Thechameleonis a hypotheticalscalar particlethat couples to matter more weakly than gravity,[1]postulated as adark energycandidate.[2]Due to a non-linear self-interaction, it has a variable effective mass which is an increasing function of the ambient energy density—as a result, the range of the force mediated by the particle is predicted to be very small in regions of high density (for example on Earth, where it is less than 1 mm) but much larger in low-density intergalactic regions: out in the cosmos chameleon models permit a range of up to several thousandparsecs.As a result of this variable mass, the hypotheticalfifth forcemediated by the chameleon is able to evade current constraints onequivalence principleviolation derived from terrestrial experiments even if it couples to matter with a strength equal or greater than that of gravity. Although this property would allow the chameleon to drive the currently observed acceleration of theuniverse's expansion,it also makes it very difficult to test for experimentally.
| Composition | Unknown |
|---|---|
| Interactions | Gravity,electroweak |
| Status | Hypothetical |
| Mass | Variable, depending on ambient energy density |
| Electric charge | 0 |
| Spin | 0 |
In 2021, physicists suggested that an excess reported at the dark matter detector experimentXENON1Trather than being a dark matter candidate could be a dark energy candidate: particularly, chameleon particles[3][4][5]yet in July 2022 a new analysis by XENONnT discarded the excess.[6][7][8]
Hypothetical properties
editChameleon particles were proposed in 2003 by Khoury andWeltman.
In most theories, chameleons have a mass that scales as some power of the local energy density:,where
Chameleons also couple to photons, allowing photons and chameleons to oscillate between each other in the presence of an externalmagnetic field.[9]
Chameleons can be confined in hollow containers because their mass increases rapidly as they penetrate the container wall, causing them to reflect. One strategy to search experimentally for chameleons is to direct photons into a cavity, confining the chameleons produced, and then to switch off the light source. Chameleons would be indicated by the presence of an afterglow as they decay back into photons.[10]
Experimental searches
editA number of experiments have attempted to detect chameleons along withaxions.[11]
The GammeV experiment[12]is a search for axions, but has been used to look for chameleons too. It consists of a cylindrical chamber inserted in a 5Tmagnetic field. The ends of the chamber are glass windows, allowing light from a laser to enter and afterglow to exit. GammeV set the limited coupling to photons in 2009.[13]
CHASE (CHameleon Afterglow SEarch) results published in November 2010,[14]improve the limits on mass by 2 orders of magnitude and 5 orders for photon coupling.
A 2014 neutron mirror measurement excluded chameleon field for values of the coupling constant,[15]where the effective potential of the chameleon quanta is written as,being the mass density of the environment,the chameleon potential andthe reduced Planck mass.
TheCERN Axion Solar Telescopehas been suggested as a tool for detecting chameleons.[16]
References
editCitations
edit- ^Cho, Adrian (2015). "Tiny fountain of atoms sparks big insights into dark energy".Science.doi:10.1126/science.aad1653.
- ^Khoury, Justin; Weltman, Amanda (2004). "Chameleon cosmology".Physical Review D.69(4): 044026.arXiv:astro-ph/0309411.Bibcode:2004PhRvD..69d4026K.doi:10.1103/PhysRevD.69.044026.S2CID119478819.
- ^"Have we detected dark energy? Scientists say it's a possibility".University of Cambridge.Retrieved18 October2021.
- ^Fernandez, Elizabeth."Signal From The XENON1T Experiment May Be A Hallmark Of Dark Energy".Forbes.Retrieved18 October2021.
- ^Vagnozzi, Sunny; Visinelli, Luca; Brax, Philippe; Davis, Anne-Christine; Sakstein, Jeremy (15 September 2021). "Direct detection of dark energy: The XENON1T excess and future prospects".Physical Review D.104(6): 063023.arXiv:2103.15834.Bibcode:2021PhRvD.104f3023V.doi:10.1103/PhysRevD.104.063023.S2CID232417159.
- ^"A new dark matter experiment quashed earlier hints of new particles".Science News.2022-07-22.Retrieved2022-08-03.
- ^Aprile, E.; Abe, K.; Agostini, F.; Maouloud, S. Ahmed; Althueser, L.; Andrieu, B.; Angelino, E.; Angevaare, J. R.; Antochi, V. C.; Martin, D. Antón; Arneodo, F. (2022-07-22). "Search for New Physics in Electronic Recoil Data from XENONnT".Physical Review Letters.129(16): 161805.arXiv:2207.11330.Bibcode:2022PhRvL.129p1805A.doi:10.1103/PhysRevLett.129.161805.PMID36306777.S2CID251040527.
