Supersymmetric Yang-Mills Plasma Research Articles

Holographic entropy production in a Bjorken expanding hot and dense strongly coupled quantum fluid

The authors study the dynamics of droplets of quark-gluon plasma created in heavy iron collisions. The relativistic quantum fluid undergoes Bjorken flow expansion and is modeled as conformal $N=4$ supersymmetric Yang-Mills plasma. In particular, they investigate the holographic entropy production far from equilibrium where the horizon area is no longer a proper measure for the entropy but the area of a dynamic apparent horizon is assumed to be the right dual observable.

Violation of energy conditions and entropy production in holographic Bjorken flow

We demonstrate that a Bjorken expanding strongly coupled $\mathcal{N}=4$ Supersymmetric Yang-Mills plasma can display dynamically-driven violations of the dominant and also the weak energy condition during hydrodynamization. In addition, we find that a period of vanishing entropy production in far-from-equilibrium stages induces later violations of the dominant energy condition in the strongly coupled plasma. Such violations cannot occur in a classical description of hydrodynamization and suggest that the inclusion of quantum effects in transport can lead to new phenomena in these regimes, even for systems without anomalies or spin.

Schwinger-Keldysh effective action for a relativistic Brownian particle in the AdS/CFT correspondence

We compute Schwinger-Keldysh effective action for a relativistic heavy quark (with constant background velocity) in strongly coupled N = 4 supersymmetric Yang-Mills plasma. The holographic dual description involves a noisy trailing string moving in Schwarzschild-AdS5 black brane. The noise is caused by Hawking radiation emitted from string worldsheet horizon. Besides quadractic terms, the effective action contains cubic interactions, which are entirely induced by the constant background velocity. The nonlinear fluctuation-dissipation relations for three-point functions are discussed based on holographic results.

Effect of back reaction on holographic Schwinger effect

Using the AdS/CFT correspondence, we study the effect of back reaction on the holographic Schwinger effect by performing the potential analysis. The back reaction discussed here arises from the presence of static heavy quarks uniformly distributed over N=4 supersymmetric Yang-Mills (SYM) plasma. The results show that the inclusion of back reaction decreases the potential barrier thus enhancing the production rate. Additionally, we evaluate the critical electric field by Dirac-Born-Infeld (DBI) action.

Back reaction effects on the imaginary potential of quarkonia in heavy quark cloud

Applying the AdS/CFT correspondence, we investigate the effect of back reaction on the imaginary part of heavy quarkonia potential in strongly coupled N=4 supersymmetric Yang-Mills (SYM) plasma. The back reaction considered here arises from the inclusion of static heavy quarks uniformly distributed over N=4 SYM plasma. It is shown that the presence of back reaction reduces the absolute value of the imaginary potential thus decreasing the thermal width. Furthermore, the results imply that back reaction enhances the quarkonia dissociation.

Drag force on heavy quarks from holographic QCD * * Supported by Guizhou Provincial Key Laboratory Of Computational Nano-Material Science (2018LCNS002)

We study the drag force of a relativistic heavy quark using a holographic QCD model with conformal invariance broken by a background dilaton. The effects of the chemical potential and the confining scale on this quantity are analyzed. The drag force in this model is shown to be larger than that of supersymmetric Yang-Mills (SYM) plasma. In particular, the inclusion of the chemical potential and confining scale both enhance the drag force, in agreement with earlier findings. Moreover, we discuss how the chemical potential and confining scale influence the diffusion coefficient.

Convergence of the Gradient Expansion in Hydrodynamics.

Hydrodynamic excitations corresponding to sound and shear modes in fluids are characterized by gapless dispersion relations. In the hydrodynamic gradient expansion, their frequencies are represented by power series in spatial momenta. We investigate the analytic structure and convergence properties of the hydrodynamic series by studying the associated spectral curve in the space of complexified frequency and complexified spatial momentum. For the strongly coupled N=4 supersymmetric Yang-Mills plasma, we use the holographic duality methods to demonstrate that the derivative expansions have finite nonzero radii of convergence. Obstruction to the convergence of hydrodynamic series arises from level crossings in the quasinormal spectrum at complex momenta.

Light quark energy loss in strongly coupled [formula omitted] SYM plasma with magnetic field

We employ the AdS/CFT correspondence to study the jet quenching of light quarks traversing in strongly coupled N=4 supersymmetric Yang-Mills (SYM) plasma under the influence of a (constant) magnetic field. We perform the analysis using falling string and shooting string, respectively. It is found that the two methods give the same result: the inclusion of magnetic field enhances the quark energy loss. In particular, this effect is more pronounced when the quark is moving transverse to the magnetic field rather than parallel, consistently with the findings of the drag force and jet quenching parameter.

