New Approach to Duality-Invariant Nonlinear Electrodynamics

We survey a new approach to the duality-invariant systems of nonlinear electrodynamics, based on introducing auxiliary bi-spinor fields. In this approach, the entire information about the given self-dual system is encoded in the U(1) invariant interaction of the auxiliary fields, while the standard self-dual Lagrangians appear on shell as a result of eliminating auxiliary fields by their equations of motion. Starting from the simplest U(1) duality, we show how this approach can be generalized to the U(N) duality (with N independent Maxwell field strengths), as well as to self-dual systems of {\cal N}=1 supersymmetric electrodynamics. Also, it works perfectly for self-dual systems with higher derivatives in the action.Comment: 13 pages, Talk given by E. Ivanov at the conference "Integrable Systems and Quantum Symmetries", Prague, June 11 - 16, 201

Relative transparency of sea water in the Green-fjord Bay (Spitsbergen)

The results of the analysis of spatial-time variability of relative transparency (depth of disappearance of a standard white Sechi disk) in the Green-fjord Bay (Spitsbergen archipelago) are presented. The data covers the period from 1986 to 1990 and were obtained during carrying- out of the oceanographic monitoring by experts of Barentsburg research station (Murmansk HydroMeteorogical Management) in frame of the program of standard coastal supervision. Some conclusions about the reasons of spatial and time variability of relative transparency depending from change of external conditions are presented