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 of slipping is not determined by friction alone?


M A Annunziata, A Baldassarri, F Dalton, A Petri and G Pontuale, Increasing ‘ease of sliding’ also increases friction: when is a lubricant effective?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 the edge modes of the topological gratings, we predict the emission of discrete laser lines. A proper design enables the engineering of the spectral features for specific applications.… 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 millimetres for clinical MR scanners).

Therefore, independently of image resolution (which is linked to the hardware of the NMR scanner) we can obtain microstructural information of human tissue at the mesoscopic length scale.… 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 7585, Sorbonne Universites, 4, place Jussieu, 75252 Paris Cedex 05, France
  3. Centro Studi e Ricerche Enrico Fermi, Via Panisperna 00184, Roma, Italia
  4. INFN Unit Rome 1, Dipartimento di Fisica, Universita di Roma Sapienza, Piazzale Aldo Moro 2, 00185 Roma, Italia

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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 a quantum wavefunction along a line of ultracold atoms in a 1D Bose–Einstein condensate. According to the pair, the work could help develop quantum-information systems that achieve high-quality wave transmission […]

read articleRead 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 shown to be one of most prolific sources of unexpected and hard-to-understand phenomena. Therefore, achieving a machine which is a paradigm for the quantum nature of a system is an engrossing challenge.… 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 conoscenza di un linguaggio di programmazione per lo sviluppo di codici di simulazione e’ auspicabile.


Diffusione anomala

Il moto di una particella soggetta a forze aleatorie e’ descritto dalle leggi del moto browniano (diffusione).… 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. Despite their ubiquiteness and importance in everyday life many aspects of such phenomena are still under debate in the theoretical physics community.

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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 fascinating ones is  the possibility to control energy flows by tuning nonlinear features of complex materials.

In the context of wave propagation trough nonlinear media, the simplest form of control would be to devise a “wave diode”  in which electromagnetic or elastic waves are transmitted differently along two opposite propagation directions.… Read the rest

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, the present challenge is to find suitable physical approaches for such conditions: this book provides a pedagogical pathway that explores various perspectives.… 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 modifica profondamente la dinamica quantistica degli spin molecolari. Ciò apre la strada al controllo dello spin mediante campi elettrici nei nano-dispositivi per la spintronica (elettronica di spin) basati sul 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 di Scienze Biochimiche Sperimentali e Cliniche “Mario Serio”, Università di Firenze, Viale G B Morgagni  50, 50134 Firenze.

Finalità del progetto

Scopo finale del progetto è l’applicazione della tecnica Surface Plasmon Resonance (SPR) alla rivelazione di  un particolare nanoanticorpo, specifico per la  sfingosina-1-fosfato (S1P), un importante agente in diverse vie metaboliche, ad esempio nel citoplasma cellulare, dove è stata dimostrata la sua funzione di regolazione dei flussi di ioni Ca2+.… 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 gases are precursors of other ices, as in some cases they may be emptied, leaving a metastable hydrogen-bound water structure. We present here the first characterization of a new form of ice, obtained from the crystalline solid compound of water and molecular hydrogen called C0-structure filled ice.… Read the rest

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

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 this has long been a mystery. Now through a careful analysis of their flight patterns, researchers have shown that seabirds are following their noses and navigate using an “odour map” – a mental patchwork picture of local odours.… 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 Bulgarian academy of sciences (IBER-BAS). The aim of the trip was to design a new project on the movement ecology of the red deer (Cervus elaphus) in Bulgaria.… 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 weakly to external perturbations but present an enormous richness of interesting phases like metallic, insulating,  magnetic, superconducting, ferroelectric,  charge order, etc.  … 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 classical physics this is usually observed within complicate models with obstacles and traps. We have demonstrated such complex non-linear phenomena in a much simpler and realistic system, ie.… 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 instance a vibrating piston. Energy dissipation provides the “second thermostat” which spontaneously forms gradient and may stabilize a convective state. Here we have demonstrated that even the simple dissipation in the collision between grains and lateral walls is sufficient to trigger convection, without any critical threshold.… 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 by non-equilibrium thermodynamics, as for heat engines. In this theoretical work we have given a mesoscopic description of this process, which allows to measure a local heat dissipation and a local non-equilibrium temperature (associated to self-propulsion and to the forces driving the active particle) which together provide a definition of active entropy production which satisfies the Clausius inequality.… 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 advantage of 3d-printed objects is in the possibility to tune certain features (here the inclination of “legs”) in order to verify theoretical predictions and establish an optimal shape for running.… 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 that at intermediate densities and temperature the same phenomenon occurs in granular liquids. At large densities and lower temperatures the late normal diffusion is replaced with superdiffusion.… 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 and lowers the melting point with respect to more classical salts, reaching values as low as -20°C.

