Colloquia of the Physics, LiMat, and Frimat departments

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October 2017

Wednesday, 04.

Colloquium Physics

Statistical Physics of Complex networks

Prof. Guido Caldarelli, Theoretical physics & Director of European Complexity Center, Lucca University

Time: 17:15 - 18:15h

Location: UNI-Perolles, Physics Department, building 8, auditorium 0.51, Chemin du Musee 3, 1700 Fribourg Switzerland

In this talk I will present later results on my group on Complex Networks Theory. I will introduce simple stochastic models able to reproduce most of the properties of very specific financial and economic networks. They will also be the basis of reconstruction methods to recover graph structure from missing and partial information.

Wednesday, 25.

Colloquium Physics

Exactly solvable models for light-matter interaction

Prof. Daniel Braak, University of Augsburg

Time: 17:15 - 18:15h

Location: UNU-Perolles, Physics Department, building 8, auditorium 0.51, Chemin du Musee 3, 1700 Fribourg

I shall review developments in the theory of elementary models to describe the interaction of light (bosons) with matter (fermions), which have been motivated by the recent dramatic progress towards experimental realization of the so-called deep strong coupling region with possible applications to quantum computing. Relations with the classical theory of analytic functions and the role of discrete and continuous symmetries are especially emphasized.

November 2017

Wednesday, 08.

Colloquium Physics

Thermal convection under our feet and beyond

Prof. Jun Zhang, Physics and Mathematics, Courant Institute, New York University

Time: 17:15 - 18:15h

Location: UNI-Perolles, Physics Department, building 8, auditorium 0.51, Chemin du Musee 3, 1700 Fribourg, Switzerland

This talk is about interdisciplinary fluid dynamics that is based on lab experiments as well as terrestrial and celestial observations. Thermal convection is ubiquitous in nature and can be found in everyday life. This subject has been studied by scientists and engineers for many decades, for its rich dynamics and vast applications. In this talk, I will first discuss an experiment as a free-moving floating boundary interacts with a fluid, which is heated from under and cooled from above. The top boundary is mobile and thermally opaque (poor conductor), causing the coupled system to oscillate. The underlying mechanism is similar to what has been powering the geophysical process of continental drift, as continents interact with the convective mantle of the earth. In the second experiment, a few seemingly impeding partitions or dividers are inserted into a convective fluid, but the heat-flux that passes through is found to be boosted by several times. Theses results are explained and some new directions and phenomena (include the recent total solar eclipse) that extend the classical picture of thermal convection are also discussed.

Wednesday, 29.

Colloquium Physics

How microwaves shed light on topological physics

Prof. Fabrice MORTESSAGNE, Unstitut de Physique de Nice (INPHYNI), Universite Nice Sophia Antipolis &CNRS

Time: 17:15 - 18:15h

Location: UNI-Perolles, Physics Department, building 8, auditorium 0.51, Chemin du Musee 3, 1700 Fribourg, Switzerland

The group Waves in complex systems in Nice (France) is interested in controlling the wave transport properties in various systems whose mastered designs range from homogeneous systems with complex geometries to either (quasi-)periodic or disordered structured materials. Thanks to a versatile experimental platform in the microwave domain, we addressed in the last years the vivid field of topological physics/photonics, and obtained different results ranging from the concept of topological reflective limiter, to a physical interpretation of the gap-labelling in a Penrose tilling, not forgetting the observation of a topological phase transition in strained artificial graphene. During the colloquium, I will give a simple introduction of topological physics, describe the experimental platform, and present a selection of results.

Monday, 28.08.2017 - Sunday, 17.12.2017

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