Editing Faster-than-light (section)

===Lorentz symmetry violation===
{{Main|Modern searches for Lorentz violation|Standard-Model Extension}}

The possibility that Lorentz symmetry may be violated has been seriously considered in the last two decades, particularly after the development of a realistic effective field theory that describes this possible violation, the so-called [[Standard-Model Extension]].<ref>{{cite journal |arxiv=hep-ph/9703464 |bibcode=1997PhRvD..55.6760C |doi=10.1103/PhysRevD.55.6760 |title=CPT violation and the standard model |year=1997 |last1=Colladay |first1=Don |last2=Kostelecký |first2=V. Alan |journal=Physical Review D |volume=55 |issue=11 |pages=6760–6774|s2cid=7651433 }}</ref><ref>{{cite journal |arxiv=hep-ph/9809521 |bibcode=1998PhRvD..58k6002C |doi=10.1103/PhysRevD.58.116002 |title=Lorentz-violating extension of the standard model |year=1998 |last1=Colladay |first1=Don |last2=Kostelecký |first2=V. Alan |journal=Physical Review D |volume=58 |issue=11 |pages=116002|s2cid=4013391 }}</ref><ref>{{cite journal |arxiv=hep-th/0312310 |bibcode=2004PhRvD..69j5009K |doi=10.1103/PhysRevD.69.105009 |title=Gravity, Lorentz violation, and the standard model |year=2004 |last1=Kostelecký |first1=V. Alan |journal=Physical Review D |volume=69 |issue=10 |pages=105009|s2cid=55185765 }}</ref> This general framework has allowed experimental searches by ultra-high energy cosmic-ray experiments<ref name="Gonzalez-Mestres2009b">{{Cite journal |last=Gonzalez-Mestres |first=Luis |year=2009 |title=AUGER-HiRes results and models of Lorentz symmetry violation |journal=Nuclear Physics B - Proceedings Supplements |language=en |volume=190 |pages=191–197 |arxiv=0902.0994 |bibcode=2009NuPhS.190..191G |doi=10.1016/j.nuclphysbps.2009.03.088 |s2cid=14848782}}</ref> and a wide variety of experiments in gravity, electrons, protons, neutrons, neutrinos, mesons, and photons.<ref name="autogenerated1">{{cite journal |arxiv=0801.0287 |bibcode=2011RvMP...83...11K |doi=10.1103/RevModPhys.83.11 |title=Data tables for Lorentz and CPT violation |year=2011 |last1=Kostelecký |first1=V. Alan |last2=Russell |first2=Neil |journal=Reviews of Modern Physics |volume=83 |issue=1 |pages=11–31|s2cid=3236027 }}</ref>
The breaking of rotation and boost invariance causes direction dependence in the theory as well as unconventional energy dependence that introduces novel effects, including [[Lorentz-violating neutrino oscillations]] and modifications to the dispersion relations of different particle species, which naturally could make particles move faster than light.

In some models of broken Lorentz symmetry, it is postulated that the symmetry is still built into the most fundamental laws of physics, but that [[spontaneous symmetry breaking]] of Lorentz invariance<ref>{{cite journal |last1=Kostelecký |first1=V. A. |last2=Samuel |first2=S. |title=Spontaneous breaking of Lorentz symmetry in string theory |journal=Physical Review D |date=15 January 1989 |volume=39 |issue=2 |pages=683–685 |doi=10.1103/PhysRevD.39.683|pmid=9959689 |bibcode=1989PhRvD..39..683K|hdl=2022/18649 |url=https://scholarworks.iu.edu/dspace/bitstream/handle/2022/18649/PhysRevD.39.683.pdf |archive-url=https://web.archive.org/web/20210713090335/https://scholarworks.iu.edu/dspace/bitstream/handle/2022/18649/PhysRevD.39.683.pdf |archive-date=2021-07-13 |url-status=live | hdl-access=free }}</ref> shortly after the [[Big Bang]] could have left a "relic field" throughout the universe which causes particles to behave differently depending on their velocity relative to the field;<ref>{{cite web |date=2004-04-05 |title=PhysicsWeb – Breaking Lorentz symmetry |url=http://physicsweb.org/article/world/17/3/7 |archive-url=https://web.archive.org/web/20040405031103/http://physicsweb.org/article/world/17/3/7 |archive-date=2004-04-05 |access-date=2011-09-26 |publisher=PhysicsWeb}}</ref> however, there are also some models where Lorentz symmetry is broken in a more fundamental way. If Lorentz symmetry can cease to be a fundamental symmetry at the Planck scale or at some other fundamental scale, it is conceivable that particles with a critical speed different from the speed of light be the ultimate constituents of matter.

In current models of Lorentz symmetry violation, the phenomenological parameters are expected to be energy-dependent. Therefore, as widely recognized,<ref name="CERNCourrier">{{cite web|last=Mavromatos |first=Nick E. |title=Testing models for quantum gravity |work=CERN Courier |url=http://cerncourier.com/cws/article/cern/28696 |date=15 August 2002}}</ref><ref name="NYT">{{Cite news |last=Overbye |first=Dennis |date=2002-12-31 |title=Interpreting the Cosmic Rays |language=en-US |work=The New York Times |url=https://www.nytimes.com/2002/12/31/science/interpreting-the-cosmic-rays.html |access-date=2023-08-24 |issn=0362-4331}}</ref> existing low-energy bounds cannot be applied to high-energy phenomena; however, many searches for Lorentz violation at high energies have been carried out using the [[Standard-Model Extension]].<ref name="autogenerated1"/>
Lorentz symmetry violation is expected to become stronger as one gets closer to the fundamental scale.