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

Topological Laser

The cascade of resonant PT-symmetric topological structures is shown to emit laser light with a frequency comb spectrum. We consider optically active topological lattices supporting edge modes at regularly spaced frequencies. When the amplified resonances in the PT-broken regime match … Read the rest

Gaussian, non Gaussian and Anomalous diffusion to improve medical diagnosis

In the biomedical field, Diffusion Magnetic Resonance (DMR) images provide a measure of water proton displacements by probing motion on the mesoscopic length scale (around 10-20 µm), which is orders of magnitude smaller than the macroscopic MR resolution (typically 1-2 … Read the rest

Transient spiral arms from far out of equilibrium gravitational evolution: Supplement Material

David Benhaiem [1,2] Michael Joyce [2] and Francesco Sylos Labini [3, 1, 4]

  1. Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche, Via dei Taurini 19, I-00185 Roma, Italia
  2. Laboratoire de Physique Nucleaire et de Hautes Energies, UPMC IN2P3 CNRS UMR
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Protected: Gravitational evolution of rotating ellipsoidal clouds

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How to build a quantum Newton’s cradle

A quantum analogue of the popular “Newton’s cradle” toy has been proposed by a duo of physicists in Italy. Like momentum transferred in the toy, the team argues that it should be possible to achieve the nearly perfect transmission of … Read the rest

Newton cradle

Newton’s cradle (Fig. 1) is a valuable paradigm of how physical mechanisms are concealed into nature. It is a device based on classical mechanics that demonstrates the conservation of momentum and energy. On the other hand, Quantum Mechanics has been … Read the rest

Meccanica statistica di non equilibrio

Meccanica statistica di non equilibrio: trasporto e diffusione in sistemi complessi

Relatore: Stefano Lepri

Gli argomenti di tesi sono di tipo teorico e riguardano il comportamento di sistemi fuori equilibrio. Una preparazione di base in meccanica statistica e’ essenziale. La … Read the rest

Anomalous Heat Transport in Low Dimensions

Many phenomena in nature occur under nonequilibrium stationary conditions. For instance, an electric current is obtained by applying an electric field along a conductor or heat is transported when a temperature gradient is established between two boundaries of a material.

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Asymmetric Wave Transport in Nonlinear System

Deterministic chaos, fractal structures and other beautiful phenomena are manifestations of the nonlinear character of forces which govern our world. Besides a revolutionary change in our approach to predictability, these discoveries had great impact on technological applications.  Among the most 

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Forthcoming book on Nonequilibrium Statistical Physics

Roberto Livi and Paolo Politi
Nonequilibrium Statistical Physics – A modern perspective
(Cambridge University Press, 2017)

 

Statistical mechanics has been proven to be successful at describing physical systems at thermodynamic equilibrium.  Since most natural phenomena occur in nonequilibrium conditions, … Read the rest

Molecole magnetiche su grafene per la spintronica

Una ricerca, svolta in collaborazione fra fisici e chimici italiani, tedeschi e spagnoli, mostra che è possibile realizzare nano-sistemi ibridi depositando magneti molecolari su grafene. L’interazione fra gli spin dei magneti molecolari e il gas bidimensionale di elettroni del grafene … Read the rest

Rivelazione di nanoanticorpi in tracce con tecniche di risonanza plasmonica di superficie

Bruno Tiribilli 1, Giancarlo Margheri 1, Federica Pierucci 2 , Ambra Vestri 2, Elisabetta Meacci 2
1 Istituto dei Sistemi Complessi, del Consiglio Nazionale delle Ricerche, via Madonna del Piano 10, 50019, Sesto Fiorentino (FI).
2 Dipartimento … Read the rest

New porous water ice metastable at atmospheric pressure obtained by emptying a hydrogen-filled ice

Leonardo del Rosso 1,2, Milva Celli 1 & Lorenzo Ulivi

The properties of some forms of water ice reserve still intriguing surprises. Besides the several stable or metastable phases of pure ice, solid mixtures of water with … Read the rest

MOVEMENT ECOLOGY OF SEABIRDS: a mechanistic explanation of their incredible navigation ability

LÉVY FLIGHT
AVIAN
OLFACTORY
NAVIGATION
EXPERIMENTS
RESULTS
THE TEAM
LÉVY 2.0

Seabirds can fly for many days and nights across featureless oceans to their preferred feeding locations and then fly back to their nests without getting lost. How they do … Read the rest

The Bulgarian red deer project

Two researches of the ISC (Stefano Focardi and Sonia Lombardi), together with Federico Morimando (Studio Proeco) have visited dr. Atidzhe Ahmed and Prof. Peter Genov, colleagues at the Institute of biodiversity and ecosystems research of the … Read the rest

