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We investigate how the choice of the magnetization distribution inside a sample affects its interaction with an extemal electromagnetic field. Strong selectivity to the time-dependence of the extemal electromagnetic field arising for particular magnetizations suggests that it can be used for storage and ciphering of information. We propose a time-dependent Aharonov-Bohm like experiment in which the time-dependence of the interference picture is due to the time variation of the magnetic flux confined to the excluded region. The arising time-dependent interference picture may be viewed as a new channel for information transfer. Examples are given of current configurations generating static electric fields adequately described by an electric vector potential rather than by a scalar one.

Accelerated and decelerated motions of a charged point particle inside medium are studied. It is shown explicitly that in addition to the bremsstrahlung and Cerenkov singular waves, previously unknown electromagnetic singular wave should be observed. It arises when the charge velocity coincides with the light velocity in medium. This wave has the same singularity as theCerenkov one and, therefore, it is more singular than the bremsstrahlung wave. The spacetime regions where these waves exist and conditions under which they appear are determined.

Abstract. We analyse the well-known Tamm problem treating the charge motion on a finite space interval with the velocity exceeding light velocity in medium. By comparing Tamm's formulae with the exact ones we prove that former do not properly describe Cherenkov radiation terms. We also investigate Tamm's formula cos θ = 1/βn defining the position of maximum of the field strengths Fourier components for the infinite uniform motion of a charge. Numerical analysis of the Fourier components of field strengths shows that they have a pronounced maximum at cos θ = 1/βn only for the charge motion on the infinitely small interval. As the latter grows, many maxima appear. For the charge motion on an infinite interval there is infinite number of maxima of the same amplitude. The quantum analysis of Tamm's formula leads to the same results.