Upcoming Events

Due to infection prevention measures, participation in events at the institute is presently not possible for guests.

Many events are currently organized online. Information on how to access these events can be found by clicking “more” below the respective entry.


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Tuesday, 19.01.2021, 15:15 (Online Event)
Oberseminar Nonlinear Dynamics
Dr. Michal Hadrava, Institute of Computer Science of the Czech Academy of Sciences, Prague, Czech Republic:
A dynamical systems approach to spectral music: Modeling the role of roughness and inharmonicity in perception of musical tension
more ... Location
Online Event

Abstract
Tension-resolution patterns seem to play a dominant role in shaping our emotional experience of music. Whereas in traditional Western music, these patterns are mainly expressed through harmony and melody, many contemporary musical compositions (e.g. so-called ?spectral music") employ sound materials lacking any perceivable pitch structure, rendering these two compositional devices useless. Motivated by recent advances in music-theoretical and neuroscientific research into the related phenomenon of dissonance, we propose a neurodynamical model of musical tension based on a spectral representation of sound and hence applicable to any kind of sound material, pitched or non-pitched.

Further Informations
Diesen Vortrag können Sie mit Zoom verfolgen unter: https://zoom.us/j/82815629022.

Host
Freie Universität Berlin
WIAS Berlin
Tuesday, 19.01.2021, 16:00 (Online Event)
Seminar Modern Methods in Applied Stochastics and Nonparametric Statistics
Dr. Dmitrii M. Ostrovskii, University of Southern California:
Near-optimal model discrimination with non-disclosure (online talk)
more ... Location
Online Event

Further Informations
Dieser Vortrag findet bei Zoom statt: https://zoom.us/j/492088715

Host
WIAS Berlin
Wednesday, 20.01.2021, 10:00 (Online Event)
Forschungsseminar Mathematische Statistik
Sven Wang, University of Cambridge:
On polynomial-time computation of high-dimensional posterior measures by Langevin-type algorithms
more ... Location
Online Event

Abstract
In this talk, we consider the task of generating random samples of high-dimensional posterior distributions. The main results consist of non-asymptotic computational guarantees for Langevin-type MCMC algorithms which scale polynomially in key quantities such as the dimension of the model, the desired precision level, and the number of statistical measurements. We also show that posterior mean vectors and maximum a posteriori (MAP) estimates are computable in polynomial time, with high probability under the distribution of the data. Those results are derived in a general non-linear regression setting where posterior measures are not necessarily log-concave. The main example is a non-linear PDE model involving the steady-state Schrödinger equation. The talk is based on the preprint https://arxiv.org/abs/2009.05298.

Further Informations
Der Vortrag findet bei Zoom statt: https://zoom.us/j/159082384

Host
Humboldt-Universität zu Berlin
WIAS Berlin
Wednesday, 20.01.2021, 11:30 (Online Event)
Seminar Interacting Random Systems
Lorenzo Taggi, University of Rome “La Sapienza”, Italien:
Exponential decay of correlations for O(N) spin systems
more ... Location
Online Event

Abstract
The Spin O(N) model is a classical statistical mechanics model whose configurations are collections of unit vectors, called spins, taking values on the surface of a N ?1 dimensional unit sphere, with each spin associated to the vertex of a graph. Some special cases of the spin O(N) model are the Ising model (N = 1), the XY model (N = 2), and the classical Heisenberg model (N = 3). Despite the fact that it is a very classical model, there remain important gaps in understanding, particularly in the case N > 2. This talk will provide an introduction on this class of models and present a new recent result about exponential decay of correlations for arbitrary (non-zero) values of the external magnetic field and arbitrary spin dimension N>1. The proof of this result employs a representation of the model as a system of coloured random paths and a sampling procedure, which allows us to bound from above the "typical lenght" of the open paths. The talk is based on a joint work with B. Lees.

Further Informations
Seminar Interacting Random Systems

Host
WIAS Berlin
Thursday, 21.01.2021, 15:00 (Online Event)
TES-Seminar on Energy-based Mathematical Methods and Thermodynamics
Dr. Pierre-Étienne Druet, Technische Universität Berlin WIAS Berlin:
The free energy of incompressible fluid mixtures: An asymptotic study (online talk)
more ... Location
Online Event

Abstract
The results presented in this talk are triggered by the modelling of multicomponent fluids at low Mach-number. We first perform the asymptotic of small compressibility for a globally stable phase, and we show that the Helmholtz free energy, which is the crucial constitutive quantity, tends to a limit in the sense of epi- or Gamma-convergence. The essential findings are: The limit model does not only prohibit thermal expansion - this is the well-known Mueller-paradox -, but it also excludes the phenomena of volume loss or excess due to mixing. In order to temper the latter unrealistic conclusion, we modify the basic scenario by performing the limit only inside of a bounded, stable phase. In this way we recover incompressible systems that are not volume additive. Moreover, the limit free energy depends continuously on the state variables. This research is joined work with D.Bothe (TU Darmstadt) and W.Dreyer (WIAS Berlin).

