Brane cosmology

Brane cosmologyrefers to several theories inparticle physicsandcosmologyrelated tostring theory,superstring theoryandM-theory.

Brane and bulk

Animation showing multiple brane universes in the bulk

The central idea is that the visible, four-dimensionalspacetimeis restricted to abraneinside ahigher-dimensionalspace, called the "bulk" (also known as "hyperspace" ). If the additionaldimensionsarecompact,then the observed universe contains the extra dimension, and then no reference to the bulk is appropriate. In the bulk model, at least some of the extra dimensions are extensive (possibly infinite), and other branes may be moving through this bulk. Interactions with the bulk, and possibly with other branes, can influence our brane and thus introduce effects not seen in more standard cosmological models.

Why gravity is weak and the cosmological constant is small

Some versions of brane cosmology, based on thelarge extra dimensionidea, can explain the weakness ofgravityrelative to the otherfundamental forcesof nature, thus solving thehierarchy problem.In the brane picture, theelectromagnetic,weakandstrong nuclear forceare localized on the brane, but gravity has no such constraint and propagates on the full spacetime, called the bulk. Much of the gravitational attractive power "leaks" into the bulk. As a consequence, the force of gravity should appear significantly stronger on small (subatomic or at least sub-millimetre) scales, where less gravitational force has "leaked". Various experiments are currently under way to test this.^[1]Extensions of the large extra dimension idea withsupersymmetryin the bulk appear to be promising in addressing the so-calledcosmological constant problem.^[2]^[3]^[4]

Models of brane cosmology

One of the earliest documented attempts to apply brane cosmology as part of a conceptual theory is dated to 1983.^[5]

The authors discussed the possibility that the Universe has $(3+N)+1$ dimensions, but ordinary particles are confined in a potential well which is narrow along $N$ spatial directions and flat along three others, and proposed a particular five-dimensional model.

In 1998/99,Merab Gogberashvilipublished onarXiva number of articles where he showed that if the Universe is considered as a thin shell (a mathematicalsynonymfor "brane" ) expanding in 5-dimensional space then there is a possibility to obtain one scale for particle theory corresponding to the 5-dimensionalcosmological constantand Universe thickness, and thus to solve thehierarchy problem.^[6]^[7]Gogberashvili also showed that the four-dimensionality of the Universe is the result of thestabilityrequirement found in mathematics since the extra component of theEinstein field equationsgiving the confined solution formatterfields coincides with one of the conditions of stability.^[8]

In 1999, there were proposed the closely relatedRandall–Sundrumscenarios, RS1 and RS2. (SeeRandall–Sundrum modelfor a nontechnical explanation of RS1). These particular models of brane cosmology have attracted a considerable amount of attention. For instance, the related Chung-Freese model, which has applications forspacetime metric engineering,followed in 2000.^[9]

Later, theekpyroticandcyclicproposals appeared. The ekpyrotic theory hypothesizes that the origin of theobservable universeoccurred when two parallel branes collided.^[10]

Empirical tests

As of now, no experimental or observational evidence oflarge extra dimensions,as required by the Randall–Sundrum models, has been reported. An analysis of results from theLarge Hadron Colliderin December 2010 severely constrains the black holes produced in theories with large extra dimensions.^[11]Therecent multi-messenger gravitational wave event GW170817has also been used to put weak limits on large extra dimensions.^[12]^[13]

