Abstract
In this talk we first overview lattice results that have led to the observation of new SU(2)CS and SU(2NF) symmetries upon artificial truncation of the near-zero modes of the Dirac operator at zero temperatute and at high temperature without any truncation. These symmetries are larger than the chiral symmetry of the QCD Lagrangian and contain chiral symmetries SU(NF)L x SU(NF)R and U(1)A as subgroups. In addition to the standard chiral transformations the SU(2)CS and SU(2NF) transformations mix the right- and left-handed components of the quark fields. It is a symmetry of the confining chromo-electric interaction while the chromo-magnetic interaction manifestly breaks it. Emergence of these symmetries upon truncation of the near-zero modes of the Dirac operator at T=0 means that all effects of the chromo-magnetic interaction are located exclusively in the near-zero modes, while confining chromo-electric interaction is distributed among all modes. Appearance of these symmetries at high T, where the temperature suppresses the near-zero modes, has radical implications because these symmetries are incompatible with the asymptotically free deconfined quarks at increasing temperature. The elementary objects in the high-temperature phase of QCD should be quarks bound by the pure chromo-electric field that is not accompanied by the chromo-magnetic effects.
Highlights
The QCD Lagrangian with NF massles quarks L = Ψ (x)(iγμDμ)Ψ(x) − T r(GμνGμν), (1)has the chiral symmetry: U(NF)L × U(NF)R = S U(NF)L × S U(NF)R × U(1)A × U(1)V . (2)The U(1)V symmetry is responsible for the vector current conservation and is irrelevant to our subject
The S U(NF)L×S U(NF)R chiral symmetry is an invariance under independent flavor S U(NF) rotations of the left- and right-handed components of quarks
It turned out that the nucleon, the rho-meson and some other hadrons, except for the pion, survive this "unbreaking" of the chiral symmetry and their mass remains large [4]. This tells that while the chiral symmetry breaking in the vacuum is important for the eventual shape of the hadron spectra, the chiral symmetry breaking is not the main mechanism of the mass generation of hadrons such as the ρ-meson or the nucleon
Summary
The S U(NF)L×S U(NF)R chiral symmetry is an invariance under independent flavor S U(NF) rotations of the left- and right-handed components of quarks. Within the Nambu and JonaLasinio model it is the vacuum fermion condensate that is responsible for a generation of a large mass of initially massless fermions This view was one of the reasons to assume that at high temperatures, where chiral symmetry is restored, there should appear the quark-gluon plasma phase, contrary to the hadron phase at low temperatures. This tells that while the chiral symmetry breaking in the vacuum is important for the eventual shape of the hadron spectra, the chiral symmetry breaking is not the main mechanism of the mass generation of hadrons such as the ρ-meson or the nucleon Still it was unclear what happens with the U(1)A symmetry upon truncation of the near-zero modes. We report recent results on these symmetries at high temperature without any truncation [11] and their consequences for the nature of the strongly interacting matter at high T
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
