Multimedialne seminarium z ekono- i socjofizyki

Water evaporation, melting of snow, loss of magnetic properties of a heated piece of iron, superconductivity - all these phenomena are examples of phase transitions. Explaining the reasons and determining the conditions of phase transition, considered to be the most fascinating property of matter, was one of the greatest challenges of physics of the last century. At that time, many issues related to these phenomena were understood and explained. In particular, it has been shown that despite the great variety of observed changes, they can be divided into two types: discontinuous and continuous. The first one happens suddenly. For example, the transition of water into ice occurs suddenly. At a given pressure and above the melting point, water is fluid and below this temperature it is constant and rigid. There is nothing between one phase and the other - water does not become less fluid before it turns into ice. At the point of change, the density of water changes abruptly. This is not the case of continuous phase transitions, termed critical. It is said that they occur in a turbulent manner. In the vicinity of critical points where these changes occur, the studied systems are extremely susceptible to various fluctuations. In such systems, even a slight change in external parameters, such as temperature, can cause huge changes. Approaching the critical points is apparent from large fluctuations of various internal parameters of the systems studied although the averaged values of these parameters behave continuously - unlike discontinuous transformations.Hybrid variants derive their name from Greek mythology. Mythical hybrids combine unmatched elements (e.g. chimera was a lion's head monster with goat's body). In hybrid phase transitions, such unmatched elements are features of discontinuous and continuous phase transformations, which have previously been thought to not coexist in the same system. During the presentation, I will discuss the properties and examples of hybrid phase transitions [1]. I will also tell about one of the few closely-defined spin models in which such a transition was exactly solved [2]. References:[1] A. Bar, D. Mukamel, Phys. Rev. Lett. 112, 015701 (2014); A. Bar, D. Mukamel, J. Stat. Mech. P11001 (2014); D. Lee, Y.S. Cho, B. Kahang, J. Stat. Mech. 124002 (2016).[2] A. Fronczak, P. Fronczak, A. Krawiecki, Phys. Rev. E 93, 012124 (2016); A. Fronczak, P. Fronczak, Phys. Rev. E 94, 012103 (2016).