525 research outputs found
Topological polaritons from photonic Dirac cones coupled to excitons in a magnetic field
No full textWe introduce an alternative scheme for creating topological polaritons (topolaritons) by exploiting the presence of photonic Dirac cones in photonic crystals with triangular lattice symmetry. As recently proposed, topolariton states can emerge from a coupling between photons and excitons combined with a periodic exciton potential and a magnetic field to open up a topological gap. We show that in photonic crystals the opening of the gap can be substantially simplified close to photonic Dirac points. Coupling to Zeeman-split excitons breaks time reversal symmetry and allows to gap out the Dirac cones in a nontrival way, leading to a topological gap similar to the strength of the periodic exciton potential. Compared to the original topolariton proposal [T. Karzig et al., Phys. Rev. X 5, 031001 (2015)], this scheme significantly increases the size of the topological gap over a wide range of parameters. Moreover, the gap opening mechanism highlights an interesting connection between topolaritons and the scheme of [F. D. M. Haldane and S. Raghu, Phys. Rev. Lett. 100, 013904 (2008)] to create topological photons in magneto-optically active materials
Niedrigdimensionale Elektronensysteme im Nichtgleichgewicht
No full text1 Introduction 2 The Luttinger model 3 Energy partitioning of tunneling
currents into Luttinger liquids 4 Curvature induced relaxation in quantum
wires 5 Relaxation and edge reconstruction in integer quantum Hall systems 6
Scattering theory of current induced forces in nanoelectromechanical systems 7
Conclusions and outlookRecent advances of experimental nanofabrication techniques draw increasing
attention to the non-equilibrium behavior of low dimensional systems. Of
particular interest are the strongly interacting one dimensional systems whose
description in out of equilibrium situations remains a theoretical challenge.
This thesis contributes to the understanding of important elementary processes
in the non-equilibrium physics of one dimensional electron systems. Tunneling
of an electron into a Luttinger liquid leads to partitioning of its charge and
energy into counter-propagating modes. This thesis studies the partitioning of
the energy which had previously remained unexplored. It turns out that energy
partitioning is essentially independent of the charge partitioning and one can
even reach conditions such that energy and charge propagate in opposite
directions. Another important difference is their experimental accessibility.
In contrast to the charge, energy partitioning provides a measurable
characteristic of the tunneling process even in dc setups and we propose
experimental geometries that allow for tuning and detecting energy
partitioning. At higher excitation energies it becomes necessary to include
curvature effects of the electron dispersion. Another part of this thesis
discusses the consequences of curvature induced three-body collisions on the
relaxation in quantum wires. This is particularly interesting due to the
integrability of the Luttinger model which does not allow for thermalization
within this paradigm of one dimensional systems. In this thesis we derive
energy relaxation rates due to three-body processes beyond the Luttinger model
within a well-defined perturbative approach. It turns out that the electron
spin and the long range Coulomb interaction are important ingredients for a
quantitative description of recent experiments which we provide in this
thesis. Furthermore, we study the influence of three-body collisions on the
energy relaxation in integer quantum Hall edge states. We specifically address
