Web accessibility issues by providing rationale for why Web designers should be interested in creating accessible sites. Specifically, this chapter identifies some of the emerging digital barriers to accessibility encountered by those with disabilities. Current efforts to address these barriers legally are identified and their effectiveness for breaking down barriers is discussed. The World Wide Web Consortium's (W3C's) Web Accessibility Initiative (WAI) is discussed, followed by a study of the 50 most visited Web sites. The chapter concludes with a discussion of the importance of this topic and future developments.

Tsutomu, A; Parton, B; Saksiri, B; Trager, B; Briggs, C; Camp, C; Clarke, C; Li, C; Coco, D; Frisina, D; Kavin, D; Miller, D; Nowak-adamczyk, D; Yao, D; Cayender, A; Raike, A; Clymer, E; Burton, G; Lylak, G; Poor, G; Choi, H; Mitchell, H; Williams, H; Par
Fonte: Rochester Institute of Technology Publicador: Rochester Institute of Technology
Tipo: Outros
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## ‣ The instability of freedom as noninterference: The case of isaiah berlin

Pettit, Philip
Fonte: University of Chicago Press Publicador: University of Chicago Press
Tipo: Artigo de Revista Científica
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In Hobbes, freedom of choice requires nonfrustration: the option you prefer must be accessible. In Berlin, it requires noninterference: every option, preferred or unpreferred, must be accessible-every door must be open. But Berlin's argument against Hobbes suggests a parallel argument that freedom requires something stronger still: that each option be accessible and that no one have the power to block access; the doors should be open, and there should be no powerful doorkeepers. This is freedom as nondomination. The claim is that freedom as noninterference is an unstable alternative between freedom as nonfrustration and freedom as nondomination.

## ‣ Realism and the epistemic accessibility of correspondence truth.

Volpe, Giorgio
Fonte: London School of Economics and Political Science Thesis Publicador: London School of Economics and Political Science Thesis
Tipo: Thesis; NonPeerReviewed Formato: application/pdf