Preface
Annotatsiya
More recently, the journal has been receiving articles in fields such as Differential and Riemannian Geometry and Classical Relativity.On the other hand, recent detection of gravitational waves from the coalescence of gravitational objects in close black hole and neutron star binaries by LIGO-VIRGO scientific collaboration, confirmation of black hole status of the Milky Way center by ESO's GRAVITY instrument and upcoming first detection of the black hole shadow in M87 and Sagittarius A* by the Event Horizon Telescope lead to the rapidly growing interest in the study of relativistic astrophysical objects.In the light of these recent successes of general theory of relativity, AJM decided to further widen its scope by opening it to researchers working in areas such as Mathematical Physics, General Relativity, and Relativistic Astrophysics.It is in this spirit that AJM is publishing two special issues on Mathematical Physics, General Relativity and Relativistic Astrophysics.Well-known scientists working in the aforementioned areas were invited to write research or review articles.Of these invited scientists, five accepted the invitation to contribute to the first issue focussing mainly on Mathematical Physics and General Relativity and five accepted to contribute to the second issue with more emphasis on Relativistic Astrophysics.A brief overview of the five articles appearing in the first issue is as follows.The first article by Dutt, Safdar and Qadir is entitled "Linearization procedure for 2-dimensional systems of second order ODEs using complex Lie symmetry analysis".The authors discuss an interesting linearization procedure and, using a complex Lie symmetry approach, obtain a linearizable form, linearization criteria, and a symmetry group classification for the two-dimensional system.The second paper entitled "Some remarks on wave solutions in general relativity theory" is contributed by Hall.In this article, the author exposes an excellent overview of one of the outstanding concepts of pp-waves and plane waves in classical relativity.Beginning with a discussion of some algebraic constructions and symmetry concepts, Hall deals with definitions of such wave solutions, their associated geometrical tensors in space-time and their Killing, homothetic, conformal and wave surface symmetries.The paper concludes with some unusual geometrical features of these solutions (compared with standard positive definite geometry).The third paper entitled "QED plasma in the early universe" is contributed by Masood.In this paper, the author considers a renormalization scheme of QED by showing that the dielectric constant,