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Please join us for this month's IoP colloquium, where Prof. Dr. Hans Jürgen Herrmann will be talking about 'Rotating Matter: The Bearing State'.

Detail Summary
Date 22 November 2018
Time 16:00 - 17:00


Granular materials are characterized by an additional degree of freedom, rotations, which become particularly relevant for spherical particles. They allow for soft modes under shear which do find realizations for instance in tectonic faults. A packing of spheres is called bi-chromatic if every loop formed by contacts is even. In three dimensions, bi-chromatic bearings have many different sliding-free configurations, so called bearing states. If all loops have length four the system exhibits four continuous degrees of freedom and a systematic way of constructing  such bearing states can be devised [1]. By considering spheres of different size, packings with bearing states can even be made space-filling. The construction and mechanical properties of such space-filling bearings will be discussed. Their bearing states can be viewed as a realization of solid turbulence exhibiting Kolmogorov scaling and anomalous heat conduction. In three dimensions a continuum of such configurations can be obtained as cuts through four-dimensional space-filling bearing states. Bearings states can be perceived as physical realizations of networks of oscillators with asymmetrically weighted couplings. These networks can exhibit optimal synchronization properties through tuning of the local interaction strength as a function of node degree or the inertia of their constituting rotor disks through a power-law mass-radius relation . Under this condition, the average participation per disk is maximized and the energy dissipation rate is homogeneously distributed among elementary rotors. The synchronization of rotations occurs in avalanches following a broad size distribution [2].
[1] D.V. Stäger, N.A.M. Araújo, H.J. Herrmann, Phys. Rev. Lett. 116, 254301 (2016)
[2] N.A.M. Araújo, H. Seybold, R.M. Baram, H.J. Herrmann, J.S. Andrade  Jr., Phys. Rev. Lett. 110, 064106 (2013)


About the speaker:


Drinks after the colloquium will be served at café ‘De Oerknal’ in the Universum (USC).



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