Scalar fields properties for flat galactic rotation curves

Abstract

Abstract. The whole class of minimally coupled and massive scalar fields which may be responsible for flattening of galactic rotation curves is found. An interesting relation with a class of scalar-tensor theories able to isotropise anisotropic models of Universe is shown. The resulting metric is found and its stability and scalar field properties are tested with respect to the presence of a second scalar field or a small perturbation of the rotation velocity at galactic outer radii.

Possible existence of wormholes in the galactic halo region

“…(1) Regarding these requirements, observe that Eq. (6) shows that the spacetime does not have an event horizon. To check the shape function, we will use a graphical approach by using some typical values of the parameters.…”

“…The second condition is satisfied, but not the first, as we can see from Eq. (6). So the wormhole cannot be arbitrarily large, which also applies to the halo region.…”

“…The term dark refers to the fact that it does not emit electromagnetic waves, nor does it interact with normal matter. A number of candidates for dark matter have been proposed over time: new particles predicted by supersymmetry [4], massive neutrinos collectively known as WIMPs (weakly interacting massive particles) [5], a source of scalar fields [6][7][8][9], global monopoles [10][11][12], brane-world effects of gravitation [13][14][15], noncommutative geometry [16], geometric effects of f (R) gravity [17], f (T ) gravity [18], etc.…”

Bianchi type IX asymptotical behaviours with a massive scalar field: chaos strikes back

“…It is also one of the best mechanism to produce inflation at early times. It could even mimic the galactic dark matter [6,7] responsible for the rotation curves flattening. What about the geometrical framework of this paper?…”

Erratum: Remarks on the spherical scalar field halo in galaxies [Phys. Rev. D80, 047301 (2009)]

“…Hence the hypothesis that there must be huge amounts of nonluminous matter hidden in the halo. This unseen matter is given a technical name dark matter.Despite the fact that the exact nature of dark matter is as yet unknown, several analytic halo models exist in the literature including those provided by scalar-tensor theories (see for instance [1]). In particular, the scalar field model first proposed by Matos, Guzmán and Nuñez [2] has received considerable attention.…”