The soft side of hard matter

Soft condensed matter is characterized by gigantic responses to  external perturbations which is the reason why these systems are extremely useful for applications, like liquid crystals in our cell phones displays. In contrast, hard condensed matter a.k.a. solids respond more … 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

Ionic liquids: a spectroscopic investigation

Ionic liquids (IL) are salts formed by organic cations, like imidazolium, pyrrolidinium, ammonium or alkyl phosphonium, and organic/inorganic anions, like hexafluorophosphate, tetrafluoroborate, triflate, dicyanamide, tetracyanamethanide or bis(trifluoromethanesulfonyl)imide (TFSI). The presence of such bulky and asymmetric ions decreases the ion-ion interactions … Read the rest

Solid state hydrogen storage

Hydrogen is attracting renewed interest as an energy carrier, due to the necessity of finding ecological energy media which may decrease the environmental pollution from fossil fuels. Hydrogen storage represents a nodal point for the development of a hydrogen economy.… Read the rest

Rules and Exceptions in Language Dynamics

In all languages, rules have exceptions in the form of irregularities. Since rules make a language efficient, the persistence of irregularity is an anomaly. How language systems become rule governed, how and why they sustain exceptions to rules? Frequent words … Read the rest

Mixing by degree in signed social networks

Social networks have empirically been found to be assortative (i.e., the degree of neighboring nodes are positively correlated), while other networks (e.g., technological, biological) show the opposite pattern (disassortative). Why is that so?
How do these patterns change in signed … Read the rest

Dynamics of Virus-Host interaction

In the case of fast mutating viruses (e.g., Influenza virus), the virus-host interaction is driven by cross-immunity: after being infected by a strain, the host acquires immunity to a set of other strains antigenically similar to the infecting one (i.e., … Read the rest

Fractures and crack propagation

The intermittent and self-similar fluctuations displayed by a slow crack during the propagation in a heterogeneous medium can be quantitatively described by an extension of a classical statistical model for fracture. The model yields the correct dynamical and morphological scaling, … 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

Soft matter

The term “soft matter” refers to a very large class of materials, whose common characteristic is that they are composed of mesoscopic particles, i.e. particles with typical sizes ranging from 1 nm to a few microns. These particles are normally … Read the rest

Volume collapse transition in Ce

Crystalline Ce has a remarkable phase diagram in that is the solid state analogue of a Van der Walls system with a line of discontinuous transitions ending at a critical point.

The two phases alpha and gamma have the same … 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 Phases

Steel spheres move on a plate. The “thermostat ” is a vibrating wall, following a sine law with frequency 20 Hz . Weak gravity (the plate has a small angle of inclination) draws the spheres toward the vibrating wall. In … Read the rest

Synchronization of extended systems

Synchronization is a long known phenomenon dating back to Huygens experiments who observed that suspending two pendula “…in the same wooden beam, the motions of each pendulum in opposite swings were so much in agreement that they never receded Read the rest

GRANULAR CHAOS

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

Statistical physics modeling of social dynamics

In recent years it has become widely recognized that many large-scale phenomena observed in social systems are the “macroscopic” complex effect of the “microscopic” simple behavior of a large number of interacting agents. This has led social scientists to the … Read the rest

Regularities and universality in large-scale social phenomena

In social phenomena every individual interacts with a limited number of peers, usually negligible as compared with the total number of people in the system. In spite of that, human societies are characterized by stunning global regularities. There are transitions … Read the rest

Fractal analysis of planetary topographies

There exists an overwhelming diversity of landscapes on Earth. A cornerstone of modern geomorphology came with the realization that all the different features of the terrestrial surface result from the accumulated effect of current geological agents [Lyell, 1830]. This principle … Read the rest

Polarons in strongly correlated systems

In system with strong electron-phonon interaction, the carriers loose mobility, ultimately acquiring polaronic character. A polaron is a state in which the phonon and electron degrees of freedom are strongly entangled, and the presence of an electron is associated to … Read the rest

GZIP: Galaxy morphology classification by zip algorithm

Even before the identification of galaxies as stellar systems, astronomers have classified them based on their visual appearance. Galaxies in the local universe can organized in a sequence of morphologies (e.g. the Hubble sequence) which must be the result of … Read the rest

Tidal tail characterization

Introduction

A globular cluster (GC) is a spherical collection of stars that orbits a galactic core as a satellite.
Globular clusters are very tightly bound by gravity, which gives them their spherical shapes and relatively high stellar densities toward their … Read the rest

Spatially correlated random walks and turbulence

The wide applicability of the random walks (RW) to natural phenomena relies just on the possibility to introduce appropriate generalizations on the probabilistic nature of displacements. A straightforward generalization is realized by assuming correlations in displacements to obtain the so … 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

Dynamics of self-gravitating systems

A System with long-range interactions is characterized by an inter-particle potential which decays at large distances with a power law exponent which is smaller than the dimension of the embedding space. Classical examples include for instance: self-gravitating systems, unscreened Coulomb … Read the rest

