A contextual extension of Spekkens' toy model

Quantum systems show contextuality. More precisely, it is impossible to reproduce the quantum-mechanical predictions using a non-contextual realist model, i.e., a model where the outcome of one measurement is independent of the choice of compatible measurements performed in the measurement context. There has been several attempts to quantify the amount of contextuality for specific quantum systems, for example, in the number of rays needed in a KS proof, or the number of terms in certain inequalities, or in the violation, noise sensitivity, and other measures. This paper is about another approach: to use a simple contextual model that reproduces the quantum-mechanical contextual behaviour, but not necessarily all quantum predictions. The amount of contextuality can then be quantified in terms of additional resources needed as compared with a similar model without contextuality. In this case the contextual model needs to keep track of the context used, so the appropriate measure would be memory. Another way to view this is as a memory requirement to be able to reproduce quantum contextuality in a realist model. The model we will use can be viewed as an extension of Spekkens' toy model [Phys. Rev. A 75, 032110 (2007)], and the relation is studied in some detail. To reproduce the quantum predictions for the Peres-Mermin square, the memory requirement is more than one bit in addition to the memory used for the individual outcomes in the corresponding noncontextual model.Comment: 10 page

Loopholes in Bell Inequality Tests of Local Realism

Bell inequalities are intended to show that local realist theories cannot describe the world. A local realist theory is one where physical properties are defined prior to and independent of measurement, and no physical influence can propagate faster than the speed of light. Quantum-mechanical predictions for certain experiments violate the Bell inequality while a local realist theory cannot, and this shows that a local realist theory cannot give those quantum-mechanical predictions. However, because of unexpected circumstances or "loopholes" in available experiment tests, local realist theories can reproduce the data from these experiments. This paper reviews such loopholes, what effect they have on Bell inequality tests, and how to avoid them in experiment. Avoiding all these simultaneously in one experiment, usually called a "loophole-free" or "definitive" Bell test, remains an open task, but is very important for technological tasks such as device-independent security of quantum cryptography, and ultimately for our understanding of the world.Comment: 42 pages, 2 figure

Meadow birds in Sweden – population trends, effects of restoration and management

