SP Seminar @SISSA Via Bonomea 265 - Tuesday 12 March at 11am - Andrea PUGLISI

[CM Section]

Joint ICTP/SISSA Statistical Physics Seminar

Tuesday 12 March at 11:00 a.m.
Luigi Stasi Seminar Room, First floor, Leonardo building

Andrea PUGLISI (Univ. di Roma)

'Granular Brownian Motion'

Abstract:
Granular materials are made of macroscopic particles, called grains: sand,
rice, sugar and powders are typical examples. They are important in our
everyday life, in many industrial applications and in the prevention of 
geophysical
hazards.
In physics, mainly in the realm of non-equilibrium statistical 
mechanics, granular
systems are an inspiring source of phenomena and questions. The simplest 
model
of granular material is a "fluid"made of inelastic hard spheres. For 
such a system -
in the dilute limit - the classical program of kinetic theory Boltzmann 
equation,
Chapman-Enskog-based hydrodynamics, and much more) has been developed
by physicists and mathematicians in the last decades.
In this seminar, after recalling a few key results of such a theoretical 
activity, I will
focus on a series of experiments made in my laboratory in the last 5 
years. They
concern the statistical properties of a massive probe immersed in a 
steady stat
granular fluid. The fluid is obtained by vibro-fluidization of a large 
number of solid
spheres of different materials, while the probe is a rigid rotator whose 
angular
displacement and angular velocity are the key observables. In the dilute 
limit one
conjectures a Markovian approximation for the rotator's dynamics which 
explains
many aspects of the experiment, including a qualitative understanding of 
"motor
effects" in the presence of rotator's geometrical asymmetries. Further 
noticeable
facts appear when the granular fluid is no more dilute, mainly anomalous 
diffusion
and non-monotonous viscosity.

References:
-A. Gnoli, L. de Arcangelis, F. Giacco, E. Lippiello, M. Pica Ciamarra, 
A. Puglisi,
A. Sarracino
Controlled viscosity in dense granular materials Phys. Rev. Lett. 120, 
138001 (2018)
-C. Scalliet, A. Gnoli, A. Puglisi, A. Vulpiani Cages and anomalous 
diffusion in vibrated
dense granular media Phys. Rev. Lett. 114, 198001 (2015)
-A. Gnoli, A. Petri, F. Dalton, G. Gradenigo, G. Pontuale, A. Sarracino, 
A. Puglisi
Brownian Ratchet in a Thermal Bath Driven by Coulomb Friction Phys. Rev. 
Lett.
110, 120601 (2013)