Methodological notes

Lagrange equations of motion of particles and photons in the Schwarzschild field

Lebedev Physical Institute, Russian Academy of Sciences, Leninsky prosp. 53, Moscow, 119991, Russian Federation

The equations of motion of a particle in the gravitational field of a black hole are considered in a formulation which uses generalized coordinates, velocities and accelerations and is convenient for finding the integrals of motion. The equations are rewritten in terms of the physical velocities and accelerations measured in the Schwarzschild frame by a stationary observer using proper local length and time standards. The attractive force due to the field and the centripetal acceleration of a particle are proportional to the particle's kinetic energy m/√1−v2, consistent with the fact that the particle's kinetic energy and the photon's energy ħω in the field increase by the same amount from their out-of-the-field values. The attraction exerted on particles and photons by the gravitational field source is proportional to their kinetic energies. The particle trajectory in the ultrarelativistic limit v → 1 coincides with the photon trajectory.

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Keywords: gravitational field, Schwarzschild's geometry, mass and energy in gravitation
PACS: 03.30.+p
DOI: 10.3367/UFNe.0185.201511h.1229
Citation: Ritus V I "Lagrange equations of motion of particles and photons in the Schwarzschild field" Phys. Usp. 58 1118–1123 (2015)
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Received: 2nd, July 2015, 22nd, September 2015

Оригинал: Ритус В И «Лагранжевы уравнения движения частиц и фотонов в шварцшильдовском поле» УФН 185 1229–1234 (2015); DOI: 10.3367/UFNr.0185.201511h.1229

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