The area of Swedish wet meadows has decreased drastically during the last century due to cultivation and abandonment. During the same time the meadow bird fauna have changed considerably. Here the population sizes and recent trends for 33 bird species commonly occurring on Swedish wet meadows are reviewed. 16 of the species have declining populations; 7 species have increasing populations, while 10 have more or less stable populations. However, several of the species also occur in other habitats, and population changes in meadow habitats have probably been more extensive than reflected by the overall data. Generally, management dependent species, such as waders, have declined strongly, while passerines connected to unmanaged habitats have had stable or increasing populations. Since the 1980s conservation of wet meadow birds have been prioritized in conservation and the area of managed wet meadows have increased. Available data suggests that some species (Lapwing, Yellow Wagtail, Curlew and Redshank) have increased at least in some restored areas. However, no general increase in bird numbers was found for all species after restoration. We present evidence for four not mutually exclusive hypotheses explaining this result: (1) An increase in population size due to restoration measures is more likely if the target species is still present in the area. (2) Restoration measures fail to increase bird numbers if landscape composition and site characteristics do not meet the habitat requirements of the target species. (3) Since there are large differences between mowing and grazing and furthermore grazing intensity on the structure and composition of grasslands, target species might not benefit from restoration measures in the presence of unfavourable grassland management. (4) The lack of effectiveness of restoration measures on target species might be caused by insufficient water levels resulting from former regulations of rivers and lakes. It is recommended that evaluations of effects of restoration measures and different management regimes should be encouraged since high quality data for such evaluations are still scarce.Die Fläche des Feuchtgrünlandes in Schweden hat sich im letzten Jahrhundert durch Nutzungsaufgabe und Kultivierung drastisch verringert. Zeitgleich sind auch erhebliche Veränderungen in der Wiesenvogelfauna feststellbar. Die vorliegende Studie beleuchtet die Bestandsentwicklung von 33 in schwedischen Grünlandgebieten auftretenden Brutvogelarten. Von diesen weisen 16 Arten abnehmende Bestände auf. Bei 7 Arten konnte eine Bestandszunahme festgestellt werden. 10 weitere Arten schließlich sind im Bestand stabil. Allerdings ist bei dieser Analyse zu berücksichtigen, dass einige dieser Arten auch in anderen Habitaten vorkommen. Deshalb ist nicht auszuschließen, dass die Populationsveränderungen im Grünland bei einigen Vogelarten möglicherweise weit reichender sind als es die landesweiten Trends vermuten lassen. Allgemein zeigt sich derzeit, dass alle auf eine landwirtschaftliche Bewirtschaftung angewiesene Brutvogelarten (z.B. viele Limikolen) deutliche Populationseinbußen verzeichnen. Singvögel dagegen, die auch eine gewisse Bindung an bestimmte Brachestadien besitzen, sind im Bestand stabil oder nehmen sogar zu. Seit den 1980er Jahren hat der Schutz von Wiesenvögeln in Schweden Priorität. Dies äußert sich u.a. in einer Zunahme restaurierter Feuchtgrünlandgebiete. Monitoringdaten legen den Schluss nahe, dass bestimmte Arten (hier: Kiebitz, Schafstelze, Großer Brachvogel und Rotschenkel) zumindest in einigen dieser restaurierten Gebiete zugenommen haben. Allerdings erfolgte keine grundsätzliche Zunahme aller Zielarten nach erfolgter Restauration. Wir präsentieren Belege für vier Hypothesen, die diesen Befund zu erklären suchen: (1) Eine Zunahme bei Zielarten ist wahrscheinlicher, wenn diese vor Durchführung der Restaurationsmaßnahmen noch als Brutvögel im Gebiet vertreten sind. (2) Restaurationsmaßnahmen führen bei Zielarten dann nicht zum Erfolg, wenn vorhandene Landschaftsstrukturen den Habitatansprüchen der Zielarten entgegenstehen. (3) Da Beweidung und Mahd, praktiziert in unterschiedlichen Intensitäten, auch zu unterschiedlichen Grünlandtypen in Struktur und Pflanzenartenzusammensetzung führen, kann die vor Ort praktizierte Grünlandnutzung durchaus nicht mit den Habitatansprüchen bestimmter Zielarten im Einklang stehen. (4) Die fehlende Effektivität von Restaurationsmaßnahmen auf bestimmte Brutvogelarten des Feuchtgrünlandes steht möglicherweise in Verbindung mit einer ungenügenden Optimierung des Wasserhaushaltes. Letztere resultiert vielfach aus früheren Eingriffen an schwedischen Flüssen und Seen. Es wird empfohlen, die Auswirkungen von Restaurations- und Managementmaßnahmen im Grünland stärker als bisher wissenschaftlich zu begleiten, da belastbare Daten in diesem Bereich nach wie vor selten sind

3D non-LTE line formation in the solar photosphere and the solar oxygen abundance

We study the formation of O I and OH spectral lines in three-dimensional hydrodynamic models of the solar photosphere. The line source function of the O I 777 nm triplet is allowed to depart from local thermodynamic equilibrium (LTE), within the two-level-atom approximation. Comparison with results from 1D models show that the 3D models alleviate, but do not remove, the discrepancy between the oxygen abundances reported from non-LTE work on the 777 nm triplet and from the [O I] 630 nm and OH lines. Results for the latter two could imply that the solar oxygen abundance is below 8.8 (lg(H) = 12). If this is confirmed, the discrepancy between theory and observation for the 777 nm triplet lines might fall within the range of errors in equivalent width measurements and f-values. The line source function of the 777 nm triplet in the 1.5D approximation is shown to differ insignificantly from the full 3D non-LTE result.Comment: 10 pages, uuencoded compressed PostScript file including figures, to appear in Astronomy & Astrophysics. Also available at ftp://www.astro.su.se/pub/da