different interaction induced edge reconstruction scenarios and find that edge
reconstruction strongly enhances the energy relaxation. This is particularly
pronounced when the reconstruction creates additional counter-propagating
modes. Finally, we discuss another system which is crucially controlled by
non-equilibrium effects. The so called nanoelectromechanical systems show a
coupling between the electronic and mechanical degrees of freedom. The
electron current can thus influence the mechanical motion which leads to a
number of interesting applications. Previous theoretical studies on the basis
of non-equilibrium Green's functions showed that these current induced forces
can be expressed in terms of intuitive scattering matrix expressions. This
thesis sheds considerable light on this observation by providing a much more
satisfactory and concise derivation of the scattering theory of current
induced forces.Jüngste experimentelle Fortschritte in der Herstellung von Nanostrukturen
werfen vermehrt Fragen zum Nichtgleichgewichtsverhalten niedrigdimensionaler
Systeme auf. Von besonderem Interesse sind dabei die stark wechselwirkenden
eindimensionalen Elektronensysteme, deren Physik jenseits des thermischen
Gleichgewichts man erst langsam zu verstehen beginnt. Die vorliegende Arbeit
trägt zu diesem Verständnis bei und diskutiert grundlegende Elementarprozesse
in der Nichtgleichgewichtsphysik eindimensionaler Elektronensysteme. Wenn ein
niederenergetisches Elektron in eine eindimensionale Luttingerflüssigkeit
tunnelt, werden seine Ladung und Energie in gegenläufige Anregungen
aufgeteilt. In dieser Doktorarbeit wird die bisher noch nicht verstandene
Energieaufteilung untersucht. Es stellte sich dabei heraus, dass sich Ladung
und Energie gänzlich unabhängig voneinander aufteilen und sich sogar
gegenläufig ausbreiten können. Ein weiterer wichtiger Unterschied besteht in
ihrer experimentellen Zugänglichkeit. Im Gegensatz zur Ladung kann die
Energieaufteilung in Gleichstromexperimenten nachgewiesen werden und wir
schlagen experimentelle Geometrien zur Steuerung und Messung der
Energieaufteilung in eindimensionalen Systemen vor. Bei höheren
Anregungsenergien wird es notwendig den Krümmungseffekt der
Elektronendispersion mit in Betracht zu ziehen. Ein weiterer Teil der
vorliegenden Arbeit diskutiert die Auswirkung von krümmungsinduzierten
Dreiteilchenstreuprozessen auf die Relaxation in Quantendrähten. Dies ist
insbesondere deshalb hochinteressant, weil das Standardmodell eindimensionaler
Systeme (Luttingermodel) integrabel ist und somit keine Thermalisierung
zulässt. In einer wohldefinierten Störungstheorie jenseits des Luttingermodels
bestimmt diese Arbeit die Energierelaxationsraten dieser
Dreiteilchenstreuprozesse. Dabei stellt sich heraus, dass der Elektronenspin
und die langreichweitige Coulombwechselwirkung von zentraler Wichtigkeit für
die Relaxation sind. Unter Betrachtung dieser liefern wir eine quantitative
Beschreibung eines kürzlich durchgeführten Experiments. Im weiteren Verlauf
der Arbeit werden die Auswirkungen der Dreiteilchenstreuprozesse auf die
Energierelaxation in Quanten-Hall Randzuständen untersucht. Dabei wird
insbesondere der Effekt einer wechselwirkungsinduzierten Randrekonstruktion
betrachtet. Letztere führt zu einer Beschleunigung der Energierelaxation, die
insbesondere dann stark ausgeprägt ist, wenn die Rekonstruktion zusätzliche
gegenläufige Randzustände erzeugt. Im abschließenden Teil der Arbeit wird ein
weiteres System untersucht, bei dem Nichtgleichgewichtseffekte eine
entscheidende Rolle spielen. Die sogenannten nanoelektromechanischen Systeme
weisen eine Kopplung von mechanischen und elektronischen Freiheitsgraden auf.
