Cosmological peculiar velocities in general relativity?

Fuente: arXiv
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Main Author: Tsagas, Christos G.
Format: Preprint
Published: 2026
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author Tsagas, Christos G.
author_facet Tsagas, Christos G.
contents Cosmological peculiar velocities have traditionally been studied within the framework of Newtonian theory. Around the turn of the century, a few quasi-Newtonian analyses appeared in the literature, but led to equations and results identical to those of the purely Newtonian approach [1]. More recently, a series of studies introduced a relativistic treatment of the peculiar-velocity problem, criticising the quasi-Newtonian approach as effectively Newtonian in nature [2]. These works also reported a linear growth-rate of $v \propto t$ for peculiar velocities, in contrast to the slower Newtonian/quasi-Newtonian scaling of $v \propto t^{1/3}$. In a manuscript uploaded to the archives a few days ago [3], the authors defended their earlier quasi-Newtonian work and criticised the more recent relativistic treatments. However, the limitations of the quasi-Newtonian approach are not a new concern, but they have been noted at least since [4]. There, it was clearly stated that the quasi-Newtonian approximation leads to Newtonian-like equations and results, and readers were cautioned against applying it to large-scale cosmological studies. Given that one of the authors of [3] was also a coauthor of [4], the self-contradiction is evident. The relativistic analyses have, in fact, confirmed the concerns of [4], clarified the underlying issues and shown how they can be resolved. Motivated by [3], we present a critical comparison of the two approaches and in the process identify several internal inconsistencies in that manuscript.
format Preprint
id arxiv_https___arxiv_org_abs_2603_28377
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Cosmological peculiar velocities in general relativity?
Tsagas, Christos G.
General Relativity and Quantum Cosmology
Cosmology and Nongalactic Astrophysics
Cosmological peculiar velocities have traditionally been studied within the framework of Newtonian theory. Around the turn of the century, a few quasi-Newtonian analyses appeared in the literature, but led to equations and results identical to those of the purely Newtonian approach [1]. More recently, a series of studies introduced a relativistic treatment of the peculiar-velocity problem, criticising the quasi-Newtonian approach as effectively Newtonian in nature [2]. These works also reported a linear growth-rate of $v \propto t$ for peculiar velocities, in contrast to the slower Newtonian/quasi-Newtonian scaling of $v \propto t^{1/3}$. In a manuscript uploaded to the archives a few days ago [3], the authors defended their earlier quasi-Newtonian work and criticised the more recent relativistic treatments. However, the limitations of the quasi-Newtonian approach are not a new concern, but they have been noted at least since [4]. There, it was clearly stated that the quasi-Newtonian approximation leads to Newtonian-like equations and results, and readers were cautioned against applying it to large-scale cosmological studies. Given that one of the authors of [3] was also a coauthor of [4], the self-contradiction is evident. The relativistic analyses have, in fact, confirmed the concerns of [4], clarified the underlying issues and shown how they can be resolved. Motivated by [3], we present a critical comparison of the two approaches and in the process identify several internal inconsistencies in that manuscript.
title Cosmological peculiar velocities in general relativity?
topic General Relativity and Quantum Cosmology
Cosmology and Nongalactic Astrophysics
url https://arxiv.org/abs/2603.28377