References

^"Session D9 - Experimental Tests of Short Range Gravitation".flux.aps.org.
^Aghababaie, Y.; Burgess, C. P.; Parameswaran, S. L.; Quevedo, F. (March 2004). "Towards a naturally small cosmological constant from branes in 6-D supergravity".Nucl. Phys. B.680(1–3): 389–414.arXiv:hep-th/0304256.Bibcode:2004NuPhB.680..389A.doi:10.1016/j.nuclphysb.2003.12.015.S2CID 14612396.
^Burgess, C. P.; van Nierop, Leo (March 2013). "Technically Natural Cosmological Constant From Supersymmetric 6D Brane Backreaction".Phys. Dark Univ.2(1): 1–16.arXiv:1108.0345.Bibcode:2013PDU.....2....1B.doi:10.1016/j.dark.2012.10.001.S2CID 92984489.
^P. Burgess, C.; van Nierop, L.; Parameswaran, S.; Salvio, A.; Williams, M. (February 2013)."Accidental SUSY: Enhanced Bulk Supersymmetry from Brane Back-reaction".JHEP.2013(2): 120.arXiv:1210.5405.Bibcode:2013JHEP...02..120B.doi:10.1007/JHEP02(2013)120.S2CID 53667729.
^Rubakov, V. A.; Shaposhnikov, M. E. (1983). "Do we live inside a domain wall?".Physics Letters.B.125(2–3): 136–138.Bibcode:1983PhLB..125..136R.doi:10.1016/0370-2693(83)91253-4.
^Gogberashvili, M. (1998). "Hierarchy problem in the shell universe model".International Journal of Modern Physics D.11(10): 1635–1638.arXiv:hep-ph/9812296.doi:10.1142/S0218271802002992.S2CID 119339225.
^Gogberashvili, M. (2000). "Our world as an expanding shell".Europhysics Letters.49(3): 396–399.arXiv:hep-ph/9812365.Bibcode:2000EL.....49..396G.doi:10.1209/epl/i2000-00162-1.S2CID 38476733.
^Gogberashvili, M. (1999). "Four dimensionality in noncompact Kaluza–Klein model".Modern Physics Letters A.14(29): 2025–2031.arXiv:hep-ph/9904383.Bibcode:1999MPLA...14.2025G.doi:10.1142/S021773239900208X.S2CID 16923959.
^Chung, Daniel J. H.; Freese, Katherine (2000-08-25). "Can geodesics in extra dimensions solve the cosmological horizon problem?".Physical Review D.62(6): 063513.arXiv:hep-ph/9910235.Bibcode:2000PhRvD..62f3513C.doi:10.1103/physrevd.62.063513.ISSN 0556-2821.S2CID 119511533.
^Musser, George; Minkel, J. R. (2002-02-11)."A Recycled Universe: Crashing branes and cosmic acceleration may power an infinite cycle in which our universe is but a phase".Scientific American Inc.Retrieved2008-05-03.
^Khachatryan, V.; et al. (2011). "Search for Microscopic Black Hole Signatures at the Large Hadron Collider".Physics Letters B.697(5): 434–453.arXiv:1012.3375.Bibcode:2011PhLB..697..434C.doi:10.1016/j.physletb.2011.02.032.S2CID 118488193.
^Visinelli, Luca; Bolis, Nadia; Vagnozzi, Sunny (March 2018). "Brane-world extra dimensions in light of GW170817".Phys. Rev. D.97(6): 064039.arXiv:1711.06628.Bibcode:2018PhRvD..97f4039V.doi:10.1103/PhysRevD.97.064039.S2CID 88504420.
^Freeland, Emily (2018-09-21)."Hunting for extra dimensions with gravitational waves".The Oskar Klein Centre for Cosmoparticle Physics blog. Archived fromthe originalon 2021-01-27.Retrieved2018-11-30.

External links

Brane cosmology on arxiv.org.
Brax, Philippe;van de Bruck, Carsten(2003). "Cosmology and Brane Worlds: A Review".Classical and Quantum Gravity.20(9): R201–R232.arXiv:hep-th/0303095.Bibcode:2003CQGra..20R.201B.doi:10.1088/0264-9381/20/9/202.S2CID 9623407.– Cosmological consequences of the brane world scenario are reviewed in a pedagogical manner.
Dimensional Shortcuts – evidence for sterile neutrino; (August 2007; Scientific American)
Langlois, David(2003). "Brane cosmology: an introduction".Progress of Theoretical Physics Supplement.148:181–212.arXiv:hep-th/0209261.Bibcode:2002PThPS.148..181L.doi:10.1143/PTPS.148.181.S2CID 9751130.– These notes (32 pages) give an introductory review on brane cosmology.
Papantonopoulos, Eleftherios(2002). "Brane Cosmology".Cosmological Crossroads.Lecture Notes in Physics. Vol. 592. pp. 458–477.arXiv:hep-th/0202044.Bibcode:2002LNP...592..458P.doi:10.1007/3-540-48025-0_15.ISBN 978-3-540-43778-9.S2CID 3084654.– Lectures (24 pages) presented at the First Aegean Summer School on Cosmology,Samos,September 2001.

[1] "Session D9 - Experimental Tests of Short Range Gravitation".flux.aps.org.

