◙ Using Einasto DM profile, Ovgun and Halilsoy showed that traversable wormholes may exist in the outer regions of spiral galaxies, while the inner and central regions prohibit such formations.
◙ In their model, the NEC is violated for the outer regions of spiral galaxy so that the flare-out condition for traversable wormhole is satisfied.
◙ Their result is not specific to Milky Way alone but is valid for any spiral galaxy once it obeys a mass distribution given by Einosto profile.
Existence of traversable wormholes is an important problem in physics both at micro and macro scales. There is no doubt that together with black holes wormholes constitute the most interesting objects in our entire universe. On the one hand collision of ultra-energetic particles may create these objects while at the other extreme they form naturally in galactic systems of cosmic dynamics. Once formed, in order to survive traversable wormholes must satisfy certain criteria of stability, otherwise they will decay instantly into more stable objects. Besides, stability energy conditions are also of prime importance concerning traversable wormholes. This demands negative energy density which is not available in classical physics although there are rooms for it in the quantum domain. However, the minimum requirement of violationg null-energy condition (NEC) provides that ρ + pr < 0, without specifying the (-) condition for the energy density.
As a matter of fact NEC provides us a jumping board into the realm of traversable wormholes. Stability, on the other hand, admittedly and for completely technical reasons remains open in our present study. This item may be considered as a separate subject in our future analysis.— said Ovgun, lead author of the study.
Ovgun and Halilsoy’s work is motivated mainly by Rahaman and colleagues, which discusses the possible formation/existence of traversable wormholes in our own galaxy, Milky Way. They concluded that traversable wormholes may exist both at the inner and outer parts of our spiral galaxy which has been revised by using a different density distribution by Ovgun and Halilsoy in their current study.
The properties of transversable wormholes under Einasto DM profile is listed below:
• Spherically symmetric, static metric,
• Satisfy the Einstein field equations,
• No event horizon, i. e. e^f(r) ≠ 0,
• ”Throat” r = r0 (where, r0 is minimum radius condition that any wormhole must satisfy) connects 2 asymptotically flat space-time regions, (for Milky Way galaxy r0 = 9.11 kpc)
• The stress-energy tensor (violating the null-energy condition (NEC) with ρ + pr < 0, where ρ is the energy density and pr the radial pressure),
• Physically reasonable construction materials, (for Milky Way galaxy ρ0 = 5 × 10-²⁴ (r0/8.6 kpc)-¹ g cm-³)
• Bearable tidal gravitational forces,
• Satisfy the flare-out condition at the throat (b'(rth) < 1), while b(r) < r near the throat,
• Finite and reasonable crossing time,
• Stable against perturbations.
Their (Ovgun’s) analysis suggested accordingly that at the central region since the NEC is not violated, they do not get any traversable wormholes. This explains also the choice of the throat outside of the central region. Yet, at the outer regions, the NEC is violated so that the flare-out condition for traversable wormhole is satisfied and they expect formation of traversable wormholes. Their result is not specific to Milky Way alone but is valid for any spiral galaxy once it obeys a mass distribution given by Einosto profile.
It is worthwhile therefore to check other mass distributions and see the resulting consequences.— said Halilsoy
Based on such a model we have shown that traversable wormholes in the outer regions of spiral galaxies are possible while the inner part regions prohibit such formations.— said Ovgun.
Reference: Övgün, A., Halilsoy, M. Existence of traversable wormholes in the spherical stellar systems. Astrophys Space Sci 361, 214 (2016). https://link.springer.com/article/10.1007/s10509-016-2803-3 https://doi.org/10.1007/s10509-016-2803-3
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