ILs posses many peculiar properties, such as an extremely low vapor pressure, a high ionic conductivity, a high thermal, chemical and electrochemical stability, a high thermal capacity and a good solvent capability.… 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.

Of the three possible ways to store hydrogen, i.e. as high pressure gas, as a liquid (~20 K at atmospheric pressure), or as hydrides in solids, the latter one appears as the most promising, due to the high mass and volume density and safety.… 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 are unlikely to change over time (e.g., frequent verbs tend to maintain an irregular past tense form). What is the role of frequency in maintaining exceptions to rules?… 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 networks, where relations indicate trust/distrust, friendship/enmity? Do individuals who dislike many others tend to dislike each other, or do they dislike those who dislike only very few others?… 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., triggering the same host immune response). The evolutionary dynamics of viruses is therefore ruled by their relative antigenic distance. Can we understand the non trivial relation between antigenic and genetic distance?… 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, and allows to demonstrate that the scale invariance originates from the presence of a non-equilibrium, reversible, critical transition which, in the presence of dissipation, gives rise to self-organized critical behaviour.… 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 Ratchet cannot perform its own task in an equilibrium environment, i.e. the fluctuations feeding energy to the ratchet cannot originate from a single thermal bath, in accordance with the second principle of thermodynamics.… 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 and are nowadays subject to an intense theoretical activity. In this work we have added a new flavour to the idea of random lasers, replacing the usually static disordered medium with a vibrofluidized granular material.… 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). The resulting motion, on the plane, is a composition of random sliding on the plate and inelastic collisions among particles. This is a “non-equilibrium” Brownian motion.… 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 dispersed in a solvent, whose molecules are much smaller in size (typically of atomic dimensions). In addition, the solution may contain other small objects, such as polymeric chains, salt ions, etc.… 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 cubic symmetry and differ only on density just like water and vapor but in the solid state!.

However unlike water and vapor the critical exponents close to the critical point are not three dimensional Ising critical exponents, as one would naively guess from symmetries, but  classical (Gaussian) exponents.… 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 two main experimental setups:


  1. Vertical vibration (2d and 3d granular experiments): an electrodynamic shaker LDS V455, which can reach a maximum acceleration of 105g, powered by a PA1000L power amplifier.
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 5 minutes, slowly increasing the amplitude, the many “phases” of a granular material are explored, from an almost perfect crystal, through several liquid/turbulent/convective regimes, up to a gas-solid coexistence.… 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 the least bit from each other and the sound of each was always heard simultaneously“. In spite of the early discovery, the phenomenon was fully understood much later with the experiments and theoretical analysis of E.… Read the rest


Granular fluids to explore non-equilibrium statistical mechanics

Founding Body: MIUR, Italy (reserved to selected ERC-Starting Grants 2007)
Total grant: € 1200k
Principal Investigator: Andrea Puglisi
Other participants:
Project duration: 2009-2014
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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 introduction of elementary models of social behavior (cellular automata, agent-based models). Many of these models are somehow relatives of models that have been introduced in modern traditional statistical physics, and it is natural to approach them using the same concepts and tools that have been successfully applied in physics.… 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 from disorder to order, like the spontaneous emergence of a common language/culture or the creation of consensus about a specific topic.… 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 established for the first time a qualitative relationship between pattern and process in geology.
More than one century later, fractal geometry gave a theoretical framework able to provide quantitative measures for the patterns of landscapes, which were identified in a first approximation as self-similar, and triggered the research on mechanistic and theoretical models to identify the underlying constructive rules responsible for their appearance.… 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 a finite lattice distortion, which in turn bind

Phonon distribution function P(n) and magnetic polaron size Lp as function of the exchange coupling J, signalizing the formation of the spin/lattice polaron

s the electron leading to the so-called self-trapping effect.… 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 the specific processes that originated them.
The relative roles over cosmic time of processes such as the merging of dark matter haloes, dissipation, starburst, feedback, active galactic nuclei (AGN) activity, etc.,… Read the rest

Tidal tail characterization


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 centers. The name of this category of star cluster is derived from the Latin globulus—a small sphere. Globular clusters are fairly common; there are about 158 currently known globular clusters in the Milky Way, with perhaps 10–20 more undiscovered.… 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 called correlated random walks (CRW).

