Cosmological phase transition: Difference between revisions

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The [[Standard Model]] of particle physics contains three [[fundamental force]]s, the [[electromagnetic force]], the [[weak force]] and the [[strong force]]. Shortly after the Big Bang, the extremely high temperatures may have modified the character of these forces. While these three forces act differently today, it has been conjectured that they may have been unified in the high temperatures of the early universe.<ref name="georgi-glashow">{{cite journal |last1=Georgi |first1=H. |last2=Glashow |first2=S. L. |title=Unity of All Elementary Forces |journal=Phys. Rev. Lett. |date=1974 |volume=32 |pages=438–441 |doi=10.1103/PhysRevLett.32.438}}</ref><ref name="weinberg-gauge">{{cite journal |last1=Weinberg |first1=Steven |title=Gauge and Global Symmetries at High Temperature |journal=Phys. Rev. D |date=1974 |volume=9 |issue=12 |pages=3357–3378|doi=10.1103/PhysRevD.9.3357 |bibcode=1974PhRvD...9.3357W }}</ref>

===Strong forceQCD phase transition===

[[File:QCD phase diagram.png|thumb|300px|right|Conjectured form of the phase diagram of QCD matter, with temperature on the vertical axis and quark [[chemical potential]] on the horizontal axis, both in mega-[[electron volt]]s.<ref name='RMP'>{{cite journal|author1=Alford, Mark G.|author2=Schmitt, Andreas|author3=Rajagopal, Krishna|author4=Schäfer, Thomas|title=Color superconductivity in dense quark matter|arxiv=0709.4635 |journal=Reviews of Modern Physics |volume=80|issue=4 |pages=1455–1515 |year=2008|doi=10.1103/RevModPhys.80.1455|bibcode=2008RvMP...80.1455A|s2cid=14117263}}</ref>]]

The strong force binds together [[quarks]] into [[protons]] and [[neutrons]], in a phenomenon known as [[color confinement]]. However, at sufficiently high temperatures, protons and neutrons disassociate into free quarks. The strong forceThis phase transition marksis also called the endquark–hadron oftransition.<ref thename=Peacock-1998>{{Cite book |last=Peacock |first=J. A. |url=https://www.cambridge.org/core/product/identifier/9780511804533/type/book |title=Cosmological Physics |date=1998-12-28 |publisher=Cambridge University Press |isbn=978-0-521-41072-4 [[quark|edition=1 epoch]]|doi=10.1017/cbo9780511804533}}</ref>{{rp|305}} Studies of this transition based on [[lattice QCD]] have demonstrated that it would have taken place at a temperature of approximately 155 [[MeV]], and would have been a smooth crossover transition.<ref name="aoki-qcd">{{cite journal |last1=Aoki |first1=Y. |last2=Endrodi |first2=G. |last3=Fodor |first3=Z. |last4=Katz |first4=S. D. |last5=Szabo |first5=K. K. |title=The order of the quantum chromodynamics transition predicted by the standard model of particle physics |journal=Nature |date=2006 |volume=443 |issue=7112 |pages=675–678 |doi=10.1038/nature05120|pmid=17035999 |arxiv=hep-lat/0611014 |bibcode=2006Natur.443..675A |s2cid=261693972 }}</ref> In the early universe the chemical potential of baryons is assumed to be near zero and the transition near 170MeV converts a quark-gluon plasma to a hadron gas.<ref name=Manzudar-2019/>{{rp|25}}

This conclusion assumes the simplest scenario at the time of the transition, and first- or second-order transitions are possible in the presence of a quark, baryon or neutrino [[chemical potential]], or strong magnetic fields.<ref name="Boeckel2011">{{cite journal |last1=Boeckel |first1=Tillman |last2=Schettler |first2=Simon |last3=Schaffner-Bielich |first3=Jurgen |title=The Cosmological QCD Phase Transition Revisited |journal=Prog. Part. Nucl. Phys. |date=2011 |volume=66 |issue=2 |pages=266–270 |doi=10.1016/j.ppnp.2011.01.017|arxiv=1012.3342|bibcode=2011PrPNP..66..266B |s2cid=118745752 }}</ref><ref name="Schwarz2009">{{cite journal |last1=Schwarz |first1=Dominik J. |last2=Stuke |first2=Maik |title=Lepton asymmetry and the cosmic QCD transition |journal=JCAP |date=2009 |volume=2009 |issue=11 |pages=025 |doi=10.1088/1475-7516/2009/11/025|arxiv=0906.3434|bibcode=2009JCAP...11..025S |s2cid=250761613 }}</ref><ref name="Cao2023">{{cite journal |last1=Cao |first1=Gaoging |title=First-order QCD transition in a primordial magnetic field |journal=Phys. Rev. D |date=2023 |volume=107 |issue=1 |pages=014021 |doi=10.1103/PhysRevD.107.014021|arxiv=2210.09794