Prof. Dr. Thomas Bohlen
Geophysical Institute
Department of Physics
Karlsruhe Institute of Technology

Dr. Stefan Jetschny
Geophysical Institute
Department of Physics
Karlsruhe Institute of Technology

Sven Heider
Geophysical Institute
Department of Physics
Karlsruhe Institute of Technology

Dr. Ekaterina Rykhlinskaya
Steinbuch Centre for Computing (SCC)
Karlsruhe Institute of Technology

Infrastructure projects worldwide often face the same demands of creating short cuts in order to keep up with the increase in public traffic and transportation. One feasible solution is to go underground. With the increasing number and dimensions of such tunneling projects, the use of tunnel boring machines (TBMs) becomes more prevalent. Tunnel boring machines have the potential for automated and continuous drilling of tunnels with low employment of workers at high performance. Nevertheless, the geologic situation along the tunnel trajectory is less predictable in urban areas due to the limited access for geological probing and geophysical measurements. This can results in uncertainties regarding the actual rock type and the spatial location of structures encountered during the tunnel construction. Sudden changes in the geological and geotechnical properties, i.e., at lithological boundaries, fracture zones or ground water bearing soil can be a serious safety threat to the TBM and usually requires specially designed TBMs. Safely predicting geological structures ahead of the tunnel construction can therefore significantly reduce safety risks and prevent expensive down times of the tunnel boring machine.

We use a parallel 3-D elastic finite difference code in order to simulate the complex elastic wave field in models of arbitrary complexity. With respect to the application in the exploration of the tunnel surrounding we observe similar wave field as shown as in Figure 1. On the basis of a random media model that accounts for small and large scale heterogeneities, typical features encountered in a tunnel construction are included, such as a tunnel tube (white), an excavating damaged zone (contour around the tunnel) and a low dipping lithological boundary (straight contour line). While the tunnel tube is extended, i.e. the tunneling is progressing, we perform several wave field simulation to image the exact position of the dipping structure. Each modeling run takes about 4h on 80 cores. The overall goal is to study the complex wave propagation, optimize the measurement geometry and parameters and finally create synthetic field data to develop new imaging and processing methods. Later on, this gained knowledge is directly applied to field cases.

• Bohlen, T., 2002: Parallel 3-D viscoelastic finite-difference seismic modelling, Computers and Geosciences, 28 (8), 887-899.
• Bohlen, T., U. Lorang, W. Rabbel, G. Müller, R. Giese, S. Lüth, and S. Jetschny, 2007: Rayleigh-to-shear wave conversion at the tunnel face - from 3D-FD modeling to ahead-of-drill exploration: Geophysics, 72, T67–T79.
• Jetschny, S., T, Bohlen and A. Kurzmann,2011:Seismic prediction of geological structures ahead of the tunnel using tunnel surface waves, accepted for publication in Geophysical Prospecting

Area: Geophysics

Software:

• SOFI3D

Links:

• SOFI3D
• Seismic Observation in Underground Development (SOUND)

Hans-Martin von Gaudecker
Fakultät für VWL, Lehrstuhl für Mikroökonometrie
Universität Mannheim

Gemeinsam mit Arthur van Soest (Tilburg) und Erik Wengstrom (Lund) untersuchen wir den Erklärungsgehalt aus ökonomischen Laborexperimenten geschätzter Präferenzparameter in Haushaltsportefeuillewahlmodellen. Zudem vergleichen wir die Verteilungen solcher Präferenzparameter und der Qualität von Entscheidungen in klassischen Laborexperimenten mit Studenten und in der allgemeinen Bevölkerung.

