6,835 research outputs found

    The stress energy tensor of a locally supersymmetric quantum field on a curved spacetime

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    For an analogon of the free Wess-Zumino model on Ricci flat spacetimes, the relation between a conserved `supercurrent' and the point-separated improved energy momentum tensor is investigated and a similar relation as on Minkowski space is established. The expectation value of the latter in any globally Hadamard product state is found to be a priori finite in the coincidence limit if the theory is massive. On arbitrary globally hyperbolic spacetimes the `supercurrent' is shown to be a well defined operator valued distribution on the GNS Hilbertspace of any globally Hadamard product state. Viewed as a new field, all n-point distributions exist, giving a new example for a Wightman field on that manifold. Moreover, it is shown that this field satisfies a new wave front set spectrum condition in a non trivial way.Comment: 100 pages, PhD Thesis, LaTeX2e + AMS-LaTeX, 5 figures appended as uuencoded ps-file

    Yardstick Competition when Quality is Endogenous: The Case of Hospital Regulation

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    In many countries hospital regulation undergoes fundamental change. In reaction to steadily increasing costs, authorities switch from cost of service regulation to prospective payment systems (PPS). While it seems clear that this new scheme sets strong cost saving incentives, this is not so clear for quality provision. As a matter of fact, everything hinges on the prices the regulator sets. Figuring out optimal prices is, however, a difficult task, be- cause the regulator faces serious informational limitations. The literature largely ignores this problem and points to Shleifer's (1985) yardstick compe- tition for a solution. Yardstick competition, however, ignores quality issues. This paper fills this gap in the literature and shows that endogenizing qual- ity changes the results of yardstick competition substantially. Quality will be zero and cost reduction efforts can be heavily distorted. In general, a simpler version of yardstick competition average cost pricing turns out to be more favorable, though not perfect.Yardstick Competition, Regulation, Hospital Market

    ER-mitochondria contacts: Actin dynamics at the ER control mitochondrial fission via calcium release.

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    The formin-like protein INF2 is an important player in the polymerization of actin filaments. In this issue, Chakrabarti et al. (2018. J. Cell Biol. https://doi.org/10.1083/jcb.201709111) demonstrate that INF2 mediates actin polymerization at the endoplasmic reticulum (ER), resulting in increased ER-mitochondria contacts, calcium uptake by mitochondria, and mitochondrial division

    Mantle formation, coagulation and the origin of cloud/core-shine: II. Comparison with observations

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    Many dense interstellar clouds are observable in emission in the near-IR, commonly referred to as "Cloudshine", and in the mid-IR, the so-called "Coreshine". These C-shine observations have usually been explained with grain growth but no model has yet been able to self-consistently explain the dust spectral energy distribution from the near-IR to the submm. We want to demonstrate the ability of our new core/mantle evolutionary dust model THEMIS (The Heterogeneous dust Evolution Model at the IaS), which has been shown to be valid in the far-IR and submm, to reproduce the C-shine observations. Our starting point is a physically motivated core/mantle dust model. It consists of 3 dust populations: small aromatic-rich carbon grains; bigger core/mantle grains with mantles of aromatic-rich carbon and cores either made of amorphous aliphatic-rich carbon or amorphous silicate. We assume an evolutionary path where these grains, when entering denser regions, may first form a second aliphatic-rich carbon mantle (coagulation of small grains, accretion of carbon from the gas phase), second coagulate together to form large aggregates, and third accrete gas phase molecules coating them with an ice mantle. To compute the corresponding dust emission and scattering, we use a 3D Monte-Carlo radiative transfer code. We show that our global evolutionary dust modelling approach THEMIS allows us to reproduce C-shine observations towards dense starless clouds. Dust scattering and emission is most sensitive to the cloud central density and to the steepness of the cloud density profile. Varying these two parameters leads to changes, which are stronger in the near-IR, in both the C-shine intensity and profile. With a combination of aliphatic-rich mantle formation and low-level coagulation into aggregates, we can self-consistently explain the observed C-shine and far-IR/submm emission towards dense starless clouds.Comment: Paper accepted for publication in A&A with companion paper "Mantle formation, coagulation and the origin of cloud/core-shine: I. Dust scattering and absorption in the IR", A.P Jones, M. Koehler, N. Ysard, E. Dartois, M. Godard, L. Gavila
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