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Manu Kurian

Publications and source records attributed to Manu Kurian.

36 records · Page 2Linked to original sources

Dragging heavy quark in an anisotropic QCD medium beyond the static limit

Heavy quark dynamics in an anisotropic QCD medium have been analyzed within the Fokker-Planck approach. Heavy quark drag force and momentum diffusion tensor have been decomposed by employing a general tensor basis for an anisotropic medium. Depending upon the relative orientation of the direction of the momentum anisotropy of the medium and heavy quark motion, two drag and four diffusion coefficients have been estimated in the anisotropic QCD medium. The relative significance of different components of drag and momentum diffusion coefficients has been explored. The dependence of the angle between the anisotropic vector and heavy quark motion to the drag and diffusion coefficients has also been studied. Further, the energy loss of heavy quarks due to the elastic collisional process in an anisotropic medium has been studied. It is seen that the anisotropic contributions to heavy quark transport coefficients and its collisional energy loss have a strong dependence on the direction and strength of momentum anisotropy in the QCD medium.

hep-ph↗

Heavy quark transport coefficients in a viscous QCD medium with collisional and radiative processes

The heavy quark drag and momentum diffusion coefficients in the presence of both the collisional and radiative processes have been studied in a hot viscous QCD medium. The thermal medium effects are incorporated by employing the effective fugacity quasiparticle model based on the lattice QCD equation of state. Viscous effects are embedded into the heavy quark transport through the near-equilibrium distribution functions of the constituent medium particles of the quark-gluon plasma. The viscous corrections to the momentum distributions have been estimated from the effective Boltzmann equation. The effect of shear viscous correction to drag and diffusion is investigated by considering the soft gluon radiation by heavy quarks along with the elastic collisional processes of the heavy quark with the light quarks and gluons within the QGP medium. The momentum and temperature dependence of the heavy quark transport coefficients are seen to be sensitive to the viscous coefficient of the QGP for the collisional and radiative processes. The collisional and radiative energy loss of the heavy quark in the viscous quark-gluon plasma has also been explored.

hep-ph↗

Electromagnetic response of hot QCD medium in the presence of background time-varying fields

The response of the hot QCD medium in the presence of external time dependent electromagnetic fields has been studied within the relativistic Boltzmann transport theory. The impact of the time dependence of the electromagnetic fields and collisional aspects of the medium to the induced electric and Hall current densities has been explored. The non-equilibrium momentum distribution of degrees of freedom has been obtained in the presence of space-time varying electromagnetic fields. Further, the analysis has been extended to an anisotropic QCD medium while incorporating the in-medium interaction effects. It is observed that the electric charge transport is sensitive to the inhomogeneity of the fields and the momentum anisotropy of the QCD medium.

hep-ph↗

Heavy quark transport in an anisotropic hot QCD medium: Collisional and Radiative processes

The impact of momentum anisotropy on the heavy quark transport coefficients due to collisional and radiative processes in the QCD medium has been studied within the ambit of kinetic theory. Anisotropic aspects (momentum) are incorporated into the heavy quark dynamics through the non-equilibrium momentum distribution function of quarks, antiquarks, and gluons. These non-equilibrium distribution functions that encode the physics of momentum anisotropy and turbulent chromo-fields have been obtained by solving the ensemble-averaged diffusive Vlasov-Boltzmann equation. The momentum dependence of heavy quark transport coefficients in the medium is seen to be sensitive to the strength of the anisotropy for both collisional and radiative processes. In addition, the collisional and radiative energy loss of the heavy quark in the anisotropic hot QCD medium have been analyzed. The effects of anisotropy on the drag and diffusion coefficients are observed to have a visible impact on the nuclear suppression factor both at the RHIC and LHC.

hep-ph↗

Response of a weakly magnetized hot QCD medium to inhomogeneous electric field

The electric charge transport in a weakly magnetized hot QCD medium has been investigated in the presence of an external inhomogeneous electric field. The current densities (electric and Hall)induced by the inhomogeneous electric field have been estimated in the regime where space-time inhomogeneity of the field is small so that the collisional effect in the medium cannot be neglected. The collisional aspect of the medium has been captured by employing both relaxation time approximation and Bhatnagar-Gross-Krook collision kernel in the relativistic Boltzmann equation. The magnetic field, momentum anisotropy, and quark chemical potential dependences of the electric current and Hall current densities have been explored, and the impacts on the respective conductivities have been studied. The inhomogeneities of the field are seen to have sizable effects on the electromagnetic responses of the collisional medium.

