252 research outputs found
Relativistic Many-Body Theory: A New Field-Theoretical Approach
No full textRelativistic Many-Body Theory treats — for the first time — the combination of relativistic atomic many-body theory with quantum-electrodynamics (QED) in a unified manner. This book can be regarded as a continuation of the book by Lindgren and Morrison, Atomic Many-Body Theory (Springer 1986), which deals with the non-relativistic theory of many-electron systems, describing several means of treating the electron correlation to essentially all orders of perturbation theory. The treatment of the present book is based upon quantum-field theory, and demonstrates that when the procedure is carried to all orders of perturbation theory, two-particle systems are fully compatible with the relativistically covariant Bethe-Salpeter equation. This procedure can be applied to arbitrary open-shell systems, in analogy with the standard many-body theory, and it is also applicable to systems with more than two particles. Presently existing theoretical procedures for treating atomic systems are, in several cases, insufficient to explain the accurate experimental data recently obtained, particularly for highly charged ions. This shortcoming is expected to be due to omission of combined QED-correlational effects, included in the new unified procedure. All methods treated in Relativistic Many-Body Theory are illustrated with numerical examples. The main text is divided into three parts. In Part I, the standard time-independent and time-dependent perturbation procedures are reviewed. Part II describes three methods for QED calculations, a) the standard S-matrix formulation, b) the Two-times Green’s-function method, developed by the St Petersburg Atomic Theory group, and c) the Covariant-evolution-operator (CEO) method, recently developed by the Gothenburg Atomic Theory group. In Part III, the CEO method is combined with electron correlation to arbitrary order to a unified MBPT-QED procedure. In this procedure the electron correlation can be included to high order, and therefore this procedure is expected to lead to faster convergence than treating the BS equation order by order. Ingvar Lindgren is also the author of the highly-cited "Atomic Many-Body Theory" book published by Springer
Combining Keynes and Schumpeter. Ingvar Svennilson's Contribution to the Swedish Growth School and Modern Economics
No full textIn a study of European growth in the interwar period, the Swedish economist Ingvar Svennilson integrated a Keynesian theory of cumulative growth with a Schumpeterian analysis of economic transformation. Svennilson emphasised that innovations and the use of new technologies had been stimulated by high demand and production growth. Svennilson’s strong commitment to "Vendoorn's Law" which actually was "Svennilson's Law", made it difficult to incorporate him in a Schumpeterian tradition. A synthesis between Keynes and Schumpeter with Svennilson as a mediator was also prevented by the decisive role of entrepreneurship and the critique of Keynesian models in works by Schumpeter and the Swedish growth school. However, a synthesis has been facilitated by neo-Schumpeterian theories of demand-led innovations and cumulative economic processes. Svennilson’s study has been superseded by later contributions to economics except for a theory of a negative, "Keynesian", relationship between unemployment and growth and an exceptional "un-Verdoornian" theory that high aggregate demand may lead to crowding-out of new firms from capital markets. Besides, Svennilson's integration of short run and long run macro analysis and of theoretical and empirical work is still a fruitful research strategy in economics.Innovations; Cumulative Growth; Productivity Growth; Verdoorn’s Law; Swedish Growth School
Emeriti 16
No full textMedverkande: Ingvar Lindgren och Karl-Erik Eriksson. Programledare: Mats Oscarson. Ingvar Lindgren, född 1931, professor emeritus i fysik, doktor i fysik 1959, professor i fysik vid Chalmers tekniska högskola 1966 och Göteborgs universitet 1995, Karl-Erik Eriksson, född 1935, professor emeritus i teoretisk fysik, doktor i teoretisk fysik 1961, professor i teoretisk fysik vid Göteborgs universitet1963, gästprofessor vid Karlstads universitet 2000. Mats Oscarson, född 1939, professor emeritus i pedagogik, doktor i engelska vid Göteborgs universitet 1973, professor i pedagogik vid Göteborgs universitet 2001
The 1st International Paderborn Computer-Othello Tournament
No full textWe present the results of an International Computer--Othello Tournament held at the University of Paderborn in October 1993. Furthermore, some participants describe their entries. 1 Organization, Participants and Results The tournament was held at the University of Paderborn (Germany) from October 5th till 7th, 1993. It was thought to be a replacement for the Othello tournament of the Computer-- Olympiad which was canceled this year because David Levy didn't find a sponsor. We called for participation on Internet in July and received many replies. In order to give authors which couldn't come to Paderborn the opportunity to enter their programs we provided PCs and SPARC--stations and found operators for the programs. The entries listed by their start positions were as follows: 1 LOGISTELLO SPARC10 Michael Buro Germany 2 OOT PC486DX-50+Card Markku Poysti Finland 3 DESDEMONA PC286+Card Ola Liljedahl, Sweden Lars Johansson, Ingvar Lindgren 4 MODOT SPARC10 Joel F. Feinstein England 5 MON..
