Welcome to the Home Page of the group of Professor Panos Argyrakis at the Department of Physics, University of Thessaloniki

Our group is theoretical dealing with a variety of complex problems in several areas of Physics and Physical Chemistry, and recently involved in newly developed fields, such as Networks, Financial Systems, Language Evolution, etc all of which are based on methods and techniques from statistical physics. The group is strong in computational methods and modeling in these areas, heavily utilizing large-scale computer simulation techniques. We use experimental data from several collaborating laboratories around the world, covering a wide area of problems, such as laser spectroscopy of excited states of new molecules, diffusion and flow in the gastro-intestinal tube, signal propagation in neural networks in the human brain, social contacts between individuals that are related through some connection, learninig of words by an individual bulding a vocabulary, fluctuations in prices of financial instruments, etc. We construct plausible models for these phenomena and observations, leading to numerical solutions of several facets of these problems that are too complicated to be attacked otherwise. We thus offer new solutions to existing problems, discover trends in empirical observations, propose the range of parameter values for an experimentalist to investigate, and explain the behavior of so-called complex systems. 

A more technical description of our activities includes: 

• Excitation dynamics in molecular assemblies and condensed phases. Spectroscopy of excited states of complex molecules. 
• Fractals and systems of non-integer dimensionality. Low-dimensional systems. Kinetics of phase transitions, critical transport phenomena, percolation, scaling theory. Effects of disorder in materials and structures. 
• Random walks in complex systems, their properties and applications to physical and biological phenomena. 
• Chemical reactions in restricted spaces. Catalytic reactions on surfaces, in porous materials, on wires. Diffusion controlled processes, diffusion-limited aggregation, etc. 
• Mathematical modeling and simulation of neural networks. Computational and artificial networks. Dynamics of signal transfer in neurons in biological brains and applications to memory, learning, and other physical processes. 
• Networks, random networks, scale free networks, small-world networks, properties of their structure and dynamics. Robustness and resiliency to external attacks. Immunization of networks. 
• Language evolution and population dynamics in interacting species. Methods of learning. Statistical mechanical approach to the use and frequency of individual words in human language. 
• Econophysics. Study of correlations in financial data, topological properties and time evolution of financial and economic networks.

Some representative publications: 

• Michail Michailov,Bogdan Ranguelov, Paraskevas Giazitzidis, PanosArgyrakis, "Thermal stability and spontaneous breakdown of free-standing metal nanowires", Journal of Crystal Growth, 457( 2017) 92-97 PDF. 
• Paraskevas Giazitzidis, Isak Avramov, Panos Argyrakis, "Variation of the critical percolation threshold with the method of preparation of the system", The European Physical Journal B, 88, 331 (2015) PDF. 
• N. Bastas, F. Lazaridis, P. Argyrakis and M. Maragakis, "Static and dynamic behavior of multiplex networks under interlink strength variation", EPL, 109, 38006 (2015) PDF. 
• L. Skarpalezos, A. Kittas, P. Argyrakis, R. Cohen and S. Havlin, "Efficiency of message transmission using biased random walks in complex networks in the presence of traps", Phys. Rev. E 91, 012817 (2015) PDF
• Maria Tsouchnika and Panos Argyrakis, "Network of participants in European research: accepted versus rejected proposals", The European Physical Journal B, 87, 292 (2014) PDF