A. Mezzalira

Note on holographic nonrelativistic Goldstone bosons

We consider a holographic setup where relativistic invariance is broken by a chemical potential, and anon-Abelian internal symmetry is broken spontaneously.We use the tool of holographic renormalization inorder to infer what can be learned purely by analytic boundary considerations. We find that the expectedWard identities are correctly reproduced. In particular, we obtain the identity which implies thenoncommutation of a pair of broken charges, which leads to the presence of Goldstone bosons withquadratic dispersion relations.

Electromagnetic response of strongly coupled plasmas

A bstractWe present a thorough analysis of the electromagnetic response of strongly coupled neutral plasmas described by the gauge/gravity correspondence. The coupling of the external electromagnetic field with the tower of quasi-normal modes of the plasmas supports the presence of various electromagnetic modes with different properties. Among them we underline the existence of negative refraction with low dissipation for a transverse mode. Previous hydrodynamical approaches have shown the ubiquitous character of negative refraction in charged plasmas and the absence thereof in neutral plasmas. Our results here extend the analysis for neutral plasmas beyond the hydrodynamical regime. As an application of these new insights we briefly discuss the case of the quark gluon plasma in the temperature dominated regime.

Supersymmetric Fluid Dynamics

Recently Navier-Stokes (NS) equations have been derived from the duality between the black branes and a conformal fluid on the boundary of AdS5. Nevertheless, the full correspondence has to be established between solutions of supergravity in AdS5 and supersymmetric field theories on the boundary. That prompts the construction of NS equations for a supersymmetric fluid. In the framework of rigid susy, there are several possibilities and we propose one candidate. We deduce the equations of motion in two ways: both from the divergenless condition on the energy-momentum tensor and by a suitable parametrization of the auxiliary fields. We give the complete component expansion and a very preliminary analysis of the physics of this supersymmetric fluid.

Analytic pseudo-Goldstone bosons

A bstractWe consider the interplay between explicit and spontaneous symmetry breaking in strongly coupled field theories. Some well-known statements, such as the Gell-Mann-Oakes-Renner relation, descend directly from the Ward identities and have thus a general relevance. Such Ward identities are recovered in gauge/gravity dual setups through holographic renormalization. In a simple paradigmatic three dimensional toy-model, we find analytic expressions for the two-point correlators which match all the quantum field theoretical expectations. Moreover, we have access to the full spectrum, which is reminiscent of linear confinement.

Fermionic corrections to fluid dynamics from BTZ black hole

A bstractWe reconstruct the complete fermionic orbit of the non-extremal BTZ black hole by acting with finite supersymmetry transformations. The solution satisfies the exact supergravity equations of motion to all orders in the fermonic expansion and the final result is given in terms of fermionic bilinears. By fluid/gravity correspondence, we derive linearized Navier-Stokes equations and a set of new differential equations from Rarita-Schwinger equation. We compute the boundary energy-momentum tensor and we interpret the result as a perfect fluid with a modified definition of fluid velocity. Finally, we derive the modified expression for the entropy of the black hole in terms of the fermionic bilinears.

Fermionic wigs for AdS-Schwarzschild black holes

A bstractWe provide the metric, the gravitino fields and the gauge fields to all orders in the fermionic zero modes for D = 5 and D = 4,N = 2 gauged supergravity solutions starting from non-extremal AdS-Schwarzschild black holes. We compute the Brown-York stress-energy tensor on the boundary of AdS5/AdS4 spaces and we discuss some implications of the fermionic corrections to perfect fluid interpretation of the boundary theory. The complete non-linear solution, which we denote as fermionic wig, is achieved by acting with supersymmetry transformations upon the supergravity fields and that expansion naturally truncates at some order in the fermionic zero modes.

Aspects of quantum fermionic T-duality

We study two aspects of fermionic T-duality: the duality in purely fermionic sigma models exploring the possible obstructions and the extension of the T-duality beyond classical approximation. We consider fermionic sigma models as coset models of supergroups divided by their maximally bosonic subgroup OSp(m|n)/SO(m) × Sp(n). Using the non-abelian T-duality and a non-conventional gauge fixing we derive their fermionic T-duals. In the second part of the paper, we prove the conformal invariance of these models at one and two loops using the Background Field Method and we check the Ward Identities.

Fermionic Wigs for BTZ Black Holes

We compute the wig for the BTZ black hole, namely the complete non–linear solution of supergravity equations with all fermionic zero modes. We use a “gauge completion” method starting from AdS3 Killing spinors to generate the gravitinos fields associated to the BH and we compute the back–reaction on the metric. Due to the anticommutative properties of the fermionic hairs the resummation of these effects truncates at some order. We illustrate the technique proposed in a precedent paper in a very explicit and analytical form. We also compute the mass, the angular momentum and other charges with their corrections.

Fermions, wigs, and attractors

Abstract We compute the modifications to the attractor mechanism due to fermionic corrections. In N = 2 , D = 4 supergravity, at the fourth order, we find terms giving rise to new contributions to the horizon values of the scalar fields of the vector multiplets.

No fermionic wigs for BPS attractors in 5 dimensions

Abstract We analyze the fermionic wigging of 1/2-BPS (electric) extremal black hole attractors in N = 2 , D = 5 ungauged Maxwell–Einstein supergravity theories, by exploiting anti-Killing spinors supersymmetry transformations. Regardless of the specific data of the real special geometry of the manifold defining the scalars of the vector multiplets, and differently from the D = 4 case, we find that there are no corrections for the near-horizon attractor value of the scalar fields; an analogous result also holds for 1/2-BPS (magnetic) extremal black string. Thus, the attractor mechanism receives no fermionic corrections in D = 5 (at least in the BPS sector).