Hydrodynamics of galactic dark matter

Cabral-Rosetti, Luis G.; Matos, Tonatiuh; Núñez, Darío; Sussman, Roberto A.

doi:10.1088/0264-9381/19/14/303

Cited by 18 publications

(21 citation statements)

References 49 publications

(73 reference statements)

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“…Confirmation of these problems would imply that structure formation is somehow suppressed on small scales. To deal with them, some kind of self-interaction has been proposed either in cold dark matter (CDM) models [25], [26], [27], [28], [29] [30] [31], [32] [33] [34], or in warm dark matter (WDM) models [35]- [40] [41] . It is quite reasonable to expect that dark matter is out of thermodynami-cal equilibrium and these same interactions are at the origin of a cosmological dissipative pressure or thermal effects.…”

Section: Dissipative Effectsmentioning

confidence: 99%

Interacting quintessence solution to the coincidence problem

et al. 2003

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We show that a suitable interaction between a scalar field and a matter fluid in a spatially homogeneous and isotropic spacetime can drive the transition from a matter dominated era to an accelerated expansion phase and simultaneously solve the coincidence problem of our present Universe. For this purpose we study the evolution of the energy density ratio of these two components.We demonstrate that a stationary attractor solution is compatible with an accelerated expansion of the Universe. We extend this study to account for dissipation effects due to interactions in the dark matter fluid. Finally, Type Ia supernovae and primordial nucleosynthesis data are used to constrain the parameters of the model.

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Section: Dissipative Effectsmentioning

confidence: 99%

Interacting quintessence solution to the coincidence problem

et al. 2003

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“…The MB distribution is a solution of the Einstein–Boltzmann equations, irrespective of whether the gas is collisional or collisionless; its applicability is only restricted by the criterion of ‘non‐degeneracy’ or ‘dilute occupancy’ (Pathria 1972): exp (μβ/ mc 2 ) ≪ 1. For typical galactic halo variables, this criterion holds for particle masses complying with m ≫ 60 eV (Cabral‐Rosetti et al 2002).…”

Section: The Non‐relativistic Maxwell–boltzmann Gasmentioning

confidence: 99%

“…The actual velocity of observers along circular geodesics follows from evaluating , which with the help of the previous equations (see Cabral‐Rosetti et al 2002) yields where we have used to eliminate dΨ/d x . Because Φ becomes the Newtonian gravitational potential in the NL, circular geodesics orbits exist and v ( r ) is well defined as long as the gravitational force field is attractive (i.e.…”

Section: Existence and Stability Of Circular Geodesic Orbitsmentioning

confidence: 99%

On the Newtonian limit and cut-off scales of isothermal dark matter haloes with cosmological constant

Sussman¹,

Hernández²

2003

Monthly Notices of the Royal Astronomical Society

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We examine isothermal dark matter haloes in hydrostatic equilibrium with a ‘Λ‐field’, or cosmological constant Λ=ΩΛρcritc2, where ΩΛ≃ 0.7 and ρcrit is the present value of the critical density with h≃ 0.65. Modelling cold dark matter (CDM) as a self‐gravitating Maxwell–Boltzmann gas, the Newtonian limit of general relativity yields equilibrium equations that are different from those arising by merely coupling an ‘isothermal sphere’ to the Λ‐field within a Newtonian framework. Using the conditions for the existence and stability of circular geodesic orbits, the numerical solutions of the equilibrium equations (Newtonian and Newtonian limit) show the existence of: (i) an ‘isothermal region’(0 ≤r < r2), where circular orbits are stable and all variables behave almost identically to those of an isothermal sphere; (ii) an ‘asymptotic region’(r > r1) dominated by the Λ‐field, where the Newtonian potential oscillates and circular orbits only exist in disconnected patches of the domain of r; (iii) a ‘transition region’(r2≤r < r1) between (i) and (ii), where circular orbits exist but are unstable. We also find that no stable configuration can exist with central density, ρc, smaller than 2Λ, hence any galactic haloes which virialized at z < 30 in a ΛCDM cosmological background must have central densities of ρc > 0.008 M⊙ pc−3, in interesting agreement with rotation curve studies of dwarf galaxies. Because r2 marks the largest radius of a stable circular orbit, it provides a characteristic boundary or ‘cut‐off’ maximal radius for isothermal spheres in equilibrium with a Λ‐field. For current estimates of ρc and velocity dispersion of virialized galactic structures, this cut‐off scale ranges from 90 kpc for dwarf galaxies, up to 3 Mpc for large galaxies and 22 Mpc for clusters. In a purely Newtonian framework, these length‐scales are about 10 per cent smaller, although in either case r2 is between five and seven times larger than the physical cut‐off scales of isothermal haloes, such as the virialization radius or the critical radius for the onset of Antonov instability. These results indicate that the effects of the Λ‐field can be safely ignored in studies of virialized structures, but could be significant in the study of structure formation models and the dynamics of superclusters still in the linear regime or of gravitational clustering at large scales (r≈ 30 Mpc).

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“…Under the conditions (58) we also have g rr 1 and g 00 ÿ1, hence the components of F a given by (27) become…”

Section: Newtonian Type Limitsmentioning

confidence: 99%

“…While the usual Newtonian approach may well be adequate on galactic scales, only a general relativistic setting can provide limits for the validity of the Newtonian approximation. In a general relativistic treatment in which DM provides the bulk of spacetime curvature, the motion of baryonic matter can be treated as test particle motion in the geometry generated by the DM (''rotation velocities'' become then velocities of circular geodesic orbits [27,28]). However, a relativistic approach will not only yield corrections to the Newtonian case, but it also provides a framework which admits theoretical generalizations, e.g., the introduction of nonstandard interactions in a systematic and self-consistent way.…”

Section: Introductionmentioning

confidence: 99%

Maxwell-Boltzmann gas with nonstandard self-interactions: A novel approach to galactic dark matter

2004

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Using relativistic kinetic theory, we study spherically symmetric, static equilibrium configurations of a collisionless Maxwell-Boltzmann gas with nonstandard self-interactions, modeled by an effective one-particle force. The resulting set of equilibrium conditions represents a generalization of the classical Tolman-Oppenheimer-Volkov equations. We specify these conditions for two types of Lorentz-like forces: one coupled to the 4-acceleration and the 4-velocity and the other one coupled to the Riemann tensor. We investigate the weak field limits in each case and show that they lead to various Newtonian type configurations that are different from the usual isothermal sphere characterizing the conventional Newtonian Maxwell-Boltzmann gas. These configurations could provide a plausible phenomenological and theoretical description of galactic dark matter halo structures. We show how the self-interaction may act phenomenologically as an effective cosmological constant and discuss possible connections with Modified Newtonian Dynamics (MOND).

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Hydrodynamics of galactic dark matter

Cited by 18 publications

References 49 publications

Interacting quintessence solution to the coincidence problem

Interacting quintessence solution to the coincidence problem

On the Newtonian limit and cut-off scales of isothermal dark matter haloes with cosmological constant

Maxwell-Boltzmann gas with nonstandard self-interactions: A novel approach to galactic dark matter

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