Art history by Martin Naraschewski
Aujourd’hui, la ville de Bamberg est liée au Rouergue par son jumelage avec la ville de Rodez et ... more Aujourd’hui, la ville de Bamberg est liée au Rouergue par son jumelage avec la ville de Rodez et par son ancien prieuré de St. Getreu, l'une des rares églises de l'ancien Empire qui se réfèrent à Sainte-Foy de Conques. Ce document commence par un bref résumé des sources historiques qui éclairent les circonstances de la fondation du prieuré de St. Getreu au XIIe siècle. Ensuite, les résultats pertinents pour le Rouergue d'une récente étude des modèles romanes tardives de la cathédrale de Bamberg sont résumés. Il s'est avéré en particulier que Conques devait être le modèle le plus important d’entre eux. Ces résultats montrent que les relations médiévales entre Bamberg et le Rouergue devaient être plus étroites et historiquement plus importantes qu'on ne le pensait jusqu'à présent.
Entangled Histories at Conques. Interdisciplinary Perspectives on a Unique Site of Medieval Heritage, Dec 2024
Bamberg Cathedral, completed in the thirteenth century, was an apex of so-called late Romanesque ... more Bamberg Cathedral, completed in the thirteenth century, was an apex of so-called late Romanesque art in the German territories of the empire. While the existence of models in Spain or France has been suspected since the 1920s, the degree of transregional influence has remained an open debate. Contributing to this debate, I suggest that Bamberg’s late Romanesque decoration and iconography had their models on a specific portion of the Way of St James, with Conques as its culmination. A small subset of these decorative elements are systematically associated with buildings that were under the direct influence of the Hohenstaufen dynasty, highlighting how the dynasty and Conques formed a complex institutional network that was driven by the pilgrimage of St James and that had a major influence on buildings in Bamberg, Sélestat and several other sites with a Hohenstaufen connection. The network possibly included Cluny and the Cistercians.
Ce document est un bref résumé en français d'une partie essentielle de Athenanea, n° 1. Le résumé... more Ce document est un bref résumé en français d'une partie essentielle de Athenanea, n° 1. Le résumé est complété par quelques informations contextuelles historiques ainsi que par des données essentielles présentées dans de nombreux tableaux et illustrations. Le résumé porte sur la question des origines du décor et de la sculpture roman tardive de la cathédrale de Bamberg. Il est démontré, à l'aide d'une nouvelle méthode analytique, que ses modèles se trouvent en grande partie sur la Via Podiensis et notamment à Conques.
Diese Publikation soll ein breiteres Gesamtbild des Bamberger Doms im Kontext seines europäischen... more Diese Publikation soll ein breiteres Gesamtbild des Bamberger Doms im Kontext seines europäischen kunst- und kulturhistorischen Umfeldes aufzeigen. Aus der Analyse möglicher kunsthistorischer Vorbilder mittels eines innovativen, quasi-statistischen Forschungsansatzes werden Schlüsse über den wahrscheinlichen Masterplan der Bamberger Bauherren gezogen. Ein wesentlicher Schwerpunkt der Untersuchung liegt dabei auf dem reichen Baudekor und der Ikonographie der Skulptur. Diese lassen sich präziser als bislang bekannt nach Frankreich und Italien zurückverfolgen, insbesondere nach Conques und an die Via Podiensis. Die identifizierten europäischen Vorbilder liefern zudem neue Ansätze für die Deutung des Skulpturenprogrammes und des Bamberger Reiters.
Business by Martin Naraschewski
Patent application, Jun 13, 2013
Theoretical physics by Martin Naraschewski
Physical Review Letters, 1998
We study the output properties of a pulsed atom laser consisting of an interacting Bose-Einstein ... more We study the output properties of a pulsed atom laser consisting of an interacting Bose-Einstein condensate (BEC) in a magnetic trap and an additional rf field transferring atoms to an untrapped Zeeman sublevel. For weak output coupling we calculate the dynamics of the decaying condensate population, of its chemical potential and the velocity of the output atoms analytically.
Physical Review Letters, Jun 1997
The macroscopic interference of two Bose condensates released from a double minimum potential has... more The macroscopic interference of two Bose condensates released from a double minimum potential has been demonstrated recently [M. R. Andrews et al., Science 275, 637 (1997)]. In this Letter we show the excellent agreement between those experiments and theoretical predictions based on the nonlinear Schrödinger equation. In addition, the transition from interference of coupled condensates, comparable with the Josephson effect in superconductors, to the interference of independent Bose condensates is studied. [S0031-9007(97)03260-2]
Physical Review A, 1999
We study first and second order coherence of trapped dilute Bose gases using appropriate correlat... more We study first and second order coherence of trapped dilute Bose gases using appropriate correlation functions. Special attention is given to the discussion of second order or density correlations. Except for a small region around the surface of a Bose-Einstein condensate the correlations can be accurately described as those of a locally homogeneous gas with a spatially varying chemical potential. The degrees of first and second order coherence are therefore functions of temperature, chemical potential, and position. The second order correlation function is governed both by the tendency of bosonic atoms to cluster and by a strong repulsion at small distances due to atomic interactions. In present experiments both effects are of comparable magnitude. Below the critical temperature the range of the bosonic correlation is affected by the presence of collective quasi-particle excitations. The results of some recent experiments on second and third order coherence are discussed. It is shown that the relation between the measured quantities and the correlation functions is much weaker than previously assumed.
