Recent years have seen surprising connections develop between physics and such re search fields as mathematics, chemistry, biology, medicine, and even economics. These connections now constitute the fascinating research area known as complex materials and systems. Statistical physics is key in exploring this new expanding field because it is able to show how phenomena and processes long thought to be unrelated can, by means of few unifying concepts, be given a common description. By generalizing methods previously used to order phenomena in simple systems, statistical physics enables us to understand real-world phenomena comprised of complex materials—e.g., biomolecules, polymers, granular substances, glasses, water, membranes, and interfaces—or exhibiting complex processes—e.g., dynamical arrest, chaos, turbulence, network propagation, epidemic spreading, biological functioning, and economic fluctuations. At its current stage of development, this generalizing approach is supported by two conceptual pillars: scaling and universality. For this reason scaling and universality was the conceptual frame for the CLXXVI Course of the International School of Physics “Enrico Fermi”, held from 29 June to 9 July 2010 in Varenna, Italy. The Course was organized and focused so that these topics would be discussed, and a special emphasis was placed on “complex materials in physics and biology”.

This volume includes most of the lectures that were presented at the School. Their focus is on recent advances and developing perspectives in the study of complex materials and processes as they relate to physics and biology. The topics are discussed in terms of both fundamental science and technological applications, and the volume organizes the contributions to give both an overview of the field and a detailed examination of the new ideas and unsolved problems currently attracting the attention of researchers. Although all of the lecturers are leading researchers in the field who have made significant contributions to the field, this collection is organized pedagogically so that a wider audience will find it coherent and accessible. We hope that having the lectures in published form will allow them to be more educationally useful—with the caveat that, because the study of complex materials and processes is rapidly expanding, with many important experimental and theoretical discoveries in recent years, no single volume can be truly comprehensive.

The organization of topics in this volume reflects the actual organization of the Course and provides a kind of conceptual “backbone” sequence that includes: Scaling and Universality, Supra-molecular System and Solutions, Polymer systems, Static and Dynamics of Liquid Water, Arrested Dynamics and Jamming, Dynamic of out-of-Equilibrium Systems, Physics of Confined Liquids, Granular Matter, Physics of Biological and Medical Systems, Networks in Physical and Social Sciences, Turbulence in Physics, Biology and Economics, and Switching Phenomena in Biology and Economics.

Because this volume provides up-to-date reviews of cutting-edge topics by leading authorities, it should be a reference work useful to both advanced research professionals and beginning graduate students. For each topic it provides both an introduction and a complete presentation of recent theoretical and experimental developments, and it is designed to both broaden the readers' competence within their own field and encourage exploration of new problems in related fields.

To facilitate the free interchange of ideas, the lecturers and seminar leaders also made themselves available as course participants. This active presence on their part made possible a constant updating of the topics discussed and kept the focus clearly on a “state-of-the-art” level. The Course scheduled extra time for informal discussion, and student participants were encouraged to participate in the poster sessions. Both the seminar contributions and the posters are included in this volume. Finally, an important goal of this open school approach was fully achieved: every lecturer that proposed and wrote a contribution did so in collaboration with a student.

The opening lectures by Ben Widom (proposed in collaboration with Sahand Hormoz) concerns the nature of effective attractive forces between hydrophobic solute molecules in a polar solvent. Sow-Hsin Chen reports recent developments on the dynamics of biopolymers and their hydration water studied by neutron scattering. A detailed examination of the wetting transitions in fluid interfaces is proposed in a second contribution of Ben Widom (with Alessio Squarcini). A deeper review on the geometrical characterization of dynamical heterogeneities in chemical gels, colloidal gels and colloidal glasses, is reported in the contribution of Antonio Coniglio.

