Yearbook 2008

An important question of Representation Theory is "what happens to an irreducible representation of a group when one restricts it to a subgroup?". Usually it stops being irreducible and it is interesting to know whether it decomposes to distinct irreducible representations. This report contains an exposition on this question and a short description of a recent proof that in the case of the pair (GL(n+1),GL(n)) over local fields the answer is positive. more

Sequences defined by recurrence relations are known since the work of Fibonacci. They occur in number theory as well as for the solutions of differential equations. This report explains why special billiard tables give rise to recurrence relations such that the corresponding sequences consists unexpectedly of integers only. more

In many applications one has to solve large-scale (linear) systems. The task to solve these as fast as possible is the goal of “fast solvers”. At the beginning only sparse systems were considered, but due to the recently at the MPI-MIS developed “hierarchical matrices” the scope has become much broader. However, even fast solvers are limited by the dimensionality of the problem under consideration – a challenge for modern mathematical methods which the group “Scientific Computing” at the MPI-MIS wants to meet. more

Glutamate is the most prevalent neurotransmitter at excitatory synapses of our nervous system and thus indispensable for the activity and accomplishments of our brain. Genetic manipulations in the model organism mouse permit an evaluation of the role of synaptic key components activated by glutamate in spatial learning paradigms. A mouse mutant reveals that a particular synaptic component is essential for a sense of familiarity with a recently encountered spatial environment, and hence functions as a molecular building block in learning and memory. more

Scientists at the MPI for Experimental Medicine developed a mouse model where they induce neurodegeneration in juvenile mice by stereotactic unilateral parietal cortical cryolesion. This procedure causes non-gliotic neurodegeneration and changes in plasticity comparable to schizophrenia which are all prevented by erythropoietin (EPO). Similarly, amelioration of cognition and deceleration of brain atrophy in schizophrenic patients is seen after a 12-week EPO treatment. Mechanistic explanation of cognitive improvement is delivered by EPO-induced increase in long term potentiation, an indicator of learning and memory. more

Performance monitoring and behavioural control are everyday phenomena in human live. Most often they take place unconsciously and without effort. In case of an outcome deviation, i.e. a mismatch between an expected and an actual action outcome, the brain has to detect this deviation and act upon it. Potential deviations are manifold, reflecting the complexity of human existence. Nearly as manifold are the factors that impact the functioning of human performance monitoring. more

The vegetation covering the continents has a decisive influence on the climate. Through the uptake of CO₂ from the atmosphere, plants play a central role in the global carbon cycle. Furthermore, they influence the exchange of energy, water, and momentum between the atmosphere and the land surface. Via land use, humans are altering these processes. The study presented here investigates the expansion of agriculture over the last millennium. It shows that humans had a strong influence on climate, especially on the regional scale, already before industrialization began. more

Recent advances in the study of bacterial cell biology have demonstrated that bacteria use complex regulatory mechanisms to ensure proper temporal and spatial regulation of cellular processes. In this article, the complexity of such systems is illustrated by the molecular pathway that coordinates chromosome segregation with cell division in Caulobacter crescentus. more

The Symbiosis Group studies associations between bacteria and marine invertebrates from chemosynthetic environments such as sulfide-rich coastal sediments, deep-sea hydrothermal vents, and cold seeps. Our research focuses on three main goals: revealing the biodiversity and biogeography of microbial symbioses, understanding the metabolic pathways the symbionts use to gain energy from the environment and feed their host, and deciphering the evolution of the symbioses and the adaptations that have led to the ecological success of these associations. more

Non-volatile solid state memories of high memory density are a promising research field, both under technological and fundamental aspects. Since the size of a single memory cell must be clearly below 100 nanometer, and the properties of storage materials can be considerably modified at such low size, the development of suitable preparation methods and the property analysis of the thus prepared memory cells represent considerable challenges. Such investigations are part of the research on nanostructured materials at Max Planck Institute of Microsctructure Physics in Halle. more

The "Cytoskeleton" group of the Max Planck Unit for Structural Molecular Biology in Hamburg focuses on the structure and dynamics of protein fibers in cells, in particular on microtubules and their associated proteins which are responsible for cell movement, cell division, or intracellular transport. One of these proteins, tau, forms pathological aggregates in nerve cells affected by Alzheimer's disease. Recent transgenic cell and mouse models of the tau pathology reveal that the pathological degeneration of synapses and neurons is closely related to aggregation, and that it is reversible. more