OPUS 4 | Physik

Strongly correlated ultracold bosons in an optical lattice (2012)

Yongqiang Li

In this thesis, we have investigated strongly correlated bosonic gases in an optical lattice, mostly based on a bosonic version of dynamical mean field theory and its real-space extension. Emphasis is put on possible novel quantum phenomena of these many-body systems and their corresponding underlying physics, including quantum magnetism, pair-superfluidity, thermodynamics, many-body cooling, new quantum phases in the presence of long-range interactions, and excitational properties. Our motivation is to simulate manybody phenomena relevant to strongly correlated materials with ultracold lattice gases, which provide an excellent playground for investigating quantum systems with an unprecedented level of precision and controllability. Due to their high controllability, ultracold gases can be regarded as a quantum simula- tor of many-body systems in solid-state physics, high energy astrophysics, and quantum optics. In this thesis, specifically, we have explored possible novel quantum phases, thermodynamic properties, many-body cooling schemes, and the spectroscopy of strongly correlated many-body quantum systems. The results presented in this thesis provide theoretical benchmarks for exploring quantum magnetism in upcoming experiments, and an important step towards studying quantum phenomena of ultracold gases in the presence of long-range interactions.

Spontaneous Symmetry Breaking and Nambu–Goldstone Bosons in Quantum Many-Body Systems (2010)

Tomáš Brauner

Spontaneous symmetry breaking is a general principle that constitutes the underlying concept of a vast number of physical phenomena ranging from ferromagnetism and superconductivity in condensed matter physics to the Higgs mechanism in the standard model of elementary particles. I focus on manifestations of spontaneously broken symmetries in systems that are not Lorentz invariant, which include both nonrelativistic systems as well as relativistic systems at nonzero density, providing a self-contained review of the properties of spontaneously broken symmetries specific to such theories. Topics covered include: (i) Introduction to the mathematics of spontaneous symmetry breaking and the Goldstone theorem. (ii) Minimization of Higgs-type potentials for higher-dimensional representations. (iii) Counting rules for Nambu–Goldstone bosons and their dispersion relations. (iv) Construction of effective Lagrangians. Specific examples in both relativistic and nonrelativistic physics are worked out in detail.

Directed deposition of silicon nanowires using neopentasilane as precursor and gold as catalyst (2012)

Britta Kämpken Verena Wulf Norbert Auner Marcel Winhold Michael Huth Daniel Rhinow Andreas Terfort

In this work the applicability of neopentasilane (Si(SiH3)4) as a precursor for the formation of silicon nanowires by using gold nanoparticles as a catalyst has been explored. The growth proceeds via the formation of liquid gold/silicon alloy droplets, which excrete the silicon nanowires upon continued decomposition of the precursor. This mechanism determines the diameter of the Si nanowires. Different sources for the gold nanoparticles have been tested: the spontaneous dewetting of gold films, thermally annealed gold films, deposition of preformed gold nanoparticles, and the use of “liquid bright gold”, a material historically used for the gilding of porcelain and glass. The latter does not only form gold nanoparticles when deposited as a thin film and thermally annealed, but can also be patterned by using UV irradiation, providing access to laterally structured layers of silicon nanowires.

A demonstrator for the Micro-Vertex-Detector of the CBM experiment (2010)

Christoph Schrader Samir Amar-Youcef Norbert Bialas Michael Deveaux Ingo Fröhlich Christian Müntz Selim Seddiki Tobias Tischler Joachim Stroth

CMOS sensors are the most promising candidates for the Micro-Vertex-Detector (MVD) of the CBM experiment at GSI, as they provide an unprecedented compromise between spatial resolution, low material budget, adequate radiation tolerance and readout speed. To study the integration of these sensors into a detector module, a so-called MVD-demonstrator has been developed. The demonstrator and its in-beam performance will be presented and discussed in this work.

A versatile method for simulating pp -> ppe+e- and dp -> pne+e-p_spec reactions (2010)

Frank Dohrmann Ingo Fröhlich Tetyana Galatyuk Romain Holzmann Philipp K. Kählitz Burkhard Kämpfer Emilie Moriniere Yvonne C. Pachmayer Beatrice Ramstein Piotr Salabura Joachim Stroth Radoslaw Trebacz Jacques Van de Wiele

We have developed a versatile software package for the simulation of di-electron production in pp and dp collisions at moderate beam kinetic energies (1-2GeV). Particular attention has been paid to incorporate different descriptions of the Dalitz decay Δ rightarrow Ne + e - via a common interface. In addition, suitable parameterizations for the virtual bremsstrahlung process NN rightarrow NNe + e - based on one-boson exchange models have been implemented. Such simulation tools with high flexibility of the framework are important for the interpretation of the di-electron data taken with the HADES spectrometer and demonstrates the wide applicability within the field of nuclear and hadronic physics.

