Can general relativity play a role in galactic dynamics?

Astesiano, Davide; Ruggiero, Matteo Luca

doi:10.1103/physrevd.106.l121501

Cited by 16 publications

(40 citation statements)

References 23 publications

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“…A somewhat different but related approach, which takes into account the gravitomagnetic effects originating from mass currents into the solution of Einstein equations in weak-field and slow-motion approximation was put forward by Ludwig [218], Ruggiero et al [219], Srivastava et al [220] and analyzed with detailed criticism by Ciotti [221]. In Astesiano and Ruggiero [222], the GR results of these papers are shown to be related to the existence of the homogeneous solutions of the gravitomagnetic field and not directly related to the mass currents. These homogeneous solutions can produce a 'strong gravitomagnetic limit' where these effects are of the same order as Newtonian ones.…”

Section: Galactic Dynamicsmentioning

confidence: 99%

A tale of analogies: a review on gravitomagnetic effects, rotating sources, observers and all that

Ruggiero,

Astesiano

2023

J. Phys. Commun.

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Gravitoelectromagnetic analogies are somewhat ubiquitous in General Relativity, and they are often used to explain peculiar effects of Einstein's theory of gravity in terms of familiar results from classical electromagnetism. Perhaps, the best known of these analogy pertains to the similarity between the equations of electromagnetism and those of the linearized theory of General Relativity. But the analogy is somewhat deeper and ultimately rooted in the splitting of spacetime, which is preliminary to the definition of the measurement process in General Relativity.In this paper we review the various approaches that lead to the introduction of a magnetic-like part of the gravitational interaction, briefly called \textit{gravitomagnetic} and, then, we provide a survey of the recent developments both from the theoretical and experimental viewpoints.

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Section: Galactic Dynamicsmentioning

confidence: 99%

A tale of analogies: a review on gravitomagnetic effects, rotating sources, observers and all that

Ruggiero,

Astesiano

2023

J. Phys. Commun.

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“…These include gravitoelectric flux confinement arising from graviton selfinteraction [11][12][13][14][15][16][17][18], non-linear GR effects arising even in the weak-gravity regime [19] and, most recently, gravitomagnetic effects in linearised GR [20]. Certain elements of [20] are further developed in [21] where (although the dark matter paradigm is not directly challenged) significant gravitomagnetic corrections to the rotation curve of a toy-model galactic baryon profile are suggested. An immediate question regarding such claims is how such significant behaviours can have been consistently missed in the long history of numerical relativity [22,23], or in the well-developed post-Newtonian formalism [24,25].…”

Section: Introductionmentioning

confidence: 99%

“…Perhaps unsurprisingly therefore, the claims in [11][12][13][14][15][16][17][18] and [19] have been subsequently shown to be non-viable in [26] and [27], respectively. The purpose of this paper is to perform the same function for the claims in [20,21], by showing that gravitomagnetism in the form used therein cannot be a significant factor in explaining flat or rising galaxy rotation curves without dark matter.…”

Section: Introductionmentioning

confidence: 99%

“…We will observe in particular the accidental involvement in [20] of homogeneous solutions to the GEM field equations: this leads us naturally to [21], where such solutions are actively employed 3 . We will show however that such solutions do not yield any deterministic phenomenology according to the suggested approximation in [21], and that they are moreover absolutely ruled out by the absence of suitable GEM boundary conditions in the galactic environment.…”

Section: Introductionmentioning

confidence: 99%

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Gravitomagnetism and galaxy rotation curves: a cautionary tale

Lasenby,

Hobson,

Barker

2023

Class. Quantum Grav.

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We investigate recent claims that gravitomagnetic effects in linearised general relativity can explain flat and rising rotation curves, such as those observed in galaxies, without the need for dark matter. If one models a galaxy as an axisymmetric, stationary, rotating, non-relativistic and pressureless 'dust' of stars in the gravitoelectromagnetic (GEM) formalism, we show that gravitomagnetic effects on the circular velocity $v$ of a star are $O(10^{-6})$ smaller than the standard Newtonian (gravitoelectric) effects and thus any modification of galaxy rotation curves must be negligible. Moreover, we find that gravitomagnetic effects are $O(10^{-6})$ too small to provide the vertical support necessary to maintain dynamical equilibrium. These issues are obscured if one constructs a single equation for $v$, as considered previously. We nevertheless solve this equation for a galaxy having a Miyamoto--Nagai density profile since this allows for an exact numerical integration and an accurate analytic approximation. We show that for the values of mass, $M$, and semi-major and semi-minor axes, $a$ and $b$, typical for a dwarf galaxy, the rotation curve depends only very weakly on $M$. Moreover, for aspect ratios $a/b > 2$, the rotation curves are concave over their entire range, which does not match observations in any galaxy. Most importantly, we show that for the poloidal gravitomagnetic flux $\psi$ to provide the necessary vertical support, it must become singular at the origin and have extremely large values near to it. This originates from the unwitting, but forbidden, inclusion of free-space solutions of the Poisson-like equation that determines $\psi$. We further show that recent deliberate attempts to leverage such free-space solutions against the rotation curve problem yield no deterministic modification outside the thin disk approximation, and that, in any case, the homogeneous contributions to $\psi$ are ruled out by the boundary value problem posed by any physical axisymmetric galaxy.

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“…Different attempts and detailed analyses based on a variety of empirical models for the visible mass distributions of specific galaxies, without including any other invisible or dark matter contribution but rather by accounting for the gravito-magnetic effects sourced by visible mass currents, have been contributed over the years in a number of publications, such as Refs. [28,29,30,31,32,33,34,35,36] (and references therein). However, these authors come to dissimilar conclusionssome (strongly) supporting the possibility, while others being not (at all) as convinced, and some others still even discouraged of pursuing such an avenue-, depending on the models being used for visible matter distributions and their dynamics.…”

Section: Introductionmentioning

confidence: 99%

The Gravito-Electromagnetic Approximation to the Gravimagnetic Dipole and its Velocity Rotation Curve

Govaerts¹

2023

Preprint

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In view of the observed flat rotation curves of spiral galaxies and motivated by the simple fact that within newtonian gravity a stationary axisymmetric mass distribution or dark matter vortex of finite extent readily displays a somewhat flattened out velocity rotation curve up to distances comparable to the extent of such a vortex transverse to the galaxy's disk, the possibility that such a flattening out of rotation curves may rather be a manifestation of some stationary axisymmetric space-time curvature of purely gravitational character, without the need of some dark matter particles, is considered in the case of the gravimagnetic dipole carrying opposite NUT charges and in the tensionless limit of its Misner string, as an exact vacuum solution to Einstein's equations. Aiming for a first assessment of the potential of such a suggestion easier than a full fledged study of its geodesics, the situation is analysed within the limits of weak field gravito-electromagnetism and nonrelativistic dynamics. Thereby leading indeed to interesting and encouraging results.

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Can general relativity play a role in galactic dynamics?

Cited by 16 publications

References 23 publications

A tale of analogies: a review on gravitomagnetic effects, rotating sources, observers and all that

A tale of analogies: a review on gravitomagnetic effects, rotating sources, observers and all that

Gravitomagnetism and galaxy rotation curves: a cautionary tale

The Gravito-Electromagnetic Approximation to the Gravimagnetic Dipole and its Velocity Rotation Curve

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