This possibility extends also to a set of particles distributed in space leading to the definition of spatially correlated random walks.… 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 and reveal, in the laboratory, its underlying microscopic reversibility? These are some of the questions addressed by the GRANULARCHAOS project, funded by an IDEAS grant (originally selected by ERC and then funded by italian FIRB) for five years.… 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 systems, ion beams, wave-particle systems of relevance to plasma physics and others.

The behaviour of the above mentioned systems is interesting both from the point of view of stable (or metastable) states, because equilibrium statistical mechanics shows new types of phase transitions and cases of ensemble inequivalence, and from the dynamical point of view, because they display peculiar fast relaxation followed by the formation of quasi-stationary states that are related to the underlying Vlasov-like equation.… 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. If one considers the paradigm of uniform distributions, the Poisson process where particles are placed completely randomly in space, the mass fluctuations in a sphere of radius R growths as the volume of the sphere.… 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 attractive pair interaction, it seems by recent works that the distinction is given by the integrability of the pair force instead of the potential.… 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 truly atomic single-layer isolated samples are available as well as epitaxially grown graphene on substrates.

Fig. 1: electronic structure of graphene and Dirac-like dispersionA large interest, for its potential technological applications, concerns the investigation of optical and transport properties of both single-layer and multi-layered graphene, which are dominated by its so-called relativistic Dirac-like electronic structure (see Figure on the right).

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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 irregular behaviors, however its role to the fundaments of statistical physics still remains debated in modern statistical mechanics. In other terms, one is tempted to think that a macroscopic system with chaotic microscopic interactions is more robust with respect to statistical mechanical principles thant the same system with non-chaotic interactions.… 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 spin models is more appropriate. We focused on the non-equilibrium properties of the random field Ising model (RFIM), to describe the competition between quenched disorder and exchange interactions and their effect on the hysteretic behavior.… 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 if the noise amplitude depends on the state variables themselves. In this sense, problems exhibiting absorbing states, i.e. fluctuation-less states in which the system can be trapped, are described by equations whose noise amplitude is proportional to the square-root of the (space and time dependent) activity density, vanishing at the absorbing state.… 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.

Tc has grow rapidly beyond 50K opening a new gate to high-Tc superconductivity. In addition the phase diagram has some similarities with the cuprates which suggest that understanding the superconductors from this new iron age can help to solve the mistery of the supercundoctors from the copper age.… 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 biochemical and biomechanical activities of organisms. Proteins, for instance, provide the building blocks of cells and tissues, they are involved in control and regulation of cellular cycles, in enzymatic catalysis, proteins are at the basis of muscle contractions and constitute part of the immunitary defence, etc… The list of biological functions which proteins are involved in is extremely long and rapidly increasing with the research advances.
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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 been devoted in the past to the analysis of absolute minima, i.e. equilibrium states. More recently, we have understood that also metastable states, i.e.… 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 finite dimensional systems also. To investigate this hypothesis a field theory for the fluctuations around the mean field solution has been developed.… 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 simple set of predominant morphologies like circular droplets and stripes in two-dimensional (2D) systems, and layers, cylindrical rods and spherical droplets in three-dimensional (3D) systems.… 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 is always associated to a large correlation length. Even though dynamical length scales were introduced and measured, nothing similar was thought to be possible for thermodynamic lengths.… 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 components should combine mechanical flexibility, low weight, transparency and low cost. Enormous progress has been made to improve the performance of these devices through optimising the synthesis processes, drastically reducing the concentration of impurities present.… 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 steady increase of the external forcing. They are typically characterized by a sequence of pulses of very different sizes and durations, separated by quiescence intervals.… 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 field, a phenomenon referred to as dynamic hysteresis. The problem has great importance from a purely theoretical point of view, for the understanding of the dynamics of disordered magnetic systems, which represents a central issue in non–equilibrium statistical mechanics.… 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 fluctuations, clustering, correlations and other nontrivial features are often a better description of many natural and man-made systems. Since many of such networks describe the topological patterns that mediate various sorts of interactions among nodes, it is natural and interesting to wonder what is the effect of complex topologies on dynamical processes taking place on them.… 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 to the emergence of detailed datasets that capture human behavior, we can now follow specific human actions in ultimate detail. One of the first measurable quantity with which one can describe the relationship between humans is the timing and order with which we perform specific tasks.… 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 systems with low symmetry. Nowadays, a number of AF systems are known to belong to the class of Dzyaloshinskii-Moriya (DM) magnets, such as ?-Fe… 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 the interstellar medium. In the presence of scatterers, as for example dust particles, photons diffuse like neutrons and, if some mechanism (following Letokhov a “negative absorption”) is able to increase their number, a sort of photonic reactor can be realized.… 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, and their critical temperature can reach around 40K. There are however many experimental evidences that seem to exclude a simple BCS (or Migdal-Eliashberg) scenario, since electron-electron correlations are likely to play a central role.… Read the rest