hep-ph↗

Dynamics of QCD Matter -- current status

In this article, there are 18 sections discussing various current topics in the field of relativistic heavy-ion collisions and related phenomena, which will serve as a snapshot of the current state of the art. Section 1 reviews experimental results of some recent light-flavored particle production data from ALICE collaboration. Other sections are mostly theoretical in nature. Very strong but transient magnetic field created in relativistic heavy-ion collisions could have important observational consequences. This has generated a lot of theoretical activity in the last decade. Sections 2, 7, 9, 10 and 11 deal with the effects of the magnetic field on the properties of the QCD matter. There are several unanswered questions about the QCD phase diagram. Sections 3, 11 and 18 discuss various aspects of the QCD phase diagram and phase transitions. Recent years have witnessed interesting developments in foundational aspects of hydrodynamics and their application to heavy-ion collisions. Sections 12, 15, 16 and 17 of this article probe some aspects of this exciting field. Transport coefficients together with their temperature- and density-dependence, are essential inputs in hydrodynamical calculations. Sections 5, 8 and 14 deal with calculation/estimation of various transport coefficients (shear and bulk viscosity, thermal conductivity, relaxation times, etc.) of quark matter and hadronic matter. Sections 4, 6 and 13 deals with interesting new developments in the field. Section 4 discusses color dipole gluon distribution function at small transverse momentum in the form of a series of Bells polynomials. Section 6 discusses the properties of Higgs boson in the quark gluon plasma using Higgs-quark interaction. Section 13 discusses modification of coalescence model to incorporate viscous corrections and application of this model.

hep-ph↗

Thermoelectric behaviour of hot collisional and magnetized QCD medium from an effective kinetic theory

The thermoelectric behaviour of quark-gluon plasma has been studied within the framework of an effective kinetic theory by adopting a quasiparticle model to incorporate the thermal medium effects. The thermoelectric response of the medium has been quantified in terms of the Seebeck coefficient. The dependence of the collisional aspects of the QCD medium on the Seebeck coefficient has been estimated by utilizing relaxation time approximation and Bhatnagar-Gross-Krook collision kernels in the effective Boltzmann equation. The thermoelectric coefficient is seen to depend on the quark chemical potential and collision aspects of the medium. Besides, the thermoelectric effect has been explored in a magnetized medium and the respective transport coefficients, such as magnetic field-dependent Seebeck coefficient and Nernst coefficient, have been estimated. The impacts of hot QCD medium interactions incorporated through the effective model and the magnetic field on the thermoelectric responses of the medium have been observed to be more prominent in the temperature regimes not very far from the transition temperature.

hep-ph↗

Momentum broadening of heavy quark in a magnetized thermal QCD medium

Anisotropic momentum diffusion coefficients of heavy quarks have been computed in a strongly magnetized quark-gluon plasma beyond the static limit within the framework of Langevin dynamics. Depending on the orientation of the motion of the heavy quark with respect to the direction of the magnetic field, five momentum diffusion coefficients of heavy quark have been estimated in the magnetized thermal medium. Specifically, we have focussed our attention to temperature range and strength of magnetic field satisfying the condition, $\it{i.e.}$ $M\gg\sqrt{eB}\gg T$, $M$ being the mass of heavy quark. The light quarks/antiquarks follow $1+1-$dimensional lowest Landau level (LLL) kinematics, and heavy quark dynamics are not directly affected by the magnetic field in the medium. The thermal gluon contribution to the diffusion coefficient is proportions to $T^3$, whereas, the contribution of light quarks in the lowest Landau state to the same is seen to be proportional to $T|eB|$. Furthermore, it is observed that for the case of heavy quark motion parallel to the magnetic field, the component of diffusion coefficient transverse both to the field and the heavy quark velocity $(κ^{\parallel}_{TT})$ turns out to be dominant as compared to the component longitudinal to both the field and motion $(κ^{\parallel}_{LL})$, $i.e.$, $κ^{\parallel}_{TT}\gg κ^{\parallel}_{LL}$. Further, for the case of heavy quark moving perpendicular to the magnetic field, it is seen that the diffusion coefficients transverse to the magnetic field are dominant, i.e., $κ^{\perp}_{LT}, κ^{\perp}_{TT}\gg κ^{\perp}_{TL}$.

hep-ph↗

Second order relativistic viscous hydrodynamics within an effective description of hot QCD medium

