Speaker 1 :Theodoros Horikis(University of Ioannina)Date & Time: May 27 (Fri.), 2022 / 10:00-10:40PM (Tokyo (JST)) (--> May 27 (Fri.), 2022 / 4:00-4:40PM (Greece (EEST)) )Title: Light meets water in nonlocal mediaAbstract: Many physically different subjects can be brought together through their common modelling and mathematical description. Perhaps the most common (and rather unlike) example is water waves and nonlinear optics. Two systems are inextricably linked with both subjects: the universal Korteweg-de Vries (KdV) and nonlinear Schrödinger (NLS) equations. Remarkable as these systems may be, for several physically relevant contexts their standard form turns out to be an oversimplified description as it cannot model, for example, higher dimensionality; for instance, the Kadomtsev-Petviashvilli (KP) equation is used as a generalization of the KdV to two spatial dimensions. Furthermore, these systems can be reduced from one to the other, thus suggesting that phenomena occurring in water waves will also exist in optics. In fact, in this talk, we demonstrate a direct analogue of surface tension in optics though a nonlocal NLS equation. In particular, using a framework of multiscale expansions, the nonlocal NLS system is reduced to a KP equation, which in turn is distinguished in the KPI and KPII systems depending on the magnitude of the surface tension. Furthermore, this surface tension, the phenomenon that causes fluids to minimize the area they occupy, is linked to the physical parameters of the original nonlocal system and it is thus shown that nonlocality is its direct analogue. We demonstrate how soliton solutions and their interaction patterns, as observed in shallow waters, can now also be observed in optics and hence, shallow water wave phenomena may find their analogue in optics through this nonlocal NLS model in (2+1)-dimensions.