Bielefeld Graduate School in Theoretical Sciences
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BGTS Colloquium

3 November, 2017

Prof. Jon Keating (University of Bristol):
The Riemann Hypothesis: recent perspectives on a grand mathematical challenge
16:15, lecture hall H3
Abstract: The Riemann Hypothesis, formulated by Riemann in 1859, is one of the great unsolved problems in mathematics. It relates to the distribution of the prime numbers and many other fundamental problems in the subject. Remarkably, it seems also to be connected to problems that arise in other areas of science, in particular in Physics. I will explain what the Riemann Hypothesis is, why it is so important and mysterious, and how it appears to connect with phenomena found in other disciplines. Furthermore, I hope to do this without assuming any significant mathematical knowledge.

19 June, 2017

Prof. Jean-Philippe Bouchaud (École polytechnique) :
Tipping points and crises: from statistical physics to macroeconomic modelling
16:15, lecture hall H6
Abstract: Using the methodology of statistical physics, which characterizes a model through its ``phase diagram", we explore the possible types of phenomena that ``agent-based" macroeconomic models with interactions, frictions and heterogeneities can reproduce. Through this looking glass, we will discuss three stylized models (interacting firms networks, agent based models of firms and households and dynamical trust networks). In each case one finds generic phase transitions (or tipping points) between a ``good economy" state where unemployment/volatility are low and confidence is high, and a ``bad economy" state where unemployment/volatility are high and confidence is low. If the parameters are such that the system is close to such transitions, any small fluctuation may be amplified, leading to a large level of endogenous volatility. This can cause the monetary policy itself to trigger instabilities and be counter-productive. We identify several theoretical scenarios for synchronization and instabilities in large economies that can generate aggregate volatility and acute crises without any identifiable idiosyncratic shocks. This suggests an interesting explanation for the unexpected outbursts of endogenous economic or financial crises, also known as the ``small shocks, large business cycles" puzzle.

10 June, 2016

Prof. Dr. Jan Plefka (Humboldt University of Berlin):
The world as a hologram: News from String Theory
16:15, lecture hall H6
Abstract: We are all familiar with holograms: Two dimensional optical structures which - when suitably lit - create the illusion of a three-dimensional object. In fact the light waves emerging from holograms are identical to the ones one would preceive from the three-dimensional object - a distant observer cannot distinguish the two. Recent research in fundamental physics has revealed that the gravitational force of nature might in fact be a holographic illusion in this sense. It is replacable by a lower dimensional structure, known as gauge field theory. The latter is the theoretical framework to describe all the non-gravitational forces in nature which reign elementary particle physics. Our lecture will begin with reviewing the basic concepts of gravitation, quantum mechanics and quantum fields. Then the holographic concept and its relation to superstrings will be presented. Finally, current insights on how to exploit this duality to answer questions in gauge field theory, which had not been accessible so far, will be presented.

12 February, 2016

Prof. Eiichiro Komatsu (Max-Planck-Institute for Astrophysics):
Critical Tests of Theory of the Early Universe using the Cosmic Microwave Background
16:15, lecture hall H6
Abstract: The Cosmic Microwave Background (CMB), the fossil light of the Big Bang, is the oldest light that one can ever hope to observe in our Universe. The CMB provides us with a direct image of the Universe when it was still an “infant” - 380,000 years old - and has enabled us to obtain a wealth of cosmological information, such as the composition, age, geometry, and history of the Universe. Yet, can we go further and learn about the primordial universe, when it was much younger than 380,000 years old, perhaps as young as a tiny fraction of a second? If so, this gives us a hope to test competing theories about the origin of the Universe at ultra high energies. In this talk I present the results from the Wilkinson Microwave Anisotropy Probe (WMAP) satellite that I contributed, and then discuss the recent results from the Planck satellite (in which I am not involved). Finally, I discuss future prospects on our quest to probe the physical condition of the very early Universe

23 June, 2015

Prof. Dr. Ulrich Horst (Humboldt University of Berlin ):
Optimal Order Display in Limit Order Markets,
18:15, lecture hall H8

11 July, 2014

Prof. Chris Shannon (University of California, Berkeley):
Risk, Uncertainty and Ambiuity in Markets,
16:15, seminar room V2.210

24 January, 2014

PD Dr. Ulf Hashagen (Forschungsinstitut für Technik- und Wissenschaftsgeschichte, Deutsches Museum München):
Kein Platz für das "Genie": Der ungarisch-jüdische Mathematiker Johann von Neumann in Deutschland,
16:15, lecture hall H6