Matter density fields in the early universe

The most prominent feature of the initial conditions of the matter spatial distribution in the early universe, in standard theoretical models, derived from inflationary mechanisms, is that matter density field presents on large scale super-homogeneous features. This means the following. … Read the rest

Total gravitational force and the classification of long range interactions

In equilibrium statistical mechanics the distinction between short and long range interactions is given by the integrability or not of the pair potential. However for what concerns only the clustering dynamics of a particle distribution under the effect of an … Read the rest

Graphene and carbon-based new materials

The investigation of the electronic properties of graphene (single hexagonal layer of carbon atoms) has attracted a renewed interest after the development of recent techniques which permit to produce and manage single-layer (and also multilayer) samples of this materials. Nowadays … Read the rest

Role of microscopic chaos to macroscopic transport

The discovery that simple deterministic nonlinear systems could display dynamical evolution characterized by a randomness similar to stochastic processes changed very much researchers’ attitude toward determinism and predictability of natural phenomena. Determinstic chaos has been successfully invoked to interpret several … Read the rest

Disorder driven non-equilibrium phase transition: the Random field Ising model

In hard magnetic materials, the domain walls movement or even creation is suppressed, and other mechanisms, like domains nucleation and coherent spin rotation enter in the process of magnetization reversal. For these kind of materials a description in terms of … Read the rest

Systems with multiplicative noise

Problems susceptible to be mathematically represented by stochastic Langevin equations including a multiplicative noise abound not only in physics, but also in biology, ecology, economy, or social sciences. In a broad sense a Langevin equation is said to be multiplicative … Read the rest

Competing orders in Iron based superconductors

In January 2008 a new family of superconductors has been discovered with FeAs layers. Iron is a magnetic ion and in traditional superconductors small amounts of magnetic impurities kill superconductivity so an iron based superconductor is at first sight surprising.… Read the rest

Protein molecules

Biopolymers such as nucleic acids (DNA and RNA) and proteins have been charged by natural evolution with the task of storing, transmitting and transforming genetic information of living matter.
In particular proteins are the macromolecules which perform most of the … Read the rest

Metastable states and supersymmetry

Both the static and the dynamical behaviour occurring in mean field spin glass models models can be interpreted as consequences of the complex (free) energy landscape that spin glasses have, with many minima, valleys and saddles. Traditionally, much attention has … Read the rest

Field theory for finite dimensional spin glasses

Many features predicted by mean field spin glass models, such as the behaviour of susceptibilities and correlation functions or the occurrence of aging and off-equilibrium dynamics, are qualitatively observed in experiments, suggesting that the mean field scenario may hold for … Read the rest

Frustrated Phase Separation

A large variety of systems with competing short and long range interactions self-organizes in domain patterns as reviewed by Seul and Andelman. Examples range from magnetic systems (left figure A) to organic systems (left figure B).

Inhomogeneous states display a … Read the rest

The growth of amorphous order in supercooled liquids

Close to the glass transition supercooled liquids display an impressive increase of the relaxation time, without any clear sign of growing thermodynamic order, nor correlation length. This is at variance with physical intuition, which suggests that a large relaxation time … Read the rest

Polarons in organic single crystal FET’s

Organic field effect transistors (OFETs) are providing exciting prospects for potential applications in electronics. The active elements of these devices use “plastic” semiconductors, based on carbon and hydrogen. Among the advantages compared to classical silicon transistors, this new generation of … Read the rest

Crackling noise: the Barkhausen effect

The term “crackling noise” refers to the signal that some disordered systems produce as a response to an external driving field smoothly changing in time. Due to the presence of disorder, crackling signals are extremely irregular, despite the … Read the rest

Dynamic hysteresis in thin and ultra-thin films

The physics of thin and ultra-thin magnetic films has been extensively studied in the recent past, because of its important implications for applications to high frequency devices. Power losses in ferromagnetic materials generally depend on the frequency of the applied … Read the rest

Dynamical Processes on Networks

During the last decade it has become clear that the topology in many systems, ranging from technological to social to biological, is not well described by regular lattices nor by random graphs. Complex networks, characterized by small-world effects, large connectivity … Read the rest

Human Dynamics

Until now, the study of human dynamics has been done only qualitatively. Actually, the present possibility to have quantitative data on the kind and nature of social relationships through social networks is driving a rapid change in the field. Thanks … Read the rest

Unconventional antiferromagnetism due to Dzyaloshinskii-Moriya interactions

The relevance of antisymmetric superexchange interactions in spin Hamiltonians describing quantum antiferromagnetic (AF) systems has been acknowledged long ago by Dzyaloshinskii. Soon after, Moriya showed that such interactions arise naturally in perturbation theory due to the spin-orbit coupling in magnetic … Read the rest

Random Lasers

In a nutshell, a random laser is the coherent emission from active stochastic resonators.

