Séminaire du LPTMS: Ken Sekimoto


11:00 - 12:00

LPTMS, salle 201, 2ème étage, Bât 100, Campus d'Orsay
15 Rue Georges Clemenceau, Orsay, 91405

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Coarse-Graining of Momentum Flow

Ken Sekimoto (MSC, Université Denis Diderot & Gulliver, ESPCI)

Like the energy and mass, the momentum is also a conserved quantity.  Usually, however, we pay less attention to the role played by the last  one as compared with the former ones. In the present talk, I will  discuss the three examples in which the concept of momentum flow helps  and simplifies our understanding of phenomena.

First we discuss the « adiabatic-piston » for which the physical origin  of the non-equilibrium force has long been unclear. The consideration of  the momentum flux of both the gases and piston allows to reach the  central results in a few lines of elementary calculation, elucidating  how the non-equilibrium force emerges.

Secondly we present a method of coarse-graining the overdamped dynamics  of dense cellular packing of matters. » We show that the coarse graining  of the momentum and angular momentum fluxes leads naturally to the  Irving-Kirkwood type formula for the stress tensor irressective of the underlying dynamics.

Lastly we discuss the Newton’s cradle with modified repulsive laws. This  classical 1D system can show the similarity to the quantum Mössbauer  absorption and emission. By considering the momentum flow through the  cluster, we reach the coarse-grained dynamics for the center of mass coupled with an « evanescent » wave.

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