Ray and colleagues have analyzed features of galactic halo regions based on two possible choices for the dark matter density profile, viz. Navarro, Frenk & White (NFW) type and Universal Rotation Curve (URC). They argued that spacetime of the galactic halo possesses some of the characteristics needed to support traversable wormholes.
During last several decades wormhole has been attracting attention to the scientific community a lot after since publication of the seminal work by Morris & Thorne (1982). In this paper they argued the possibility of the existence of traversable wormholes permitting to travel through space and time. Actually, a wormhole does act role for a passage/tunnel in spacetime which is supposed to connect the widely separated regions of our universe or different universes in the multiverse model. According to Morris & Thorne, the normal matter is unable to hold a wormhole open rather the matter is responsible for sustaining a traversable wormhole is exotic in Nature which violates the standard null energy condition.
By drawing attention to the galactic level where one can notice a kind of peculiar phenomena known as the flat rotation curves in galaxies. Now, the ordinary luminous matters in space are composed mainly of neutral hydrogen clouds. But this bizarre galactic rotation curves can not be explained by the standard model. Therefore, to explain the rotation curves in the outer regions of galaxies it has been supposed that galaxies and even clusters of galaxies must contain some non-luminous matter. This kind of exotic stuff, now known as dark matter, does not emit electromagnetic waves nor interact with normal matter. It has arguably proved by the scientists that dark matter can explain properly, the so called “flat rotation curves”.
Previous some studies in connection to flat rotation curves (Rahaman et al. 2014a, Rahaman et al. 2014b) have used ad hoc functional forms of rotation velocity. However, by using the experimental data of the rotational velocities at different distance of outer regions of galaxies, Ray and colleagues in their paper have estimated fifth degree polynomial that yields the expression for the velocity as a function of the radial coordinate ‘r’, which is almost of the same nature of the experimental feature.
“We have studied the exact observational results and confirm the existence of wormhole in all the galaxies containing the dark matter. These dark matters actually play the role of fuel for developing wormhole-like geometry. This study is a combination of Einstein’s theory and experimental result, therefore, reasonably more physical than the previous studies.”, said Ray.
This rotational velocity they used to find the geometry of galactic halo regions within the framework of general theory of relativity. The estimated rotational velocity function vφ is well behaved within the range 0.1 kpc ≤ r ≤ 100 kpc. They have used this rotational velocity function vφ to find the spacetime geometries of outer region as well as central parts of the galactic halo. Basically, they have in hand the data of galactic rotational velocities from 0.1 kpc to 100 kpc and they have estimated fifth degree polynomial which is the best fitted curve for velocity within this range. Therefore, from their model they couldn’t able to predict what happens in galactic centre. Also the wormhole exists outside the core of the galactic halo. Following Maccio et al. (2012) they have assumed core radius as 9.11 kpc. One can define the central region as 9.11 kpc up to 30 kpc and outer region as above 30 kpc. May be it needs further research to predict the event in the galactic centre.
“In this respect it is to note that we do not know whether it is possible to explain the results without postulating the existence of wormholes, rather by attributing some specific physical properties to dark matter. However, according to our observations, the dark matter in the galactic halo region produces the space-time geometry which is very similar to wormhole like geometry.”, said Farook Rahaman.
This study provides a clue for possible existence of wormholes in most of the galaxies and provides a theoretical platform to seek observational evidence for wormholes by studying the scattering of scaler waves or from past data using ordinary light as well as one can use the method of gravitational lensing as a possible experiment (Kuhfittig 2014). Another suggestion have given by Torres et al. (1998) that wormholes can be probed using light curves of gamma-ray bursts.
Reference: Rahaman, F., Shit, G.C., Sen, B. et al. Could wormholes form in dark matter galactic halos?. Astrophys Space Sci 361, 37 (2016). https://link.springer.com/article/10.1007/s10509-015-2626-7 https://doi.org/10.1007/s10509-015-2626-7
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