Significance of c/sqrt(2) in Relativistic Physics

In the description of \emph{relative} motion in accelerated systems and gravitational fields, inertial and tidal accelerations must be taken into account, respectively. These involve a critical speed that in the first approximation can be simply illustrated in the case of motion in one dimension. For one-dimensional motion, such first-order accelerations are multiplied by $(1-V^2/V_c^2)$, where $V_c=c/\sqrt{2}$ is the critical speed. If the speed of relative motion exceeds $V_c$, there is a sign reversal with consequences that are contrary to Newtonian expectations.Comment: 7 pages, 1 figure, slightly expanded version accepted for publication in Class. Quantum Gra

On the kinematics of a corotating relativistic plasma stream in the perpendicular rotator model of a pulsar magnetosphere

An investigation of the kinematics of a rotating relativistic plasma stream in the perpendicular rotator model of the pulsar magnetosphere is presented. It is assumed that the plasma (ejected from the pulsar) moves along the pulsar magnetic field lines and also corotates with them. The field lines are considered to be radial straight lines, located in the plane which is perpendicular to the pulsar rotation axis. The necessity of taking particle inertia into account is discussed. It is argued that the "massless" ("force-free") approximation cannot be used for the description of this problem. The frame selection is discussed and it is shown that it is convenient to discuss the problem in the noninertial frame of ZAMOs (Zero Angular Momentum Observers). The equation of motion and the exact set of equations describing the behaviour of a relativistic plasma stream in the pulsar magnetosphere is obtained. The possible relevance of this investigation for the understanding of the formation process of a pulsar magnetosphere is discussed.Comment: Plain LaTe