arXiv subjects

Ying Shan Zhao

Publications and source records attributed to Ying Shan Zhao.

4 recordsLinked to original sources

arXiv2026

Constrained Hamiltonian Formulation of Kinetic Theory for Relativistic Spin-$1/2$ Particles

Describing spin transport away from equilibrium requires a kinetic theory that consistently incorporates spin dynamics and phase space structure. We construct such a collisionless kinetic theory for relativistic spin-$1/2$ particles in external electromagnetic fields using the constrained Hamiltonian formalism. The formulation yields both a covariant kinetic equation and its form in independent physical phase space variables, together with the associated noncanonical Poisson brackets and invariant measure. For massive particles, the interplay between the spin constraints and the electromagnetic field makes the particle velocity generally nonparallel to its kinetic momentum and modifies the momentum and spin evolution. The invariant measure in the reduced phase space obeys an exact Liouville identity even for time-dependent fields. This identity and the equations of motion give local conservation of charge and Boltzmann entropy, as well as balance equations for energy-momentum and total angular momentum. The global equilibrium conditions are consistent with covariant statistical mechanics and the Wigner function approach. The massless construction recovers the standard chiral kinetic equations and phase space measure. This framework provides a consistent Hamiltonian description of spin transport beyond equilibrium.

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arXiv2026

Responses of multiparticle observables to multidimensional nuclear deformation in relativistic heavy-ion collisions

Relativistic heavy-ion collisions provide a unique opportunity to probe ground-state nuclear structure through its imprint on the initial collision geometry. We investigate how multiparticle observables respond to combined variations of quadrupole deformation, triaxiality, and hexadecapole deformation, using $^{129}$Xe+$^{129}$Xe collisions as a representative testing ground. We perform a joint analysis in the three-dimensional $(β_2,γ,β_4)$ parameter space and construct initial-state estimators for several flow and mean transverse momentum correlation observables. At the initial-state level, $ρ_2$ is primarily sensitive to $β_2$ and $γ$, with its sensitivity to $γ$ enhanced at nonzero $β_2$. The nonlinear response coefficient $χ_{4,22}$ is predominantly sensitive to $β_4$, while its dependence on $β_2$ and $γ$ remains comparatively weak. Higher-order correlators exhibit more complex multidimensional response patterns; in particular, $ρ_{224}$ shows a dependence on $γ$ and $β_4$ that becomes more pronounced at finite $β_2$. We further employ the iEBE-VISHNU hybrid model to examine whether these deformation sensitivities survive the subsequent dynamical evolution. The final-state calculations indicate that the sensitivity of $ρ_2$ to $β_2$ and $γ$ is largely preserved, whereas the $β_4$ sensitivity of $χ_{4,22}$ is substantially reduced. For the other higher-order observables, the initial-state sensitivities are modified by the evolution or cannot be resolved with the present statistics.

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arXiv2026

Covariant equations of motion of massive spinning particles in a background Yang-Mills field

The dynamics of a spinning colored particle in a background non-Abelian Yang-Mills field is of broad interest in many areas of physics. A physically important application arises in relativistic heavy-ion collisions, where hard probes such as heavy quarks and jets propagate through the strong early-time classical color fields collectively referred to as the glasma. The standard framework for describing the classical dynamics of colored particles in a background Yang-Mills field is provided by the Wong equations, but it does not incorporate spin degrees of freedom. Although several extensions of the Wong equations have been proposed to include spin, they generally fail to satisfy all the necessary requirements simultaneously, such as Lorentz covariance, allowance for an arbitrary chromomagnetic moment, and preservation of the required physical constraints. In this work, we extend the framework of a relativistic classical spinning particle in an electromagnetic field to describe spin-1/2 quarks propagating in a generic background non-Abelian Yang-Mills field. By systematically applying the Dirac-Bergmann algorithm, we derive a self-consistent set of equations of motion for the particle's coordinates, momenta, spin, and color charge that satisfies all these requirements. This formalism provides a more complete and physically consistent description of spinning colored particles in background Yang-Mills fields, and offers a suitable framework for studying momentum diffusion and spin polarization phenomena of hard probes in heavy-ion collisions, particularly in the glasma.

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arXiv2026

Memory effect on the heavy quark dynamics in hot QCD matter

We study the heavy quark dynamics in the presence of memory within the framework of a generalized Langevin equation. Time correlated thermal noise with power-law decay is generated by a fractional differential equation, formulated using the Caputo fractional derivative with order parameter $ν$. The effect of memory is calculated through the momentum correlation, the time evolution of the average squared momentum, the average squared displacement, and the average kinetic energy. The effect of memory is further studied for the higher normalised central moments of the heavy quark transverse-momentum distribution. The results indicate that time correlated thermal noise substantially influences heavy quark dynamics in the quark gluon plasma.

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