False vacuum
In quantum field theory, a false vacuum is a hypothetical vacuum that is somewhat, but not entirely, stable. It may last for a very long time in that state, and might eventually move to a more stable state. The most common suggestion of how such a change might happen is called bubble nucleation – if a small region of the universe by chance reached a more stable vacuum, this "bubble" (also called "bounce")[1][2] would spread.
A false vacuum exists at a local minimum of energy and is therefore not stable, in contrast to a true vacuum, which exists at a global minimum and is stable. It may be very long-lived, or metastable.
Definition of true vs false vacuum
A vacuum is defined as a space with as little energy in it as possible. Despite the name, the vacuum still has quantum fields. A true vacuum is a global minimum of energy, and is commonly assumed to coincide with a physical vacuum state we live in.
Synonyms for physical vacuum state are the following: Standard Model vacuum, normal vacuum, normal space, physical space, our space-time, fabric of space-time, universe.
The configuration with quantum fields at global energy minimum is stable. The false vacuum is a local minimum, but not the lowest energy state of quantum fields.
It is possible that a physical vacuum state is a configuration of quantum fields representing a local minimum but not global minimum of energy. In this case vacuum state is called a "false vacuum".
Implications
Existential threat
If a more stable vacuum state were able to arise, the effects may vary from complete cessation of existing fundamental forces, elementary particles and structures comprising them, to subtle change in some cosmological parameters, mostly depending on potential difference between true and false vacuum. Some false vacuum decay scenarios are compatible with survival of structures like galaxies and stars[3][4] or even life[5] while others involve the full destruction of baryonic matter[6] or even immediate gravitational collapse of the universe,[7]^Note 1 although in this last case the possibility to causally connect (i.e nucleate) the true vacuum from inside of the false vacuum area is dubious.[8]
In a 2005 paper published in Nature, as part of their investigation into global catastrophic risks, MIT physicist Max Tegmark and Oxford philosopher Nick Bostrom calculate the natural risks of the destruction of the Earth at less than 1 per gigayear from all events, including a transition to a lower vacuum state. They argue that due to observer selection effects, we might underestimate the chances of being destroyed by vacuum decay because any information about this event would reach us only at the instant when we too were destroyed. This is in contrast to events like risks from impacts, gamma-ray bursts, supernovae and hypernovae, the frequencies of which we have adequate direct measures.[9]
Inflation
- The inflation itself may be the consequence of the Higgs field trapped in a false vacuum state[10] with Higgs self-coupling λ and its βλ function very close to zero at the Planck scale.[11]:218 A future electron-positron collider would be able to provide the precise measurements of the top quark needed for such calculations.[11]
- Chaotic Inflation Theory suggests that the universe may be in either a false vacuum or a true vacuum state.
- Alan Guth, in his original proposal for cosmic inflation,[12] proposed that inflation could end through quantum mechanical bubble nucleation of the sort described above. See History of Chaotic inflation theory. It was soon understood that a homogeneous and isotropic universe could not be preserved through the violent tunneling process. This led Andrei Linde[13] and, independently, Andreas Albrecht and Paul Steinhardt,[14] to propose "new inflation" or "slow roll inflation" in which no tunnelling occurs, and the inflationary scalar field instead graphs as a gentle slope.
Vacuum decay varieties
Electroweak vacuum decay
The stability criteria for Electroweak interaction was first formulated in 1979 [15] as a function of the masses of the theoretical Higgs boson and the heaviest fermion. Discovery of the Top quark in 1995 and the Higgs boson in 2012 have allowed physicists to validate the criteria against experiment, therefore since 2012 Electroweak interaction is considered as the most promising candidate for metastable fundamental force.[11]. The corresponding false vacuum hypothesis is called either 'Electroweak vacuum instability' or 'Higgs vacuum instability'.[16]. The present false vacuum state is called (De Sitter space), while tentative true vacuum is called (Anti-de Sitter space).[17][18]
The diagrams on the right show the uncertainty ranges of Higgs boson and top quark masses as oval-shaped lines. Underlying colors indicate if the electroweak vacuum state is likely to be stable, merely long-lived or completely unstable for given combination of masses.[19] [20] The "electroweak vacuum decay" hypothesis was sometimes misreported as the Higgs boson "ending" the universe.[21] [22][23] A 125.18±0.16 GeV/c2[24] Higgs boson mass is likely to be on the metastable side of stable-metastable boundary (estimated in 2012 as 123.8–135.0 GeV. [11] ) However, a definitive answer requires much more precise measurements of the top quark's pole mass,[11], although improved measurement precision of Higgs boson and top quark masses further reinforced the claim of physical electroweak vacuum being in the metastable state as of 2018.[2] Nonetheless, new physics beyond the Standard Model of Particle Physics could drastically change the stability landscape division lines, rendering previous stability and metastability criteria incorrect. [25][26]
If measurements of the Higgs boson and top quark suggest that our universe lies within a false vacuum of this kind, this would imply that, more than likely in many billions of years,[27] the bubble's effects will propagate across the universe at nearly the speed of light from its origin in space-time.
