Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userOn non-conformal kinetic theory and hydrodynamics for Bjorken flow
98
0
0.0
(
0
)
Authors
Sunil Jaiswal
Ask ChatGPT about the research
No Arabic abstract
Using and comparing kinetic theory and second-order Chapman-Enskog hydrodynamics, we study the non-conformal dynamics of a system undergoing Bjorken expansion. We use the concept of `free-streaming fixed lines for scaled shear and bulk stresses in non-conformal kinetic theory and hydrodynamics, and show that these `fixed lines behave as early-time attractors and repellors of the evolution. In the conformal limit, the free-streaming fixed lines reduce to the well-known fixed points of conformal Bjorken dynamics. A new fixed point in the free streaming regime is identified which lies at the intersection of these fixed lines. Contrary to the conformal scenario, both kinetic theory and hydrodynamics predict the absence of attractor behavior in the normalised shear stress channel. In kinetic theory a far-off-equilibrium attractor is found for the normalised effective longitudinal pressure, driven by rapid longitudinal expansion. Second-order viscous hydrodynamics fails to accurately describe this attractor. From a thorough analysis of the free-streaming dynamics in Chapman-Enskog hydrodynamics we conclude that this failure results from an inaccurate approximation of the fixed lines and a related incorrect description of the nature of the fixed point. A modified anisotropic hydrodynamic description is presented that provides excellent agreement with kinetic theory results and reproduces the far-from-equilibrium attractor for the scaled longitudinal pressure.
rate research
Read More
Motivated by recent interest in collectivity in small systems, we calculate the harmonic flow response to initial geometry deformations within weakly coupled QCD kinetic theory using the first correction to the free-streaming background. We derive a parametric scaling formula that relates harmonic flow in systems of different sizes and different generic initial gluon distributions. We comment on similarities and differences between the full QCD effective kinetic theory and the toy models used previously. Finally we calculate the centrality dependence of the integrated elliptic flow $v_2$ in oxygen-oxygen, proton-lead and proton-proton collision systems.
In the Einestein-dilaton theory with a Liouville potential parameterized by $eta$, we find a Schwarzschild-type black hole solution. This black hole solution, whose asymptotic geometry is described by the warped metric, is thermodynamically stable only for $0 le eta < 2$. Applying the gauge/gravity duality, we find that the dual gauge theory represents a non-conformal thermal system with the equation of state depending on $eta$. After turning on the bulk vector fluctuations with and without a dilaton coupling, we calculate the charge diffusion constant, which indicates that the life time of the quasi normal mode decreases with $eta$. Interestingly, the vector fluctuation with the dilaton coupling shows that the DC conductivity increases with temperature, a feature commonly found in electrolytes.
High-energy nuclear collisions produce a nonequilibrium plasma of quarks and gluons which thermalizes and exhibits hydrodynamic flow. There are currently no practical frameworks to connect the early particle production in classical field simulations to the subsequent hydrodynamic evolution. We build such a framework using nonequilibrium Greens functions, calculated in QCD kinetic theory, to propagate the initial energy-momentum tensor to the hydrodynamic phase. We demonstrate that this approach can be easily incorporated into existing hydrodynamic simulations, leading to stronger constraints on the energy density at early times and the transport properties of the QCD medium. Based on (conformal) scaling properties of the Greens functions, we further obtain pragmatic bounds for the applicability of hydrodynamics in nuclear collisions.
We derive a quantum kinetic theory for QED including both elastic and inelastic collisions with screening effect. By assuming parity invariance at the lowest order in $hbar$, we find the classical limit of the kinetic theory generalizes the well-known classical kinetic theory to massive case. The resulting classical kinetic theory simplifies when fermion bare mass is much greater than thermal mass. In this case only elastic collision is relevant and screening is only needed for Coulomb scattering. For a given solution to the classical kinetic theory, we find at $O(hbar)$ non-dynamical part of the quantum correction to Wigner functions for fermion and photon, which gives rise to spin polarization for fermion and photon respectively. Other contributions to spin polarizations from dynamical part of the correction to Wigner function are possible when parity violating sources are present.
Using relativistic conformal hydrodynamics coupled to the linear $sigma$ model we study the evolution of matter created in heavy--ion collisions. We focus the study on the influence of the dynamics of the chiral fields on the charged-hadron elliptic flow $v_2$ for a temperature--independent as well as for a temperature--dependent $eta/s$ that is calculated from kinetic theory. We find that $v_2$ is not very sensitive to the coupling of chiral fields to the hydrodynamic evolution, but the temperature dependence of $eta/s$ plays a much bigger role on this observable.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
