The Sound of Strongly Coupled Field Theories: Quasinormal Modes In AdS

The AdS/CFT correspondence has developed over the last years into a very useful and powerful tool for studying strongly coupled field theories at finite temperature and density. Of particular interest is the regime of near equilibrium real time evolution that can be captured via linear response theory. The AdS/CFT correspondence allows the calculation of retarded two point functions of gauge invariant operators by studying fluctuations around asymptotically AdS black holes. A major role is played by the poles of these holographic response functions: the quasinormal frequencies. I will review the applications of these ideas to the hydrodynamics of the strongly coupled quark gluon plasma and the holographic realization of strongly coupled superfluids.Comment: 16 pages, 8 figures, 1 cow, Contribution to Proceedings of ERE2011, v2: minor changes, refs adde

Quasi-Particles in Non-Commutative Field Theory

After a short introduction to the UV/IR mixing in non-commutative field theories we review the properties of scalar quasi-particles in non-commutative supersymmetric gauge theories at finite temperature. In particular we discuss the appearance of super-luminous wave propagation.Comment: 12 pages, 3 figures, Talk given at NATO ARW "Non-Commutative Structures in Mathematics and Physics", Kyiv, Ukraine, 24-27 Sep. 200

Konishi Anomalies and Curves without Adjoints

Generalized Konishi anomaly relations in the chiral ring of N=1 supersymmetric gauge theories with unitary gauge group and chiral matter field in two-index tensor representations are derived. Contrary to previous investigations of related models we do not include matter multiplets in the adjoint representation. The corresponding curves turn out to be hyperelliptic. We also point out equivalences to models with orthogonal or symplectic gauge groups.Comment: 21 pages, v2: References added, misprints correcte

The holographic Weyl semi-metal

We present a holographic model of a Weyl semi-metal. We show that upon varying a mass parameter the model undergoes a quantum phase transition from a topologically non-trivial state to a trivial one. The order parameter for this phase transition is the anomalous Hall effect (AHE). We give an interpretation of the results in terms of a holographic RG flow and compare to a weakly coupled field theoretical model. Since there are no quasiparticle excitations in the strongly coupled holographic model the topological phase can not be bound to notions of topology in momentum space.Comment: 5 pages, 5 figure

Anomalous transport model with axial magnetic fields

The transport properties of massless fermions in spacetime dimension have been in the focus of recent theoretical and experimental research. New transport properties appear as consequences of chiral anomalies. The most prominent is the generation of a current in a magnetic field, the so-called chiral magnetic effect leading to an enhancement of the electric conductivity (negative magnetoresistivity). We study the analogous effect for axial magnetic fields that couple with opposite signs to fermions of different chirality. We emphasize local charge conservation and study the induced magneto-conductivities proportional to an electric field and a gradient in temperature. We find that the magnetoconductivity is enhanced whereas the magneto-thermoelectric conductivity is diminished. As a side result we interpret an anomalous contribution to the entropy current as a generalized thermal Hall effectThe research of K.L. has been supported by FPA2015-65480-P and by the Centro de Excelencia Severo Ochoa Programme under grant SEV-2012-0249 and SEV-2016-0597. The research of Y.L. has been supported by the Thousand Young Talents Program of China and grants ZG216S17A5 and KG12003301 from Beihang Universit

The Thermodynamic Potentials of Kerr-AdS Black Holes and their CFT Duals

String or M-theory in the background of Kerr-AdS black holes is thought to be dual to the large n limit of certain conformal field theories on a rotating sphere at finite temperature. The five dimensional black hole is associated to N=4 supersymmetric Yang-Mills theory on a rotating three-sphere and the four dimensional one to the superconformal field theory of coinciding M2 branes on a rotating two-sphere. The thermodynamic potentials can be expanded in inverse powers of the radius of the sphere. We compute the leading and subleading terms of this expansion in the field theory at one loop and compare them to the corresponding supergravity expressions. The ratios between these terms at weak and strong coupling turns out not to depend on the rotation parameters in the case of N=4 SYM. For the field theory living on one M2 brane we find a subleading logarithmic term. No such term arises from the supergravity calculation.Comment: 14 pages (harvmac b-mode), signs corrected, minor changes otherwis

On Sp(0) factors and orientifolds

We discuss the geometric engineering of SO/Sp gauge theories with symmetric or antisymmetric tensor matter and show that the `mysterious' rank zero gauge group factors observed by a few authors can be traced back to the effects of an orientifold which survives the geometric transition. By mapping the Konishi constraints of such models to those of the U(N) theory with adjoint matter, we show that the required shifts in the ranks of the unbroken gauge group components is due to the flux contribution of the orientifold after the transition.Comment: 14 page