Other decay modes
- Decay to smaller Vacuum expectation value, resulting in decrease of Casimir effect and destabilization of proton.[6]
- Decay to vacuum with larger neutrino mass (may have happened relatively recently).[3]
- Decay to vacuum with no dark energy[4]
True vacuum bubble nucleation
In the theoretical physics of the false vacuum, the system moves to a lower energy state – either the true vacuum, or another, lower energy vacuum – through a process known as bubble nucleation.[28][29][30][31][32][1] In this, instanton effects cause a bubble to appear in which fields have their true vacuum values inside. Therefore, the interior of the bubble has a lower energy. The walls of the bubble (or domain walls) have a surface tension, as energy is expended as the fields roll over the potential barrier to the lower energy vacuum. The critical size of the bubble is determined in the semi-classical approximation to be such that the bubble has zero total change in the energy: the decrease in energy by the true vacuum in the interior is compensated by the tension of the walls.
To convert initially small true vacuum bubble (bounce) into bubble with zero total energy, an energy barrier must be overcome, and barrier height is follows equation[1]
-
(Eq. 1)
, where is the potential difference between true and false vacuums, is the unknown constant (surface tension of interface between different vacua), and is the radius of the bubble. Perhaps the unknown constant is so high that a bubble large enough to have barrier vanished has never yet been formed anywhere in the universe. Rewriting the Eq. 1, one can get true vacuum bubble critical radius as
-
(Eq. 2)
Bubble of true vacuum smaller than critical size can overcome the potential barrier due to the quantum tunnelling of instantons to lower energy states. Tunneling can be caused by quantum fluctuations, and tunneling rate to expanding state for bubble smaller than critical size can be expressed as[33]
-
(Eq. 3)
where is Planck constant.
Also, small bubbles of true vacuum can be inflated to critical size by externally supplied energy,[34] although required energy densities are several orders of magnitude beyond the capability of any natural or artificial process.[6] Energy-driven bubble inflation mechanism should not be confused with the speculative nucleation barrier lowering by gravity field of miniature black holes.
False vacuum decay nucleation seeds
- In a study in 2015,[35] it was pointed out that the vacuum decay rate could be vastly increased in the vicinity of black holes, which would serve as a nucleation seed.[36] According to this study a potentially catastrophic vacuum decay could be triggered at any time by primordial black holes, should they exist. The subsequent study in 2017 has indicated that the nucleated true vacuum bubble would collapse into a primordial black hole rather than originate from it.[37] In 2019, it was found that although small non-spinning black holes may increase true vacuum nucleation rate, rapidly spinning black holes will stabilize false vacuums to decay rates lower than expected for flat space-time.[38]
- If particle collisions produce mini black holes then energetic collisions such as the ones produced in the Large Hadron Collider (LHC) could trigger such a vacuum decay event. This scenario is publicized yet more than likely unrealistic, because if such mini black holes can be created in collisions, they would also be created in the much more energetic collisions of cosmic radiation particles with planetary surfaces or during early epoch as tentative primordial black holes.[39] Hut and Rees[40] note that, because we have observed cosmic ray collisions at much higher energies than those produced in terrestrial particle accelerators, these experiments should not, at least for the foreseeable future, pose a threat to our current vacuum. Particle accelerators have reached energies of only approximately eight tera electron volts (8×1012 eV). Cosmic ray collisions have been observed at and beyond energies of 5*1019 eV, six million times more powerful – the so-called Greisen–Zatsepin–Kuzmin limit – and cosmic rays in vicinity of origin may be more powerful yet. Against this, John Leslie has argued[41] that if present trends continue, particle accelerators will exceed the energy given off in naturally occurring cosmic ray collisions by the year 2150. Fears of this kind were raised by critics of both the Relativistic Heavy Ion Collider and the Large Hadron Collider at the time of their respective proposal, and determined to be unfounded by scientific inquiry.
