Coordinators: D.W. Heermann M. Salmhofer, U. Schwarz

Thursdays 14-16 Uhr
Institute for Theoretical Physics
Seminar room Philosophenweg 19


  • Thu 19.04.12   14 Uhr c.t.
    Thomas Barthel   Department of Physics and Arnold Sommerfeld Center for Theoretical Physics, Ludwig-Maximilians-Universität Munich
    Solving condensed matter ground state problems by semidefinite relaxations

    I will present a new generic approach to the condensed matter ground state problem which is complementary to variational techniques and works directly in the thermodynamic limit. Relaxing the ground state problem in a certain manner, one obtains semidefinite programs (SDP). These can be solved efficiently, yielding lower bounds to the ground state energy and approximations to the few-particle Green?s functions. As the method is applicable for all particle statistics, it represents in particular a novel route for the study of strongly correlated fermionic and frustrated spin systems in D>1 spatial dimensions. It is demonstrated for the XXZ model and the Hubbard model of spinless fermions. The results are compared against exact solutions, Quantum Monte Carlo, and Anderson bounds, showing the competitiveness of the SDP method.

  • Thu 26.04.12   14 Uhr c.t.
    Symposium: Physics on all Scales
  • Thu 14.06.12   14 Uhr c.t.
    Thomas Weikl   MPI für Kolloid- und Grenzflächenforschung in Potsdam
    The elusive binding affinity and dynamics of membrane adhesion receptors: Insights from Monte Carlo and dissipative particle dynamics simulations

  • Thu 05.07.12   14 Uhr c.t.
    Peter Lenz   Marburg University
    Self-organized biological patterns in systems with density-suppressed motility

    Periodic stripe patterns are ubiquitous in living organisms. In many cases, however, the underlying developmental processes are complex and difficult to disentangle. In a novel synthetic biology approach we have implemented a genetic circuit that couples cell density and motility into the bacterium E. coli. This system enabled the programmed cells to form periodic stripes of high- and low- cell densities sequentially and autonomously. To study theoretically the origin and mechanism of this process we have developed a kinetic model that includes growth and density-suppressed motility of the cells. In this model we analyze the onset of pattern formation by calculating the front profile of a region of immotile cells that spreads into an initially cell-free region. From the calculated front profile we provide an analytic ansatz to determine the phase boundary between the stripe and the no-stripe phases. The influence of various parameters on the phase boundary is discussed.

  • Thu 12.07.12   14 Uhr c.t.
    55. Treffen des Gesprächskreises Rhein-Neckar
    Venue: Kirchhoff-Institut für Physik