| 1. |
- Kehoe, Laura, et al.
(författare)
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Make EU trade with Brazil sustainable
- 2019
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 364:6438, s. 341-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 2. |
- Almbladh, Carl-Olof, et al.
(författare)
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IMPORTANCE OF SURFACE EFFECTS AND DYNAMICAL CORE-HOLE EFFECTS IN AUGER SPECTRA OF METALS AND SEMICONDUCTORS
- 1987
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Ingår i: Journal de Physique. Colloques. ; 48:c-9, s. 879-890
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Tidskriftsartikel (refereegranskat)abstract
- Auger CVV spectra of sp-bonded materials are generally believed to be well described by one-electron theory in the bulk. We here perform detailed calculations on several simple metals and on silicon and obtain results which differ markedly from experiments. To explain these discrepancies we investigate effects of the surface and dynamical effects of the sudden disappearance of the core hole in the final state. To study core-hole effects we solve Mahan-Nozières-DeDominicis (MND) model numerically over the entire band. The core-hole potential and other parameters in the MND model are determined by self-consistent calculations on systems with a core-hole impurity. To study surface and mean free path effects we perform slab calculations in the case of silicon, whereas we for the metals use a simpler infinite barrier model in which the valence states near the surface are constructed from Bloch states in a simple way. In all cases investigated either the effects of the surface or the effects of the core hole give important modifications and a much improved agreement with experiments.
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| 3. |
- Almbladh, Carl-Olof, et al.
(författare)
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Many-Body Theory of Auger Processes in Metals and Semiconductors
- 1988
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Ingår i: Recent Progress in Many-Body Theories. - 9781461309734 ; 1, s. 317-328
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Bokkapitel (refereegranskat)abstract
- Auger spectra of solids arise from radiationless decay of innershell vacancies created by x-ray or electron bombardment. In a corevalence-valence (CVV) Auger process, for instance, one valence electron is filling the core hole while another valence electron is ejected and carries away the excess energy. The core hole is essentially dispersionless, and thus the spectrum of emitted electrons would, in the simplest one-electron picture, reflect the self-folded valence-electron state density. Such a simple model is, of course, grossly oversimplified, and the importance of matrix element effects has been demonstrated by several authors.1 However, no detailed investigation of many-body effects has been presented thus far for sp-bonded materials, and the current view is that one electron theory and bulk wavefunctions suffice to explain the experimental results.
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| 4. |
- Almbladh, Carl-Olof, et al.
(författare)
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Phonon effects in deep-level spectra of metals: Beyond the linear-screening and linear-coupling models
- 1983
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Ingår i: Physical Review B. - 1550-235X. ; 28:12, s. 7362-7365
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Tidskriftsartikel (refereegranskat)abstract
- A priori calculations of phonon broadening of core levels in metals are presented. The effects of nonlinear screening and higher-order couplings are taken into account for the first time. The nonlinear screening effects are very important for Li and must be accounted for in order to obtain agreement with experiment.
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| 5. |
- Almbladh, Carl-Olof, et al.
(författare)
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Phonon effects on deep-level excitations in metals: Beyond the linear-screening and linear-coupling models
- 1985
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Ingår i: Journal of Physics F: Metal Physics. - 0305-4608. ; 15:4, s. 991-1012
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Tidskriftsartikel (refereegranskat)abstract
- New theoretical developments in impurity lattice dynamics are presented, with the emphasis on phonon broadening of core levels in metals. Detailed calculations have been made for Li and Na. The effects of non-linear screening are evaluated for the first time and are shown to increase the phonon broadening by about 70% for Li compared with the linear-screening value. The present a priori estimate of the phonon broadening of the Li 1s level is the first which agrees with experiment. The effects of core-hole-lattice couplings of second order in ion displacements are also evaluated and shown to be unimportant for Li and Na. The usual linear-screening theory for lattice dynamics and for impurity-lattice couplings is analysed critically with regard to its sensitivity to the approximations for the pseudopotential and for the screening function. Both optimised model potentials and norm-conserving a priori potentials are considered. Finally, an indirect phonon broadening mechanism proposed previously is analysed and shown to give a negligible effect.
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| 6. |
- Almbladh, Carl-Olof, et al.
