scholarly journals Transport coefficients of heavy quarks aroundTcat finite quark chemical potential

Physical Review C â—˝  
2014 â—˝  
Vol 90 (5) â—˝  
Author(s):  
H. Berrehrah â—˝  
P. B. Gossiaux â—˝  
J. Aichelin â—˝  
W. Cassing â—˝  
J. M. Torres-Rincon â—˝  
...  
Keyword(s):  
Chemical Potential â—˝  
Transport Coefficients â—˝  
Heavy Quarks

scholarly journals Critical behaviour of hydrodynamic series

2021 â—˝  
Vol 2021 (5) â—˝  
Author(s):  
M. Asadi â—˝  
H. Soltanpanahi â—˝  
F. Taghinavaz
Keyword(s):  
Chemical Potential â—˝  
Transport Coefficients â—˝  
Hydrodynamic Modes â—˝  
Third Order â—˝  
Hydrodynamic Mode â—˝  
Strongly Coupled â—˝  
Conformal Theory â—˝  
Shear Dispersion â—˝  
Type Iib String Theory â—˝  
Hydrodynamic Transport

Abstract We investigate the time-dependent perturbations of strongly coupled $$ \mathcal{N} $$ N = 4 SYM theory at finite temperature and finite chemical potential with a second order phase transition. This theory is modelled by a top-down Einstein-Maxwell-dilaton description which is a consistent truncation of the dimensional reduction of type IIB string theory on AdS5×S5. We focus on spin-1 and spin-2 sectors of perturbations and compute the linearized hydrodynamic transport coefficients up to the third order in gradient expansion. We also determine the radius of convergence of the hydrodynamic mode in spin-1 sector and the lowest non-hydrodynamic modes in spin-2 sector. Analytically, we find that all the hydrodynamic quantities have the same critical exponent near the critical point θ = $$ \frac{1}{2} $$ 1 2 . Moreover, we propose a relation between symmetry enhancement of the underlying theory and vanishing of the only third order hydrodynamic transport coefficient θ1, which appears in the shear dispersion relation of a conformal theory on a flat background.

scholarly journals Exploring the Partonic Phase at Finite Chemical Potential in and out-of Equilibrium

Particles â—˝  
2020 â—˝  
Vol 3 (1) â—˝  
pp. 178-192 â—˝  
Author(s):  
O. Soloveva â—˝  
P. Moreau â—˝  
L. Oliva â—˝  
V. Voronyuk â—˝  
V. Kireyeu â—˝  
...  
Keyword(s):  
Cross Sections â—˝  
Chemical Potential â—˝  
Transport Coefficients â—˝  
Gluon Plasma â—˝  
Entropy Density â—˝  
Baryon Chemical Potential â—˝  
Equilibrium Study â—˝  
200 Gev â—˝  
Quasiparticle Model â—˝  
Scattering Cross Sections

We study the influence of the baryon chemical potential μ B on the properties of the Quark–Gluon–Plasma (QGP) in and out-of equilibrium. The description of the QGP in equilibrium is based on the effective propagators and couplings from the Dynamical QuasiParticle Model (DQPM) that is matched to reproduce the equation-of-state of the partonic system above the deconfinement temperature T c from lattice Quantum Chromodynamics (QCD). We study the transport coefficients such as the ratio of shear viscosity η and bulk viscosity ζ over entropy density s, i.e., η / s and ζ / s in the ( T , μ ) plane and compare to other model results available at μ B = 0 . The out-of equilibrium study of the QGP is performed within the Parton–Hadron–String Dynamics (PHSD) transport approach extended in the partonic sector by explicitly calculating the total and differential partonic scattering cross sections based on the DQPM and the evaluated at actual temperature T and baryon chemical potential μ B in each individual space-time cell where partonic scattering takes place. The traces of their μ B dependences are investigated in different observables for symmetric Au + Au and asymmetric Cu + Au collisions such as rapidity and m T -distributions and directed and elliptic flow coefficients v 1 , v 2 in the energy range 7.7 GeV ≤ s N N ≤ 200 GeV.

scholarly journals Thermoelectric Relations in the Conformal Limit in Dirac and Weyl Semimetals

Symmetry â—˝  
10.3390/sym12050814 â—˝  
2020 â—˝  
Vol 12 (5) â—˝  
pp. 814
Author(s):  
Vicente Arjona â—˝  
Juan Borge â—˝  
María A. H. Vozmediano
Keyword(s):  
Chemical Potential â—˝  
Transport Coefficients â—˝  
Three Dimensional â—˝  
Anomalous Behavior â—˝  
Conformal Anomaly â—˝  
Electronic Systems â—˝  
Electric Transport â—˝  
Thermo Electric â—˝  
Weyl Semimetals â—˝  
Band Crossing