The large proper-time expansion of Yang-Mills plasma as a resurgent transseries

We show that the late-time expansion of the energy density of mathcal{N} = 4 supersymmetric Yang-Mills plasma at infinite coupling undergoing Bjorken flow takes the form of a multi-parameter transseries. Using the AdS/CFT correspondence we find a gravity solution which supplements the well known large proper-time expansion by exponentially-suppressed sectors corresponding to quasinormal modes of the AdS black-brane. The full solution also requires the presence of further sectors which have a natural interpretation as couplings between these modes. The exponentially-suppressed sectors represent nonhydrodynamic contributions to the energy density of the plasma. We use resurgence techniques on the resulting transseries to show that all the information encoded in the nonhydrodynamic sectors can be recovered from the original hydrodynamic gradient expansion.

The effect of magnetic field on holographic entanglement entropy

Applying the AdS/CFT correspondence, we study the entanglement entropy in strongly coupled $\mathcal{N}=4$ supersymmetric Yang-Mills (SYM) plasma under the influence of a (constant) magnetic field $\mathcal{B}$. We consider the entangling surface transverse and parallel to $ \mathcal{B}$, respectively. For both cases, it is shown that the inclusion of $ \mathcal{B}$ enhances the entanglement entropy. Moreover, we observe that in this case the entanglement entropy does not exhibit a transition due to $ \mathcal{B}$.

Universal behaviour, transients and attractors in supersymmetric Yang–Mills plasma

Numerical simulations of expanding plasma based on the AdS/CFT correspondence as well as kinetic theory and hydrodynamic models strongly suggest that some observables exhibit universal behaviour even when the system is not close to local equilibrium. This leading behaviour is expected to be corrected by transient, exponentially decaying contributions which carry information about the initial state. Focusing on late times, when the system is already in the hydrodynamic regime, we analyse numerical solutions describing expanding plasma of strongly coupled N=4 supersymmetric Yang–Mills theory and identify these transient effects, matching them in a quantitative way to leading transseries corrections corresponding to least-damped quasinormal modes of AdS black branes. In the process we offer additional evidence supporting the recent identification of the Borel sum of the hydrodynamic gradient expansion with the far-from-equilibrium attractor in this system.

Studying a charged quark gluon plasma via holography and higher derivative corrections

We compute finite ’t Hooft coupling corrections to observables related to charged quantities in a strongly coupled mathcal{N} = 4 supersymmetric Yang-Mills plasma. The coupling corrected equations of motion of gauge fields are explicitly derived and differ from findings of previous works, which contained several small errors with large impact. As a consequence the mathcal{O}left(gamma right) -corrections to the observables considered, including the conductivity, quasinormal mode frequencies, in and off equilibrium spectral density and photoemission rates, become much smaller. This suggests that infinite coupling results obtained within AdS/CFT are little modified for the real QCD coupling strength.

Drag force in strongly coupled supersymmetric Yang–Mills plasma in a magnetic field

Applying AdS/CFT correspondence, we study the effect of a constant magnetic field on the drag force associated with a heavy quark moving through a strongly-coupled supersymmetric Yang–Mills plasma. The quark is considered moving transverse and parallel to . It is shown that for transverse case, the drag force is linearly dependent on in all regions, while for parallel case, the drag force increases monotonously with increasing and also reveals a linear behavior in the regions of strong . In addition, we find that has a more important effect in the transverse case than for the parallel.

Damping of hard excitations in strongly coupled N $$ \mathcal{N} $$ = 4 plasma

The damping of high momentum excitations in strongly coupled maximally supersymmetric Yang-Mills plasma is studied. Previous calculations of the asymptotic behavior of the quasinormal mode spectrum are extended and clarified. We confirm that subleading corrections to the lightlike dispersion relation $\omega({\bf q}) = |{\bf q}|$ have a universal $|{\bf q}|^{-1/3}$ form. Sufficiently narrow, weak planar shocks may be viewed as coherent superpositions of short wavelength quasinormal modes. The attenuation and evolution in profile of narrow planar shocks are examined as an application of our results.

Phase transitions of an anisotropic N=4 super Yang-Mills plasma via holography

Black hole solutions of type IIB supergravity were previously found that are dual to N=4 supersymmetric Yang-Mills plasma with an anisotropic spatial deformation. In the zero temperature limit, these black holes approach a Liftshitz like scaling solution in the IR. It was recently shown that these black holes are unstable, and at low temperatures there is a new class of black hole solutions that are thermodynamically preferred. We extend this analysis, by considering consistent truncations of the Kaluza-Klein reduction of IIB supergravity on a five-sphere that preserves multiple scalar and $U(1)$ gauge fields. We show that the previously constructed black holes become unstable at low temperatures, and construct new classes of exotic black hole solutions. We study the DC thermo-electric conductivity of these $U(1)$ charged black holes, and find a diverging DC conductivity at zero temperature due to the divergence of the gauge field coupling.