(författare)
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Theory of Auger core-valence-valence processes in simple metals. I. Total yields and core-level lifetime widths
- 1989
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Ingår i: Physical Review B. - 1550-235X. ; 39:6, s. 3489-3502
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Tidskriftsartikel (refereegranskat)abstract
- There is a considerable disagreement in the literature on the description of lifetime effects arising from core-valence transitions in solids. We calculate here Auger and radiative widths of shallow core levels in Li, Be, Na, Mg, and Al with use of principles consistent with dynamical theories of secondary-emission processes developed earlier. The lifetime has no simple relation to the usual self-energy but is instead directly related to emission yields. The problem of choosing reliable approximations for Auger rates and matrix elements is analyzed theoretically and computationally. We also comment on some earlier approaches. Much of our discussion pertains also to calculations of Auger line shapes from first principles. For long hole lifetimes the total and partial level widths obey an initial-state rule and follow from wave functions perturbed by a static core hole. To obtain these impurity wave functions we perform self-consistent supercell calculations. The core-hole screening increases the Auger rates by factors of the order 2–4 compared with results from ground-state orbitals but has never been properly included before. The width of the 1s level in Li is rather accurately known because it monitors large effects of incomplete lattice relaxation. For Li we obtain here a width 17 meV in excellent agreement with the value 16 meV deduced earlier from measurements by Callcott et al.
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| 7. |
- Almbladh, Carl-Olof, et al.
(författare)
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Theory of Auger core-valence-valence processes in simple metals. II. Dynamical and surface effects on Auger line shapes
- 1989
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Ingår i: Physical Review B. - 1550-235X. ; 39:6, s. 3503-3516
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Tidskriftsartikel (refereegranskat)abstract
- Auger CVV spectra of simple metals are generally believed to be well described by one-electron-like theories in the bulk which account for matrix elements and, in some cases, also static core-hole screening effects. We present here detailed calculations on Li, Be, Na, Mg, and Al using self-consistent bulk wave functions and proper matrix elements. The resulting spectra differ markedly from experiment and peak at too low energies. To explain this discrepancy we investigate effects of the surface and dynamical effects of the sudden disappearance of the core hole in the final state. To study core-hole effects we solve Mahan-Nozières-De Dominicis (MND) model numerically over the entire band. The core-hole potential and other parameters in the MND model are determined by self-consistent calculations of the core-hole impurity. The results are compared with simpler approximations based on the final-state rule due to von Barth and Grossmann. To study surface and mean-free-path effects we perform slab calculations for Al but use a simpler infinite-barrier model in the remaining cases. The model reproduces the slab spectra for Al with very good accuracy. In all cases investigated either the effects of the surface or the effects of the core hole give important modifications and a much improved agreement with experiment.
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| 8. |
- Barack, Leor, et al.
(författare)
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Black holes, gravitational waves and fundamental physics : a roadmap
- 2019
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Ingår i: Classical and quantum gravity. - : IOP Publishing. - 0264-9381 .- 1361-6382. ; 36:14
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Forskningsöversikt (refereegranskat)abstract
- The grand challenges of contemporary fundamental physics dark matter, dark energy, vacuum energy, inflation and early universe cosmology, singularities and the hierarchy problem all involve gravity as a key component. And of all gravitational phenomena, black holes stand out in their elegant simplicity, while harbouring some of the most remarkable predictions of General Relativity: event horizons, singularities and ergoregions. The hitherto invisible landscape of the gravitational Universe is being unveiled before our eyes: the historical direct detection of gravitational waves by the LIGO-Virgo collaboration marks the dawn of a new era of scientific exploration. Gravitational-wave astronomy will allow us to test models of black hole formation, growth and evolution, as well as models of gravitational-wave generation and propagation. It will provide evidence for event horizons and ergoregions, test the theory of General Relativity itself, and may reveal the existence of new fundamental fields. The synthesis of these results has the potential to radically reshape our understanding of the cosmos and of the laws of Nature. The purpose of this work is to present a concise, yet comprehensive overview of the state of the art in the relevant fields of research, summarize important open problems, and lay out a roadmap for future progress. This write-up is an initiative taken within the framework of the European Action on 'Black holes, Gravitational waves and Fundamental Physics'.
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| 9. |
- Hudson, Lawrence N, et al.
(författare)
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The database of the PREDICTS (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems) project
- 2017
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Ingår i: Ecology and Evolution. - : John Wiley & Sons. - 2045-7758. ; 7:1, s. 145-188
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Tidskriftsartikel (refereegranskat)abstract
- The PREDICTS project-Projecting Responses of Ecological Diversity In Changing Terrestrial Systems (www.predicts.org.uk)-has collated from published studies a large, reasonably representative database of comparable samples of biodiversity from multiple sites that differ in the nature or intensity of human impacts relating to land use. We have used this evidence base to develop global and regional statistical models of how local biodiversity responds to these measures. We describe and make freely available this 2016 release of the database, containing more than 3.2 million records sampled at over 26,000 locations and representing over 47,000 species. We outline how the database can help in answering a range of questions in ecology and conservation biology. To our knowledge, this is the largest and most geographically and taxonomically representative database of spatial comparisons of biodiversity that has been collated to date; it will be useful to researchers and international efforts wishing to model and understand the global status of biodiversity.
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