@article{ErdmengerHoyosO'Bannonetal.2017,
  author    = {Erdmenger, Johanna and Hoyos, Carlos and O'Bannon, Andy and Papadimitriou, Ioannis and Probst, Jonas and Wu, Jackson M.S.},
  title     = {Two-point functions in a holographic Kondo model},
  series = {Journal of High Energy Physics},
  volume    = {3},
  journal   = {Journal of High Energy Physics},
  number    = {39},
  doi       = {10.1007/JHEP03(2017)039},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-171139},
  year      = {2017},
  abstract  = {We develop the formalism of holographic renormalization to compute two-point functions in a holographic Kondo model. The model describes a (0 + 1)-dimensional impurity spin of a gauged SU(N ) interacting with a (1 + 1)-dimensional, large-N , strongly-coupled Conformal Field Theory (CFT). We describe the impurity using Abrikosov pseudo-fermions, and define an SU(N )-invariant scalar operator O built from a pseudo-fermion and a CFT fermion. At large N the Kondo interaction is of the form O\(^{†}\)O, which is marginally relevant, and generates a Renormalization Group (RG) flow at the impurity. A second-order mean-field phase transition occurs in which O condenses below a critical temperature, leading to the Kondo effect, including screening of the impurity. Via holography, the phase transition is dual to holographic superconductivity in (1 + 1)-dimensional Anti-de Sitter space. At all temperatures, spectral functions of O exhibit a Fano resonance, characteristic of a continuum of states interacting with an isolated resonance. In contrast to Fano resonances observed for example in quantum dots, our continuum and resonance arise from a (0 + 1)-dimensional UV fixed point and RG flow, respectively. In the low-temperature phase, the resonance comes from a pole in the Green's function of the form -i〈O〉\(^{2}\), which is characteristic of a Kondo resonance.},
  language  = {en}
}
@article{AmorettiAreanArgurioetal.2017,
  author    = {Amoretti, Andrea and Are{\´a}n, Daniel and Argurio, Riccardo and Musso, Daniele and Zayas, Leopoldo A. Pando},
  title     = {A holographic perspective on phonons and pseudo-phonons},
  series = {Journal of High Energy Physics},
  volume    = {5},
  journal   = {Journal of High Energy Physics},
  number    = {51},
  doi       = {10.1007/JHEP05(2017)051},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-170882},
  year      = {2017},
  abstract  = {We analyze the concomitant spontaneous breaking of translation and conformal symmetries by introducing in a CFT a complex scalar operator that acquires a spatially dependent expectation value. The model, inspired by the holographic Q-lattice, provides a privileged setup to study the emergence of phonons from a spontaneous translational symmetry breaking in a conformal field theory and offers valuable hints for the treatment of phonons in QFT at large. We first analyze the Ward identity structure by means of standard QFT techniques, considering both spontaneous and explicit symmetry breaking. Next, by implementing holographic renormalization, we show that the same set of Ward identities holds in the holographic Q-lattice. Eventually, relying on the holographic and QFT results, we study the correlators realizing the symmetry breaking pattern and how they encode information about the low-energy spectrum.},
  language  = {en}
}