Finite coupling corrections to holographic predictions for hot QCD

Finite 't Hooft coupling corrections to multiple physical observables in strongly coupled $N=4$ supersymmetric Yang-Mills plasma are examined, in an attempt to assess the stability of the expansion in inverse powers of the 't Hooft coupling $\lambda$. Observables considered include thermodynamic quantities, transport coefficients, and quasinormal mode frequencies. Although large $\lambda$ expansions for quasinormal mode frequencies are notably less well behaved than the expansions of other quantities, we find that a partial resummation of higher order corrections can significantly reduce the sensitivity of the results to the value of $\lambda$.

A new phase for the anisotropic N=4 super Yang-Mills plasma

Black hole solutions of type IIB supergravity have been previously constructed that describe the N=4 supersymmetric Yang-Mills plasma with an anisotropic spatial deformation. The zero temperature limit of these black holes approach a Lifshitz-like scaling solution in the infrared. We show that these black holes become unstable at low temperature and we construct a new class of black hole solutions which are thermodynamically preferred. The phase transition is third order and incorporates a spontaneous breaking of the $SO(6)$ global symmetry down to $SO(4)\times SO(2)$. The critical exponents for the phase transition are given by $(\alpha,\beta,\gamma,\delta)=(-1,1,1,2)$ which differ from the standard mean-field exponents usually seen in holography. At low temperatures the black holes approach a novel kind of scaling behaviour in the far IR with spatial anisotropy and hyperscaling violation. We show that the new ground states are thermal insulators in the direction of the anisotropy.

Far-from-equilibrium dynamics of a strongly coupled non-Abelian plasma with non-zero charge density or external magnetic field

Using holography, we study the evolution of a spatially homogeneous, far from equilibrium, strongly coupled $$ \mathcal{N}=4 $$ supersymmetric Yang-Mills plasma with a non-zero charge density or a background magnetic field. This gauge theory problem corresponds, in the dual gravity description, to an initial value problem in Einstein-Maxwell theory with homogeneous but anisotropic initial conditions. We explore the dependence of the equilibration process on different aspects of the initial departure from equilibrium and, while controlling for these dependencies, examine how the equilibration dynamics are affected by the presence of a non-vanishing charge density or an external magnetic field. The equilibration dynamics are remarkably insensitive to the addition of even large chemical potentials or magnetic fields; the equilibration time is set primarily by the form of the initial departure from equilibrium. For initial deviations from equilibrium which are well localized in scale, we formulate a simple model for equilibration times which agrees quite well with our results.

Nonlocal probes of thermalization in holographic quenches with spectral methods

We describe the application of pseudo-spectral methods to problems of holographic thermal quenches of relevant couplings in strongly coupled gauge theories. We focus on quenches of a fermionic mass term in a strongly coupled N=4 supersymmetric Yang-Mills plasma, and the subsequent equilibration of the system. From the dual gravitational perspective, we study the gravitational collapse of a massive scalar field in asymptotically anti-de Sitter geometry with a prescribed boundary condition for its non-normalizable mode. Access to the full background geometry of the gravitational collapse allows for the study of nonlocal probes of the thermalization process. We discuss the evolution of the apparent and the event horizons, the two-point correlation functions of operators of large conformal dimensions, and the evolution of the entanglement entropy of the system. We compare the thermalization process from the viewpoint of local (the one-point) correlation functions and these nonlocal probes, finding that the thermalization time as measured by the probes is length dependent, and approaches the thermalization time of the one-point function for longer probes. We further discuss how the different energy scales of the problem contribute to its thermalization.

Shining a gluon beam through quark-gluon plasma

We compute the energy density radiated by a quark undergoing circular motion in strongly coupled $\mathcal{N}=4$ supersymmetric Yang-Mills plasma. If it were in vacuum, this quark would radiate a beam of strongly coupled radiation whose angular distribution has been characterized and is very similar to that of synchrotron radiation produced by an electron in circular motion in electrodynamics. Here, we watch this beam of gluons getting quenched by the strongly coupled plasma. We find that a beam of gluons of momenta $\ensuremath{\sim}q\ensuremath{\gg}\ensuremath{\pi}T$ is attenuated rapidly, over a distance $\ensuremath{\sim}{q}^{1/3}(\ensuremath{\pi}T{)}^{\ensuremath{-}4/3}$ in a plasma with temperature $T$. As the beam propagates through the plasma at the speed of light, it sheds trailing sound waves with momenta $\ensuremath{\lesssim}\ensuremath{\pi}T$. Presumably these sound waves would thermalize in the plasma if they were not hit soon after their production by the next pulse of gluons from the lighthouselike rotating quark. At larger and larger $q$, the trailing sound wave becomes less and less prominent. The outward-going beam of gluon radiation itself shows no tendency to spread in angle or to shift toward larger wavelengths, even as it is completely attenuated. In this regard, the behavior of the beam of gluons which we analyze is reminiscent of the behavior of jets produced in heavy ion collisions at the LHC which lose a significant fraction of their energy without appreciable change in their angular distribution or their momentum distribution as they plow through the strongly coupled quark-gluon plasma produced in these collisions.