The second-order hydrodynamic equations for evolution of shear and bulk viscous pressure have been derived within the framework of covariant kinetic theory based on the effective fugacity quasiparticle model. The temperature-dependent fugacity parameter in the equilibrium distribution function leads to a mean field term in the Boltzmann equation which affects the interactions in the hot QCD matter. The viscous corrections to distribution function, up to second-order in gradient expansion, have been obtained by employing a Chapman-Enskog like iterative solution of the effective Boltzmann equation within the relaxation time approximation. The effect of mean field contributions to transport coefficients as well as entropy current has been studied up to second-order in gradients. In contrast to the previous calculations, we find non-vanishing entropy flux at second order. The effective description of relativistic second-order viscous hydrodynamics, for a system of interacting quarks and gluons, has been quantitatively analyzed in the case of the $1+1-$dimensional boost invariant longitudinal expansion. We study the proper time evolution of temperature, pressure anisotropy, and viscous corrections to entropy density for this simplified expansion. The second order evolution of quark-gluon plasma is seen to be affected significantly with the inclusion of mean field contributions and the realistic equation of state.

hep-ph↗

A study of charm quark dynamics in quark-gluon plasma with 3+1 D viscous hydrodynamics

The drag and diffusion coefficients are studied within the framework of Fokker-Planck dynamics for the case of a charm quark propagating in an expanding quark-gluon plasma. The space-time evolution of the nuclear matter created in the relativistic heavy-ion collision is modelled using MUSIC, a 3+1 D relativistic viscous hydrodynamic approach. The effect of viscous corrections to the heavy quark transport coefficients is explored by considering scattering processes with thermal quarks and gluons in the medium. It is observed that the momentum diffusion of the heavy quarks is sensitive to the shear and bulk viscosity to entropy ratios. The collisional energy loss of the charm quark in the viscous quark-gluon plasma is analyzed.

hep-ph↗

Thermal transport in a weakly magnetized hot QCD medium

The thermal transport coefficients in a weakly magnetized quark-gluon plasma have been investigated within the ambit of a quasiparticle model to encode the effects of the realistic equation of state. The presence of a weak magnetic field leads to the Hall-type conductivity associated with thermal transport in the medium. An effective covariant kinetic theory has been employed to quantify the thermal dissipation while incorporating the mean field contributions in the medium. The interplay of thermal transport and electric charge transport in the weakly magnetized medium has been explored in terms of the Wiedemann-Franz law. Strong violation of the Wiedemann-Franz law has been observed in temperature regimes near to the transition temperature. The behaviour of thermal conductivity in the strong magnetic field limit has also been studied. It is observed that both the magnetic field and equation of state have a significant impact on the thermal dissipation in the medium.

nucl-th↗

Impact of longitudinal bulk viscous effects to heavy quark transport in a strongly magnetized hot QCD medium

The effects of longitudinal bulk viscous pressure on the heavy quark dynamics have been estimated in a strongly magnetized quark-gluon plasma within the Fokker-Planck approach. The bulk viscous modification to the momentum distribution of bulk degrees of freedom has been obtained in the presence of a magnetic field while incorporating the realistic equation of state of the hot magnetized QCD medium. As the magnetic field breaks the isotropy of the medium, the analysis is done along the directions longitudinal and transverse to the field. The longitudinal bulk viscous contribution is seen to have sizable effects in the heavy quark momentum diffusion in the magnetized medium. The dependence of higher Landau levels and the equation of state on the viscous correction to the heavy quark transport has been explored in the analysis.

nucl-th↗

First order dissipative hydrodynamics and viscous corrections to the entropy four-current from an effective covariant kinetic theory

The first order hydrodynamic evolution equations for the shear stress tensor, the bulk viscous pressure and the charge current have been studied for a system of quarks and gluons, with a non-vanishing quark chemical potential and finite quark mass. The first order transport coefficients have been obtained by solving an effective Boltzmann equation for the grand-canonical ensemble of quasiquarks and quasigluons. We adopted temperature dependent effective fugacity for the quasiparticles to encode the hot QCD medium effects. The non-trivial energy dispersion of the quasiparticles induces mean field contributions to the transport coefficients whose origin could be directly related to the realization of conservation laws from the effective kinetic theory. Both the QCD equation of state and chemical potential are seen to have a significant impact on the quark-gluon plasma evolution. The shear and bulk viscous corrections to the entropy-four current have been investigated in the framework of the effective kinetic theory. The effect of viscous corrections to the entropy density have been quantified in the case of one dimensional boost-invariant expansion of the system. Further, the first order viscous corrections to the time evolution of temperature along with the description of pressure anisotropy and Reynolds number of the system have been explored for the longitudinal boost-invariant expansion.volution of temperature along with the description of pressure anisotropy of the system have also been explored.

