Препринты / Preprints

The argumentation is developed which shows that the massive Yang-Mills theory has m0 limit, coinciding with the massless Yang-Mills theory and that both the theories are nonanalitic with respect to the coupling constant.


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The review of various methods of time-resolved investigations on nonstationary plasmas and of other fast processes is given here. The up-to-date development of laser techniques, particularly of methods of short and ultrashort light pulse generation has made it possible to widely employ lasers for speed and high-speed optical diagnostics of plasmas fast varying its parameters in time. In this work a laser as a light source is considered, and a more detailed examination is given to some special problems of their usage for high-speed photography in scientific investigations. The laser application in photography made it possible (in some cases) to shorten resolution time to the value IO-11 and even less at the number of resolved elements about ICr+IO . A large monochromacity of laser radiation significantely widened the possibilities of special optical methods of interferometric, schlieren and shadow photography. The employment of nonlinear crystals simplified the schemes of photography in several wavelength simultaneously. The applications of lasers significantely increased the possibilities of stroboscopic schemes and methods of photography of highly shining objects.
It is somewhat difficult yet to give a clear classification of laser diagnostic methods. As a rule, for diagnostic purposes a laser is used in a combination with a more or less known high-speed camera . As in a usual photogra- phyjfchere’xB three photographic schemes available i firstly, the streak operation schemes projecting and shifting the slit object image in time; secondly, the schemes of multi- frame photography securing a two-dimensional image of the object, and, thirdly, three-dimensional holographic photography.
In time characteristics there differ qualitatively the multilrame devices with time resolution 10-8 sec and less, in which the Q-switched lasers and corresponding light delays are employed, end the devices of micro-second range, in which the smear type arrangements such as a rotating mirror and an image-converter tube with linear scanning and etc. are used in order to separate the frames.
And, besides, due to the recent investigations of high- temperature phenomena in a laser focus there appeared a possibility of employment of laser plasma as a pulse light source


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Some features of plasma in a strong radiation fieldare considered. Plasma electric conductivity at frequencies different from that of an intense electromagnetic waves in plasma, one of them being strong, is considered here. An interaction of these waves with plasma causes the scattering of the weak wave by the strong one. The scattered field intensity is found. General expressions are obtained and their asymptotic benaviour is investigated in the case of a very strong radiation field.


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The dynamical symmetry of some nonstationary quantum systems is considered. The noncompact group U(2,1) is found to be the group of dynamical symmetry for a charged particle motion in a time-dependent uniform electromagnetic field. It is known that the U(3,1) group is the noninva-riance group for the 3 — dimensional oscillator. The same group U(3,1) describes the dynamical symmetry of an isotropic 3
— dimensional oscillator in a time-dependent electromagnetic field.
For a special type of electromagnetic field which is constant in the remote past and future the transition amplitudes between Lanlau levels are connected with the matrix elements of the representations of groups* In the case of a charged particle in an electromagnetic field this group is
U(2,1), for a charged particle in cross electric and magnetic fields the correspondent group is the group of motion of pseudoeuclidean complex plane.
The problem of the symmetry of equations is briefly discussed.

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