Effect of a spectral modification of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>ρ</mml:mi></mml:math>meson on the shear viscosity of a pion gas

Mitra, Sukanya; Ghosh, Sabyasachi; Sarkar, Sourav

doi:10.1103/physrevc.85.064917

Cited by 32 publications

(75 citation statements)

References 45 publications

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“…[32], it was shown that a KT approach leads to an η of the pionic medium that increases with T when a phenomenological interaction is used, while a decreasing function of T is obtained when using χ PT in that same approach. An increasing trend of η with T was also observed by Mitra et al [40,41], who incorporated a medium dependent π -π cross section in the transport equation for a pion gas. They also found a significant effect of a temperature-dependent pionic chemical potential [41].…”

Section: Introductionsupporting

confidence: 49%

“…[36,40,44,45] predicted a shear viscosity η of pionic matter that increases with T , whereas using a Kubo approach, Lang et al [39] predicted η to decrease with T . For the interaction of pions in the medium, Lang et al [39] used lowest order chiral perturbation theory (χ PT), which describes well the experimental data on π -π cross sections up to center-of-mass energies of √ s = 0.500 GeV.…”

Section: Introductionmentioning

confidence: 99%

“…[32,39] predicted an η ≈ 0.001 GeV 3 ; in Refs. [31,40,45], η = 0.002 − 0.003 GeV 3 ; and in Refs. [26,27], η = 0.4 GeV 3 .…”

Section: Introductionmentioning

confidence: 99%

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Shear viscosity of a pion gas resulting fromρππandσππinteractions

2014

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We have evaluated the shear viscosity of pion gas with vanishing chemical potential taking into account its scattering with the low mass resonances σ and ρ during propagation in the medium. The thermal width (or collisional rate) of pions is calculated from πσ and πρ loop diagrams using effective interactions in the real-time formulation of finite temperature field theory. A very small value of shear viscosity by entropy density ratio (η/s), close to the quantum bound, is obtained which approximately matches the range of values of η/s used by Niemi et al.

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Section: Introductionsupporting

confidence: 49%

Section: Introductionmentioning

confidence: 99%

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Shear viscosity of a pion gas resulting fromρππandσππinteractions

2014

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“…I |M I | 2 and ignoring the non-resonant I = 2 contribution, the cross-section is found to agree very well [28,29] with the estimate based on measured phase-shifts given in [6]. In this way it is ensured that the dynamical model is normalized against experimental data although, this approach of introducing the width is not quite in agreement with low energy theorems based on chiral symmetry.…”

Section: Sukanya Mitra and Sourav Sarkarmentioning

confidence: 57%

“…In almost all estimations of the transport coefficients a vacuum cross-section was employed. In [28,29] a medium dependent cross-section was used in the evaluation of shear and bulk viscosities of a pion gas which resulted in a significant deviation from the results obtained with the ππ cross-section in vacuum.In this work we study the temperature dependence of the thermal conductivity of a pion gas. In particular, our intention is to emphasize on the effect of the medium on its temperature dependence brought in by the crosssection.…”

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confidence: 99%

Medium effects on the thermal conductivity of a hot pion gas

Mitra

Sarkar

2014

Phys. Rev. D

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We investigate the effect of the medium on the thermal conductivity of a pion gas out of chemical equilibrium by solving the relativistic transport equation in the Chapman-Enskog and relaxation time approximations. Using an effective model for the ππ cross-section involving ρ and σ meson exchange, medium effects are incorporated through thermal one-loop self-energies. The temperature dependence of the thermal conductivity is observed to be significantly affected.The observation of large elliptic flow of hadrons in heavy ion collisions at RHIC has led to the description of quark-gluon plasma as a nearly perfect fluid [1]. This interpretation is based on the small but finite value of the shear viscosity to entropy density ratio required in a relativistic hydrodynamic description of the collision. The effects of dissipation on the dynamical evolution of matter produced in relativistic heavy ion collisions have thus been a major topic of discussion in recent times [2]. At the microscopic level dissipative phenomena are studied by considering small departures from equilibrium. In kinetic theory the transport of momenta and heat as a result of collisions is quantitatively expressed in terms of coefficients of viscosity and thermal conductivity [3,4]. A large number of studies on the viscous coefficients have been performed in the transport approach. The shear viscosity η has been most commonly discussed followed by the bulk viscosity ζ, both for partonic as well as hadronic systems . The interesting issue concerning the behaviour of the viscosities in the vicinity of the transition from partonic to hadronic matter have also been discussed [1,12,14,15,[18][19][20]. While the value of η/s is expected to go through a minimum near the critical temperature [1, 18], ζ/s is believed to be large or diverging [12,15,19] at or near the transition.The effects of heat flow in heavy ion collisions has received much less attention. This is presumably on account of the fact that the net baryon number in the central rapidity region at the RHIC and LHC is very small. However, at FAIR energies or in the low energy runs at RHIC the baryon chemical potential is expected to be significant and heat conduction by baryons may play a more important role. On the other hand, a thermal system consisting of pions can sustain heat conduction despite the fact that the pions themselves do not carry baryon number [5]. This is due to the fact that the total number of pions in heavy ion collisions is essentially conserved. Pion number changing reactions are not sustained towards the late stages where collisions are mostly elastic and the system undergoes chemical freezeout. As the system expands and cools a pion chemical potential develops in order to keep the pion number fixed. Based on such a scenario a few studies of heat conduction by pions have been carried out. Using the experimental ππ cross-section the thermal conductivity of a pion gas was estimated in [5][6][7] whereas in [22] a unitarized scattering amplitude was employed. The heat conductiv...

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Shear Viscosity of Pionic and Nucleonic Components from Their Different Possible Mesonic and Baryonic Thermal Fluctuations

Ghosh

2015

Braz J Phys

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Owing to the Kubo relation, the shear viscosities of pionic and nucleonic components have been evaluated from their corresponding retarded correlators of viscous stress tensor in the static limit, which become non-divergent only for the non-zero thermal widths of the constituent particles. In the real-time thermal field theory, the pion and nucleon thermal widths have respectively been obtained from the pion self-energy for different meson, baryon loops and the nucleon self-energy for different pion-baryon loops. We have found a non-monotonic momentum distributions of pion and nucleon thermal widths, which have been integrated out by their respective Bose-enhanced and Pauli-blocked phase space factors during evaluation of their shear viscosities. The viscosity to entropy density ratio for this mixed gas of pion-nucleon system decreases and approaches toward its lower bound as the temperature and baryon chemical potential increase within the relevant domain of hadronic matter.

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Effect of a spectral modification of theρmeson on the shear viscosity of a pion gas

Cited by 32 publications

References 45 publications

Shear viscosity of a pion gas resulting fromρππandσππinteractions

Shear viscosity of a pion gas resulting fromρππandσππinteractions

Medium effects on the thermal conductivity of a hot pion gas

Shear Viscosity of Pionic and Nucleonic Components from Their Different Possible Mesonic and Baryonic Thermal Fluctuations

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