1 Some aspects of p Some aspects of p hase transition hase transition in dense quark matter in dense quark matter Qun Wang University of Science and Technology of China Phases in QCD Lattice results at finite temperature Dense baryonic matter Diquarks in cold baryonic matter QCD phase transition and RHIC physics Weihai, August 9-14, 2009
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Some aspects of p hase transition in dense quark matter
Some aspects of p hase transition in dense quark matter. Qun Wang University of Science and Technology of China. Phases in QCD Lattice results at finite temperature Dense baryonic matter Diquarks in cold baryonic matter. QCD phase transition and RHIC physics - PowerPoint PPT Presentation
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Some aspects of pSome aspects of phase transition hase transition in dense quark matterin dense quark matter
Qun WangUniversity of Science and Technology of China
Phases in QCD Lattice results at finite temperature Dense baryonic matter Diquarks in cold baryonic matter
QCD phase transition and RHIC physics Weihai, August 9-14, 2009
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Research groups in China Research groups in China (QCD phase transition theory)(QCD phase transition theory)
The problem of fermion sector: 1. Fermion number doubling2. Essential symmetries (chiral symmetry) of the continuum action are violated
Solution: 1. Wilson fermion, add a higher derivative term2. Staggered fermion, distribute components of the fermion Dirac spinors over several lattice sites, [Kogut and Susskind, PRD1975].
The Kogut-Susskind staggered fermion action:
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Lattice QCD partition functionLattice QCD partition function
C
Wilson loop C
reflect confinement property
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ConfinementConfinement
C
confining potential
T: virtual time
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Polyakov LoopPolyakov Loop
Polyakov loop
Free energy for qq-bar
Polyakov loop as order parameter for phase transtion
Meissner effects in weak coupling: resultsMeissner effects in weak coupling: results
■ Rotated photon in CSL phase has a non-vanishing mass: ElectromagneticMeissner effect.■ Although rotated photon in polar phase has a zero mass but a system with 2 or 3 favors still exhibits Electromagnetic Meissner effect because of different chemical potential or no single mixing angle for all favors.
Schmitt, QW, Rischke, PRL(2003)
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Effective Theory of dense matterEffective Theory of dense matter
Relativistic boson-fermion Relativistic boson-fermion model (model (MFAMFA))
With With bosonicbosonic and and fermionicfermionic degrees of freedom and their degrees of freedom and their coupling, but neglect the coupling of thermal bosons coupling, but neglect the coupling of thermal bosons
and fermions as and fermions as MMean ean FField ield AApproximationpproximation Friedberg-Lee model, 1989
zero mode of boson
J. Deng, A. Schmitt, QW, Phys.Rev.D76:034013,2007
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Thermodynamic potetialThermodynamic potetial
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Density and gap Density and gap equationsequations
Crossover parameterCrossover parameter
x<0, BCS regimex>0, BEC regime
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At zero T or critical TAt zero T or critical T
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Dispersion Dispersion relationrelation
In In BCSBCS regime, fermions are slightly gapped, anti- regime, fermions are slightly gapped, anti-fermions are strongly gapped. fermions are strongly gapped.
In In BECBEC regime, both are strongly gapped, indicating the regime, both are strongly gapped, indicating the formation of bound states with large binding energyformation of bound states with large binding energy
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Unitary RegimeUnitary Regime
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Pairing with imbalance populationPairing with imbalance population----Fermi surface topologiesFermi surface topologies
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Homogeneous Homogeneous solutionsolution
The fermion-boson mixture in BCS-BEC regime has been found The fermion-boson mixture in BCS-BEC regime has been found in cold atomic system. Stable gapless phase in strong in cold atomic system. Stable gapless phase in strong coupling (see also Kitazawa,Rischke, Shovkovy, 2006) coupling (see also Kitazawa,Rischke, Shovkovy, 2006)
[ Realization of a strongly interacting Bose-Fermi mixture [ Realization of a strongly interacting Bose-Fermi mixture from a two-component Fermi gas, MIT group, arXiv:0805.0623 from a two-component Fermi gas, MIT group, arXiv:0805.0623 ]]
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Phase diagramPhase diagram
Shaded area: unstable, with negative susceptibility
Non-relativistic relativistic
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Beyond mean-field aproximationBeyond mean-field aproximation----At small TAt small T
The results are similar to the The results are similar to the MFAMFA results results
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At T=TcAt T=Tc
Fluctuations become important in Fluctuations become important in BECBEC regime.regime.In In BECBEC regime T*>Tc. regime T*>Tc.
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T-dependenceT-dependence
The fluctuation effects become larger.The fluctuation effects become larger.BEC criterion is related to the minimization BEC criterion is related to the minimization of the thermodynamic potential.of the thermodynamic potential.
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Introduction of term in : Introduction of term in :
B.I.Halperin, T.C.Lubensky and S. Ma 1974B.I.Halperin, T.C.Lubensky and S. Ma 1974 (magnetic field fluctuations)(magnetic field fluctuations)I. Giannakis, D. f. Hou, H. c. Ren and D. H. Rischke, 2004I. Giannakis, D. f. Hou, H. c. Ren and D. H. Rischke, 2004 ((Gauge Field Fluctuations)Gauge Field Fluctuations)Sasaki, Friman, Redlich, 2007Sasaki, Friman, Redlich, 2007 (baryon number fluctuation in 1st chiral phase transition)(baryon number fluctuation in 1st chiral phase transition)
1st order phase transition from 1st order phase transition from fluctuations: fixed fluctuations: fixed μμ
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Diquarks in baryonsDiquarks in baryons
Quarks, diquarks and pentaquarks, Jaffe, Wilczek, 2004[Diquarks as building blocks of exotic hadrons]
Diquark models:Anselmino, et al., 1993Abu-Raddad,Hosaka,Ebert,Toki, 2002Many other papers……
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Diquarks in baryonsDiquarks in baryons
Diquark-cluster Meson Cloud
Diquark configuration in proton: positive magnetic moments from strange quarks Zou, Riska, 2005
u
du
SS
Su
uS
d
Diquark configuration: inverse mass order in resonances Zou, 2007
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Quark-baryonic matter crossover Quark-baryonic matter crossover in N_f=3 dense matter in N_f=3 dense matter
BCS-BEC crossoverwith boson-fermion model
crossover of quark-baryonic matter
■ Continuity of quark and hadron matter, Schafer, Wilczek, 2000[ CFL-hadronic matter: a weak coupling realization of confinement and chiral symmetry breaking in idealization of QCD ]
■ New critical point induced by the axial anomaly in dense QCD, Hatsuda, Tachibana, Yamamoto, Baym, 2006
■ N_f=3, there is a new critical point near chemical potential axis due to coupling of chiral and diquark condensate: quark-nuclear matter crossover
■ N_f=2, no critical point: quark-nuclear matter transition
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SummarySummary
There are many efforts in exploring the QCD phase diagram boThere are many efforts in exploring the QCD phase diagram both experimentally and theoretically. th experimentally and theoretically.
On the theory side, there are lattice and effective model approOn the theory side, there are lattice and effective model approach to QCD phase diagram. ach to QCD phase diagram.
A lot of progress has been made in dense regime of phase diagrA lot of progress has been made in dense regime of phase diagram where diquark correlation plays an important role. am where diquark correlation plays an important role.
The community of QCD phase transition is in small scale and stThe community of QCD phase transition is in small scale and still has room to expand. ill has room to expand.