- ^Lin, Tongyan (2020-10-12)."Dark Matter Detector Delivers Enigmatic Signal".Physics.13:135.Bibcode:2020PhyOJ..13..135L.doi:10.1103/Physics.13.135.S2CID226325594.
- ^Erickcek, A. L.;Barnaby, N; Burrage, C; Huang, Z (2013). "Catastrophic consequences of kicking the chameleon".Physical Review Letters.110(17): 171101.arXiv:1304.0009.Bibcode:2013PhRvL.110b1101S.doi:10.1103/PhysRevLett.110.171101.PMID23679701.S2CID118730981.
- ^Steffen, Jason H.; Gammev Collaboration (2008). "Constraints on chameleons and axions-like particles from the GammeV experiment".Proceedings of Identification of dark matter 2008 — PoS(idm2008).Vol. 2008. p. 064.arXiv:0810.5070.Bibcode:2008idm..confE..64S.doi:10.22323/1.064.0064.S2CID16823913.
{{cite book}}:|journal=ignored (help) - ^Rybka, G; Hotz, M; Rosenberg, L. J.; Asztalos, S. J.; Carosi, G; Hagmann, C; Kinion, D; Van Bibber, K; Hoskins, J; Martin, C; Sikivie, P; Tanner, D. B.; Bradley, R; Clarke, J (2010). "Search for chameleon scalar fields with the axion dark matter experiment".Physical Review Letters.105(5): 051801.arXiv:1004.5160.Bibcode:2010PhRvL.105a1801B.doi:10.1103/PhysRevLett.105.051801.PMID20867906.S2CID55204188.
- ^GammeV experiment at Fermilab
- ^Chou, A. S.; Wester, W.; Baumbaugh, A.; Gustafson, H. R.; Irizarry-Valle, Y.; Mazur, P. O.; Steffen, J. H.; Tomlin, R.; Upadhye, A.; Weltman, A.; Yang, X.; Yoo, J. (22 Jan 2009). "Search for Chameleon Particles Using a Photon-Regeneration Technique".Physical Review Letters.102(3): 030402.arXiv:0806.2438.Bibcode:2009PhRvL.102c0402C.doi:10.1103/PhysRevLett.102.030402.PMID19257328.S2CID12327360.
- ^Steffen, Jason H. (2011). "The CHASE laboratory search for chameleon dark energy".Proceedings of 35th International Conference of High Energy Physics — PoS (ICHEP 2010).Vol. 2010. p. 446.arXiv:1011.3802.Bibcode:2010iche.confE.446S.doi:10.22323/1.120.0446.
{{cite book}}:|journal=ignored (help) - ^Jenke, T.; Cronenberg, G.; Burgdörfer, J.; Chizhova, L. A.; Geltenbort, P.; Ivanov, A. N.; Lauer, T.; Lins, T.; Rotter, S.; Saul, H.; Schmidt, U.; Abele, H. (Apr 16, 2014). "Gravity Resonance Spectroscopy Constrains Dark Energy and Dark Matter Scenarios".Physical Review Letters.112(15): 151105.arXiv:1404.4099.Bibcode:2014PhRvL.112o1105J.doi:10.1103/PhysRevLett.112.151105.PMID24785025.S2CID38389662.
- ^V. Anastassopoulos; M. Arik; S. Aune; K. Barth; A. Belov; H. Bräuninger;... K. Zioutas (March 16, 2015). "Search for chameleons with CAST".Physics Letters B.749:172–180.arXiv:1503.04561.Bibcode:2015PhLB..749..172A.doi:10.1016/j.physletb.2015.07.049.S2CID59375694.
Journal articles
edit- Brax, P.; van de Bruck, C.;Davis, A.-C.;Khoury, J.; Weltman, A. (2004). "Detecting dark energy in orbit: The cosmological chameleon".Physical Review D.70(12): 123518.arXiv:astro-ph/0408415.Bibcode:2004PhRvD..70l3518B.doi:10.1103/PhysRevD.70.123518.S2CID119100816.
- Khoury, J.; Weltman, A. (2004). "Chameleon fields: awaiting surprises for tests of gravity in space".Physical Review Letters.93(17): 171104.arXiv:astro-ph/0309300.Bibcode:2004PhRvL..93q1104K.doi:10.1103/PhysRevLett.93.171104.PMID15525066.S2CID17570608.
- Khoury, J.; Weltman, A. (2004). "Chameleon cosmology".Physical Review D.69(4): 044026.arXiv:astro-ph/0309411.Bibcode:2004PhRvD..69d4026K.doi:10.1103/PhysRevD.69.044026.S2CID119478819.