The stellar atmosphere simulation code Bifrost

Context: Numerical simulations of stellar convection and photospheres have been developed to the point where detailed shapes of observed spectral lines can be explained. Stellar atmospheres are very complex, and very different physical regimes are present in the convection zone, photosphere, chromosphere, transition region and corona. To understand the details of the atmosphere it is necessary to simulate the whole atmosphere since the different layers interact strongly. These physical regimes are very diverse and it takes a highly efficient massively parallel numerical code to solve the associated equations. Aims: The design, implementation and validation of the massively parallel numerical code Bifrost for simulating stellar atmospheres from the convection zone to the corona. Methods: The code is subjected to a number of validation tests, among them the Sod shock tube test, the Orzag-Tang colliding shock test, boundary condition tests and tests of how the code treats magnetic field advection, chromospheric radiation, radiative transfer in an isothermal scattering atmosphere, hydrogen ionization and thermal conduction. Results: Bifrost completes the tests with good results and shows near linear efficiency scaling to thousands of computing cores

Commensurability and beyond: from Mises and Neurath to the future of the socialist calculation debate

Mises' 'calculation argument' against socialism argues that monetary calculation is indispensable as a commensurable unit for evaluating factors of production. This is not due to his conception of rationality being purely 'algorithmic,' for it accommodates non-monetary, incommensurable values. Commensurability is needed, rather, as an aid in the face of economic complexity. The socialist Neurath's response to Mises is unsatisfactory in rejecting the need to explore possible non-market techniques for achieving a certain degree of commensurability. Yet Neurath's contribution is valuable in emphasizing the need for a balanced, comparative approach to the question of market versus non-market that puts the commensurability question in context. These central issues raised by adversaries in the early socialist calculation debate have continued relevance for the contemporary discussion

Theorising Disability: Beyond Common Sense

This article seeks to introduce the topic of disability to political theory via a discussion of some of the literature produced by disability theorists. The author argues that these more radical approaches conceptualise disability in ways that conflict with ‘common-sense’ notions of disability that tend to underpin political theoretical considerations of the topic. Furthermore, the author suggests that these more radical conceptualisations have profound implications for current debates on social justice, equality and citizenship that highlight the extent to which these notions are also currently underpinned by ‘common-sense’ notions of ‘normality’

Radiative transfer with scattering for domain-decomposed 3D MHD simulations of cool stellar atmospheres

We present the implementation of a radiative transfer solver with coherent scattering in the new BIFROST code for radiative magneto-hydrodynamical (MHD) simulations of stellar surface convection. The code is fully parallelized using MPI domain decomposition, which allows for large grid sizes and improved resolution of hydrodynamical structures. We apply the code to simulate the surface granulation in a solar-type star, ignoring magnetic fields, and investigate the importance of coherent scattering for the atmospheric structure. A scattering term is added to the radiative transfer equation, requiring an iterative computation of the radiation field. We use a short-characteristics-based Gauss-Seidel acceleration scheme to compute radiative flux divergences for the energy equation. The effects of coherent scattering are tested by comparing the temperature stratification of three 3D time-dependent hydrodynamical atmosphere models of a solar-type star: without scattering, with continuum scattering only, and with both continuum and line scattering. We show that continuum scattering does not have a significant impact on the photospheric temperature structure for a star like the Sun. Including scattering in line-blanketing, however, leads to a decrease of temperatures by about 350\,K below log tau < -4. The effect is opposite to that of 1D hydrostatic models in radiative equilibrium, where scattering reduces the cooling effect of strong LTE lines in the higher layers of the photosphere. Coherent line scattering also changes the temperature distribution in the high atmosphere, where we observe stronger fluctuations compared to a treatment of lines as true absorbers.Comment: A&A, in pres

Unorthodoxy in legislation: The Hungarian experience

This paper deals with legal unorthodoxy. The main idea is to study the so-called unorthodox taxes Hungary has adopted in recent years. The study of unorthodox taxes will be preceded by a more general discussion of how law is made under unorthodoxy, and what are the special features of unorthodox legal policy. Unorthodoxy challenges equality before the law and is critical towards mass democracies. It also raises doubts on the operability of the rule of law, relying on personal skills, or loyalty, rather than on impersonal mechanisms arising from checks and balances as developed by the division of political power. Besides, for lack of legal suppositions, legislation suffers from casuistry and regulatory capture

Evidence for Exotic J^{PC}=1^{-+} Meson Production in the Reaction pi- p --> eta pi- p at 18 GeV/c

Details of the analysis of the eta pi- system studied in the reaction pi^{-} p --> eta pi^{-} p at 18 GeV/c are given. Separate analyses for the 2 gamma and pi+ pi- pi0 decay modes of the eta are presented. An amplitude analysis of the data indicates the presence of interference between the a(2)(1320)- and a J^{PC}=1^{-+} wave between 1.2 and 1.6 GeV/c^2. The phase difference between these waves shows phase motion not attributable solely to the a(2)(1320)-. The data can be fitted by interference between the a(2)(1320)- and an exotic 1^{-+} resonance with M = 1370 +-16 +50 -30} MeV/c^2 and Gamma = 385 +- 40 +65 -105 MeV/c^2. Our results are compared with those of other experiments.Comment: 50 pages of text and 34 figure

Small States in the Rearview Mirror: Legitimacy in the Management of Economy and Society

Small States in World Markets is about political efficacy and legitimation rather than scoring who is ahead in the economic sweepstakes. Its case for democratic corporatism rests on norms, particularly stability, rather than on narrow measures of economic efficiency. But stability and the efficacious management of the economy and social problems requires a degree of technocracy that undermines the legitimacy of the management process itself by helping to produce populist revolts

Partial-wave analysis of the eta pi+ pi- system produced in the reaction pi-p --> eta pi+ pi- n at 18 GeV/c

A partial-wave analysis of 9082 eta pi+ pi- n events produced in the reaction pi- p --> eta pi+ pi- n at 18.3 GeV/c has been carried out using data from experiment 852 at Brookhaven National Laboratory. The data are dominated by J^{PC} = 0^{-+} partial waves consistent with observation of the eta(1295) and the eta(1440). The mass and width of the eta(1295) were determined to be 1282 +- 5 MeV and 66 +- 13 Mev respectively while the eta(1440) was observed with a mass of 1404 +- 6 MeV and width of 80 +- 21 MeV. Other partial waves of importance include the 1++ and the 1+- waves. Results of the partial wave analysis are combined with results of other experiments to estimate f1(1285) branching fractions. These values are considerably different from current values determined without the aid of amplitude analyses.Comment: 22 pages, 8 figure