Article

# Fermionic operator mixing in holographic p-wave superfluids

• ##### Andy O’Bannon
Journal of High Energy Physics (Impact Factor: 5.62). 2010(5):1-67. DOI: 10.1007/JHEP05(2010)053
Source: arXiv

ABSTRACT 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 N = 4 \mathcal{N} = 4 supersymmetric SU(N

c
) Yang-Mills theory, in the ’t Hooft limit and with large coupling, coupled to two massless flavors of (2+1)-dimensional N = 4 \mathcal{N} = 4 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 AdS
5 × S
5 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.

KeywordsGauge-gravity correspondence-AdS-CFT Correspondence-Brane Dynamics in Gauge Theories

0 Bookmarks
·
88 Views
• Source
##### Article: Towards a Holographic Realization of Homes’ Law
[Hide abstract]
ABSTRACT: Gauge/gravity duality has proved to be a very successful tool for describing strongly coupled systems in particle physics and heavy ion physics. The application of the gauge/gravity duality to quantum matter is a promising candidate to explain questions concerning non-zero temperature dynamics and transport coefficients. To a large extent, the success of applications of gauge/gravity duality to the quark-gluon plasma is founded on the derivation of a universal result, the famous ratio of shear viscosity and entropy density. As a base for applications to condensed matter physics, it is highly desirable to have a similar universal relation in this context as well. A candidate for such a universal law is given by Homes’ law : high Tc superconductors, as well as some conventional su- perconductors, exhibit a universal scaling relation between the superfluid density at zero temperature and the conductivity at the critical temperature times the critical temper- ature itself. In this work we describe progress in employing the models of holographic superconductors to realize Homes’ law and to find a universal relation governing strongly correlated quantum matter. We calculate diffusive processes, including the backreaction of the gravitational matter fields on the geometry. We consider both holographic s-wave and p-wave superconductors. We show that a particular form of Homes’ law holds in the absence of backreaction. Moreover, we suggest further steps to be taken for holographically realizing Homes’ law more generally in the presence of backreaction.
Journal of High Energy Physics 10/2012; 2012(21-10). · 5.62 Impact Factor
• Source
##### Article: Holographic Constraints on a Vector Boson
[Hide abstract]
ABSTRACT: We show that holography poses non-trivial restrictions on various couplings of an interacting field. For a vector boson in the AdS Reissner-Nordstrom background, the dual boundary theory is pathological unless its electromagnetic and gravitational multipole moments are constrained. Among others, a generic dipole moment afflicts the dual CFT with superluminal modes, whose remedy bounds the gyromagnetic ratio in a range around the natural value g=2. We discuss the CFT implications of our results, and argue that similar considerations can shed light on how massive higher-spin fields couple to electromagnetism and gravity.
Journal of High Energy Physics 12/2012; 2013(4). · 5.62 Impact Factor
• Source
##### Article: A universal fermionic analogue of the shear viscosity
[Hide abstract]
ABSTRACT: We holographically compute supercharge diffusion constants in supersymmetric field theories, dual to AdS black brane solutions of arbitrary dimension. This includes the extension of earlier work by Kontoudi and Policastro for D3-branes to M2- and M5-brane theories. We consider the case of vanishing chemical potential. In particular, we relate the product of a diffusion constant and the energy density to a universal result for the fermionic absorption cross section. This relation is analogous to the famous proof of universality of $\eta / s$. We calculate the diffusion constants in two different ways: First, the computation is performed via the low frequency, low momentum pole of the correlator of supersymmetry currents. This pole describes the hydrodynamic phonino mode, the massless Goldstone fermion of spontaneous supersymmetry breaking by temperature. Second, the calculation is carried out using the dual transversal mode of the bulk gravitino, with the help of a new Kubo formula. Moreover, we provide some evidence for the applicability of generalized dimensional reduction for fermions when computing the corresponding D$p$-brane diffusion constants.
Journal of High Energy Physics 02/2013; 2013(7). · 5.62 Impact Factor