Area: Economics

Software:

• Python, Fortran, Stata

Links:

• http://www.vwl.uni-mannheim.de/gaudecker/research-preferences.htm

Andras Niedermayer
Fakultaet fuer VWL, Lehrstuhl fuer Mikrooekonomische Theorie
Universität Mannheim

Mechanisms where intermediaries charge a commission fee and have the sellers set the price are widely used in practice e.g. by real estate agents, stock brokers, art galleries, or auction houses. We model competition between intermediaries in a dynamic random matching model, where in every period a buyer, a seller, and an intermediary are randomly matched. In any period, every intermediary has a temporary monopoly and designs an exchange mechanism that maximizes his own expected profits. Traders' valuations for the indivisible good depend on their option value of future trade. The following results obtain. First, we show that the intermediary can achieve the highest possible profit with a fee setting mechanism. Second, we characterize when these fees are linear. Third, fee setting is an equilibrium outcome in a dynamic market. Fourth, when the rematching probability increases or, equivalently, the period length decreases, the equilibrium fees become smaller. Our model is applicable to stock brokers and auction houses as intermediaries. It can further explain several of the stylized facts observed in real estate brokerage, such as the 6 percent fee, the relation between listing price and time on market, inefficient free entry, higher prices for houses owned by brokers, and home owners who bought during a boom asking higher prices. We also provide various extensions.

• Andras Niedermayer; Seminar at University of New South Wales; "Fee Setting Intermediaries: On Real Estate Agents, Stock Brokers, and Auction Houses"; online
• Andras Niedermayer; Seminar at Northwestern University; "Fee Setting Intermediaries: On Real Estate Agents, Stock Brokers, and Auction Houses"; online

Area: Economics

Software:

• Matlab, Fortran

Links:

• http://andras.niedermayer.ch/index.php?page=research

Dirk Junge
MZES
Universität Mannheim

A central objective of political research is to obtain a general understanding of how legislative negotiations work and what factors shape their outcomes. Among the most influential analytical frameworks for the study of legislative negotiations count the Baron and Ferejohn bargaining model and its extensions. These models allow insights into the determinants of democratic policies, the mechanisms of legislative negotiations and the impact of institutional design on its outcomes based on the general idea from game theory to perceive bargaining as alternating offer games . However, despite their importance for the theoretical understanding of legislative negotiations , empirical studies often lack the statistical models to appropriately test their predictive power.

The goal of this project is a) to develop statistical models that can help to obtain more accurate insights on the explanatory power of legislative bargaining theories based on quantal response analysis and b) to evaluate the explanatory power of the theories based on detailed data on lawmaking in the European Union. The statistical estimation of the models is computationally demanding due to the complexity of the model, the structure of the data negotiations and the estimation technique that involves advanced sampling methods. The research allows new insights on the explanatory power of the most important analystical framework for the study of legislative negotiations and provides practical evidence on how policies in the European Union are negotiated and how specific actors and aspects of the institutional design of the European Union affect the nature of laws produced by the European Union.

• Dirk Junge; "Game Theoretic Models and the Empirical Analysis of EU Policy Making: Strategic Interaction, Collective Decisions, and Statistical Inference." In Thomas König, George Tsebelis and Marc Debus (Eds): "Reform Processes and Policy Change: Veto Players and Decision Making in Modern Democracies"; Springer: New York, Heidelberg, London; 2010.

Area: Political Science

Denes Sexty
Institut für Theoretische Physik
Universität Heidelberg

We have investigated the critical point of a field theoritical model in the Ising universality class. We have measured the critical exponent 'z' which corresponds to the time dependent processes near the critical point, by measuring the spectral function of the model.

• J. Berges, S. Schlichting, D. Sexty, Dynamic critical phenomena from spectral functions on the lattice, Nuclear Physics B Volume 832, Issues 1-2, 11 June 2010, Pages 228-240, online.

