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Chiral transition in dense, magnetized matter

In the presence of a chemical potential, the effect of a magnetic field on chiral symmetry breaking goes beyond the well-known magnetic catalysis. Due to a subtle interplay with the chemical potential, the magnetic field may work not only in favor but also against the chirally broken phase. At sufficiently large coupling, the magnetic field favors the broken phase only for field strengths beyond any conceivable value in nature. Therefore, in the interior of magnetars, a possible transition from chirally broken hadronic matter to chirally symmetric quark matter might occur at smaller densities …

Electromagnetic spectral functions in hot and dense chirally imbalanced quark matter

The photon self-energy from chirally imbalanced quark matter is evaluated at finite temperature and density using the real time formulation of thermal field theory. The analytic structure is explored in detail exposing the cut structure which corresponds to a variety of physical scattering and decay processes in the medium and their thresholds. The mass of the quarks in the chiral symmetry broken phase are obtained from the gap equation of the Nambu--Jona-Lasinio model. It is found that, in presence of finite chiral chemical potential, the chiral condensate tends to get stronger at low tempera…

Confining but chirally symmetric dense and cold matter

The possibility for existence of cold, dense chirally symmetric matter with confinement is reviewed. The answer to this question crucially depends on the mechanism of mass generation in QCD and interconnection of confinement and chiral symmetry breaking. This question can be clarified from spectroscopy of hadrons and their axial properties. Almost systematical parity doubling of highly excited hadrons suggests that their mass is not related to chiral symmetry breaking in the vacuum and is approximately chirally symmetric. Then there is a possibility for existence of confining but chirally symm…

Confined but chirally symmetric hadrons at large density and the Casher's argument

Casher's argument, which is believed to be quite general, states that in the confining regime chiral symmetry is necessarily broken. In the large-N_c limit and at moderate and low temperatures QCD is confining up to arbitrary large densities, and there should appear a quarkyonic matter. It has been demonstrated, within a manifestly confining and chirally symmetric model, which is a 3+1 dimensional generalization of the 't Hooft model, that, at zero temperature and at a density exceeding a critical one, the chiral symmetry is restored while quarks remain confined in color-singlet hadrons. This …

Vacuum phenomenology of the chiral partner of the nucleon in a linear sigma model with vector mesons

We investigate a linear sigma model with global chiral $U(2)_{R} \times U(2)_{L}$ symmetry. The mesonic degrees of freedom are the standard scalar and pseudoscalar mesons and the vector and axial-vector mesons. The baryonic degrees of freedom are the nucleon, $N$, and its chiral partner, $N^{*}$, which is usually identified with N(1535). The chiral partner is incorporated in the so-called mirror assignment, where the nucleon mass is not solely generated by the chiral condensate but also by a chirally invariant mass term, $m_{0}$. The presence of (axial-) vector fields modifies the expressions …

最小加倍费米子的对称性破缺

Broken Symmetries from Minimally Doubled Fermions

最近文献中提出了新的包含最小量费米子加倍的手征对称费米子作用量。我们研究这些行动的对称性和重整化，并发现在每种情况下，离散的对称性，如奇偶校验和时间反演，明确打破。因此，当包括规范相互作用时，这些理论辐射地产生相关的和边际的算子。因此，恢复这些对称性和接近连续极限需要微调几个参数。在一些假设下，我们证明了这种行为是不可避免的行动显示最小的费米子加倍。