Stefan A. Stricker

Anomalies and the chiral magnetic effect in the Sakai-Sugimoto model

In the chiral magnetic effect an imbalance in the number of left- and right-handed quarks gives rise to an electromagnetic current parallel to the magnetic field produced in noncentral heavy-ion collisions. The chiral imbalance may be induced by topologically nontrivial gluon configurations via the QCD axial anomaly, while the resulting electromagnetic current itself is a consequence of the QED anomaly. In the Sakai-Sugimoto model, which in a certain limit is dual to large-Nc QCD, we discuss the proper implementation of the QED axial anomaly, the (ambiguous) definition of chiral currents, and the calculation of the chiral magnetic effect. We show that this model correctly contains the so-called consistent anomaly, but requires the introduction of a (holographic) finite counterterm to yield the correct covariant anomaly. Introducing net chirality through an axial chemical potential, we find a nonvanishing vector current only before including this counterterm. This seems to imply the absence of the chiral magnetic effect in this model. On the other hand, for a conventional quark chemical potential and large magnetic field, which is of interest in the physics of compact stars, we obtain a nontrivial result for the axial current that is in agreement with previous calculations and known exact results for QCD.

Probing the pattern of holographic thermalization with photons

A bstractWe investigate the behavior of the retarded Green’s function of a U(1) gauge field in holographic

Holographic dilepton production in a thermalizing plasma

\mathcal{N}

Holographic thermalization in {{\mathcal N}}=4 super Yang–Mills theory at finite coupling

= 4 Super Yang-Mills plasma, taking the leading strong coupling corrections into account. First, we use the thermal limit of this quantity to determine the flow of the photon quasinormal mode spectrum away from the infinite ’t Hooft coupling limit, and after this specialize to a specific model of holographic thermalization, in which we evaluate the corresponding spectral density. In the latter case, our primary interest lies in the pattern, with which the spectral density approaches its equilibrium form, and how this process depends on the value of the coupling as well as the photon virtuality. All of the results obtained point consistently towards the weakening of the usual top-down pattern of holographic thermalization, once the coupling is decreased from the λ = ∞ limit.

Meson supercurrents and the Meissner effect in the Sakai-Sugimoto model

A bstractWe use the AdS/CFT correspondence to determine the out-of-equilibrium production rate of dileptons at rest in strongly coupled

Evolution of holographic entanglement entropy in an anisotropic system

\mathcal{N} = 4

Gauge independence of IR singularities in non-commutative QFT — and interpolating gauges

Super Yang-Mills plasma. Thermalization is achieved via the gravitational collapse of a thin shell of matter in AdS5 space and the subsequent formation of a black hole, which we describe in a quasistatic approximation. Prior to thermalization, the dilepton spectral function is observed to oscillate as a function of frequency, but the amplitude of the oscillations decreases when thermal equilibrium is approached. At the same time, we follow the flow of the quasinormal spectrum of the corresponding U(1) vector field towards its equilibrium limit.

Bootstrapping gravity solutions

We investigate the behavior of energy-momentum tensor correlators in holographic

Gravitational collapse of thin shells: Time evolution of the holographic entanglement entropy

{\mathcal N}=4