Talks

Synchronization of flagella due to multiplicative noise

We argue physically that the coupling of eukaryotic flagella is noisy. We demonstrate that such multiplicative noise surprisingly leads to improved synchronisation of the flagella in the sense of the stationary distribution of the phase differences of the two flagella. We derive analytics to show how the maximum and the full width half maximum are reduced for increasing multiplicative noise strength according to the same function. We show that these results are robust when considering additional additive noise.

Algebraic Curves and Grassmannians via the KP Hierarchy

Algebraic curves are fundamental objects in the mathematical sciences. Integrable systems, particularly the Kadomtsev-Petviashvili hierarchy, provide an example of such phenomena and reaffirm the significance of Grassmannians. In this talk, we will examine the connections between algebraic curves and Grassmannians guided by the hierarchy. We will explore these connections within transcendental, real, and combinatorial algebraic geometry from a computational perspective. We will conclude by touching upon potential applications of this geometry in biology.

Dynamics of quantum impurity models with semi-group influence matrices

Quantum impurity models (QIMs) play a central role in describing many strongly correlated materials, including Kondo systems, quantum dots and molecular junctions. Calculating real-time dynamics of QIMs remains challenging for the established methods designed for equilibrium settings. In this talk, I present a novel framework for QIM dynamics where the multi-time dynamical propagator of the impurity (the influence matrix) is expressed in terms of a temporal matrix product state (MPS). Leveraging a uniform MPS representation of the influence matrix, this method establishes a dynamical semi-group formalism, where the environmental effects are encoded via compressed auxiliary degrees of freedom. I showcase the power of this approach through applications to the dynamics of spin-boson models and fermionic impurity systems.

Quantum simulation of a topological insulator at high electric field

We consider two bosonic modes coupled to a two-level system. We can interpret this system as a quantum simulator of a single particle in a two dimensional lattice by considering the number of photons in each mode as a synthetic dimension [1,2]. With a suitable coupling between the modes and the qubit, we obtain a quantum optical simulation of a topological insulator at high electric field. Motivated by these recent works, we study the fate of band topology at high electric fields. We show how the electric field hybridizes the edge modes with the bulk states. We describe this hybridization as an extension in energy of the spectral flow of edge modes. [1] I. Martin, G. Refael, B. Halperin, Phys. Rev. X 7, 041008 (2017). [2] Deng et al., Science 378, 966–971 (2022).

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Low-energy excitations in glasses: Universal statistics, localization and the boson peak

Glassy systems exhibit various universal anomalies compared to their crystalline counterparts, manifested in their vibrational, thermodynamic, transport and strongly dissipative properties. At the heart of understanding these phenomena resides the need to quantify glassy disorder, which is self-generated during the non-equilibrium glass formation process, and to identify the emerging elementary excitations. In this talk, I will review recent progress made in relation to this basic problem. Using a combination of theory, computer simulations and experimental data, I will elucidate the statistical and micro-mechanical nature and properties of low-frequency glassy (non-phononic) excitations, including their universal statistics, spatial localization, non-equilibrium history dependence, relations to spatially extended phonons and the emergence of a boson peak.

Quantum Dynamics Seminar: Potential Energy Surfaces, Newton Trajectories and Catch Bonds in Theoretical Chemistry

The talk begins with a discussion of the problems involved in defining a reaction pathway, in particular the steepest descent, the intrinsic reaction coordinate (IRC) and gradient extremals (GE). As an alternative, we propose Newton trajectories (NT) [1]. An NT is a curve where the gradient of the PES points in the same direction at every point. Other definitions of NTs and further methods for different calculations are reported [2]. NTs connect stationary points of the PES, so they can be used to find saddle points. Another important property of NTs is that they bifurcate at valley-ridge inflection points (VRI). Application: NTs describe the curves of the change of stationary points under a mechanochemical force [3]. A special application is the study of so-called catch bonds: counterintiutive bonds that become stronger under a mechanochemical force [4]. Two example PES are explained. 1] W.Quapp, M.Hirsch, O.Imig, D.Heidrich, J.Computat.Chem. 19 (1998) 1087; W.Quapp, M.Hirsch, D.Heidrich, Theor.Chem.Acc. 100 (1998) 285. 2] W.Quapp, J.Theoret.Computat.Chem. 2 (2003) 385, and 8 (2009) 101. 3] W.Quapp, J.M.Bofill, J.Phys.Chem.B 120 (2016) 2644. 4] W.Quapp, J.M.Bofill, J.Phys.Chem.B 128 (2024) 4097.

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IMPRS

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IMPRS Seminar

IMPRS Seminar

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