- In a study in 2020, it was proposed that cosmic string may also serve as nucleation site for the false vacuum decay.[42]
- Nucleation energy barrier can be overcome by extreme energy density associated with magnetic monopole.[6]
Expansion of bubble
As soon as a bubble of lower-energy vacuum grows beyond the critical radius defined by Eq. 2, the bubble's wall will begin to accelerate outward. The expansion will then decrease the bubble`s potential energy, as the energy of the wall increases as the surface area of a sphere but the negative contribution of the interior increases more quickly, as the volume of a sphere . With the expected large potential differences between false and true vacuum states in most vacuum decay scenarios, the velocity of the bubble surface becomes practically indistinguishable from the speed of light in a fraction of second. The single bubble does not produce any gravitational effects on surrounding objects during expansion, because the negative energy density of the bubble interior is cancelled by the positive kinetic energy of the wall.[7] If two bubbles are nucleated and they eventually collide, it is thought that particle production would occur where the walls collide.
False vacuum decay in fiction
False vacuum decay event is occasionally used as a plot device in works picturing a doomsday event.
- 1988 by Geoffrey A. Landis in a science-fiction story[43]
- 2000 by Stephen Baxter[44]
- 2002 by Greg Egan in his science fiction novel Schild's Ladder
- 2008 by Koji Suzuki in his science fiction novel EDGE
- 2015 by Alastair Reynolds in his novel Poseidon's Wake
- 2015 by Phillip P. Peterson in his science fiction novel Paradox
See also
- Eternal inflation
- Inflation (cosmology) – Theory of rapid universe expansion
- Supercooling – Lowering the temperature of a liquid or gas below freezing without it becoming a solid
- Superheating
- Void
Notes
- ^Note 1 A paper by Coleman and de Luccia which attempted to include simple gravitational assumptions into these theories noted that if this was an accurate representation of nature, then the resulting universe "inside the bubble" in such a case would appear to be extremely unstable and would almost immediately collapse:
In general, gravitation makes the probability of vacuum decay smaller; in the extreme case of very small energy-density difference, it can even stabilize the false vacuum, preventing vacuum decay altogether. We believe we understand this. For the vacuum to decay, it must be possible to build a bubble of total energy zero. In the absence of gravitation, this is no problem, no matter how small the energy-density difference; all one has to do is make the bubble big enough, and the volume/surface ratio will do the job. In the presence of gravitation, though, the negative energy density of the true vacuum distorts geometry within the bubble with the result that, for a small enough energy density, there is no bubble with a big enough volume/surface ratio. Within the bubble, the effects of gravitation are more dramatic. The geometry of space-time within the bubble is that of anti-de Sitter space, a space much like conventional de Sitter space except that its group of symmetries is O(3, 2) rather than O(4, 1). Although this space-time is free of singularities, it is unstable under small perturbations, and inevitably suffers gravitational collapse of the same sort as the end state of a contracting Friedmann universe. The time required for the collapse of the interior universe is on the order of ... microseconds or less.
The possibility that we are living in a false vacuum has never been a cheering one to contemplate. Vacuum decay is the ultimate ecological catastrophe; in the new vacuum there are new constants of nature; after vacuum decay, not only is life as we know it impossible, so is chemistry as we know it. However, one could always draw stoic comfort from the possibility that perhaps in the course of time the new vacuum would sustain, if not life as we know it, at least some structures capable of knowing joy. This possibility has now been eliminated.
The second special case is decay into a space of vanishing cosmological constant, the case that applies if we are now living in the debris of a false vacuum which decayed at some early cosmic epoch. This case presents us with less interesting physics and with fewer occasions for rhetorical excess than the preceding one. It is now the interior of the bubble that is ordinary Minkowski space ...
