Statistical Physics, Quantum Mechanics, and Complex Systems

Systems composed of a large number of particles or elements can give rise to complex unexpected behaviour and totally new emergent collective properties. Statistical Physics deals indeed with systems composed of many interacting degrees of freedom. Starting from microscopic models, it can describe and predict these unexpected behavior on a large scale, in which collective effects are more than the sum of the properties of the individual constituents. The research at SMFI deals with topics at the borders of Statistical Mechanics, Quantum Mechanics and Condensed Matter Physics, with a strong interdisciplinary content from Biology and Social Sciences. In our research topics, classical and quantum complexity emerges from networks of interactions with non-trivial geometric and dynamical properties. We deal with synchronisation of classical and quantum units, dynamical processes on complex temporal networks, quantum control and complex transport phenomena.

The members of the group are involved in the local INFN group and they are part of the INFN project BIOPHYS.

The group hosts the National Conference on Statistical Physics and Complex Systems.

For more information:

Prof. Raffaella Burioni

http://www.fis.unipr.it/~raffaella.burioni/Site/Home.html

Prof. Sandro Wimberger

http://www.thphys.uni-heidelberg.de/~wimberge

Complex dynamics on networks:

Networks and graphs are the most general mathematical description of a set of elements connected pairwise by a relation. Therefore, it is not surprising that graph theory has been successfully

applied to a wide range of very different disciplines, from physics to biology, to social science, computing, psychology, economy and chemistry.

In recent times, physicists have been mainly interested in networks as models of complex

systems and they have used them to describe condensed matter structures such as disordered materials, glasses, polymers, biomolecules. More recently, Networks have become the main language for the description of communication networks, webs, social and economic systems, power grids, statistical models of algorithms, and many others interdisciplinary frameworks.

The function of networks in physics, however, is not purely descriptive. Geometry and

topology have a deep influence on the physical properties of complex systems. The Network structure can indeed affect the dynamical and thermodynamical behaviour of the system it describes, and can give rise to surprising collective effects.

In Parma, we are studying at the moment dynamical models for synchronization on neural networks in collaboration with the University of Granada and models for the evolution of social networks and for epidemics spreading, in collaboration with the MoBS Labs at Boston Northeastern University, with the Institute for Scientific Interchange in Torino, and with several theoretical and experimental groups in Italy, Europe and the United States.

Fundamental Aspects of Nonequilibrium Quantum Mechanics:

Complex systems and their modeling are interesting simply because matter is typically complex. On small scales, quantum mechanics describes interactions and dynamics. One typical example of a complex quantum system are photosynthetic molecules (complexes) in which transport properties seem to be governed by quantum mechanical interference. Strong correlations between the constituents make even "small" systems very complicated. In the helium atom, for instance, classical three-body chaos turns into complicated ionization spectra. The modern experimental tools of atom optics allow for a bottom-up construction of strongly correlated many-body quantum systems. We are studying their behavior on the level of single atoms and their interaction. Ongoing collaborations with experimental groups the world over enrich our research on fundamental aspects of quantum transport and its control in view of applications in atomtronics and quantum information.

Random walks, anomalous diffusion and large deviations effects

How does matter diffuse in a complex material? How is information transmitted in a complex network, can a disease spread over an entire population? These are typical non equilibrium questions that we ask in our research. The effect of large fluctuations on these processes is extremely important. In particular, complex systems can often experience Big Jumps, that is sudden huge events that can complete shift the non equilibrium process. Identifying these events and develop a mathematical framework to deal with them is what we do.

Modificato il 06/12/2023