2020年

(7) Kenji Fukushima, Shi Pu. Spin hydrodynamics and symmetric energy-momentum tensors - A current induced by the spin vorticity -.  Phys.Lett.B 817 (2021) 136346. arXiv:2010.01608.

We discuss a puzzle in relativistic spin hydrodynamics; in the previous formulation the spin source from the antisymmetric part of the canonical energy-momentum tensor (EMT) is crucial. The Belinfante improved EMT is pseudo-gauge transformed from the canonical EMT and is usually a physically sensible choice especially when gauge fields are coupled as in magnetohydrodynamics, but the Belinfante EMT has no antisymmetric part. We find that pseudo-transformed entropy currents are physically inequivalent in nonequilibrium situations. We also identify a current induced by the spin vorticity read from the Belinfante symmetric EMT.

(6) Jianfei Wang, Shi Pu. Relativistic Kelvin Circulation Theorem for Ideal Magnetohydrodynamics. Nucl.Phys.Rev. 37 (2020) 3, 679-683. arXiv:2008.07789.

We have studied the relativistic Kelvin circulation theorem for ideal Magnetohydrodynamics. The relativistic Kelvin circulation theorem is a conservation equation for the called T-vorticity, We have briefly reviewed the ideal magnetohydrodynamics in relativistic heavy ion collisions. The highlight of this work is that we have obtained the general expression of relativistic Kelvin circulation theorem for ideal Magnetohydrodynamics. We have also applied the analytic solutions of ideal magnetohydrodynamics in Bjorken flow to check our results. Our main results can also be implemented to relativistic magnetohydrodynamics in relativistic heavy ion collisions.

(5) Patrick Copinger, Shi Pu. Chirality production with mass effects -- Schwinger pair production and the axial Ward identity. Int.J.Mod.Phys.A 35 (2020) 28, 2030015. arXiv: 2008.03635. (Invited review) 

The anomalous generation of chirality with mass effects via the axial Ward identity and its dependence on the Schwinger mechanism is reviewed, utilizing parity violating homogeneous electromagnetic background fields. The role vacuum asymptotic states play on the interpretation of expectation values is examined. It is discussed that observables calculated with an in–out scattering matrix element predict a scenario under Euclidean equilibrium. A notable ramification of which is a vanishing of the chiral anomaly. In contrast, it is discussed observables calculated under an in–in, or real-time, formalism predict a scenario out-of equilibrium, and capture effects of mean produced particle–antiparticle pairs due to the Schwinger mechanism. The out-of equilibrium chiral anomaly is supplemented with exponential quadratic mass suppression as anticipated for the Schwinger mechanism. Similar behavior in and out-of equilibrium is reviewed for applications including the chiral magnetic effect and chiral condensate.

(4) Rajesh Biswas, Ashutosh Dash, Najmul Haque, Shi Pu, Victor Roy, Causality and stability in relativistic viscous non-resistive magneto-fluid dynamics, JHEP 10 (2020) 171, arXiv: 2007.05431 [nucl-th]

We investigate the causality and the stability of the relativistic viscous non-resistive magneto-hydrodynamics in the framework of the Israel-Stewart (IS) second-order theory, and also within a modified IS theory which incorporates the effect of magnetic fields in the relaxation equations of the viscous stress. We compute the dispersion relation by perturbing the fluid variables around their equilibrium values. In the ideal magnetohydrodynamics limit, the linear dispersion relation yields the well-known propagating modes: the Alfvén and the magneto-sonic modes. In the presence of bulk viscous pressure, the causality bound is found to be independent of the magnitude of the magnetic field. The same bound also remains true, when we take the full non-linear form of the equation using the method of characteristics. In the presence of shear viscous pressure, the causality bound is independent of the magnitude of the magnetic field for the two magneto-sonic modes. The causality bound for the shear-Alfvén modes, however, depends both on the magnitude and the direction of the propagation. For modified IS theory in the presence of shear viscosity, new non-hydrodynamic modes emerge but the asymptotic causality condition is the same as that of IS. In summary, although the magnetic field does influence the wave propagation in the fluid, the study of the stability and asymptotic causality conditions in the fluid rest frame shows that the fluid remains stable and causal given that they obey certain asymptotic causality condition.

  

(3) Jian-Hua Gao, Guo-Liang Ma, Shi Pu, Qun Wang, Recent developments in chiral and spin polarization effects in heavy-ion collisions, Nucl. Sci. Tech. 31 (2020) 9, 90, arXiv: 2005.10432 [hep-ph] (Invited review) 

We give a brief overview of recent theoretical and experimental results on the chiral magnetic effect and spin polarization effect in heavy-ion collisions. We present updated experimental results for the chiral magnetic effect and related phenomena. The time evolution of the magnetic fields in different models is discussed. The newly developed quantum kinetic theory for massive fermions is reviewed. We present theoretical and experimental results for the polarization of Λ hyperons and the ρ00 value of vector mesons.

 

(2) Ren-jie Wang, Patrick Copinger, Shi Pu, Anomalous magnetohydrodynamics with constant anisotropic electric conductivities, Nucl. Phys. A 1005 (2021) 121869, arXiv: 2004.06408 [hep-ph] 

We study anomalous magnetohydrodynamics in a longitudinal boost invariant Bjorken flow with constant anisotropic electric conductivities as outlined in Ref. [I. Siddique, R.-j. Wang, S. Pu, Q. Wang, Anomalous magnetohydrodynamics with longitudinal boost invariance and chiral magnetic effect, Phys. Rev. D 99 (11) (2019) 114029. arXiv: 1904.01807, doi: 10.1103/Phys. Rev. D.99.114029.]. For simplicity, we consider a neutral fluid and a force-free magnetic field in the transverse direction. We derived analytic solutions of the electromagnetic fields in the laboratory frame, the chiral density, and the energy density as functions of proper time.

 

(1) Kenji Fukushima, Shi Pu, Relativistic decomposition of the orbital and the spin angular momentum in chiral physics and Feynman's angular momentum paradox, Lect. Notes Phys. 987 (2021) 381-396, arXiv: 2001.00359 [hep-ph] (Invited review) 

 

Over recent years we have witnessed tremendous progresses in our understanding on the angular momentum decomposition. In the context of the proton spin problem in high energy processes the angular momentum decomposition by Jaffe and Manohar, which is based on the canonical definition, and the alternative by Ji, which is based on the Belinfante improved one, have been revisited under light shed by Chen et al. leading to seminal works by Hatta, Wakamatsu, Leader, etc. In chiral physics as exemplified by the chiral vortical effect and applications to the relativistic nucleus-nucleus collisions, sometimes referred to as a relativistic extension of the Barnett and the Einstein--de Haas effects, such arguments of the angular momentum decomposition would be of crucial importance. We pay our special attention to the fermionic part in the canonical and the Belinfante conventions and discuss a difference between them, which is reminiscent of a classical example of Feynman's angular momentum paradox. We point out its possible relevance to early-time dynamics in the nucleus-nucleus collisions, resulting in excess by the electromagnetic angular momentum.