hep-ph↗

Heavy quark dynamics in a hot magnetized QCD medium

The heavy quark drag and momentum diffusion have been investigated in a hot magnetized quark-gluon plasma, along the directions parallel and perpendicular to the magnetic field. The analysis is done within the framework of Fokker-Planck dynamics by considering the heavy quark scattering with thermal quarks and gluons at the leading order in the coupling constant. An extended quasiparticle model is adopted to encode the thermal QCD medium interactions in the presence of a magnetic field. Further, the higher Landau level effects on the temperature behaviour of the parallel and perpendicular components of the drag force and diffusion coefficients have studied. It has been observed that both the equation of state and the magnetic field play key roles in the temperature dependence of the heavy quark dynamics.

nucl-th↗

Longitudinal conductivity of hot magnetized collisional QCD medium in the inhomogeneous electric field

The longitudinal current density induced by the inhomogeneous electric field in the hot magnetized quark-gluon plasma has been investigated and utilized in obtaining the conductivity of the medium. The analysis has been done in the regime where inhomogeneity of the field is small so that the collision effect could be significant. The modeling of the QCD medium is based on a quasiparticle description where the medium effects have been encoded in the effective quarks, antiquarks and gluons. The temperature dependence of the linear longitudinal current density (in terms of the electric field) and the additional components of current density due to the inhomogeneity of electric field (in terms of its derivatives) have been obtained by solving the $(1+1)-$dimensional effective covariant kinetic theory with a proper collision term. The conductivity has been obtained from the current density in the presence of the inhomogeneous field. The collisional aspects of the medium have been captured by including both thermal relaxation approximation and the Bhatnagar-Gross-Krook collision kernels in the analysis. Further, the hot QCD medium effects and higher Landau level contributions to the current density and the conductivity have been investigated. It has been seen that the effects of inhomogeneity of the field and the mean field corrections to the current density and the conductivity are more visible in the temperature regions which are not far from the transition temperature.

nucl-th↗

Transport coefficients of hot magnetized QCD matter beyond the lowest Landau level approximation

In this article, shear viscosity, bulk viscosity, and thermal conductivity of a hot QCD medium have been studied in the presence of a strong magnetic field. To model the hot magnetized QCD matter, an extended quasi-particle description of the hot QCD equation of state in the presence of the magnetic field has been adopted. The effects of higher Landau levels on the temperature dependence of viscous coefficients (bulk and shear viscosities) and thermal conductivity have been obtained by considering the $1\rightarrow 2$ processes in the presence of the strong magnetic field. An effective covariant kinetic theory has been set up in (1+1)-dimensional that includes mean field contributions in terms of quasi-particle dispersions and magnetic field to describe the Landau level dynamics of quarks. The sensitivity of these parameters to the magnitude of the magnetic field has also been explored. Both the magnetic field and mean field contributions have seen to play a significant role in obtaining the temperature behaviour of the transport coefficients of hot QCD medium.

nucl-th↗

Bulk viscosity of a hot QCD/QGP medium in strong magnetic field within relaxation-time approximation

The bulk viscosity of hot QCD medium has been obtained in the presence of strong magnetic field. The present investigation involves the estimation of the quark damping rate and subsequently the thermal relaxation time for quarks in the presence of magnetic field while realizing the hot QCD medium as an effective Grand-canonical ensemble of effective gluons and quarks-antiquarks. The dominant process in the strong field limit is $1\rightarrow 2$ ($g\rightarrow q \bar{q}$) which contributes to the bulk viscosity in a most significant way. Further, setting up the linearized transport equation in the framework of an effective kinetic theory with hot QCD medium effects and employing the relaxation time approximation, the bulk viscosity has been estimated in lowest Landau level (LLL) and beyond. The temperature dependence of the ratio of the bulk viscosity to entropy density indicates towards its rising behavior near the transition temperature.

nucl-th↗

Effective description of hot QCD medium in strong magnetic field and longitudinal conductivity

Hot QCD medium effects have been studied in the effective quasi-particle description of quark-gluon plasma. This model encodes the collective excitation of gluons and quarks/anti-quarks in the thermal medium in terms of effective quarks and gluons having non-trivial energy dispersion relation. The present investigation involves the extension of the effective quasi-particle model in strong magnetic field limit. Realizing, hot QCD medium in the strong magnetic field as an effective grand canonical system in terms of the modified quark, anti-quark and gluonic degrees of freedom, the thermodynamics has been studied. Further, the Debye mass in hot QCD medium has to be sensitive to the magnetic field, and subsequently the same has been observed for the effective hot QCD coupling. As an implication, electrical conductivity (longitudinal) has been studied within an effective kinetic theory description of hot QCD in the presence of the strong magnetic field. The hot QCD equation of state (EoS), dependence entering through the effective coupling and quasi-parton distribution function, found to have a significant impact on the longitudinal electrical conductivity in strong magnetic field background.

nucl-th↗