Human myocardial protein pattern reveals cardiac diseases (2012)

Jonas Bergquist Gökhan Baykut Maria Bergquist Matthias Witt Franz-Josef Mayer Doan Baykut

Proteomic profiles of myocardial tissue in two different etiologies of heart failure were investigated using high performance liquid chromatography (HPLC)/Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Right atrial appendages from 10 patients with hemodynamically significant isolated aortic valve disease and from 10 patients with isolated symptomatic coronary heart disease were collected during elective cardiac surgery. As presented in an earlier study by our group (Baykut et al., 2006), both disease forms showed clearly different pattern distribution characteristics. Interesting enough, the classification patterns could be used for correctly sorting unknown test samples in their correct categories. However, in order to fully exploit and also validate these findings there is a definite need for unambiguous identification of the differences between different etiologies at molecular level. In this study, samples representative for the aortic valve disease and coronary heart disease were prepared, tryptically digested, and analyzed using an FT-ICR MS that allowed collision-induced dissociation (CID) of selected classifier masses. By using the fragment spectra, proteins were identified by database searches. For comparison and further validation, classifier masses were also fragmented and analyzed using HPLC-/Matrix-assisted laser desorption ionization (MALDI) time-of-flight/time-of-flight (TOF/TOF) mass spectrometry. Desmin and lumican precursor were examples of proteins found in aortic samples at higher abundances than in coronary samples. Similarly, adenylate kinase isoenzyme was found in coronary samples at a higher abundance. The described methodology could also be feasible in search for specific biomarkers in plasma or serum for diagnostic purposes.

Status of the Micro Vertex Detector of the Compressed Baryonic Matter Experiment (2010)

Michael Deveaux Samir Amar-Youcef Norbert Bialas Dennis Doering Melissa Domachowski Horst Düring Ingo Fröhlich Tetyana Galatyuk Jan Michael Christian Müntz Sarah Ottersbach Paul Scharrer Christoph Schrader Joachim Stroth Tobias Tischler Christian Trageser Bernhard Wiedemann Jérome Baudot Grégory Bertolone Nathalie Chon-Sen Claude Colledani Rita De Masi Andrei Dorokhov Wojchiech Dulinski Jean-Charles Fontaine Mathieu Goffe Abdelkader Himmi Christine Hu Kimmo Jaaskelainen Michal Koziel Frédéric Morel Fouad Rami Mathieu Specht Isabelle Valin Marc Winter Christina Dritsa Selim Seddiki Franz M. Wagner

The CBM experiment will investigate heavy-ion collisions at beam energies from 8 to 45 AGeV at the future accelerator facility FAIR. The goal of the experiment is to study the QCD phase diagram in the vincinity of the QCD critical point. To do so, CBM aims at measuring rare probes among them open charm. In order to identify those rare and short lived particles despite the rich combinatorial background generated in heavy ion collisions, a micro vertex detector (MVD) providing an unprecedented combination of high rate capability and radiation hardness, very light material budget and excellent granularity is required. In this work, we will discuss the concept of this detector and summarize the status of the R&D.

Fragmentation of exotic oxygen isotopes (2003)

Armin Leistenschneider Thomas Aumann Konstanze Boretzky Luiz Felipe Canto Brett Vern Carlson Dolores Cortina Ushasi Datta Pramanik Thomas W. Elze Hans Emling Hans Geissel Alexander Grünschloss Kerttuli Helariutta Margareta Hellström Mahir S. Hussein Stamenko Ilievski Jens-Volker Kratz Reinhard Kulessa Le Hong Khiem Edvard Lubkiewicz Gottfried Münzenberg Rudrayoti Palit Peter Reiter Christoph Scheidenberger Karl-Heinz Schmidt Haik Simon Klaus Sümmerer Eugeniusz Wajda Wladek Walús

Abrasion-ablation models and the empirical EPAX parametrization of projectile fragmentation are described. Their cross section predictions are compared to recent data of the fragmentation of secondary beams of neutron-rich, unstable 19,20,21O isotopes at beam energies near 600 MeV/nucleon as well as data for stable 17,18O beams.

Measuring shear viscosity using correlations (2007)

Sean Gavin Mohamed Abdel-Aziz

Measurements of transverse momentum fluctuations can be used to determine the shear viscosity [1]. We use current data to estimate the viscosity-to-entropy ratio in the range from 0.08 to 0.3, and discuss how future measurements can reduce this uncertainty.

Ion beam analysis based on cellular nonlinear networks (2011)

Vanessa Senger Ronald Tetzlaff Hermine Reichau Ulrich Ratzinger

The development of a non- destructive measurement method for ion beam parameters has been treated in various projects. Although results are promising, the high complexity of beam dynamics has made it impossible to implement a real time process control up to now. In this paper we will propose analysing methods based on the dynamics of Cellular Nonlinear Networks (CNN) that can be implemented on pixel parallel CNN based architectures and yield satisfying results even at low resolutions.

Physik

Refine

Author

Year of publication

Document Type

Language

Has Fulltext

Keywords

Institute

963 search hits