Dark matter distribution function from non-extensive statistical mechanics

Hansen, Steen H.; Egli, Daniel; Hollenstein, Lukas; Salzmann, Christoph G.

doi:10.1016/j.newast.2005.01.005

Cited by 74 publications

(69 citation statements)

References 35 publications

(36 reference statements)

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“…Such a trend with shallower density slope implying larger q's was suggested from simplified theoretical considerations [17]. It is interesting to note that ref.…”

Section: Dependence On Initial Conditions?mentioning

confidence: 60%

A universal velocity distribution of relaxed collisionless structures

Hansen¹,

Moore²,

Zemp³

et al. 2006

J. Cosmol. Astropart. Phys.

106

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Abstract. Several general trends have been identified for equilibrated, selfgravitating collisionless systems, such as density or anisotropy profiles. These are integrated quantities which naturally depend on the underlying velocity distribution function (VDF) of the system. We study this VDF through a set of numerical simulations, which allow us to extract both the radial and the tangential VDF. We find that the shape of the VDF is universal, in the sense that it depends only on two things namely the dispersion (radial or tangential) and the local slope of the density. Both the radial and the tangential VDF's are universal for a collection of simulations, including controlled collisions with very different initial conditions, radial infall simulation, and structures formed in cosmological simulations.

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“…Such a trend with shallower density slope implying larger q's was suggested from simplified theoretical considerations [17]. It is interesting to note that ref.…”

Section: Dependence On Initial Conditions?mentioning

confidence: 60%

A universal velocity distribution of relaxed collisionless structures

Hansen¹,

Moore²,

Zemp³

et al. 2006

J. Cosmol. Astropart. Phys.

106

View full text Add to dashboard Cite

show abstract

“…They study a Milky Way sized object at redshift z = 0 that includes gas, stars and dark matter to characterize the co-rotating dark disk, which could play an important role in direct detection experiments [117]. Equilibrated self-gravitating collisionless structures have been shown to exhibit Tsallis distributions [118][119][120][121]:…”

Section: Smooth Halo Componentmentioning

confidence: 99%

Colloquium: Annual modulation of dark matter

2013

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Direct detection experiments, which are designed to detect the scattering of dark matter off nuclei in detectors, are a critical component in the search for the Universe's missing matter. The count rate in these experiments should experience an annual modulation due to the relative motion of the Earth around the Sun. This modulation, not present for most known background sources, is critical for solidifying the origin of a potential signal as dark matter. In this article, we review the physics of annual modulation, discussing the practical formulae needed to interpret a modulating signal. We focus on how the modulation spectrum changes depending on the particle and astrophysics models for the dark matter. For standard assumptions, the count rate has a cosine dependence with time, with a maximum in June and a minimum in December. Well-motivated generalizations of these models, however, can affect both the phase and amplitude of the modulation. We show how a measurement of an annually modulating signal could teach us about the presence of substructure in the Galactic halo or about the interactions between dark and baryonic matter. Although primarily a theoretical review, we briefly discuss the current experimental situation for annual modulation and future experimental directions.

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“…Nonextensive thermodynamics (sometimes referred to as q-statistics) has been designed to describe systems with long dynamical memories, as in self-gravitating collisionless objects. Although other applications have been discussed by Tsallis (1999), specific applications of nonextensive thermodynamics to astrophysical situations have been discussed by Plastino & Plastino (1993), Aly (1993), Hansen et al (2005), Leubner (2005), and most recently by KLK06. One of the more interesting results of the nonextensive approach is that the associated distribution function has the same form as for a polytrope (Plastino & Plastino 1993).…”

Section: Nonextensive Thermodynamicsmentioning

confidence: 99%

Velocity Distributions from Nonextensive Thermodynamics

Barnes

Williams²,

Babul

et al. 2007

ApJ

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There is no accepted mechanism that explains the equilibrium structures that form in collisionless cosmological N-body simulations. Recent work has identified nonextensive thermodynamics as an innovative approach to the problem. The distribution function that results from adopting this framework has the same form as for polytropes, but the polytropic index is now related to the degree of nonextensiveness. In particular, the nonextensive approach can mimic the equilibrium structure of dark matter density profiles found in simulations. We extend the investigation of this approach to the velocity structures expected from nonextensive thermodynamics. We find that the nonextensive and simulated N-body v rms distributions do not match one another. The nonextensive v rms profile is either monotonically decreasing or displays little radial variation, each of which disagrees with the v rms distributions seen in simulations. We conclude that the currently discussed nonextensive models require further modifications in order to corroborate dark matter halo simulations.

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Dark matter distribution function from non-extensive statistical mechanics

Cited by 74 publications

References 35 publications

A universal velocity distribution of relaxed collisionless structures

A universal velocity distribution of relaxed collisionless structures

Colloquium: Annual modulation of dark matter

Velocity Distributions from Nonextensive Thermodynamics

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