Combining rotation curves and gravitational lensing: how to measure the equation of state of dark matter in the galactic halo

Faber, Tristan; Visser, Matt

doi:10.1111/j.1365-2966.2006.10845.x

Cited by 81 publications

(94 citation statements)

References 22 publications

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“…Taking the fluid interpretation literally, we predict an unusual equation of state (15) for dark matter that could be tested by combining gravitational lensing and rotation curve data, as explained in Ref. [24]. This could provide the simplest route to falsify our model.…”

Section: -Dimensional Interpretationmentioning

confidence: 99%

Erratum: Model for Gravity at Large Distances [Phys. Rev. Lett.105, 211303 (2010)]

Grumiller¹

2011

Phys. Rev. Lett.

108

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We construct an effective model for gravity of a central object at large scales. To leading order in the large radius expansion we find a cosmological constant, a Rindler acceleration, a term that sets the physical scales and subleading terms. All these terms are expected from general relativity, except for the Rindler term. The latter leads to an anomalous acceleration in geodesics of test-particles. 95.35.+d, Gravity at large distances poses some of the most difficult puzzles in contemporary gravitational physics. The cosmological constant problem [1] and the nature of dark matter [2] are the most prominent ones. At a somewhat smaller scale, both in terms of actual size and in terms of scientific credibility, there are fly-by anomalies [3] and the Pioneer anomaly [4]. The word "anomalous" here refers to the difference between the observed trajectory of a test-particle in the gravitational field of a central object and the calculated trajectory. The pair test-particle/central object can mean e.g. galaxy/cluster, star/galaxy, Sun/Pioneer spacecraft, Earth/satellite, etc.Conceptually, there are three ways to resolve the anomalies. Either we modify the matter content of the theory (dark matter), or we modify the gravitational theory itself. The third alternative is that we might not be applying the theory correctly or beyond its realm of validity. Namely, even though effects that go beyond general relativity (GR) or its Newtonian limit are small locally, they may accumulate over large distances and/or through averaging, see [5][6][7] for various approaches that advocate this idea and implement it in different ways. In this Letter we advocate a new approach to describe gravity at large distances that is agnostic about the issue which of these three alternatives is realized in Nature. The main strength of our method lies in its rigidity -there is only one new free parameter -and in its ab initio nature.One well-established key ingredient to our approach is to construct an effective field theory by writing down the most general action consistent with all the required symmetries and with additional assumptions (power counting renormalizability, analyticity, ...). A crucial point is that we impose spherical symmetry in addition to diffeomorphism invariance, which often is a good approximation in the IR [27]. Spherical symmetry effectively reduces the theory to two dimensions. The main result of this Letter is that the most general action consistent with our assumptions leads to an additional term in the gravitational potential as compared to GR. This novel term generates accelerations similar to the ones observed in various "anomalous" systems in Nature and has a beautifully simple geometric interpretation as Rindler acceleration. EFFECTIVE FIELD THEORY FOR IR GRAVITYTo address the issue of anomalous acceleration of testparticles in the gravitational field of a central object we first simplify the underlying theory as much as possible. We assume that spacetime is described by a spherically symmetric metric in four dim...

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Section: -Dimensional Interpretationmentioning

confidence: 99%

Erratum: Model for Gravity at Large Distances [Phys. Rev. Lett.105, 211303 (2010)]

Grumiller¹

2011

Phys. Rev. Lett.

108

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“…However, due to the lack of direct detection room is left for approaches where p dm = 0 [4]. The dark matter equation of state can be inferred using gravitational lensing and kinematic techniques at astrophysical scales as proposed by Faber and Visser [5]. Relaxing the assumption p dm = 0, dark matter in clusters of galaxies exhibits a negative equation of state parameter w dm < 0 [6].…”

Section: Introductionmentioning

confidence: 99%

Dissipation of dark matter

2012

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Fluids often display dissipative properties. We explore dissipation in the form of bulk viscosity in the cold dark matter fluid. We constrain this model using current data from supernovae, baryon acoustic oscillations and the cosmic microwave background. Considering the isotropic and homogeneous background only, viscous dark matter is allowed to have a bulk viscosity 10 7 Pa·s, also consistent with the expected integrated Sachs-Wolfe effect (which plagues some models with bulk viscosity). We further investigate the small-scale formation of viscous dark matter halos, which turns out to place significantly stronger constraints on the dark matter viscosity. The existence of dwarf galaxies is guaranteed only for much smaller values of the dark matter viscosity, 10 −3 Pa·s. PACS numbers: 98.80-k, 95.36+x

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“…One can see that the matter contribution to the energy density remains positive for all values of r. 7 Now, we make some comments about the possible equation of state (EOS) of dark matter in our model. This topic has received some interest of late, following the work of [2], [27]. In [28], [29], the authors computed an effective EOS parameter…”

Section: Bsts In the Metric F (R) Gravity Paradigmmentioning

confidence: 99%

Galactic space-times in modified theories of gravity

2015

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We study Bertrand space-times (BSTs), which have been proposed as viable models of space-times seeded by galactic dark matter, in modified theories of gravity. We first critically examine the issue of galactic rotation curves in General Relativity, and establish the usefulness of BSTs to fit experimental data in this context. We then study BSTs in metric f (R) gravity and in Brans-Dicke theories. For the former, the nature of the Newtonian potential is established, and we also compute the effective equation of state and show that it can provide good fits to some recent experimental results. For the latter, we calculate the Brans-Dicke scalar analytically in some limits and numerically in general, and find interesting constraints on the parameters of the theory. Our results provide evidence for the physical nature of Bertrand space-times in modified theories of gravity. *

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Combining rotation curves and gravitational lensing: how to measure the equation of state of dark matter in the galactic halo

Cited by 81 publications

References 22 publications

Erratum: Model for Gravity at Large Distances [Phys. Rev. Lett.105, 211303 (2010)]

Erratum: Model for Gravity at Large Distances [Phys. Rev. Lett.105, 211303 (2010)]

Dissipation of dark matter

Galactic space-times in modified theories of gravity

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