Bulletin of the American Physical Society
2015 Annual Spring Meeting of the APS Ohio-Region Section
Volume 60, Number 3
Friday–Saturday, March 27–28, 2015; Kent, Ohio
Session E2: Heavy Ion Theory II |
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Chair: Ulrich Heinz, Ohio State University Room: KSU Student Center 314 |
Saturday, March 28, 2015 10:10AM - 10:25AM |
E2.00001: New Exact Solution of the Relativistic Boltzmann Equation and its Hydrodynamic Limit Jorge Noronha, Gabriel Denicol, Michael Strickland, Mauricio Martinez, Ulrich Heinz We present an exact solution of the relativistic Boltzmann equation for a system undergoing boost-invariant longitudinal and azimuthally symmetric transverse flow (``Gubser flow''). The resulting exact nonequilibrium dynamics is compared to first and second order relativistic hydrodynamic approximations for various shear viscosity to entropy density ratios. This novel solution can be used to test the validity and accuracy of different hydrodynamic approximations in conditions similar to those generated in relativistic heavy-ion collisions. [Preview Abstract] |
Saturday, March 28, 2015 10:25AM - 10:40AM |
E2.00002: The Gubser solution of the relativistic Boltzmann equation and its domain of validity Mauricio Martinez Guerrero, Ulrich Heinz In this work we study the evolution of the one particle phase space distribution which is an exact solution to the relativistic Boltzmann equation. This solution describes a conformal system undergoing Gubser flow in the de Sitter space times a line $dS_3\otimes R$. We show that depending on the initial condition the distribution function can become negative in certain kinematic regions of the available phase space. This non-physical behaviour of the distribution function restricts the validity of its applicability and imposes physical constraints on the initial conditions. [Preview Abstract] |
Saturday, March 28, 2015 10:40AM - 10:55AM |
E2.00003: Anisotropic hydrodynamics for conformal Gubser flow Mohammad Nopoush, Radoslaw Ryblewski, Michael Strickland We derive the equations of motion for a system undergoing boost-invariant longitudinal and azimuthally-symmetric transverse ``Gubser flow'' using leading-order anisotropic hydrodynamics. This is accomplished by assuming that the one-particle distribution function is ellipsoidally-symmetric in the momenta conjugate to the de Sitter coordinates used to parameterize the Gubser flow. We then demonstrate that the $SO(3)_q$ symmetry in de Sitter space further constrains the anisotropy tensor to be of spheroidal form. The resulting system of two coupled ordinary differential equations for the de Sitter-space momentum scale and anisotropy parameter are solved numerically and compared to a recently obtained exact solution of the relaxation-time-approximation Boltzmann equation subject to the same flow. We show that anisotropic hydrodynamics describes the spatio-temporal evolution of the system better than all currently known dissipative hydrodynamics approaches. In addition, we prove that anisotropic hydrodynamics gives the exact solution of the relaxation-time approximation Boltzmann equation in the ideal, $\eta/s \rightarrow 0$, and free-streaming, $\eta/s \rightarrow \infty$, limits. [Preview Abstract] |
Saturday, March 28, 2015 10:55AM - 11:10AM |
E2.00004: Nonconformal viscous anisotropic hydrodynamics Dennis Bazow, Mauricio Martinez, Ulrich Heinz In relativistic heavy-ion collisions the rapid longitudinal expansion compared to the relatively weaker transverse expansion leads to highly anisotropic local momentum distributions. This breaks the assumption made in canonical viscous hydrodynamics that the system is close to local thermal equilibrium. To account for these large deviations from local momentum isotropy, the one-particle phase-space distribution function is expanded around an anisotropic state rather than its local equilibrium form, using Grad's 14-moment approximation. This procedure leads to the effective macroscopic equations of second-order anisotropic hydrodynamics. We perform a quantitative test of this approximation scheme by applying it to the case of a massive gas undergoing one-dimensional boost-invariant expansion. We use the relaxation time approximation in which case the Boltzmann equation can be solved exactly. We show that the second-order anisotropic hydrodynamics approach significantly outperforms all other hydrodynamic approximation schemes. [Preview Abstract] |
Saturday, March 28, 2015 11:10AM - 11:25AM |
E2.00005: Pre-equilibrium evolution effects on heavy-ion collision observables Jia Liu, Chun Shen, Ulrich Heinz Pre-equiliibrium dynamics has a non-negligible influence on the final observables of heavy-ion collisions. We take free-streaming, the weak interaction limit of pre-equilibrium, to model the evolution of MC-KLN and MC-Glb initial conditions. The free streamed matter is matched to a viscous hydrodynamic evolution model by imposing Landau matching at a variable switching time. We consider the switching time, the shear viscosity during hydrodynamic evolution and the decoupling temperature as free parameters and perform a parameter search to find the preferable parameter space, by assessing the fit of mean transverse momenta for pions, kaons, and protons and the charged hadron elliptic and triangular flow between simulated results and experimental data. This parameter search is implemented on both types of initial conditions, with or without pre-equilibrium evolution. The result shows MC-KLN initial conditions prefer a smaller switching time and larger shear viscosity than MC-Glb. And MC-KLN initial conditions require a smaller switching time if it goes through a pre-equilibrium stage, while MC-Glb allows a larger range of switching time. [Preview Abstract] |
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