Area: Physics

Kaspar Sakmann
Physikalisch-Chemisches Institut
Universität Heidelberg

Alexej Streltsov
Physikalisch-Chemisches Institut
Universität Heidelberg

Ofir Alon
Physikalisch-Chemisches Institut
Universität Heidelberg

Lorenz Cederbaum
Physikalisch-Chemisches Institut
Universität Heidelberg

Bose-Einstein condensates constitute controllable interacting quantum many-body systems. In this project we investigate the true many-body dynamics of interacting Bose-Einstein condensates by solving the full time-dependent many-body Schrödinger equation. The MCTDHB algorithm which we employ has allowed us to obtain the first numerically exact results of the full many-body Schrödinger equation for up to one hundred(!) bosons in a bosonic Josephson junction. Thereby, we could show that the true many-body dynamics of such systems is very different from that of the widely used Gross-Pitaevskii theory and the Bose-Hubbard model, even in parameter regimes where these approximations are commonly believed to be valid. Thus, our research allowed us to investigate a whole new class of many-body phenomena which are not accessible to such simplifying models.

As an example for such phenomena the figure shows the loss of coherence after some time (right panels) of an initially coherent state (left panels). Shown are the results of the full many-body Schrödinger equation (top panels) and the Bose-Hubbard (bottom panels) model. At long times we found an equilibration phenomenon in which the density and other observables approach stationary values, much like a thermalization of the system. All of the above occurs in a closed quantum system at zero temperature.

• Exact quantum dynamics of a bosonic Josephson junction; K. Sakmann, A. I. Streltsov, O. E. Alon and L. S. Cederbaum, Phys. Rev. Lett. 103, 220601 (2009).
• Quantum dynamics of attractive versus repulsive bosonic Josephson junctions: Bose-Hubbard and full-Hamiltonian results; K. Sakmann, A. I. Streltsov, O. E. Alon and L. S. Cederbaum, Phys. Rev A, 82, 013620 (2010).
• Kaspar Sakmann; Laser Physics '09 conference talk on the bosonic Josephson Junction pdf

Area: Physics

Software:

• Multiconfigurational time-dependent Hartree for bosons (MCTDHB)

Links:

• http://www.pci.uni-heidelberg.de/tc/usr/kaspar

Carlos Alberto Parra Murillo
Institut für Theoretische Physik
Universität Heidelberg

Javier Madronero
Institut für Theoretische Physik
Universität Heidelberg

Sandro Wimberger
Institut für Theoretische Physik
Universität Heidelberg

The so-called, Lanczos algorithm is implemented to make the full diagonalization of the two-band Bose-Hubbard Hamiltonian. From the Floquet theory, the spectral properties of this hamiltonian can be studied either (i) by diagonalizing the evolution operator U over one Bloch period (Tb), and the respective analysis of eigenvalues (Kolovsky et al., Phys Rev. E, vol 68 056213, 2003), or (ii) by directly diagonalizing the Floquet hamiltonian, which read off the time integration needed in (i) (Buchleitner et al., J. Opt. Soc. Am. B, Vol. 12, No. 4/April 1995). Our physical system consists of N ultracold atoms loaded into a tilted optical lattice with L antinodes, which is well described by the Bose-Hubbard model as the ratio N/L~1. The dimension of the hamiltonian matrices (dim_H) depends exponentially on the number of atoms used to find the spectra as function of the tilt F. The time integration needed to construct the evolution operator depends on Tb~1/F, it means, as F tends to zero (where the chaotic regime is reached) takes long time to compute the matrix elements of U. That is the reason why we implement the method (ii), in which the time integration is not necessary but the dimension of the new Floquet hamiltonian (2k+1)*dim_H, where k is a Fourier's component. The number of k needed is Nk~1/F, it means, as the chaotic regime is reached, we must diagonalize larger matrices for every values of F, and in this way to construct the desired energy spectra, from which interesting physical properties can be extracted. As seen above, reading off the time integration implies the diagonalization of larger matrices, ie, it is needed enough computational memory as N is increased.

• Carlos Parra-Murillo; Javier Madronero; Sandro Wimberger; Floquet-Lanczos diagonalization for a two-band Bose-Hubbard Hamiltonian; IX. Billiard workshop; AG Quantenchaos, FB Physik, Philipps-University of Marburg, Marburg, October 2010

Area: Physics

Software:

• Lapack, GNU gsl, Message Passing Interface (MPI), Fortran, C

Links:

• http://www.thphys.uni-heidelberg.de/~wimberge