We give a solution of the Riemann problem in relativistic hydrodynamics in the case of ultrarelativistic equation of state and nonvanishing components of the velocity tangent to the initial discontinuity. Simplicity of the ultrarelativistic equation of state (the pressure being directly proportional to the energy density) allows us to express this solution in analytical terms. The result can be used both to construct and test numerical schemes for relativistic Euler equations in (3+1) dimensions.
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http://dx.doi.org/10.1103/PhysRevE.81.046313 | DOI Listing |
Phys Rev E
November 2024
Department of Physics "A. Pontremoli," University of Milan, via Celoria 16, 20133 Milan, Italy and Institute of Theoretical Physics, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany.
The shear viscosity is a fundamental transport property of matter. Here we derive a general theory of the viscosity of gases based on the relativistic Langevin equation (deduced from a relativistic Lagrangian) and nonaffine linear response theory. The proposed relativistic theory is able to recover the viscosity of nonrelativistic classical gases, with all its key dependencies on mass, temperature, particle diameter, and Boltzmann constant, in the limit of Lorentz factor γ=1.
View Article and Find Full Text PDFUltrarelativistic nuclear collisions create a strongly interacting state of hot and dense quark-gluon matter that exhibits a remarkable collective flow behavior with minimal viscous dissipation. To gain deeper insights into its intrinsic nature and fundamental degrees of freedom, we determine the speed of sound in an extended volume of quark-gluon plasma using lead-lead (PbPb) collisions at a center-of-mass energy per nucleon pair of 5.02 TeV.
View Article and Find Full Text PDFEur Phys J C Part Fields
April 2024
Department of Physics, University of Jyväskylä, P.O. Box 35, 40014 Jyväskylä, Finland.
We derive an expression for the energy-momentum tensor in the discrete lattice formulation of pure glue QCD. The resulting expression satisfies the continuity equation for energy conservation up to numerical errors with a symmetric procedure for the time discretization. In the case of the momentum conservation equation, we obtain an expression that is of higher accuracy in lattice spacing () than the naive discretization where fields in the continuum expressions are replaced by discretized counterparts.
View Article and Find Full Text PDFPhys Rev Lett
August 2022
Department of Physics, Sogang University, 35 Baekbeom-ro, Mapo-gu, Seoul 04107, Korea.
We perform post-Newtonian analysis of double field theory as a test of string theory in gravitational sector against observations. We identify the Eddington-Robertson-Schiff parameters β_{PPN}, γ_{PPN} with the charges of electric H flux and dilaton respectively, and further relate them to stress-energy tensor. We show β_{PPN}=1 from weak energy condition and argue that the observation of γ_{PPN}≃1 signifies the ultrarelativistic equation of state in baryons, or the suppression of gluon condensate.
View Article and Find Full Text PDFEntropy (Basel)
December 2021
Department of Mathematics and Alma Mater Research Center on Applied Mathematics AM2, University of Bologna, 40126 Bologna, Italy.
A relativistic version of the rational extended thermodynamics of polyatomic gases based on a new hierarchy of moments that takes into account the total energy composed by the rest energy and the energy of the molecular internal mode is proposed. The moment equations associated with the Boltzmann-Chernikov equation are derived, and the system for the first 15 equations is closed by the procedure of the maximum entropy principle and by using an appropriate BGK model for the collisional term. The entropy principle with a convex entropy density is proved in a neighborhood of equilibrium state, and, as a consequence, the system is symmetric hyperbolic and the Cauchy problem is well-posed.
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