Conformal Transformations as Observables

C denotes either the conformal group in 3+1 dimensions, or in one chiral dimension. Let U be a unitary, strongly continuous representation of C satisfying the spectrum condition and inducing, by its adjoint action, automorphisms of a v.Neumann algebra A. We construct the unique inner representation U^A of the universal covering group of C implementing these automorphisms. U^A satisfies the spectrum condition and acts trivially on any U-invariant vector. This means in particular: Conformal transformations of a field theory having positive energy are weak limit points of local observables. Some immediate implications for chiral subnets are given. We propose the name ``Borchers-Sugawara construction''.Comment: 13 pages, no figures; analysis now covers conformal group of Minkowski space, minor additions, some typos correcte

Conformal Covariance Subalgebras

We give a direct Lie algebraic characterisation of conformal inclusions of chiral current algebras associated with compact, reductive Lie algebras. We use straightforward quantum field theoretic arguments and prove a long standing conjecture of Schellekens and Warner on grounds of unitarity and positivity of energy. We explore the structures found to characterise ``conformal covariance subalgebras'' and ``coset current algebras''.Comment: 9 pages, no figures; typos and minor improvement

The profession of (agricultural) economists and the experience of transition

The objective of the paper is to survey the state of knowledge of economists and agricultural economists at the onset of transition and seventeen years later. The "standard" economic reasoning in the early nineties were based on neoclassical economics and documented was has been termed the Washington Consensus. It is shown that the discrepancy between expectations and reality as well as the evolution of institutional economics has challenged economists. A "blue print" favoured in the early nineties seems to be opposed by many economist nowadays. Agricultural economists have been influenced by the lines of thought in the main profession, but there approach became country-specific in early years of the transition period. Nevertheless, there are some open questions concerning assessment and approach in giving policy advice.Washington Consensus, land reform, farm organization, Teaching/Communication/Extension/Profession,

Super-large Farms: The Importance of Institutions

There are many reasons for the evolution of super-farms in some of the CIS. This paper does not intend to elaborate on the whole set of reasons. There are already many studies which provide surveys on the background and the rationale of these organisations. This paper aims at focusing on one specific determinant of the rise of super-large farms, namely institutions. The focus is chosen as this determinant seems to have been overlooked, partly because it is completely beyond the neoclassical approach. Institutions as rules of the game can be classified into four levels according to Williamson. The paper mainly deals with embedded institutions. It is shown that these institutions are country-specific and vary widely across countries. It is argued that the evolution of super-large farms could only arise because cooperative and corporate farms survived up to bankruptcy and because embedded institutions impeded the foundation of family farms. Mental models of policy makers did contribute to the amalgation of corporate and cooperatives into super-large farms. However, it is noted that embedded institutions had such strong effects because markets did not work adequately and legislation and its enforcement was not supportive for the foundation of family farms. The paper ends with an evaluation from the economic point of view of the existence of super-large farms and with a projection of what may happen in the future.Agribusiness,

Carbon-rich (DQ) white dwarfs in the Sloan Digital Sky Survey

Among the spectroscopically identified white dwarfs, a fraction smaller than 2% have spectra dominated by carbon lines, mainly molecular C2, but also in a smaller group by CI and CII lines. These are together called DQ white dwarfs. We want to derive atmospheric parameters Teff,log g, and carbon abundances for a large sample of these stars and discuss implications for their spectral evolution. Sloan Digital Sky Survey spectra and ugriz photometry were used, together with GAIA Data Release 2 parallaxes and G band photometry. These were fitted to synthetic spectra and theoretical photometry derived from model atmospheres. We found that the DQs hotter than Teff ~10000 K have masses ~0.4 Msun larger than the cooler ones, which have masses typical for the majority of white dwarfs, ~0.6 Msun. A significant fraction of the hotter objects with Teff > 14500 K have atmospheres dominated by carbon.Comment: Accepted by Astronomy & Astrophysic

High-speed waveguide-coupled graphene-on-graphene optical modulators

An electro-absorption optical modulator concept based upon a dual-graphene layer is presented. The device consists of a silicon-on-insulator waveguide upon which two graphene layers reside, separated by a thin insulating region. The lower graphene acts as a tunable absorber, while the upper layer functions as a transparent gate electrode. Calculations based upon realistic graphene material properties show that 3-dB bandwidths over 100 GHz (30 GHz) are possible at near- (\lambda=1.55 \mu m) and mid- (\lambda=3.5\mu m) infrared bands. The effect of background doping and potential fluctuations on the bandwidth, modulation depth and insertion loss are also quantified.Comment: 18 pages, 4 figur

An empirical initial-final mass relation from hot, massive white dwarfs in NGC 2168 (M35)

The relation between the zero-age main sequence mass of a star and its white-dwarf remnant (the initial-final mass relation) is a powerful tool for exploration of mass loss processes during stellar evolution. We present an empirical derivation of the initial-final mass relation based on spectroscopic analysis of seven massive white dwarfs in NGC 2168 (M35). Using an internally consistent data set, we show that the resultant white dwarf mass increases monotonically with progenitor mass for masses greater than 4 solar masses, one of the first open clusters to show this trend. We also find two massive white dwarfs foreground to the cluster that are otherwise consistent with cluster membership. These white dwarfs can be explained as former cluster members moving steadily away from the cluster at speeds of <~0.5 km/s since their formation and may provide the first direct evidence of the loss of white dwarfs from open clusters. Based on these data alone, we constrain the upper mass limit of WD progenitors to be >=5.8 solar masses at the 90% confidence level for a cluster age of 150 Myr.Comment: 14 pages, 3 figures. Accepted for publication in the Astrophysical Journal Letters. Contains some acknowledgements not in accepted version (for space reasons), otherwise identical to accepted versio