In a series of articles around 1966, a Russian scientist V. S. Letokhov, of the Lebedev Physics Institute in Dubna considered the generation of light in … Read the rest

Strongly Correlated Superconductivity: how can repulsion enhance Tc?

In conventional superconductors, the repulsive interaction between electrons opposes to phonon-mediated pairing. We have shown that even phonon-mediated superconductivity can be favoured by repulsion under suitable conditions which are realized in fullerenes.

Trivalent alkali-doped fullerenes are almost certainly electron-phonon superconductors, … Read the rest

The INFM-CNR/STARFLAG team

Here follows a very synthetic description of the role each one of the people in the INFM-CNR/STARFLAG team had:

  • Michele Ballerini (CNR-INFM)
    electronics, data taking
  • Nicola Cabibbo (La Sapienza)
    electronics design, experimental setup design
  • Raphael Candelier (La Sapienza and CEA)
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Spin Glasses: a brief introduction

Spin Glasses are dilute magnetic alloys where the interactions between spins are randomly ferromagnetic or anti-ferromagnetic, and are considered as paradigmatic examples of frozen disorder. The presence of disorder (the random interactions) induces frustration and a greater difficulty for the … Read the rest

What is Econophysics?

Collective phenomena in economics, social sciences and ecology are very attractive for statistical physicists, especially in view of the empirical abundance of non-trivial fluctuation patterns and statistical regularities — think of returns in financial markets or of allometric scaling in … Read the rest

Spin-orbit interaction and spintronics

One of the new frontiers in condensed matter physics is development and engineering of electronic devices which carrier “bit” informations in the spin degree of freedom of the electronc instead of their charge. This research line is called indeed “spintronics”. … Read the rest

Inhomogeneities in Cuprates

If the mechanism of high-Tc superconductivity is electronic, to understand the electronic excitation spectrum is as important as to understand phonons was important to develop BCS theory. In this regard charge and spin inhomogeneous states, often found in … Read the rest

Unconventional electron-phonon interaction and nonadiabatic effects

The conventional understanding of the electron-phonon phenomenology in condensed matter strongly relies on the adiabatic assumption, i.e. that nuclei dynamics is much slower than the electron one. In solid crystals the validity of this assumption is usually related to the … Read the rest

Topological vs. Metric distance

Basically all existing models of collective animal behaviour (bird flocks, fish schools, etc) assume that the interaction between different individuals depends on the metric distance, just as in physics. This implies, for example, that two birds 5 meters apart … Read the rest

Protein Folding

Protein Folding is a specific chemical and physical transition by which a linear sequence of aminoacids finds its functional (native) three dimensional structure. The theoretical study of protein folding represents perhaps one of the most challenging research with a marked

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Home Page of Andrea Cavagna

Education:

Post-Doc, Theoretical Physics, Physics Dept, Manchester University, UK, 2001 (with Alan Bray and Mike Moore)

Post-Doc, Condensed Matter, Theoretical Physics Dept, Oxford University, UK, 1999 (with David Sherrington)

Ph.D. in Theoretical Physics, University of Rome Sapienza, Italy, 1998 … Read the rest

STARFLAG: a project on collective animal behaviour

Collective animal behaviour is a fascinating phenomenon. How does global co-ordination emerge in a flock of thousands starlings swirling at dusk? How does a school of sardines organize in a circular pattern? What is the evolutionary function of collective behaviour? Read the rest

Scale-free networks

Scale-Free Networks are present in a wide list of phenomena. Examples range from the structure of the Internet and that of the WWW (we shall see in the following that they are different systems) to the interconnections between financial agents … Read the rest

Transport in binary mixtures

When a binary fluid mixture at the critical concentration is cooled from a high temperature to a sufficiently low temperature (below a critical one), the original homogeneous phase becomes unstable and spontaneously evolves into two phases separated by an interface. … Read the rest

Lagrangian Turbulence

Recently, part of the research activity on turbulence has focused on temporal properties of turbulent statistics which are much less known than the equivalent spatial properties, and are expected to bring information on some of the mechanisms responsible for intermittency … Read the rest

Scalar Turbulence

The ability of efficiently mixing transported substances is one of the most distinctive properties of turbulence. For instance, it is turbulence (induced by the spoon) that allows cream to rapidly invade a cup of coffee, indeed if only molecular diffusion … Read the rest

Inertial Particles in Turbulent Flows

We already mentioned that enhanced mixing is probably one of the most distinguishing feature of turbulence. When a turbulent flow is seeded with particulate matter having a finite size and/or density different from that of the carrier fluid, new features … Read the rest

La fisica della sabbia a… cena

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