First-principles scattering matrices for spin-transport

Details are presented of an efficient formalism for calculating transmission and reflection matrices from first principles in layered materials. Within the framework of spin density functional theory and using tight-binding muffin-tin orbitals, scattering matrices are determined by matching the wave-functions at the boundaries between leads which support well-defined scattering states and the scattering region. The calculation scales linearly with the number of principal layers N in the scattering region and as the cube of the number of atoms H in the lateral supercell. For metallic systems for which the required Brillouin zone sampling decreases as H increases, the final scaling goes as H^2*N. In practice, the efficient basis set allows scattering regions for which H^{2}*N ~ 10^6 to be handled. The method is illustrated for Co/Cu multilayers and single interfaces using large lateral supercells (up to 20x20) to model interface disorder. Because the scattering states are explicitly found, ``channel decomposition'' of the interface scattering for clean and disordered interfaces can be performed.Comment: 22 pages, 13 figure

Galactic cold cores. VI. Dust opacity spectral index

Context. The Galactic Cold Cores project has carried out Herschel photometric observations of 116 fields where the Planck survey has found signs of cold dust emission. The fields contain sources in different environments and different phases of star formation. Previous studies have revealed variations in their dust submillimetre opacity. Aims. The aim is to measure the value of dust opacity spectral index and to understand its variations spatially and with respect to other parameters, such as temperature, column density, and Galactic location. Methods. The dust opacity spectral index β and the dust colour temperature T are derived using Herschel and Planck data. The relation between β and T is examined for the whole sample and inside individual fields. Results. Based on IRAS and Planck data, the fields are characterised by a median colour temperature of 16.1 K and a median opacity spectral index of β = 1.84. The values are not correlated with Galactic longitude. We observe a clear T–β anti-correlation. In Herschel observations, constrained at lower resolution by Planck data, the variations follow the column density structure and β_(FIR) can rise to ~2.2 in individual clumps. The highest values are found in starless clumps. The Planck 217 GHz band shows a systematic excess that is not restricted to cold clumps and is thus consistent with a general flattening of the dust emission spectrum at millimetre wavelengths. When fitted separately below and above 700 μm, the median spectral index values are β_(FIR) ~ 1.91 and β(mm) ~ 1.66. Conclusions. The spectral index changes as a function of column density and wavelength. The comparison of different data sets and the examination of possible error sources show that our results are robust. However, β variations are partly masked by temperature gradients and the changes in the intrinsic grain properties may be even greater

Critical research on populism: Nine rules of engagement

This article formulates precise questions and ‘rules of engagement’ designed to advance our understanding of the role populism can and should play in the present political conjuncture, with potentially significant implications for critical management and organization studies and beyond. Drawing on the work of Ernesto Laclau and others working within the post-Marxist discourse theory tradition, we defend a concept of populism understood as a form of reason that centres around a claim to represent ‘the people’, discursively constructed as an underdog in opposition to an illegitimate ‘elite’. A formal discursive approach to populism brings with it important advantages. For example, it establishes that a populist logic can be invoked to further very different political goals, from radical left to right, or from progressive to regressive. It sharpens too our grasp of important issues that are otherwise conflated and obfuscated. For instance, it helps us separate out the nativist and populist dimensions in the discourses of the United Kingdom Independence Party (UKIP), Trump or the Front National (FN). Our approach to populism, however, also points to the need to engage with the rhetoric about populism, a largely ignored area of critical research. In approaching populism as signifier, not only as a concept, we stress the added need to focus on the uses of the term ‘populism’ itself: how it is invoked, by whom, and to what purpose and effect. This, we argue, requires that we pay more systematic attention to anti-populism and ‘populist hype’, and reflect upon academia’s own relation to populism and anti-populism

Is the Good Polity Attainable? Measuring the Quality of Democracy

This article introduces a discussion on defining, measuring, and assessing the quality of democracy. Providing a short overview of the papers of the Symposium, it places them within a broader context of current academic debate on various methodological, theoretical, and policy outreach dimensions of the topic

Understanding and Challenging Populist Negativity towards Politics: The Perspectives of British Citizens

This article adapts and develops the idea of a cynical or ‘stealth’ understanding of politics to explore how citizens’ estrangement from formal politics is processed cognitively through a populist lens. Earlier work has shown the widespread presence of stealth attitudes in the United States and Finland. We show that stealth attitudes are also well established in Britain, demonstrate their populist character and reveal that age, newspaper readership and concerns about governing practices help predict their adoption by individuals. Yet our survey findings also reveal a larger body of positive attitudes towards the practice of democracy suggesting that there is scope for challenging populist cynicism. We explore these so-called ‘sunshine’ attitudes and connect them to the reform options favoured by British citizens. If we are to challenge populist negativity towards politics, we conclude that improving the operation of representative politics is more important than offering citizens new forms of more deliberative participation

Anger, anxiety and corruption perceptions: Evidence from France

British Academy grant SG-101785

Honesty above all else? Expectations and perceptions of political conduct in three established democracies

The authors gratefully acknowledge financial support from the ESRC (grant number RES-000-22-3459) and British Academy (grant numbers SG-101785 and SG-52322). They would also like to thank two anonymous reviewers for their helpful comments and suggestions

“Democra-city”: bringing the city back into democratic theory for the 21st century?

Almost 50 years ago Robert Dahl maintained "we can […] reasonably hope 1 day to achieve great democratic cities. As the optimum unit for democracy in the 21st century, the city has a greater claim, I think, than any other alternative" (Am Polit Sci Rev 61: 953–970, 1967). This article intends to ascertain whether the words of one of the greatest scholars of democracy have had a concrete outcome along the pathways taken by democratic theory and whether, therefore, as was the case in classical theory, real superiority has therefore been restored to the city compared with the other territorial institutions of democracy. In this article we begin with two assumptions, each concerning the theoretical status of democratic theory. The first maintains that a realistic and an idealistic dimension coexist in variable dimensions in theoretical democratic models. According to the second assumption, it can be stated that democratic theory envisages the presence of a local territorial dimension, the importance of which is nevertheless variable in the different theoretical models. The thesis we intend to demonstrate here is that the variable nature of the importance of the local-urban territorial dimension depends on the type of balance created between the idealistic and realistic dimensions of the different models of democracy. Concluding, we aim to theoretically demonstrate why (and at which conditions) the city can become, more and better than any other institutional place, the ultimate arena within which the best results may be achieved for democracy in 21st century