Developments in physical modeling and physical techniques as applied to the study of water (and other anomalous liquids) are discussed in the lectures of David Chandler, Giancarlo Franzese, Sow-Hsin Chen, Maria Antonietta Ricci, and Lars Pettersson. An important research topic is introduced by David Chandler (collaborating with Patrick Varilly): molecular- and nano-scale fluctuations in water. Results of research on water and anomalous liquids are presented by Giancarlo Franzese (with Valentino Bianco and Romina Ruberto). Presentations on the properties of confined water are given by Sow-Hsin Chen (“The Dynamic Crossover Phenomenon in Confined Water and its Relation to the Liquid-Liquid Critical Point: Experiments and MD Simulations”) and Maria Antonietta Ricci (“Uno, Nessuno e Centomila: The intricate structure of confined water”). Finally, the findings of an experimental study are presented in the Lars Pettersson contribution (“Liquid Water Structure from X-ray Spectroscopy and Simulations”).

The interaction of moving fluids with particles is the subject of the Hainz Herrmann lecture. The use of the precise tools of statistical physics to understand economic fluctuations is discussed by Luciano Pietronero (“Critical Overview of Agent-Based Models for Economics”).

Aspects of complex systems are treated in detail in complementary lectures. A discussion of long-term memory in climate records and the detection problem is provided by Armin Bunde. David Campbell (with Yasmine Meroz) discusses how a “little discovery” led to an entirely new field with a series of novel approaches to a range of phenomena in the natural world in his lecture entitled “The Fermi Pasta Ulam (FPU) Problem: A Path to Complexity.” Finally, Shlomo Havlin presents, using a new application of modern statistical physics to social network structure and dynamics, a description of the “Catastrophic Cascade of failures in interdependent networks.”

The Course faculty included 12 lecturers and 10 invited seminar speakers. The participants were an extremely gifted group of young students and practitioners who actively contributed to the School not only through questions and discussions, but also through the presentation of short, highly articulate, and original seminars and posters—some of which are published here.

The aim of the Course was not only to present reviews of all the various phenomena, but also to stimulate the search for a unified approach to the area by gathering together participants from a variety of specialized backgrounds. We all worked very hard, attending nearly 50 hours of lectures, seminars and discussions within a period of only two weeks. We hope this effort was rewarding for everyone attending.

Three “ground rules” were adopted: i) each session was to consider coherent arguments, ii) lecturers could be interrupted at any time during the talks for questions, and iii) speakers, young researchers, and students were encouraged to mix in the dining rooms, the coffee breaks, and the long after-lunch recess. The outcome was as we had hoped: numerous spontaneous discussions and lively debates took place in an honest, friendly atmosphere of work. Many of these discussions occurred in the beautiful gardens of Villa Monastero and Villa Cipressi. Judging from the positive and often enthusiastic reactions of the lecturers and participants during and after the Course, the event was extraordinarily successful in achieving its intended objectives.

It is fortunate that we are able to present in this volume the final versions of nearly all the lectures and seminars presented at the Course. So much important and high quality material was presented that it defies condensation or hierarchical ordering: the participants—experienced scientists, postdocs, and graduate students—have contributed with skill and enthusiasm.

On behalf of all the participants of the course we would like to express our gratitude to the Italian Physical Society for the opportunity to expand our knowledge by means of the School, and for providing hospitality in the exquisite Villa Monastero setting. Special thanks go to Professor Luisa Cifarelli, President of both the Italian and European Physical Societies and fair lady of our community, for the encouragement and advice she offered during the preparation period and during the School itself. We also thank the Istituto Nazionale di Fisica Nucleare (Italy), the Consorzio Nazionale Interuniversitario per la Struttura della Materia (CNISM-Italy), the Italian Research Project of National Interest (MIUR-PRIN08 project AFW2JS), and the Fondazione Bonino-Pulejo (Messina-Italy) for their generous financial support. We are grateful for the invaluable contributions and suggestions by G. Maino, scientific secretary for the School.

Last, but certainly not least, we offer our heartfelt appreciation to Barbara Alzani and Monica Bonetti of the SIF for their valuable, excellent cooperation before, during, and after the School period, and for their heroic work in producing the present volume.

Before concluding, some personal remarks. First, we wish to thank the Ente Villa Monastero for making available to us invaders such beautiful buildings and gardens. And, lastly, we thank the citizens of Varenna for their warmth and hospitality.

We offer this volume to the reader in the hope that it will provide something of the enjoyment and reward that we and the other participants in the School experienced.

F. Mallamace and H. E. Stanley