Ein elektrischer Strom kann somit die mechanische Bewegung beeinflussen, was
eine Reihe von interessanten Anwendungen ermöglicht. Vorangehende theoretische
Untersuchungen mit Hilfe von Nichtgleichgewichts-Greenfunktionen haben
gezeigt, dass sich die strominduzierten Kräfte letztendlich durch intuitive
Streumatrixausdrücke beschreiben lassen. Diese Arbeit gibt nun tiefere
Einblicke in diesen Zusammenhang und liefert eine vollständig
streutheoretische Beschreibung der strominduzierten Kräfte
Entwicklung einer schnellen Pulsformanalyse für asymmetrische AGATA-Germanium-Detektoren
No full textOnTEAM metadata: GDSID: DOC-2007-May-32; Attribute ID: LIBRARY-thesis_diss-2007-005; Title: [GSI Diss 2007-05] Entwicklung einer schnellen Pulsformanalyse für asymmetrische AGATA-Germanium-Detektoren; Author(s): Beck, Torsten; Corporate author(s): ; Publication date: 20070501; Creator: manton; Creation date: 15.05.2007 16:02:12; Change date: 29.10.2008 16:29:34; Access: nur berechtigte Gruppen; Attribute type: Text.Thesis.Diss; Directory path: ['GSI Publications', 'GSI as Publisher']; Attribute path: ['Infrastructure', 'Library and Documentation', 'thesis_diss', 'Added in 2007']; File name(s): ['DOC-2007-May-32-1.pdf']; File title(s): ['']; File access: ['nur berechtigte Gruppen'
Manifolds, sheaves, and cohomology
No full textThis book explains techniques that are essential in almost all branches of modern geometry such as algebraic geometry, complex geometry, or non-archimedian geometry. It uses the most accessible case, real and complex manifolds, as a model. The author especially emphasizes the difference between local and global questions. Cohomology theory of sheaves is introduced and its usage is illustrated by many examples. Content Topological Preliminaries - Algebraic Topological Preliminaries - Sheaves - Manifolds - Local Theory of Manifolds - Lie Groups - Torsors and Non-abelian Cech Cohomology - Bundles - Soft Sheaves - Cohomology of Complexes of Sheaves - Cohomology of Sheaves of Locally Constant Functions - Appendix: Basic Topology, The Language of Categories, Basic Algebra, Homological Algebra, Local Analysis Readership Graduate Students in Mathematics / Master of Science in Mathematics About the Author Prof. Dr. Torsten Wedhorn, Department of Mathematics, Technische Universität Darmstadt, Germany
James Watson, Maclyn McCarty, and Torsten Wiesel
No full textTorsten Wiesel (right) with Professor Emeritus Maclyn McCarty (center), co-author of the paper with Oswald Avery and Colin MacLeod, and James D. Watson, director of Cold Spring Harbor Laboratory, 1994
Photo by Leif Carlsson
To commemorate the fiftieth anniversary of the discovery at The Rockefeller University that genes are made of DNA - considered by many to be the single most important biological discovery of the twentieth century - the university has kicked off a year-long series of events that were running through May 1994. The celebration was formally inaugurated in November 1993 with a lecture by Nobel laureate James D. Watson, best known for discovering the double-helical structure of DNA.
See also Search Winter 1994, vol. 4, no. 1https://digitalcommons.rockefeller.edu/group-portraits/1013/thumbnail.jp
Seltsame Schauspiele. Torsten Fogelqvists Deutschlandreise 1934
No full textIn 1934 Torsten Fogelqvist, a prominent member of the Swedish Academy and a well-known journalist and intellectual, visits Nazi Germany. He writes about his visit to the Third Reich in 17 articles published in the Stockholm daily newspaper Dagens Nyheter. The author, highly critical of the Hitler regime, scrutinizes several aspects of the nazified German society such as the attempts to re-educate the German citizen in accordance with the ideology of the new regime, the hero cult in the Nazi movement, and the relationship between the German state and the churches. In order to further an understanding of political and social developments in Germany Fogelqvist uses a specific strategy. He “translates” them into an imaginary Swedish context. This paper compares his views with those of other Swedish visitors
PISM glacial cycle sensitivity experiments of the Antarctic Ice Sheet
No full textThis dataset contains PISM simulation results (http://www.pism-docs.org) of the Antarctic Ice Sheet based on code release v1.0-paleo-ensemble (https://doi.org/10.5281/zenodo.3574033). PISM is the open-source Parallel Ice Sheet Model developed mainly at UAF, USA and PIK, Germany.
With the help of added python scripts, all figures can be reproduced as in the journal publication:
- Albrecht et al., 2020, doi:10.5194/tc-14-599-2020.
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Data:
Find PISM results as netCDF data. See 'README.md' for a list of all performed experiment.