Physical Review a, 1999
We study first- and second-order coherence of trapped dilute Bose gases using appropriate correla... more We study first- and second-order coherence of trapped dilute Bose gases using appropriate correlation functions. Special attention is given to the discussion of second-order or density correlations. Except for a small region around the surface of a Bose-Einstein condensate the correlations can be accurately described as those of a locally homogeneous gas with a spatially varying chemical potential. The degrees of first- and second-order coherence are therefore functions of temperature, chemical potential, and position. The second-order correlation function is governed both by the tendency of bosonic atoms to cluster and by a strong repulsion at small distances due to atomic interactions. In present experiments both effects are of comparable magnitude. Below the critical temperature the range of the bosonic correlation is affected by the presence of collective quasiparticle excitations. The results of some recent experiments on second- and third-order coherence are discussed. It is shown that the relation between the measured quantities and the correlation functions is much weaker than previously assumed.
Physical Review A, Apr 1999
We compare the semiclassical Hartree-Fock approximation for a trapped Bose gas to a direct path-i... more We compare the semiclassical Hartree-Fock approximation for a trapped Bose gas to a direct path-integral quantum Monte Carlo simulation. The chosen parameters correspond to current 87 Rb experiments. We observe corrections to the mean-field density profile: the path-integral calculation reveals an increase of the number of condensed particles, which is of the same order as a previously computed result for a homogeneous system. We discuss the experimental observability of the effect and propose a method to analyze data of in situ experiments. ͓S1050-2947͑99͒02404-X͔
Physical Review A, Apr 1999
The regions of validity of the Markov approximation for the coupling of atoms out of an atomic tr... more The regions of validity of the Markov approximation for the coupling of atoms out of an atomic trap are determined. We consider radio-frequency output coupling in the presence of gravity and collisional repulsion, and Raman output coupling. The Markov approximation is crucial in most theoretical descriptions of an atom laser that assume a continuous process of output coupling from a trapped Bose-Einstein condensate. In this regime many techniques proved to be useful for modeling the optical laser, such as master equations, can be used to describe the dynamics of the damping of the condensate mode undergoing output coupling.
Physical Review A, Sep 1998
Present experiments with Bose condensed gases can be largely described by a semi-ideal two-gas mo... more Present experiments with Bose condensed gases can be largely described by a semi-ideal two-gas model. In this model, the condensate is influenced only by the mean-field repulsion among condensed atoms, while the thermal cloud is considered an ideal gas confined by an effective potential that consists of the external trap and the mean-field repulsion by the condensate. This simple, intuitive model provides explicit analytical expressions for the density distributions of the condensate and the thermal component. It describes the reduction of the condensate fraction relative to that of an ideal gas as a consequence of the positive chemical potential due to interactions in the condensate. ͓S1050-2947͑98͒09209-9͔
arXiv: Condensed Matter, 1998
The existence of a geometric phase in magnetic traps can be used to Bose condense a magnetically ... more The existence of a geometric phase in magnetic traps can be used to Bose condense a magnetically trapped atomic gas into a vortex state. We propose an experimental setup where a magnetic trap together with a blue detuned laser beam form a multiply connected trap geometry. The local variation of the magnetic quantization axis induces a geometric or Berry's phase that allows the atoms to acquire an effective gauge charge interacting with the analog of a magnetic solenoid. It is shown that the ground state of such a system may be given by a vortex state. We also discuss the influence of atomic interactions on the proposed vortex production scheme in the context of present Bose-Einstein condensation experiments with dilute gases.
Materials Science and Engineering: B, 1997
We studied theoretically the macroscopic interference of two independent Bose condensates release... more We studied theoretically the macroscopic interference of two independent Bose condensates released from a double potential trap. The observation of fringes could serve as a test for the paradigm of broken gauge symmetry. By numerical solution of the non-linear Schriidinger equation in three dimensions, the consecutive stages of expansion, overlap and interference were investigated in order to facilitate the design of future experiments. It turns out that the period of the interference fringes grows linearly in time with a velocity inversely proportional to the initial distance of the two condensates. G 1997 Elsevier Science S.A.
Journal of Modern Optics, 1997
Abstract We study the coherence of interacting Bose condensates in recent magnetic trap experimen... more Abstract We study the coherence of interacting Bose condensates in recent magnetic trap experiments. The coherent evolution manifests itself in the macroscopic interference of two independent Bose condensates. The theoretical predictions from the time-dependent Gross–Pitaevskii equation are in excellent agreement with the measured interference patterns. A coherent coupling of two condensates represents the atomic analogon of a Josephson junction. The dependence of the magnetic confinement on the nuclear spin orientation allows one to build a controllable beam splitter by magnetic resonance. The application of this beam splitter to realize an atom laser is studied theoretically. The coherence of the output beam is limited only by phase diffusion of the condensate.
Physical Review A, 1997
We study theoretically the macroscopic interference of two independent Bose condensates released ... more We study theoretically the macroscopic interference of two independent Bose condensates released from a double potential trap. The observation of fringes could serve as a test for the paradigm of broken gauge symmetry. By numerical solution of the nonlinear Schr\"odinger equation in three dimensions, the consecutive stages of expansion, overlap, and interference are investigated in order to facilitate the design of future experiments. The phase-space dynamics of the condensates is analyzed by means of the Wigner function. It turns out that the distance of interference fringes grows linearly in time with a velocity inversely proportional to the initial distance of the two condensates. The collisional reduction of the fringe visibility is estimated.
Physical Review A, Jul 1, 1997
Physical Review A, Nov 1996
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Art history by Martin Naraschewski
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Theoretical physics by Martin Naraschewski