Phantom energy

Phantom energy is a hypothetical form of dark energy satisfying the equation of state ${\displaystyle P=w\rho c^{2}}$ with ${\displaystyle w<-1}$. It possesses negative kinetic energy, and predicts expansion of the universe in excess of that predicted by a cosmological constant, which leads to a Big Rip. The idea of phantom energy is often dismissed, as it would suggest that the vacuum is unstable with negative mass particles bursting into existence.^[1] The concept is hence tied to emerging theories of a continuously created negative mass dark fluid, in which the cosmological constant can vary as a function of time.^[2][3]

Big Rip mechanism

Main article: Big Rip

The existence of phantom energy could cause the expansion of the universe to accelerate so quickly that a scenario known as the Big Rip, a possible end to the universe, occurs. The expansion of the universe reaches an infinite degree in finite time, causing expansion to accelerate without bounds. This acceleration necessarily passes the speed of light (since it involves expansion of the universe itself, not particles moving within it), causing more and more objects to leave our observable universe faster than its expansion, as light and information emitted from distant stars and other cosmic sources cannot "catch up" with the expansion. As the observable universe expands, objects will be unable to interact with each other via fundamental forces, and eventually, the expansion will prevent any action of forces between any particles, even within atoms, "ripping apart" the universe, making distances between individual particles infinite.

One application of phantom energy in 2007 was to a cyclic model of the universe, which reverses its expansion extremely shortly before the would-be Big Rip.^[4] This cyclic model can be more complicated if the mass–energy of every point in the universe dense enough to collapse into black hole core substance that will bounce after reaching a maximum threshold of compression causing the next big bang (the overall scenario is highly unlikely).

See also

• Quintessence (physics)

References

1. Carroll, Sean (September 14, 2004). "Vacuum stability". Preposterous Universe Blog. Retrieved February 1, 2019.; however, note that the preceding source also contains a link to another blog post on the same blog (a post dated one day earlier!) that also discusses (a lot) the topic of "${\displaystyle w<-1}$", etc.; therefore, [feel free to] "see also": Carroll, Sean (September 13, 2004). "Phantom Energy". "Preposterous Universe" [blog]. Archived from the original on October 28, 2014. Retrieved November 2, 2020.
2. Farnes, J. S. (2018). "A Unifying Theory of Dark Energy and Dark Matter: Negative Masses and Matter Creation within a Modified ΛCDM Framework". Astronomy and Astrophysics. 620: A92. arXiv:1712.07962. Bibcode:2018A&A...620A..92F. doi:10.1051/0004-6361/201832898. S2CID 53600834.
3. Farnes, Jamie (December 17, 2018). "Bizarre 'Dark Fluid' with Negative Mass Could Dominate the Universe". Space.com.
4. Lauris Baum and Paul Frampton (2007). "Turnaround In Cyclic Cosmology". Phys. Rev. Lett. 98 (7): 071301. arXiv:hep-th/0610213. Bibcode:2007PhRvL..98g1301B. doi:10.1103/PhysRevLett.98.071301. PMID 17359014. S2CID 17698158.

Further reading

• Robert R. Caldwell et al.: Phantom Energy and Cosmic Doomsday