When is a lubricant effective?

A plate shearing an interstitial granular medium and driven by an always ongoing spring feels less fricion when only few layers are present. Adding more layers results in an increase of friction,
nevertheless the plate slides more often. The ease … Read the rest

Differential and absolute negative mobility in steady laminar flows

  Nonlinear response in out-of-equilibrium systems can show counter-intuitive behaviors, for instance cases where the force increases but the response decreases (negative differential mobility). Sometimes the response crosses zero and changes sign with respect to the force (absolute negative mobility). In … Read the rest

Thermal convection in granular gases with dissipative lateral walls

Convection in molecular fluids is provided by the competition between gravity and an adverse temperature gradient (two thermostats, the hotter below, the colder above). In a granular gas it can be achieved by a single thermostat at the base, for … Read the rest

Heat, temperature and Clausius inequality in a model for active brownian particles

Living matter at the microscale, many kinds of cells, bacteria and other organisms, self-propel through a viscous fluid which acts as a thermal bath, dissipating the energy provided by the internal motor (pseudopoda, flagella, etc.). This energetic balance is ruled … Read the rest

Mechanism of self-propulsion in 3D-printed active granular particles



 We have reproduced the self propulsion of bacteria and animals with 3d-printed “active granular particles”. Those small artificial insects walk on a rough vibrated plate because of a subtle interplay between material elastic properties and solid-on-solid friction. The … Read the rest

Cages and anomalous diffusion in vibrated dense granular media

Caging is the typical microscopic phenomenon that “traps” molecules in a liquid at low temperature. The usual Brownian Motion of a tracer experiences a temporary “dynamical arrest” which eventually is broken restoring normal diffusion. In this work we have shown … Read the rest

Radio 3 Scienza on “Rappresentanza o governabilità”, A. Petri interviewed

Alberto Petri interviewed on “Rappresentanza o governabilità”, RAI ”Radio 3 Scienza”, February 3rd, 2014

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Brownian Ratchet in a Thermal Bath Driven by Coulomb Friction

A Brownian Ratchet is a small engine which is conceived to extract work from molecular fluctuations. Examples of Brownian Ratchets occur in the cell, see for instance this nice movie about kinesin.

As well explained by Richard Feynmann, a Brownian … Read the rest

Shaken Granular Lasers


A random laser is usually obtained pumping light through a disordered medium. The dynamics of light through a heterogeneous configuration of scatterers and cavities provides emitted spectra with random and fluctuating peaks which have a wide range of applications … Read the rest

Quasi 2D granular dynamics

4000 spheres of steel (diameter 2mm) are deposited on a horizontal rough plate (200mm diameter, only a square 100mm X 100mm is shown) and are put in motion by vertical vibration of the plate (sinusoidal shaking, amplitude 0.7mm, frequency 200Hz). … Read the rest

Granular Dynamics Laboratory

Since July 2010, the Granular Dynamics Laboratory is operative – originally in room “010” and (from november 2012) –  in room “012” (ground floor of Fermi Building of the Physics Department) at the Sapienza unit of ISC. The laboratory includes … Read the rest


Granular fluids to explore non-equilibrium statistical mechanics.

Funding Body: MIUR, Italy (reserved to selected ERC-Starting Grants 2007)
(2009-2014) EURO: 1.2 M
Andrea Puglisi
GranularChaos is a theoretical and experimental project focused on understanding the connection between microscopic and mesoscopic … Read the rest

Granular Gases to explore Non-Equilibrium Statistical Mechanics

How do properties of molecular trajectories reflect on large scale transport and relaxation properties? Is it possible to directly and experimentally verify the Boltzmann’s program, connecting the microscopic level to the macroscopic description? Can we zoom into an out-of-equilibrium fluid … Read the rest

La fisica della sabbia a… cena

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