arXiv subjects

Dmitri Lebedev

Publications and source records attributed to Dmitri Lebedev.

3 recordsLinked to original sources

arXiv2026

General Expressions for Measurable Parameters in Curved Spacetime

General covariant expressions for measurable angles, distances, velocities, and accelerations are provided in terms of fundamental parameters that can be applied in any setup. The relativistic aberration of light relationship is presented in full generality, which is applicable to any orientation of observers and light rays. An expansion for the geometrical exponential map is established and used to form an expression for the physical distance between an observer and a nearby object within its extended local frame. Curvature effects on measurable distances, velocities, and accelerations are made explicit and appear in general tensorial form. The concepts of Fermi frames on timelike worldlines and the Fermi-Walker derivative are discussed in detail and used throughout; and in examining the meaning of relative stationarity between timelike observers, the Fermi-Walker derivative is established from first principles through physically meaningful consideration. A generalized type of Taylor expansion is provided for tensors of any rank in a covariant form. Expressions for the optically based angular diameter distance and luminosity distance are provided in general forms, and the reciprocity theorem is discussed and verified. A generalized version of the geodesic deviation equation, applicable to extreme relative motion, is provided as well.

gr-qc↗

arXiv2016

Relativistic Aberration and the Cosmological Constant in Gravitational Lensing I: Introduction

An analysis of null geodesics in Schwarzschild de Sitter space is presented with special attention to their global `bending angles', local measurable angles, and the involvement of the cosmological constant. We make use of a general technique which allows for finding observable intersection angles of null trajectories analytically. A general relativistic aberration relationship is established as one of its applications. The question of whether or not the cosmological constant, $Λ$, contributes to orbits of light and to related observable quantities is addressed in detail. We also discuss the ongoing debate on this issue and respond to some recent papers on the topic. The dependence of measurable quantities on the motion of observers is stressed throughout. Exact formulas for measurable intersection angles, as well as gravitational lens equations for observers in the Schwarzschild de Sitter background are provided.

gr-qc↗

arXiv2013

On the influence of the cosmological constant on trajectories of light and associated measurements in Schwarzschild de Sitter space

In this paper we review and build on the common methods used to analyze null geodesics in Schwarzschild de Sitter space. We present a general technique which allows finding measurable intersection angles of null trajectories analytically, and as one of its applications we establish a general relativistic aberration relationship. The tools presented are used to analyze some standard setups of gravitational deflection of light and gain a clear understanding of the role that the cosmological constant, $Λ$, plays in gravitational lensing phenomena. Through reviewing some recent papers on the topic with the present results in mind, we attempt to explain the major sources of disagreement in the ongoing debate on the subject, which started with Rindler and Ishak's original paper, regarding the influence of $Λ$ on lensing phenomena. To avoid ambiguities and room for misunderstanding we present clear definitions of the quantities used in the present analysis as well as in other papers we discuss.

gr-qc↗