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)
    data taking, experimental setup
  • Andrea Cavagna (CNR-INFM)
    coordinator of the INFM-CNR node; experimental setup design, matching algorithm, data analysis
  • Alessio Cimarelli (La Sapienza)
    experimental setup, data taking, data analysis
  • Evaristo Cisbani (ISS)
    electronics design
  • Irene Giardina (CNR-INFM)
    deputy coordinator of the INFM-CNR node; matching algorithm, data analysis
  • Vivien Lecomte (LMSC, Paris VII)
    numerical simulations
  • Alberto Orlandi (CNR-INFM)
    computer vision, trifocal matching, data analysis
  • Giorgio Parisi (La Sapienza, CNR-INFM)
    coordinator of the EU project, experimental setup design, optimization, data analysis
  • Andrea Procaccini (La Sapienza)
    experimental setup design, data taking, data analysis
  • Raffaele Santagati (La Sapienza)
    experimental setup, data taking, data analysis
  • Fabio Stefanini (La Sapienza)
    experimental setup, data taking, data analysis
  • Massimiliano Viale (La Sapienza and Roma 3)
    matching, optimization
  • Vladimir Zdravkovic (CNR-INFM)
    experimental setup design, data taking
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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 system to find optimal configurations. As a consequence, these systems exhibit non trivial thermodynamic and dynamic properties, different and richer than those observed in their non disordered counterpart.… 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 ecosystems — which pose intriguing theoretical challenges. On an abstract level, the problems at stake are indeed not too different from, say, understanding how spontaneous magnetization may arise in a magnetic system, since what one wants in both cases is to understand how the effects of interactions at the microscopic scale can build up to the macroscopic scale.… 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”. Within this context the spin-or

Rashba band-spilling and spin ordering: from J. Sinova et al., Phys. Rev. Lett. 92, 126603 (2004).

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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 strongly correlated systems, are interesting because they can support new collective modes, “electronic phonons”, that would not be present in a weakly interacting fluid.… 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 comparison of the phonon frequencies  with the Fermi energy EF. In conventional systems , assuring thus the reliability of the adiabatic assumption.… 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 interact more strongly than two birds 10 meters apart.

Models developed by biologists are based on a “behavioural zones” scheme, where each zone is associated to one of the three basic ingredients of all models: short range repulsion, alignment, long range attraction.… 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 interdisciplinary character, where biology, chemistry, physics, mathematics and computer science can fruitfully interact each other.

Our activity in this field concerns the prediction of folding mechanisms by the knowledge of tertiary structure only.

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Home Page of Andrea Cavagna


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 (Spin-Glasses – advisor Giorgio Parisi)

M.S. and B.A. in Theoretical Physics, University of Milan and SISSA – Trieste, Italy, 1995 (Conformal Field Theory – advisor Giuseppe Mussardo)

I was trained as a theoretical physicist and I have studied for some years the statistical mechanics of disordered systems, with a particular interest in spin-glasses, structural glasses and supercooled liquids. … 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? Is it purely defensive, or has it some other purpose, perhaps social? INFM-CNR was the leader node of a European project – FP6-NEST 12682 STARFLAG (2005-2008) – dedicated to the study of collective animal 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 or species predation in ecological food webs. Thanks to the simplicity of graph theory it is very easy to provide a network description for different systems.… 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. As time advances, an out-of-equilibrium process of phase ordering takes place through the formation of domains of a single phase that grows algebraically in time as L(t)~t1/3.… 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 in turbulence, for example lagrangian motion is strongly affected by the presence of vortical motion around vortex filaments (see Figure 1).… 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 would be at play in the coffee at rest the same process would require many hours! Given the statistical complexity of a turbulent velocity field, it is natural to wonder about the resulting complexity in the statistical features of the transported concentration field of a substance (e.g.… 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 appear. The figure on the left show the instantaneous position particles which are heavier (e.g. water drops in air) resp. lighter (e.g.… Read the rest