Dirac and Weyl semimetals are three-dimensional electronic systems with the Fermi level at or near a band crossing. Their low energy quasi-particles are described by a relativistic Dirac Hamiltonian with zero effective mass, challenging the standard Fermi liquid (FL) description of metals. In FL systems, electrical and thermo–electric transport coefficient are linked by very robust relations. The Mott relation links the thermoelectric and conductivity transport coefficients. In a previous publication, the thermoelectric coefficient was found to have an anomalous behavior originating in the quantum breakdown of the conformal anomaly by electromagnetic interactions. We analyze the fate of the Mott relation in the system. We compute the Hall conductivity of a Dirac metal as a function of the temperature and chemical potential and show that the Mott relation is not fulfilled in the conformal limit.

scholarly journals Passage of heavy quarks through the fluctuating hot QCD medium

2021 â—˝  
Vol 81 (7) â—˝  
Author(s):  
Mohammad Yousuf Jamal â—˝  
Bedangadas Mohanty
Keyword(s):  
Chemical Potential â—˝  
Equations Of State â—˝  
Collision Frequency â—˝  
Heavy Quarks â—˝  
Baryon Density â—˝  
Momentum Dependence â—˝  
Theory Approach â—˝  
Gain Energy â—˝  
Field Fluctuations â—˝  
Experimental Facilities

AbstractThe change in the energy of the moving heavy (charm and bottom) quarks due to field fluctuations present in the hot QCD medium has been studied. A finite quark chemical potential has been considered while modeling the hot QCD medium counting the fact that the upcoming experimental facilities such as Facility for Anti-proton and Ion Research (FAIR) and Nuclotron-based Ion Collider fAcility (NICA) are expected to operate at finite baryon density and moderate temperature. The effective kinetic theory approach has been adopted where the collisions have been incorporated using the well-defined collisional kernel, known as Bhatnagar–Gross–Krook (BGK). To incorporate the non-ideal equations of state (EoSs) effects/medium interaction effects, an extended effective fugacity model has been adopted. The momentum dependence of the energy change due to fluctuation for the charm and bottom quark has been investigated at different values of collision frequency and chemical potential. The results are exciting as the heavy quarks are found to gain energy due to fluctuations while moving through the produced medium at finite chemical potential and collision frequency.

scholarly journals Thermoelectric properties of the (an-)isotropic QGP in magnetic fields

2021 â—˝  
Vol 81 (7) â—˝  
Author(s):  
He-Xia Zhang â—˝  
Jin-Wen Kang â—˝  
Ben-Wei Zhang
Keyword(s):  
Magnetic Field â—˝  
Seebeck Coefficient â—˝  
Strong Magnetic Field â—˝  
Landau Level â—˝  
Electric Fields â—˝  
Chemical Potential â—˝  
Thermal Structure â—˝  
Transport Coefficients â—˝  
Transverse Motion â—˝  
Thermoelectric Transport

AbstractThe Seebeck effect and the Nernst effect, which reflect the appearance of electric fields along x-axis and along y-axis ($$E_{x}$$ E x and $$E_{y}$$ E y ), respectively, induced by the thermal gradient along x-axis, are studied in the QGP at an external magnetic field along z-axis. We calculate the associated Seebeck coefficient ($$S_{xx}$$ S xx ) and Nernst signal (N) using the relativistic Boltzmann equation under the relaxation time approximation. In an isotropic QGP, the influences of magnetic field (B) and quark chemical potential ($$\mu _{q}$$ ÎĽ q ) on these thermoelectric transport coefficients are investigated. In the presence (absence) of weak magnetic field, we find $$S_{xx}$$ S xx for a fixed $$\mu _{q}$$ ÎĽ q is negative (positive) in sign, indicating that the dominant carriers for converting heat gradient to electric field are negatively (positively) charged quarks. The absolute value of $$S_{xx}$$ S xx decreases with increasing temperature. Unlike $$S_{xx}$$ S xx , the sign of N is independent of charge carrier type, and its thermal behavior displays a peak structure. In the presence of strong magnetic field, due to the Landau quantization of transverse motion of (anti-)quarks perpendicular to magnetic field, only the longitudinal Seebeck coefficient ($$S_{zz}$$ S zz ) exists. Our results show that the value of $$S_{zz}$$ S zz at a fixed $$\mu _{q}$$ ÎĽ q in the lowest Landau level (LLL) approximation always remains positive. Within the effect of high Landau levels, $$S_{zz}$$ S zz exhibits a thermal structure similar to that in the LLL approximation. As the Landau level increases further, $$S_{zz}$$ S zz decreases and even its sign changes from positive to negative. The computations of these thermoelectric transport coefficients are also extended to a medium with momentum-anisotropy induced by initial spatial expansion as well as strong magnetic field.

