Features of galactic halo in a brane world model and observational constraints

Abstract

Several aspects of the 4d imprint of the 5d bulk Weyl radiation are investigated within a recently proposed model solution. It is shown that the solution has a number of physically interesting properties. The constraints on the model imposed by combined measurements of rotation curve and lensing are discussed. A brief comparison with a well-known scalar field model is also given.Key words: gravitation -galaxies: general -galaxies: structure -dark matter. I N T RO D U C T I O NEarly observations led to the hypothesis that there could be large amounts of non-luminous matter hidden in the galactic haloes (Oort 1930;Zwicky 1933Zwicky , 1937. Later observations of flat rotation curves of spiral galaxies confirmed the hypothesis (Freeman 1970;Roberts & Rots 1973;Ostriker, Peebles & Yahill 1974;Einasto, Kaasik & Saar 1974;Rubin, Thonnard & Ford 1978;Rubin, Roberts & Ford 1979;Sofue & Rubin 2001;Kochanek et al. 2005). Doppler emissions from stable circular orbits of neutral hydrogen clouds in the halo allow the measurement of tangential velocity v tg (r) of the clouds treated as probe particles. According to Newton's laws, centrifugal acceleration v 2 tg /r should balance the gravitational attraction GM(r)/r 2 , which immediately gives v 2 tg = GM(r)/r. That is, one would expect a fall-off of v 2 tg (r) with r. However, observations indicate that this is not the case: v tg approximately levels off with r in the halo region. The only way to reconcile this result of observation is to hypothesize that the mass M(r) increases linearly with distance r. Luminous mass distribution in the galaxy does not follow this behaviour. Hence, we conclude that there must be huge amounts of non-luminous matter hidden in the halo. This unseen matter is given a technical name, dark matter.

Possible existence of wormholes in the central regions of halos

“…1. Moreover, for sufficiently large r, v φ ∼ 250 km/s ≈ 0.00083 [13,14]. One can note that our proposed curve and observed curve profile for tangential velocity are almost similar to each other for the specific values of the parameters i.e.…”

Could wormholes form in dark matter galactic halos?

“…Here, the velocity v φ is given in km/s which is equivalent to (Rahaman et al 2008;Nandi 2009) Observed data Fitted polynomial (5th degree) Fig. 1 The rotational velocity from observational data (Table 1) and estimated fifth degree polynomial.…”

Possible existence of wormholes in the galactic 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.…”