References
- C. Callan; S. Coleman (1977). "Fate of the false vacuum. II. First quantum corrections". Phys. Rev. D16 (6): 1762–68. Bibcode:1977PhRvD..16.1762C. doi:10.1103/physrevd.16.1762.
- Tommi Markkanen et al., Cosmological Aspects of Higgs Vacuum Metastability
- Lorenz, Christiane S.; Funcke, Lena; Calabrese, Erminia; Hannestad, Steen (2019). "Time-varying neutrino mass from a supercooled phase transition: Current cosmological constraints and impact on the Ωm−σ8 plane". Physical Review D. 99 (2): 023501. arXiv:1811.01991. doi:10.1103/PhysRevD.99.023501. S2CID 119344201.
- Landim, Ricardo G.; Abdalla, Elcio (2017). "Metastable dark energy". Physics Letters B. 764: 271–276. arXiv:1611.00428. Bibcode:2017PhLB..764..271L. doi:10.1016/j.physletb.2016.11.044. S2CID 119279028.
- Crone, Mary M.; Sher, Marc (1991). "The environmental impact of vacuum decay". American Journal of Physics. 59 (1): 25. Bibcode:1991AmJPh..59...25C. doi:10.1119/1.16701.
- M.S. Turner; F. Wilczek (1982). "Is our vacuum metastable?" (PDF). Nature. 298 (5875): 633–634. Bibcode:1982Natur.298..633T. doi:10.1038/298633a0. S2CID 4274444. Retrieved 2015-10-31.
- Coleman, Sidney; De Luccia, Frank (1980-06-15). "Gravitational effects on and of vacuum decay" (PDF). Physical Review D. 21 (12): 3305–3315. Bibcode:1980PhRvD..21.3305C. doi:10.1103/PhysRevD.21.3305.
- Banks, T. (2002). "Heretics of the False Vacuum: Gravitational Effects on and of Vacuum Decay 2". arXiv:hep-th/0211160.
- M. Tegmark; N. Bostrom (2005). "Is a doomsday catastrophe likely?" (PDF). Nature. 438 (5875): 754. Bibcode:2005Natur.438..754T. doi:10.1038/438754a. PMID 16341005. S2CID 4390013. Archived from the original (PDF) on 2014-04-09. Retrieved 2016-03-16.
- [http://publish.uwo.ca/~csmeenk2/files/FalseVacuum.pdf Chris Smeenk, False Vacuum: Early Universe Cosmology and the Development of Inflation]
- Alekhin, S.; Djouadi, A.; Moch, S.; Hoecker, A.; Riotto, A. (2012-08-13). "The top quark and Higgs boson masses and the stability of the electroweak vacuum". Physics Letters B. 716 (1): 214–219. arXiv:1207.0980. Bibcode:2012PhLB..716..214A. doi:10.1016/j.physletb.2012.08.024. S2CID 28216028.
- A. H. Guth (1981-01-15). "The Inflationary Universe: A Possible Solution to the Horizon and Flatness Problems". Physical Review D. 23 (2): 347–356. Bibcode:1981PhRvD..23..347G. doi:10.1103/physrevd.23.347. OCLC 4433735058.
- A. Linde (1982). "A New Inflationary Universe Scenario: A Possible Solution Of The Horizon, Flatness, Homogeneity, Isotropy And Primordial Monopole Problems". Phys. Lett. B. 108 (6): 389. Bibcode:1982PhLB..108..389L. doi:10.1016/0370-2693(82)91219-9.
- A. Albrecht; P. J. Steinhardt (1982). "Cosmology For Grand Unified Theories With Radiatively Induced Symmetry Breaking". Phys. Rev. Lett. 48 (17): 1220–1223. Bibcode:1982PhRvL..48.1220A. doi:10.1103/PhysRevLett.48.1220.
- N. Cabibbo, L. Maiani, G. Parisi and R. Petronzio, Bounds on the Fermions and Higgs Boson Masses in Grand Unified Theories, 1979
- Kohri, Kazunori; Matsui, Hiroki (2018). "Electroweak vacuum instability and renormalized vacuum field fluctuations in Friedmann-Lemaitre-Robertson-Walker background". Physical Review D. 98 (10): 103521. arXiv:1704.06884. Bibcode:2018PhRvD..98j3521K. doi:10.1103/PhysRevD.98.103521. S2CID 39999058.
