New look at the relativistic particle dynamics in external field

The assumption is made that external field effects the nature of particle’s movement not only straight by force effect but also implicitly through particle rest mass change. The concept of the local effective rest mass of a particle in an external field is introduced. The expressions Lagrange and Hamilton functions, which explicitly take into account such change, are proposed and justified. Based on these expressions the new equation of relativistic particle motion in external scalar field, new expressions for conservation laws and changes of the total particle energy and its angular momentum and a number of other relations between particle dynamic parameters are produced. It is shown that the obtained equations and relations have a number of undoubted advantages over the corresponding well-known equations and equalities of traditional relativistic physics. An explanation of the «mass defect» phenomenon is given and the physical sense of the effect is revealed. It is shown that despite the possibility of the existence of particles with negative local effective rest masses in separate limited areas of the field the proposed model does not allow particles to move at superlight speed.