Using gauge/gravity duality techniques, we discuss the sound-channel retarded correlators of vector and tensor conserved currents in a class of $(2+1)$-dimensional strongly-coupled field theories at zero temperature and finite charge density, assumed to be holographically dual to the extremal Reissner-Nordstr\"{o}m AdS$_4$ black hole. Using a combination of analytical and numerical methods, we determine the quasinormal mode spectrum at finite momentum for the coupled gravitational and electromagnetic perturbations, and discuss the appropriate choice of gauge-invariant variables (master fields) in order for the black hole quasinormal frequencies to reproduce the field theory spectrum. We discuss the role of the near horizon AdS$_{2}$ geometry in determining the low-frequency behavior of retarded correlators in the boundary theory, and comment on the emergence of criticality in the IR. In addition, we establish the existence of a sound mode at zero temperature and compute the speed of sound and sound attenuation constant numerically, obtaining a result consistent with the expectations from the zero temperature limit of hydrodynamics. The dispersion relation of higher resonances is also investigated.Comment: 36 pages, 15 figures, PDFLaTeX; v2, corrected typos and figure caption
We consider a (2 + 1)-dimensional field theory, assumed to be holographically dual to the extremal Reissner-Nordström AdS 4 black hole background, and calculate the retarded correlators of charge (vector) current and energy-momentum (tensor) operators at finite momentum and frequency. We show that, similar to what was observed previously for the correlators of scalar and spinor operators, these correlators exhibit emergent scaling behavior at low frequency. We numerically compute the electromagnetic and gravitational quasinormal frequencies (in the shear channel) of the extremal Reissner-Nordström AdS 4 black hole corresponding to the spectrum of poles in the retarded correlators. The picture that emerges is quite simple: there is a branch cut along the negative imaginary frequency axis, and a series of isolated poles corresponding to damped excitations. All of these poles are always in the lower half complex frequency plane, indicating stability. We show that this analytic structure can be understood as the proper limit of finite temperature results as T is taken to zero holding the chemical potential µ fixed.
We study the properties of fermion correlators in a boundary theory dual to the ReissnerNordström AdS d+1 background in the presence of a bulk dipole (Pauli) interaction term with strength p. We show that by simply changing the value of the parameter p we can tune continuously from a Fermi liquid (small p), to a marginal Fermi liquid behavior at a critical value of p, to a generic non-Fermi liquid at intermediate values of p, and finally to a Mott insulator at large values of the bulk Pauli coupling. As all of these phases are seen in the cuprate phase diagram, the holographic model we study has the key elements of the strong coupling physics typified by Mott systems. In addition, we extend our analysis to finite temperature and show that the Mott gap closes. Of particular interest is that it closes when the ratio of the gap to the critical temperature is of the order of ten. This behavior is very much similar to that observed in the classic Mott insulator VO2. We then analyze the non-analyticities of the boundary theory fermion correlators for generic values of frequency and momentum by calculating the quasi-normal modes of the bulk fermions. Not surprisingly, we find no evidence for the dipole interaction inducing an instability in the boundary theory. Finally, we briefly consider the introduction of superconducting condensates, and find that in that case, the fermion gap is driven by scalar-fermion couplings rather than by the Pauli coupling.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.