All forcing input data for the experiments and plots can be downloaded and remapped via https://github.com/pism/pism-ais. Some of the original input data files are freely available, for others please contact the author or the corresponding data publisher.
Figure plotting scripts (jupyter notebook based on python, see https://jupyter.org) in 'plot_scripts' access the uploaded PISM results in 'model_data' and save the plots to 'final_figures'. Jupyter notebook can be run in the browser and shared, see https://nbviewer.jupyter.org/url/www.pik-potsdam.de/~albrecht/notebooks/paleo_paper/paleo_paper_final.ipynb.
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Contact:
Albrecht, Torsten ([email protected]) ; Potsdam-Institute for Climate Impact Research (PIK), Potsdam, German
Die Erfolgsfaktoren für unternehmerisches E-Mail-Marketing nach Dr. Torsten Schwarz am Praxisbeispiel ERGOTOPIA GmbH
No full textThis scientific document reveals the results of an empirical examination within the realm of entrepreneurial e-mail-marketing which is based on a literature review by technical author Dr. Torsten Schwarz. Using the start-up company ERGOTOPIA as a practical example, the author of the master thesis investigates whether the explanations of Dr. Schwarz match with the practical implementation of ERGOTOPIA.
Precisely, the scientific paper focuses on the examination of the four aspects lead generation, newsletter-design, software-requirements and performance measurement through monitoring with regard to successful realization of e-mail-marketing campaigns. The empirical part of this examination is made of the introduction as well as the analysis of two conducted so called split-tests that compare specific aspects of the newsletter-design and measure data-driven results to show which kind of aspect produced the more successful campaign.
This way the author proves whether the recommendations by Dr. Schwarz are practically relevant for the company ERGOTOPIA
Invitation to Dialogue - A Progress Report
No full textFragmentation of knowledge and life milieux, so often associated with specialization in science and planning, provided the broad challenge in science and planning, provided the broad challenge for a DIALOGUE PROJECT initiated by Torsten Hägerstrand and Anne Buttimer in Sweden during the Academic Years 1977-1979. The initial incentive for confronting such a wide-ranging set of issues arose from a paper on Values in Geography (Buttimer, 1974), after which the author was invited as a Fulbright lecturer to offer a series of seminars in Lund on problems of knowledge and experience. More than forty participants from ten widely different disciplines took part in this seminar, and foundations were laid for an experientially-grounded approach to the problems of communication across disciplines. The present project was initiated when Anne Buttimer was invited to accept a full time position in Sweden by the Humanistisk-Samhällsvetenskapliga Forskningsrådet (Council for Humanities and Social Science) in 1977. Financial support for this pilot phase of the Dialogue Project was granted by the Swedish Committee for Future Oriented Research and the Bank of Sweden Tercentenary Foundation. The geography department at the University of Lund continues to provide material and administrative help, with Torsten Hägerstrand as Co-Director
Invitation to Dialogue - A Progress Report
No full textFragmentation of knowledge and life milieux, so often associated with specialization in science and planning, provided the broad challenge in science and planning, provided the broad challenge for a DIALOGUE PROJECT initiated by Torsten Hägerstrand and Anne Buttimer in Sweden during the Academic Years 1977-1979. The initial incentive for confronting such a wide-ranging set of issues arose from a paper on Values in Geography (Buttimer, 1974), after which the author was invited as a Fulbright lecturer to offer a series of seminars in Lund on problems of knowledge and experience. More than forty participants from ten widely different disciplines took part in this seminar, and foundations were laid for an experientially-grounded approach to the problems of communication across disciplines. The present project was initiated when Anne Buttimer was invited to accept a full time position in Sweden by the Humanistisk-Samhällsvetenskapliga Forskningsrådet (Council for Humanities and Social Science) in 1977. Financial support for this pilot phase of the Dialogue Project was granted by the Swedish Committee for Future Oriented Research and the Bank of Sweden Tercentenary Foundation. The geography department at the University of Lund continues to provide material and administrative help, with Torsten Hägerstrand as Co-Director
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