Matthias Kaminski

Holographic operator mixing and quasinormal modes on the brane

We provide a framework for calculating holographic Green’s functions from general bilinear actions and fields obeying coupled differential equations in the bulk. The matrix-valued spectral function is shown to be independent of the radial bulk coordinate, and hence, free from renormalization ambiguities. Applying this framework we improve the analysis of fluctuations in the D3/D7 system at finite baryon density, where the longitudinal perturbations of the world-volume gauge field couple to the scalar fluctuations of the brane embedding. We compute the spectral function and show how its properties are related to those of the quasinormal mode spectrum. We study the crossover from the hydrodynamic diffusive to the reactive regime and the movement of quasinormal modes as functions of temperature and density. We also compute their dispersion relations and find that they asymptote to the lightcone for large momenta.

Parity-violating hydrodynamics in 2 + 1 dimensions

A bstractWe study relativistic hydrodynamics of normal fluids in two spatial dimensions. When the microscopic theory breaks parity, extra transport coefficients appear in the hy- drodynamic regime, including the Hall viscosity, and the anomalous Hall conductivity. In this work we classify all the transport coefficients in first order hydrodynamics. We then use properties of response functions and the positivity of entropy production to restrict the possible coefficients in the constitutive relations. All the parity-breaking transport coeffi- cients are dissipationless, and some of them are related to the thermodynamic response to an external magnetic field and to vorticity. In addition, we give a holographic example of a strongly interacting relativistic fluid where the parity-violating transport coefficients are computable.

Fermionic operator mixing in holographic p-wave superfluids

We use gauge-gravity duality to compute spectral functions of fermionic operators in a strongly-coupled defect field theory in p-wave superfluid states. The field theory is (3+1)-dimensional

Sum Rules from an Extra Dimension

\mathcal{N} = 4

Quasinormal modes of massive charged flavor branes

supersymmetric SU(Nc) Yang-Mills theory, in the ’t Hooft limit and with large coupling, coupled to two massless flavors of (2+1)-dimensional

Isospin diffusion in thermal AdS/CFT with flavor

\mathcal{N} = 4

Quasinormal modes of magnetic and electric black branes versus far from equilibrium anisotropic fluids

supersymmetric matter. We show that a sufficiently large chemical potential for a U(1) subgroup of the global SU(2) isospin symmetry triggers a phase transition to a p-wave superfluid state, and in that state we compute spectral functions for the fermionic superpartners of mesons valued in the adjoint of SU(2) isospin. In the spectral functions we see the breaking of rotational symmetry and the emergence of a Fermi surface comprised of isolated points as we cool the system through the superfluid phase transition. The dual gravitational description is two coincident probe D5-branes in AdS5 × S5 with non-trivial worldvolume SU(2) gauge fields. We extract spectral functions from solutions of the linearized equations of motion for the D5-branes’ worldvolume fermions, which couple to one another through the worldvolume gauge field. We develop an efficient method to compute retarded Green’s functions from a system of coupled bulk fermions. We also perform the holographic renormalization of free bulk fermions in any asymptotically Euclidean AdS space.

Flavor Superconductivity and Superfluidity

Using the gravity side of the AdS/CFT correspondence, we investigate the analytic properties of thermal retarded Green’s functions for scalars, conserved currents, the stress tensor, and massless fermions. We provide some results concerning their large and small frequency behavior and their pole structure. From these results, it is straightforward to prove the validity of various sum rules on the field theory side of the duality. We introduce a novel contraction mapping we use to study the large frequency behavior of the Green’s functions.

Hydrodynamics in 1+1 dimensions from Maxwell-Chern-Simons theory in AdS_3

We present an analysis and classiffication of vector and scalar fluctuations in a D3/D7-brane setup at finite temperature and baryon density. The system is dual to an