- Hook, Anson; Kearney, John; Shakya, Bibhushan; Zurek, Kathryn M. (2015). "Probable or improbable universe? Correlating electroweak vacuum instability with the scale of inflation". Journal of High Energy Physics. 2015 (1): 61. arXiv:1404.5953. Bibcode:2015JHEP...01..061H. doi:10.1007/JHEP01(2015)061. S2CID 118737905.
- Kohri, Kazunori; Matsui, Hiroki (2017). "Electroweak vacuum instability and renormalized Higgs field vacuum fluctuations in the inflationary universe". Journal of Cosmology and Astroparticle Physics. 2017 (8): 011. arXiv:1607.08133. Bibcode:2017JCAP...08..011K. doi:10.1088/1475-7516/2017/08/011. S2CID 119216421.
- Ellis, J.; Espinosa, J.R.; Giudice, G.F.; Hoecker, A.; Riotto, A. (2009). "The Probable Fate of the Standard Model". Phys. Lett. B. 679 (4): 369–375. arXiv:0906.0954. Bibcode:2009PhLB..679..369E. doi:10.1016/j.physletb.2009.07.054. S2CID 17422678.
- Masina, Isabella (2013-02-12). "Higgs boson and top quark masses as tests of electroweak vacuum stability". Phys. Rev. D. 87 (5): 053001. arXiv:1209.0393. Bibcode:2013PhRvD..87e3001M. doi:10.1103/physrevd.87.053001.
- Klotz, Irene (2013-02-18). "Universe Has Finite Lifespan, Higgs Boson Calculations Suggest". Huffington Post. Reuters. Retrieved 21 February 2013.
Earth will likely be long gone before any Higgs boson particles set off an apocalyptic assault on the universe
- Hoffman, Mark (2013-02-19). "Higgs Boson Will Destroy The Universe Eventually". ScienceWorldReport. Retrieved 21 February 2013.
- "Higgs boson will aid in creation of the universe—and how it will end". Catholic Online/NEWS CONSORTIUM. 2013-02-20. Archived from the original on 26 September 2013. Retrieved 21 February 2013.
[T]he Earth will likely be long gone before any Higgs boson particles set off an apocalyptic assault on the universe
- M. Tanabashi et al. (Particle Data Group) (2018). "Review of Particle Physics". Physical Review D. 98 (3): 1–708. Bibcode:2018PhRvD..98c0001T. doi:10.1103/PhysRevD.98.030001. PMID 10020536.
- Salvio, Alberto (2015-04-09). "A Simple Motivated Completion of the Standard Model below the Planck Scale: Axions and Right-Handed Neutrinos". Physics Letters B. 743: 428–434. arXiv:1501.03781. Bibcode:2015PhLB..743..428S. doi:10.1016/j.physletb.2015.03.015. S2CID 119279576.CS1 maint: ref=harv (link)
- Branchina, Vincenzo; Messina, Emanuele; Platania, Alessia (2014). "Top mass determination, Higgs inflation, and vacuum stability". Journal of High Energy Physics. 2014 (9): 182. arXiv:1407.4112. Bibcode:2014JHEP...09..182B. doi:10.1007/JHEP09(2014)182. S2CID 102338312.
- Boyle, Alan (2013-02-19). "Will our universe end in a 'big slurp'? Higgs-like particle suggests it might". NBC News' Cosmic log. Retrieved 21 February 2013.
[T]he bad news is that its mass suggests the universe will end in a fast-spreading bubble of doom. The good news? It'll probably be tens of billions of years
. The article quotes Fermilab's Joseph Lykken: "[T]he parameters for our universe, including the Higgs [and top quark's masses] suggest that we're just at the edge of stability, in a "metastable" state. Physicists have been contemplating such a possibility for more than 30 years. Back in 1982, physicists Michael Turner and Frank Wilczek wrote in Nature that "without warning, a bubble of true vacuum could nucleate somewhere in the universe and move outwards..." - M. Stone (1976). "Lifetime and decay of excited vacuum states". Phys. Rev. D. 14 (12): 3568–3573. Bibcode:1976PhRvD..14.3568S. doi:10.1103/PhysRevD.14.3568.