«Det absurde ved å være fanget i blodbankende materie»: Om rus og litteratur i Ingvar Ambjørnsens \u27Skogens hjerte\u27
No full textThis article explores Norwegian author Ingvar Ambjørnsen’s short story «The Heart of the Forest» from his collection Dark Dawn (1997) and focuses on the story’s prime experience, that of drugs. Peter Sloterdijk’s account of the historical development of drugs from the early Greek era to modernity is the theoretical framework. His understanding is found in Ambjørnsen’s short text, which also contains a notion of intertextuality. Therefore, the article highlights both literary (Vesaas) and philosophical references (Huxley). «The Heart of the Forest» is also the precursor for Ambjørnsen’s novel The Night Dreaming of Day (2012), which implies that the author sampled his own short story and gave it a pessimistic reinterpretation.Artikkelen undersøker Ingvar Ambjørnsens novelle «Skogens hjerte» fra novellesamlingen Natt til mørk morgen (1997) og fokuserer på fremstillingen av ruserfaringer som står sentralt i teksten. Utgangspunktet for lesningen er Peter Sloterdijks beskrivelse av den historiske utviklingen av ruserfaringer fra antikken til det moderne. Hans forståelse finner man også i Ambjørnsens korttekst, men denne omfatter dessuten en bestemt bruk av intertekstualitet. Herved fokuseres det både på litterære (f.eks. Vesaas) og idéhistoriske referanser (Huxley). «Skogens hjerte» ble i tillegg det intertekstuelle forelegget for deler av Ambjørnsens roman Natten drømmer om dagen (2012). På en måte ‘sampler’ forfatteren sin egen novelle, som får en mer pessimistisk omfortolking
Going beyond "no-pair relativistic quantum chemistry"
No full textThe current field of relativistic quantum chemistry (RQC) has been built upon the no-pair and no-retardation approximations. While retardation effects must be treated in a time-dependent manner through quantum electrodynamics (QED) and are hence outside RQC, the no-pair approximation (NPA) has to be removed from RQC for it has some fundamental defects. Both configuration space and Fock space formulations have been proposed in the literature to do this. However, the former is simply wrong, whereas the latter is still incomplete. To resolve the old problems pertinent to the NPA itself and new problems beyond the NPA, we propose here an effective many-body (EMB) QED approach that is in full accordance with standard methodologies of electronic structure. As a first application, the full second order energy E-2 of a closed-shell many-electron system subject to the instantaneous Coulomb-Breit interaction is derived, both algebraically and diagrammatically. It is shown that the same E-2 can be obtained by means of 3 Goldstone-like diagrams through the standard many-body perturbation theory or 28 Feynman diagrams through the S-matrix technique. The NPA arises naturally by retaining only the terms involving the positive energy states. The potential dependence of the NPA can be removed by adding in the QED one-body counter terms involving the negative energy states, thereby leading to a "potential-independent no-pair approximation" (PI-NPA). The NPA, PI-NPA, EMB-QED, and full QED then span a continuous spectrum of relativistic molecular quantum mechanics. (C) 2013 AIP Publishing LLC.Physics, Atomic, Molecular & ChemicalSCI(E)PubMed11ARTICLE101410813
Time-Dependent Perturbation Theory as a Basis for Combined Many-Body-Perturbation and QED
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