Author: Christian Beck

This year’s prize of the EPS Statistical and Nonlinear Physics Division honours two outstanding scientists, who are pioneers in their respective fields. The 2021 EPS Statistical and Nonlinear Physics Prize was awarded during the 3^rd  EPS conference “Statistical Physics of Complex Systems” at SISSA/ICTP Trieste, 8-10 September 2021.

Albert-László Barabási  (Northeastern University and Harvard Medical School, Boston & Central European University, Budapest)

was awarded the prize “for his pioneering contributions to the development of complex network science, in particular for his seminal work on scale-free networks, the preferential attachment model, error and attack tolerance in complex networks, controllability of complex networks, the physics of social ties, communities, and human mobility patterns, genetic, metabolic, and biochemical networks, as well as applications in network biology and network medicine”.

Barabási is a pioneer in network science. He played a leading role in the development of this new area of science, not only at its beginning, but also taking an active part in many of its major advances and breakthroughs in the past two decades. His first breakthrough was presented at the turn of the century, in 1999, with the discovery (together with Reka Albert) that many real-world networks exhibit a scale-free structure, with the number of interactions of each component spanning orders of magnitude. This discovery exposed a deep universality, observed in networks from social, biological and technological domains. In a broader perspective, this discovery in 1999 is often considered as the birth of network science. He went further to introduce a statistical physics model for the emergence of scale-free phenomena, the preferential attachment model, one of the most cited papers in the history of physics. His work has connected researchers from different disciplines in an interdisciplinary way. In biology – his work has shown the crucial role of genetic, metabolic and biochemical networks in modeling cellular processes. In medicine – he has introduced the concept of network medicine, linking pathologies based on shared genetic roots, and predicting novel therapeutics. In social systems – his works have uncovered the underlying physics of social ties, communities and human mobility patterns.

The impact of Barabási’s research activity is well beyond the borders of physics, touching many interdisciplinary fields, representing a major extension in the range of applicability of statistical physics, reflected by the 270000 citations that his work has received. It embraces a vast array of research areas including social network analysis, internet and information technology, and biology and medicine. He contributed to the evidence that the scaling of networks is not a feature of man-made systems only, but characterizes e.g. metabolic networks as well. Today the concepts and tools introduced by him in network science are used on a daily basis by a huge number of scientists to study the millions of networks characterizing living and man-made complex systems. 

Angelo Vulpiani (Sapienza University, Rome)

was award the prize “for his seminal contributions to statistical and nonlinear physics, touching fundamentally important issues in dynamical systems theory and statistical mechanics, including the mechanism of stochastic resonance, multifractality of invariant sets of dynamical systems, the dynamics and multifractal properties of turbulent flows, chaos in Hamiltonian systems, and the limits of predictability in complex systems”.

Vulpiani is an outstanding physicist who has made seminal contributions to statistical and nonlinear physics. His research interests are distinguished by their strong connection to fundamental issues of statistical mechanics and to the works of classics like Boltzmann, Kolmogorov and Khinchin.

Over the years he has also built up a strong environment in Rome with many young researchers who have gone on to contribute elsewhere. Furthermore, he is a prolific author of books for the general scientific public, both in Italian and in English, as well as the author of several well-regarded monographs. His immense productivity is reflected by almost 500 co-authored scientific publications.  Most relevant, some of his works mark major break-throughs in their field or have opened up completely new fields of research. The most prominent example is stochastic resonance which, in 1981, was introduced by him together with Roberto Benzi, Alfonso Sutera, and the current (2021) physics nobel prize winner Giorgio Parisi. This developed into an immensely active research area afterwards.

In 1984, Vulpiani (together with Paladin) showed that multifractality (originally defined by Mandelbrot in a purely mathematical setting) is of relevance for the characterization of invariant sets in dynamical systems, and also in turbulent flows. Today, the concept of multifractality is an inherent part of dynamical systems theory and also highly relevant for data analysis, where it has moved into the time domain, i.e. it is used to characterize a variety of measured time series observed in many applications. Other important works of his are his contributions to chaos in Hamiltonian systems and the equipartition of energy (follow-ups of the Fermi-Pasta-Ulam problem), his contributions to diffusion and transport in various nonlinear settings, and his repeated efforts to understanding, defining, and investigating complexity in general.

The prizes of the Division also contain the EPS-SNPD Early Career Prize, which is traditionally shared by two younger scientists and which was also awarded in Trieste. This year the prize went to Federico Battiston and Caterina De Bacco.

Federico Battiston (Central European University, Vienna)

was honoured for “for his outstanding work on nonlinear dynamics and emergent collective phenomena in multilayer and higher-order networks, including diffusion, synchronization, social and evolutionary processes”.

Caterina De Bacco (Max Planck Institute for Intelligent Systems, Tuebingen)

was honoured for “her outstanding work on statistical physics of random walkers on random graphs, stochastic search processes, routing optimization on networks and effective algorithms for community detection”.

Due to the Covid-19 situation, the conference in Trieste was a hybrid conference, with many participants participating online, but some participants being present in person as well. The photograph shows the prize winners and some members of the Board of the EPS Statistical and Nonlinear Physics Division. From left to right: Federico Battiston, Erik Aurell, Angelo Vulpiani, Albert-László Barabási (on screen), Christian Beck, Caterina De Bacco, Raul Toral, Guido Caldarelli.