Graviton — разлика између измена
Садржај обрисан Садржај додат
м Разне исправке |
. |
||
Ред 119:
|doi=10.1142/S0218271815440010
|bibcode = 2015IJMPD..2444001D }}</ref>
== Energija i talasna dužina ==
{{rut}}
While gravitons are presumed to be [[massless particle|massless]], they would still carry [[energy]], as does any other quantum particle. [[Photon energy]] and [[gluon energy]] are also carried by massless particles. It is unclear which variables might determine graviton energy, the amount of energy carried by a single graviton.
Alternatively, [[massive gravity|if gravitons are massive at all]], the analysis of [[gravitational wave]]s yielded a new upper bound on the [[mass]] of gravitons. The graviton's [[Compton wavelength]] is at least {{val|1.6|e=16|u=[[metre|m]]}}, or about 1.6 [[light-year]]s, corresponding to a graviton mass of no more than {{val|7.7|e=-23|u=[[electronvolt|eV]]/[[speed of light|c]]<sup>2</sup>}}.<ref name="Abbott2017">{{cite journal|doi=10.1103/PhysRevLett.118.221101|title=GW170104: Observation of a 50-Solar-Mass Binary Black Hole Coalescence at Redshift 0.2|journal=[[Physical Review Letters]]|date=1 June 2017|author=B. P. Abbott|display-authors=etal|collaboration=[[LIGO Scientific Collaboration]] and [[Virgo interferometer|Virgo Collaboration]]|volume=118|pages=221101|bibcode=2017PhRvL.118v1101A|arxiv=1706.01812}}</ref> This relation between wavelength and mass-energy is calculated with the [[Planck–Einstein relation]], the same formula that relates electromagnetic [[wavelength]] to [[photon energy]]. However, if gravitons are the quanta of gravitational waves, then the relation between wavelength and corresponding particle energy is fundamentally different for gravitons than for photons, since the Compton wavelength of the graviton is not equal to the gravitational-wave wavelength. Instead, the lower-bound graviton Compton wavelength is about {{val|9|e=9}} times greater than the gravitational wavelength for the [[GW170104]] event, which was ~ 1,700 km. The report<ref name="Abbott2017" /> did not elaborate on the source of this ratio. It is possible that gravitons are not the quanta of gravitational waves, or that the two phenomena are related in a different way.
== Eksperimentalna opservacija ==
Unambiguous detection of individual gravitons, though not prohibited by any fundamental law, is impossible with any physically reasonable detector.<ref name="Rothman">
{{cite journal
|last=Rothman |first=T.
|last2=Boughn |first2=S.
|date=2006
|title=Can Gravitons be Detected?
|journal=[[Foundations of Physics]]
|volume=36 |issue=12 |pages=1801–1825
|arxiv=gr-qc/0601043
|bibcode=2006FoPh...36.1801R
|doi=10.1007/s10701-006-9081-9
}}</ref> The reason is the extremely low [[cross section (physics)|cross section]] for the interaction of gravitons with matter. For example, a detector with the mass of [[Jupiter]] and 100% efficiency, placed in close orbit around a [[neutron star]], would only be expected to observe one graviton every 10 years, even under the most favorable conditions. It would be impossible to discriminate these events from the background of [[neutrino]]s, since the dimensions of the required neutrino shield would ensure collapse into a [[black hole]].<ref name="Rothman" />
[[LIGO]] and [[Virgo interferometer|Virgo]] collaborations' observations have [[First observation of gravitational waves|directly detected]] [[gravitational waves]].<ref name="Abbot">{{cite journal |title=Observation of Gravitational Waves from a Binary Black Hole Merger| author=Abbott, B. P. et al. (LIGO Scientific Collaboration and Virgo Collaboration)| journal=Physical Review Letters| year=2016| volume=116|issue=6| doi=10.1103/PhysRevLett.116.061102|arxiv = 1602.03837 |bibcode = 2016PhRvL.116f1102A | pmid=26918975 | pages=061102}}</ref><ref name="Discovery 2016">{{cite journal |title=Einstein's gravitational waves found at last |journal=Nature News|date=February 11, 2016 |last=Castelvecchi |first=Davide |last2=Witze |first2=Witze |doi=10.1038/nature.2016.19361 }}</ref><ref name="NSF">{{cite web|title = Gravitational waves detected 100 years after Einstein's prediction {{!}} NSF - National Science Foundation|url = https://www.nsf.gov/news/news_summ.jsp?cntn_id=137628|website = www.nsf.gov|access-date = 2016-02-11}}</ref> Others have postulated that graviton scattering yields gravitational waves as particle interactions yield [[coherent state]]s.<ref>{{cite journal | last1 = Senatore | first1 = L. | last2 = Silverstein | first2 = E. | last3 = Zaldarriaga | first3 = M. | year = 2014 | title = New sources of gravitational waves during inflation | url = | journal = Journal of Cosmology and Astroparticle Physics | volume = 2014 | issue = 8| page = 016 | doi=10.1088/1475-7516/2014/08/016| arxiv = 1109.0542 | bibcode = 2014JCAP...08..016S }}</ref> Although these experiments cannot detect individual gravitons, they might provide information about certain properties of the graviton.<ref name="detecting graviton">{{cite journal|first=Freeman |last= Dyson|date=8 October 2013|journal=[[International Journal of Modern Physics A]]|volume=28|issue=25|pages=1330041–1–1330035–14|title=Is a Graviton Detectable?|doi=10.1142/S0217751X1330041X|bibcode = 2013IJMPA..2830041D }}</ref> For example, if gravitational waves were observed to propagate slower than ''c'' (the [[speed of light]] in a vacuum), that would imply that the graviton has mass (however, gravitational waves must propagate slower than ''c'' in a region with non-zero mass density if they are to be detectable).<ref>
{{cite journal
|last=Will |first=C. M.
|date=1998
|title=Bounding the mass of the graviton using gravitational-wave observations of inspiralling compact binaries
|journal=[[Physical Review D]]
|volume=57 |issue=4 |pages=2061–2068
|arxiv=gr-qc/9709011
|bibcode=1998PhRvD..57.2061W
|doi=10.1103/PhysRevD.57.2061
|url=http://cds.cern.ch/record/333219/files/9709011.pdf}}</ref> Recent observations of gravitational waves have put an upper bound of {{val|1.2|e=-22|u=eV/c2}} on the graviton's mass.<ref name="Abbot" /> Astronomical observations of the kinematics of galaxies, especially the [[galaxy rotation curve|galaxy rotation problem]] and [[modified Newtonian dynamics]], might point toward gravitons having non-zero mass.<ref>Trippe, S. (2013), "A Simplified Treatment of Gravitational Interaction on Galactic Scales", J. Kor. Astron. Soc. '''46''', 41. {{arxiv|1211.4692}}</ref>
== Vidi još ==
| |||