[2] Aghababaie, Y.; Burgess, C. P.; Parameswaran, S. L.; Quevedo, F. (March 2004). "Towards a naturally small cosmological constant from branes in 6-D supergravity".Nucl. Phys. B.680(1–3): 389–414.arXiv:hep-th/0304256.Bibcode:2004NuPhB.680..389A.doi:10.1016/j.nuclphysb.2003.12.015.S2CID 14612396.

[3] Burgess, C. P.; van Nierop, Leo (March 2013). "Technically Natural Cosmological Constant From Supersymmetric 6D Brane Backreaction".Phys. Dark Univ.2(1): 1–16.arXiv:1108.0345.Bibcode:2013PDU.....2....1B.doi:10.1016/j.dark.2012.10.001.S2CID 92984489.

[4] P. Burgess, C.; van Nierop, L.; Parameswaran, S.; Salvio, A.; Williams, M. (February 2013)."Accidental SUSY: Enhanced Bulk Supersymmetry from Brane Back-reaction".JHEP.2013(2): 120.arXiv:1210.5405.Bibcode:2013JHEP...02..120B.doi:10.1007/JHEP02(2013)120.S2CID 53667729.

[5] Rubakov, V. A.; Shaposhnikov, M. E. (1983). "Do we live inside a domain wall?".Physics Letters.B.125(2–3): 136–138.Bibcode:1983PhLB..125..136R.doi:10.1016/0370-2693(83)91253-4.

[6] Gogberashvili, M. (1998). "Hierarchy problem in the shell universe model".International Journal of Modern Physics D.11(10): 1635–1638.arXiv:hep-ph/9812296.doi:10.1142/S0218271802002992.S2CID 119339225.

[7] Gogberashvili, M. (2000). "Our world as an expanding shell".Europhysics Letters.49(3): 396–399.arXiv:hep-ph/9812365.Bibcode:2000EL.....49..396G.doi:10.1209/epl/i2000-00162-1.S2CID 38476733.

[8] Gogberashvili, M. (1999). "Four dimensionality in noncompact Kaluza–Klein model".Modern Physics Letters A.14(29): 2025–2031.arXiv:hep-ph/9904383.Bibcode:1999MPLA...14.2025G.doi:10.1142/S021773239900208X.S2CID 16923959.

[9] Chung, Daniel J. H.; Freese, Katherine (2000-08-25). "Can geodesics in extra dimensions solve the cosmological horizon problem?".Physical Review D.62(6): 063513.arXiv:hep-ph/9910235.Bibcode:2000PhRvD..62f3513C.doi:10.1103/physrevd.62.063513.ISSN 0556-2821.S2CID 119511533.

[10] Musser, George; Minkel, J. R. (2002-02-11)."A Recycled Universe: Crashing branes and cosmic acceleration may power an infinite cycle in which our universe is but a phase".Scientific American Inc.Retrieved2008-05-03.

[arxiv.org-11] Khachatryan, V.; et al. (2011). "Search for Microscopic Black Hole Signatures at the Large Hadron Collider".Physics Letters B.697(5): 434–453.arXiv:1012.3375.Bibcode:2011PhLB..697..434C.doi:10.1016/j.physletb.2011.02.032.S2CID 118488193.

[12] Visinelli, Luca; Bolis, Nadia; Vagnozzi, Sunny (March 2018). "Brane-world extra dimensions in light of GW170817".Phys. Rev. D.97(6): 064039.arXiv:1711.06628.Bibcode:2018PhRvD..97f4039V.doi:10.1103/PhysRevD.97.064039.S2CID 88504420.

[13] Freeland, Emily (2018-09-21)."Hunting for extra dimensions with gravitational waves".The Oskar Klein Centre for Cosmoparticle Physics blog. Archived fromthe originalon 2021-01-27.Retrieved2018-11-30.

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v t e String theory
Background	Strings Cosmic strings History of string theory First superstring revolution Second superstring revolution String theory landscape
Theory	Nambu–Goto action Polyakov action Bosonic string theory Superstring theory Type I string Type II string Type IIA string Type IIB string Heterotic string N=2 superstring F-theory String field theory Matrix string theory Non-critical string theory Non-linear sigma model Tachyon condensation RNS formalism GS formalism
String duality	T-duality S-duality U-duality Montonen–Olive duality
Particles and fields	Graviton Dilaton Tachyon Ramond–Ramond field Kalb–Ramond field Magnetic monopole Dual graviton Dual photon
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