Further Informations
TES-Seminar on Energy-based Mathematical Methods and Thermodynamics (online talk)

Host
Technische Universität Berlin
WIAS Berlin
Wednesday, 27.01.2021, 15:15 (Online Event)
Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Dr. Sebastian Throm, Westfälische Wilhelms-Universität Münster:
Universal long-time asymptotics for coagulation equations (online talk)
more ... Location
Online Event

Abstract
In this talk, we will consider the long-time behaviour of coagulating systems. Clustering phenomenon can be observed in many processes in nature and industry and also on a broad range of scales. Our focus will be on Smoluchowski's coagulation equation and the question of universal scaling for large times - a problem which is known as scaling hypothesis. In particular, we will present a recent result proving this conjecture for perturbations of a constant rate kernel.

Further Informations
Oberseminar “Nichtlineare Partielle Differentialgleichungen” (Langenbach Seminar)

Host
Humboldt-Universität zu Berlin
WIAS Berlin
Thursday, 28.01.2021, 15:00 (Online Event)
TES-Seminar on Energy-based Mathematical Methods and Thermodynamics
Ass. Prof. Markus Hütter, Eindhoven University of Technology, Niederlande:
Finite-size effects in complex fluids: Phenomenology of fluctuations, stochastics, and statistical mechanics (online talk)
more ... Location
Online Event

Abstract
In general, in every system with dissipation there are also fluctuations; the fluctuation-dissipation theorem is a key result of nonequilibrium statistical mechanics, which is encoded e.g. in the GENERIC framework [1,2,3]. Correspondingly, also complex fluids, which contain the relaxation of the microstructure (e.g. polymer chains), must show behavior with fluctuations. Fluctuations are relevant particularly for the behavior on small scales, where they are not averaged out, e.g. in micro-/nano-fluidics and microrheology. To date, models for complex fluids do not include fluctuations systematically. In our recent work, we have extended conformation-tensor based models for complex fluids by including thermal fluctuations in a thermodynamically consistent way [4]. Furthermore, this work has been complemented by establishing a link between the fluctuating conformation-tensor models and the underlying description of polymer chains as bead-spring dumbbells [5]. To achieve this link, we follow two routes: (1) stochastic calculus, followed by averaging (direct approach); (2) nonequilibrium statistical mechanics, which includes the derivation of the coarse-grained relaxation tensor, the fluctuations, and the thermodynamic potential (particularly entropy). Denoting the number of polymer chains by N, it is shown that a finite (rather than infinite) value for N gives rise to a correction to the conventional entropy for the conformation tensor and leads to the fluctuations that vanish only in the thermodynamic limit (N to infinity). Finally, some subtleties are pointed out related to the appearance of the so-called spurious drift in the stochastic differential equation for the conformation tensor. References: [1] M. Grmela, H.C. Öttinger, Phys. Rev. E 56(6) (1997) 6620?6632 (http://dx.doi.org/10.1103/PhysRevE.56.6620) [2] H.C. Öttinger, M. Grmela, Phys. Rev. E 56(6) (1997) 6633?6655 (http://dx.doi.org/10.1103/PhysRevE.56.6633) [3] H.C. Öttinger, Beyond Equilibrium Thermodynamics, Wiley, Hoboken, 2005. [4] M. Hütter, M.A. Hulsen, P.D. Anderson, J. Non-Newtonian Fluid Mech. 256 (2018) 42?56 (https://doi.org/10.1016/j.jnnfm.2018.02.012) [5] M. Hütter, P.D. Olmsted, D.J. Read, Eur. Phys. J. E 43 (2020) 71 (http://dx.doi.org/10.1140/epje/i2020-11999-x)

Further Informations
TES-Seminar on Energy-based Mathematical Methods and Thermodynamics

Host
Technische Universität Berlin
WIAS Berlin
Wednesday, 03.02.2021, 11:30 (Online Event)
Seminar Interacting Random Systems
Elena Pulvirenti, Delft University of Technology, Niederlande:
tba (online talk)
more ... Location
Online Event

Further Informations
Seminar Interacting Random Systems

Host
WIAS Berlin
Thursday, 04.02.2021, 16:00 (Online Event)
Forschungsseminar Mathematische Modelle der Photonik
Dr. Shalva Amiranashvili, WIAS Berlin:
Parallel splitting methods
more ... Location
Online Event

Host
WIAS Berlin
Thursday, 25.02.2021, 16:00 (Online Event)
Forschungsseminar Mathematische Modelle der Photonik
Siavash Qodratipur, HU Berlin:
Surface plasmon polaritons in nano-structures
more ... Location
Online Event

Host
WIAS Berlin