Topic: 
DNA Origami Tools for Plasmonics, Superresolution and Sensing 
Date: 
03.07.17 
Time: 
16:15 
Place: 
H6 
Guest: 

TU Braunschweig 

Abstract: 
In recent years, DNA nanotechnology has matured to enable robust production of complex nanostuctures and hybrid materials. We have combined DNA nanotechnology with sensitive optical detection to create functional singlemolecule devices that enable new applications in singlemolecule biophysics. Starting with superresolution nanorulers [1], a singlemolecule mirage [2] and energy transfer switches [3] we developed DNA origami nanoadapters for targeted placement of single molecules in zeromode waveguides used for DNA sequencing [4].
Furthermore, a plasmonic fluorescence amplifier [5] is used for sensitive biosensing and singlemolecule detection on lowtec detection devices such as a smartphone. Finally, we present a new molecular force spectroscopy employing DNA origami force clamps that work autonomously without any physical connection to the macroscopic world [6]. We used the conformer switching of a Holliday junction as a benchmark and studied the TATAbinding protein–induced bending of a DNA duplex under tension. The observed suppression of bending above 10 piconewtons provides further evidence of mechanosensitivity in gene regulation.

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Topic: 
Random field of gradients  Critical Phenomena and Scaling limits 
Date: 
02.06.17 
Time: 
16:15 
Place: 
V2210/216 
Guest: 

University of Warwick 

Abstract: 
Random fields of gradients are families of highly correlated random variables arising in the studies of e.g. random surfaces & interfaces and discrete Gaussian Free Fields (GFFs), random geometry, field theory, and elasticity theory. Recently their study has attained a lot of attention. There are several reasons for that. On one hand, these are approximations of critical systems and natural models for a macroscopic description of elastic systems as well as, in a different setting, for fluctuating phase interfaces. In addition, over continuum, the level lines of the GFF are connected to Schramm's SLE (an active field of modern mathematics for understanding critical phenomena) and the fields are natural spacetime analog of Brownian motions and as such a simple random object of widespread application and great intrinsic beauty. Gradient fields are likely to be an universal class of models combining probability, analysis and physics in the study of critical phenomena, and these massless fields are also a starting point for many constructions in field theory. A more recent connection are mathematical models for the CauchyBorn rule of materials, i.e., a microscopic approach to nonlinear elasticity. The latter class of models requires that interaction energies are nonconvex functions of the gradients. Open problems over the last decades include unicity of Gibbs measures and strict convexity of the free energy as well as scaling limits to the Gaussian Free Field and the decay behaviour of twopoint correlation functions. After giving a broad introduction to this recently active field of research we present in the talk Gaussian decay of correlations and the scaling to the Gaussian Free Field for a class of massless fields with nonconvex interaction using a recent renormalisation group approach. 
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Topic: 
Relativistic wideangle galaxy bispectrum on the lightcone: Allsky analysis 
Date: 
18.07.17 
Time: 
14:15 
Place: 
D6135 
Guest: 

Argelander Institut für Astronomie, Bonn 

Abstract: 
Given the important role that the galaxy bispectrum has recently acquired in cosmology and the scale and precision of forthcoming galaxy clustering observations, it is timely to derive the full expression of the largescale bispectrum going beyond approximated treatments which neglect integrated terms or higherorder bias terms or use the Limber approximation. On cosmological scales, relativistic effects that arise from observing on the past lightcone alter the observed galaxy number counts, therefore leaving their imprints on Npoint correlators at all orders. Working in spherical Bessel coordinates, in this talk I will show that it is possible to derive a compact expression for the power spectrum and bispectrum that encompasses all the physical effects at first and second order, including integrated (along the line of sight) terms. 
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Topic: 
Connecting Spin Hamiltonians from DFT Calculations to Experiment 
Date: 
06.04.17 
Time: 
14:15 
Place: 
D5153 
Guest: 
Shadan Ghassemi 
TU Berlin 

Abstract: 

Contact person: 
Topic: 
Nonorthogonality of eigenvectors from the HaagerupLarsen theorem 
Date: 
01.06.17 
Time: 
17:00 
Place: 
D5153 
Guest: 
Wojciech Tarnowski 
Jagiellonian University Krakow 

Abstract: 
Biunitarily invariant ensembles have been thoroughly studied in recent years from the point of view of statistics of eigenvalues. An enhanced symmetry of the probability distribution function allows us to expect that all spectral properties will be determined by the singular values only. Indeed, for large matrices, a mapping between onepoint densities is known as the HaagerupLarsen theorem. Recently, this mapping has been extended to all kpoint functions (KieburgKösters). During my talk, I will present a recent extension of the HaagerupLarsen theorem, which gives a simple mapping between the radial spectral cumulative distribution function and a certain onepoint eigenvector correlation function, built out of (nonorthogonal) left and right eigenvectors. I will discuss also its relation with the stability of the spectrum. 
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Topic: 
Matrix product ensembles of Hermitetype 
Date: 
21.06.17 
Time: 
16:00 
Place: 
V3201 
Guest: 
DangZheng Liu 
Institute of Science and Technology Austria & University of Science and Technology of China 

Abstract: 
We investigate spectral properties of a Hermitised random matrix product which, contrary to previous product ensembles, allows for eigenvalues on the full real line. We find an explicit expression of the joint probability density function as a biorthogonal ensemble. As an interesting example, we focus on the product of GUE and LUE matrices and provide explicit expressions both for the biorthogonal functions and the correlation kernel. Then a new doubleside kernel is found at the origin, which is slightly different from the Bessel kernel. This talk is based on joint work with P. J. Forrester and J. R. Ipsen. 
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