scholarly journals Dissipation in holographic superfluids

2021 â—˝  
Vol 2021 (9) â—˝  
Author(s):  
Aristomenis Donos â—˝  
Polydoros Kailidis â—˝  
Christiana Pantelidou
Keyword(s):  
Phase Transition â—˝  
Black Hole â—˝  
Chemical Potential â—˝  
Constitutive Relations â—˝  
Transport Coefficients â—˝  
Heat Current â—˝  
Goldstone Mode â—˝  
Thermodynamic Quantities â—˝  
Conserved Current â—˝  
Dissipative Terms

Abstract We study dissipation in holographic superfluids at finite temperature and zero chemical potential. The zero overlap with the heat current allows us to isolate the physics of the conserved current corresponding to the broken global U(1). By using analytic techniques we write constitutive relations including the first non-trivial dissipative terms. The corresponding transport coefficients are determined in terms of thermodynamic quantities and the black hole horizon data. By analysing their behaviour close to the phase transition we show explicitly the breakdown of the hydrodynamic expansion. Finally, we study the pseudo-Goldstone mode that emerges upon introducing a perturbative symmetry breaking source and we determine its resonant frequency and decay rate.

scholarly journals Transport coefficients for the hot quark-gluon plasma at finite chemical potential ÎĽB

Physical Review C â—˝  
2020 â—˝  
Vol 101 (4) â—˝  
Author(s):  
Olga Soloveva â—˝  
Pierre Moreau â—˝  
Elena Bratkovskaya
Keyword(s):  
Quark Gluon Plasma â—˝  
Chemical Potential â—˝  
Transport Coefficients â—˝  
Gluon Plasma

scholarly journals Nonperturbative effects on radiative energy loss of heavy quarks

2020 â—˝  
Vol 2020 (8) â—˝  
Author(s):  
Shuai Y.F. Liu â—˝  
Ralf Rapp
Keyword(s):  
Energy Loss â—˝  
Scattering Amplitude â—˝  
Transport Coefficients â—˝  
Power Spectra â—˝  
Heavy Quarks â—˝  
Radiative Energy â—˝  
Spectral Functions â—˝  
Fixed Temperature â—˝  
Strong Suppression â—˝  
Radiative Energy Loss

Abstract The radiative energy loss of fast partons traveling through the quark-gluon plasma (QGP) is commonly studied within perturbative QCD (pQCD). Nonperturbative (NP) effects, which are expected to become important near the critical temperature, have been much less investigated. Here, we utilize a recently developed T -matrix approach to incorporate NP effects for gluon emission off heavy quarks propagating through the QGP. We set up four cases that contain, starting from a Born diagram calculation with color- Coulomb interaction, an increasing level of NP components, by subsequently including (remnants of ) confining interactions, resummation in the heavy-light scattering amplitude, and off-shell spectral functions for both heavy and light partons. For each case we compute the power spectra of the emitted gluons, heavy-quark transport coefficients (drag and transverse-momentum broadening, $$ \hat{q} $$ q ̂ ), and the path-length dependent energy loss within a “QGP brick” at fixed temperature. Investigating the differences in these quantities between the four cases illustrates how NP mechanisms affect gluon radiation processes. While the baseline perturbative processes experience a strong suppression of soft radiation due to thermal masses of the emitted gluons, confining interactions, ladder resummations and broad spectral functions (re-)generate a large enhancement toward low momenta and low temperatures. For example, for a 10 GeV charm quark at 200 MeV temperature, they enhance the transport coefficients by up to a factor of 10, while the results smoothly converge to perturbative results at sufficiently hard scales.

scholarly journals QCD thermodynamics with nonzero chemical potential atNt=6and effects from heavy quarks

Physical Review D â—˝  
2010 â—˝  
Vol 81 (11) â—˝  
Author(s):  
C. DeTar â—˝  
L. Levkova â—˝  
Steven Gottlieb â—˝  
U. M. Heller â—˝  
J. E. Hetrick â—˝  
...  
Keyword(s):  
Chemical Potential â—˝  
Heavy Quarks
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