- P.H. Frampton (1976). "Vacuum Instability and Higgs Scalar Mass". Phys. Rev. Lett. 37 (21): 1378–1380. Bibcode:1976PhRvL..37.1378F. doi:10.1103/PhysRevLett.37.1378.
- M. Stone (1977). "Semiclassical methods for unstable states". Phys. Lett. B. 67 (2): 186–188. Bibcode:1977PhLB...67..186S. doi:10.1016/0370-2693(77)90099-5.
- P.H. Frampton (1977). "Consequences of Vacuum Instability in Quantum Field Theory". Phys. Rev. D. 15 (10): 2922–28. Bibcode:1977PhRvD..15.2922F. doi:10.1103/PhysRevD.15.2922.
- S. Coleman (1977). "Fate of the false vacuum: Semiclassical theory". Phys. Rev. D. 15 (10): 2929–36. Bibcode:1977PhRvD..15.2929C. doi:10.1103/physrevd.15.2929.
- Wenyuan Ai, Aspects of False Vacuum Decay (2019)
- Arnold, Peter (1992). "A Review of the Instability of Hot Electroweak Theory and its Bounds on $m_h$ and $m_t$". arXiv:hep-ph/9212303.
- Burda, Philipp; Gregory, Ruth; Moss, Ian G. (2015). "Vacuum metastability with black holes". Journal of High Energy Physics. 2015 (8): 114. arXiv:1503.07331. Bibcode:2015JHEP...08..114B. doi:10.1007/JHEP08(2015)114. ISSN 1029-8479. S2CID 53978709.
- "Could Black Holes Destroy the Universe?". 2015-04-02.
- Deng, Heling; Vilenkin, Alexander (2017). "Primordial black hole formation by vacuum bubbles". Journal of Cosmology and Astroparticle Physics. 2017 (12): 044. arXiv:1710.02865. Bibcode:2017JCAP...12..044D. doi:10.1088/1475-7516/2017/12/044. S2CID 119442566.
- Oshita, Naritaka; Ueda, Kazushige; Yamaguchi, Masahide (2020). "Vacuum decays around spinning black holes". Journal of High Energy Physics. 2020 (1): 015. arXiv:1909.01378. Bibcode:2020JHEP...01..015O. doi:10.1007/JHEP01(2020)015. S2CID 202541418.
- Cho, Adrian (2015-08-03). "Tiny black holes could trigger collapse of universe—except that they don't". Sciencemag.org.
- P. Hut; M.J. Rees (1983). "How stable is our vacuum?". Nature. 302 (5908): 508–509. Bibcode:1983Natur.302..508H. doi:10.1038/302508a0. S2CID 4347886.
- John Leslie (1998). The End of the World:The Science and Ethics of Human Extinction. Routledge. ISBN 978-0-415-14043-0.
- Firouzjahi, Hassan; Karami, Asieh; Rostami, Tahereh (2020). "Vacuum decay in the presence of a cosmic string". Physical Review D. 101 (10): 104036. arXiv:2002.04856. Bibcode:2020PhRvD.101j4036F. doi:10.1103/PhysRevD.101.104036. S2CID 211082988.
- Geoffrey A. Landis (1988). "Vacuum States". Isaac Asimov's Science Fiction: July.
- Stephen Baxter (2000). Time. ISBN 978-0-7653-1238-9.
Further reading
- Johann Rafelski and Berndt Muller (1985). The Structured Vacuum – thinking about nothing. Harri Deutsch. ISBN 978-3-87144-889-8.
- Sidney Coleman (1988). Aspects of Symmetry: Selected Erice Lectures. ISBN 978-0-521-31827-3.
External links
- The SimpleBounce package calcualtes the Euclidean action for the bounce solution which contribute to the false vacuum decay
- Free pdf copy of The Structured Vacuum – thinking about nothing by Johann Rafelski and Berndt Muller (1985) ISBN 3-87144-889-3.
- An Eternity of Bubbles? by Alan Guth
- The Decay of the False Vacuum by Sten Odenwald
- Simulation of False Vacuum Decay by Bubble Nucleation on YouTube – Joel Thorarinson