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Register a new userQuark Spectrum near Chiral Transition Points
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Near the critical temperature of the chiral phase transition, a collective excitation due to fluctuation of the chiral order parameter appears. We investigate how it affects the quark spectrum near but above the critical temperature. The calculated spectral function has many peaks. We show this behavior can be understood in terms of resonance scatterings of a quark off the collective mode.
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We explore the quark properties at finite temperature near but above the critical temperature of the chiral phase transition. We investigate the effects of the precursory soft mode of the phase transition on the quark dispersion relation and the spectral function. It is found that there appear novel excitation spectra of quasi-quarks and quasi-antiquarks with a three-peak structure, which are not attributed to the hard-thermal-loop approximation. We show that the new spectra originate from the mixing between a quark (anti-quark) and an anti-quark hole (quark hole) caused by a ``resonant scattering of the quasi-fermions with the thermally-excited soft mode which has a small but finite excitation energy.
The spectrum of the SU(2) flavor baryons is studied in the frame of a relativistic chiral quark potential model based on the one-pion and one-gluon exchange mechanisms. It is argued that the N* and Delta* resonances strongly coupled to the pi-N channel are identified with the orbital configurations $(1S_{1/2})^2(nlj)$ with a single valence quark in the excited state (nlj). With the obtained selection rules based on the chiral constraint, we show that it is possible to construct a schematic periodic table of baryon resonances, consistent with the experimental data and yielding no missing resonances. A new original method for the treatment of the center of mass problem is suggested, which is based on the separation of the three-quark Dirac Hamiltonian into the parts, corresponding to the Jacobi coordinates. The numerical estimations for the energy positions of the Nucleon and Delta baryons (up to and including F-wave resonances), obtained within the field-theoretical framework by using time ordered perturbation theory, yield an overall good description of the experimental data at the level of the relativized CQM of S. Capstick and W. Roberts without any fitting parameters. The Delta(1232) is well reproduced. However, N g. s. and most of the radially excited baryon resonances (including Roper) are overestimated. Contrary, the first band of the orbitally excited baryon resonances with a negative parity are underestimated. At the same time, the second band of the orbitally excited Delta* states with the negative parity are mostly overestimated, while the N* states are close to the experimental boxes. The positive parity baryon resonances with J=5/2, 7/2 are close to the experimental data. At higher energies, where the experimental data are poor, we can extend our model schematically and predict an existence of seven N* and four Delta* new states with larger spin values.
We investigate the quark spectrum near but above the critical temperature of the chiral transition, taking into account the precursory soft modes. It is found that there appear novel excitation spectra of quasi-quarks and quasi-antiquarks with a three-peak structure. By a detailed analysis on the formation of the three-peak structure using Yukawa models, it is shown that the new quark spectra originate from the mixing between a quark (anti-quark) and an antiquark hole (quark hole) caused by a resonant scattering of the quasi-quark with the soft modes which have a small but finite excitation energy with a small width near the critical temperature.
With analyzing the mass function obtained by solving Dyson-Schwinger Equations, we propose a cut-off independent definition of quark condensate beyond chiral limit. With this well-defined condensate, we then analyze the evolution of the condensate and its susceptibility with the current quark mass. The susceptibility shows a critical mass in the neighborhood of the s-quark current mass, which defines a transition boundary for internal hadron dynamics.
Considering the density wave of scalar and pseudoscalar condensates, we study the response of quark matter to a weak external magnetic field. In an external magnetic field, the energy spectrum of the lowest Landau level becomes asymmetric about zero, which is closely related to chiral anomaly, and gives rise to the spontaneous magnetization. This mechanism may be one of candidates for the origin of the strong magnetic field in pulsars and/or magnetars.
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