Knowledge Management in the Learning Economy

The purpose of this paper is to show why to build ‘learning organisations’ must be a central element of knowledge management. The paper argues that the wide use of information technology has a contradictory impact on knowledge management. On the one hand it extends the potential for codifying knowledge. On the other hand it makes tacit knowledge scarcer and it contributes to the formation of ‘a learning economy’. The argument is supported by an empirical analysis of survey data from Denmark showing that firms that introduce several organisational practices, assumed to characterise the learning organisation, are more innovative than the average firm. The paper contributes to the empirical foundation for the argument that learning organisations stimulate innovation and competence building and it makes an original conceptual contribution of practical relevance by linking knowledge management to HRM and innovation management.Knowledge management, learning economy, interactive learning, organisational change

One Knowledge Base or Many Knowledge Pools?

It is increasingly realized that knowledge is the most important resource and that learning is the most important process in the economy. Sometimes this is expressed by coining the current era as characterised by a ‘knowledge based economy’. But this concept might be misleading by indicating that there is one common knowledge base on which economic activities can be built. In this paper we argue that it is more appropriate to see the economy as connecting to different ‘pools of knowledge’. The argument is built upon a conceptual framework where we make distinctions between private/public, local/global, individual/collective and tacit/codified knowledge. The purpose is both ‘academic’ and practical. Our analysis demonstrates the limits of a narrowly economic perspective on knowledge and we show that these distinctions have important implications both for innovation policy and for management of innovation.Knowledge, economic development

The University in the Learning Economy

In all parts of the world, universities are exposed to a growing pressure to change. This is caused by the emergence of new relationship between the economic dynamics and the production of knowledge as well as by policy and administrative initiatives finding their rationale in interpretations of these changes. In this paper an attempt is made to specify some of the new challenges, and suggest appropriate responses. Under the heading ‘the learning economy’ changes in the context of universities are identified. One important conclusion is that traditional modes of organisation, characterised by sharp and rigid borders between disciplines and isolation from the society at large are being challenged and alternatives have to be developed. Another conclusion is that strategies of alliance and networking have become a key factor behind the success of universities. A third conclusion is that the universities’ most significant contribution to society and the economy will remain welleducated graduates with critical minds and good learning skills.Production of knowledge, education, networks

Tight Bounds for the Pearle-Braunstein-Caves Chained Inequality Without the Fair-Coincidence Assumption

In any Bell test, loopholes can cause issues in the interpretation of the results, since an apparent violation of the inequality may not correspond to a violation of local realism. An important example is the coincidence-time loophole that arises when detector settings might influence the time when detection will occur. This effect can be observed in many experiments where measurement outcomes are to be compared between remote stations because the interpretation of an ostensible Bell violation strongly depends on the method used to decide coincidence. The coincidence-time loophole has previously been studied for the Clauser-Horne-Shimony-Holt (CHSH) and Clauser-Horne (CH) inequalities, but recent experiments have shown the need for a generalization. Here, we study the generalized "chained" inequality by Pearle-Braunstein-Caves (PBC) with two or more settings per observer. This inequality has applications in, for instance, Quantum Key Distribution where it has been used to re-establish security. In this paper we give the minimum coincidence probability for the PBC inequality for all N and show that this bound is tight for a violation free of the fair-coincidence assumption. Thus, if an experiment has a coincidence probability exceeding the critical value derived here, the coincidence-time loophole is eliminated.Comment: 7 pages, 2 figures, minor correction

The Social Dimension of the Learning Economy

This paper is a slightly revised version of Bengt-Åke Lundvall's Inaugural Lecture, the 10th of November at Department for Business Studies, Aalborg University. The general message is that the growing frequency of so-called paradoxes in economic theory and of unsolved socioeconomic problems reflects that neither economic theory nor policy has been adapted to the fact that we have entered a new phase: the 'Learning Economy'. It is shown that in the learning economy the capacity to learn increasingly determines the relative position of individuals, firms and national systems. The growing polarisation in the OECD-labour markets is explained by the increasing importance of learning and the acceleration in the rate of change. Finally, it is argued that the learning economy will not be sustainable if these tendencies are not countered by a New New Deal which puts the focus on the distribution of capabilities to learn