Galactic dynamics in general relativity: the role of gravitomagnetism

Ruggiero, Matteo Luca; Ortolan, A.; Speake, C. C.

doi:10.1088/1361-6382/ac9949

Cited by 15 publications

(10 citation statements)

References 46 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Therefore, we assume that the main dynamics of a galaxy with the mentioned properties can be modelled as a stationary and axially symmetric rotating dust fluid; this means that we will consider o fluid of stars, which can themselves be treated as test masses and whose motion can be studied using the geodesic equation. Accordingly, as discussed by Ruggiero et al [26], Einstein's field equations in weak-field and slow-motion approximation can be written in the so-called gravitoelectromagnetic analogy in the form…”

Section: The Gravitomagnetic Approachmentioning

confidence: 99%

Can general relativity play a role in galactic dynamics?

Astesiano

Ruggiero²

2022

Phys. Rev. D

Self Cite

View full text Add to dashboard Cite

We use the gravitoelectromagnetic approach to the solutions of Einstein's equations in the weakfield and slow-motion approximation to investigate the impact of General Relativity on galactic dynamics. In particular, we focus on a particular class of the solutions for the gravitomagnetic field, and show that, contrary to what is expected, they may introduce non negligible corrections to the Newtonian velocity profile. The origin and the interpretation of these corrections are discussed and explicit applications to some galactic models are provided. These are the homogeneous solutions (HS) for the gravitomagnetic field, i.e. solutions with vanishing matter currents.

show abstract

Section: The Gravitomagnetic Approachmentioning

confidence: 99%

Can general relativity play a role in galactic dynamics?

Astesiano

Ruggiero²

2022

Phys. Rev. D

Self Cite

View full text Add to dashboard Cite

show abstract

“…via direct computations of GEM effects [28], identification of singularities [30] and gross lensing effects [31] -see also [32] and more careful attempts such as [33] which use the parameterised post-Newtonian formulation). Neither [29], nor the associated series [34][35][36] diverts the attention of this article from the innovations in [21], which are especially interesting and clear. We also take note of [37,38] which appeared whilst this work was in review.…”

Section: Linearised Grmentioning

confidence: 92%

Gravitomagnetism and galaxy rotation curves: a cautionary tale

Lasenby,

Hobson,

Barker

2023

Class. Quantum Grav.

View full text Add to dashboard Cite

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.

show abstract

“…In the studies of Astesiano and Ruggiero [6] (hereafter AR22) and [7], the specific role of the post-Newtonian gravitomagnetic effect was made clear in these 'GR without Dark Matter' models. Closely related to this, Ruggiero et al [8] argued that the gravitomagnetic field can act as an effective Newtonian density, and affect the galactic dynamics accordingly. Some aspects of this body of work have already received critical appraisal.…”

Section: Introductionmentioning

confidence: 93%

Pitfalls in applying gravitomagnetism to galactic rotation curve modelling

Glampedakis

Jones

2023

Class. Quantum Grav.

View full text Add to dashboard Cite

The flatness of galaxy rotation curves at large radii is generally considered to be a significant piece of evidence in support of the existence of dark matter. Several studies have claimed that post-Newtonian corrections to the Newtonian equations of galaxy dynamics may remove (at least to some degree) the need for dark matter. A few recent studies have examined these claims, and identified errors in their reasoning. We add to this critique by giving what we consider to be particularly simple and transparent description of the errors made in these post-Newtonian calculations, some of which were of a rather technical nature, others more fundamental, e.g.\ the loss of the correct relativistic scaling, promoting small corrections to order unity changes. Our work reinforces the orthodoxy that post-Newtonian effects are indeed too small to significantly alter galactic rotation curves, and will hopefully serve as a useful guide for others, pointing out subtle errors that one might inadvertently make in such calculations.

show abstract

Galactic dynamics in general relativity: the role of gravitomagnetism

Cited by 15 publications

References 46 publications

Can general relativity play a role in galactic dynamics?

Can general relativity play a role in galactic dynamics?

Gravitomagnetism and galaxy rotation curves: a cautionary tale

Pitfalls in applying gravitomagnetism to galactic rotation curve modelling

Contact Info

Product

Resources

About