TY  - JOUR
A1  - Erdmenger, Johanna
A1  - Hoyos, Carlos
A1  - O'Bannon, Andy
A1  - Papadimitriou, Ioannis
A1  - Probst, Jonas
A1  - Wu, Jackson M.S.
T1  - Two-point functions in a holographic Kondo model
JF  - Journal of High Energy Physics
N2  - 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.
KW  - holography and condensed matter physics (AdS/CMT)
KW  - AdS-CFT Correspondence
KW  - gauge-gravity correspondence
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-171139
VL  - 3
IS  - 39
ER  - 
TY  - JOUR
A1  - Erdmenger, Johanna
A1  - Fernández, Daniel
A1  - Flory, Mario
A1  - Megías, Eugenio
A1  - Straub, Ann-Kathrin
A1  - Witkowski, Piotr
T1  - Time evolution of entanglement for holographic steady state formation
JF  - Journal of High Energy Physics
N2  - Within gauge/gravity duality, we consider the local quench-like time evolution obtained by joining two 1+1-dimensional heat baths at different temperatures at time \(t\) = 0. A steady state forms and expands in space. For the 2+1-dimensional gravity dual, we find that the “shockwaves” expanding the steady-state region are of spacelike nature in the bulk despite being null at the boundary. However, they do not transport information. Moreover, by adapting the time-dependent Hubeny-Rangamani-Takayanagi prescription, we holographically calculate the entanglement entropy and also the mutual information for different entangling regions. For general temperatures, we find that the entanglement entropy increase rate satisfies the same bound as in the ‘entanglement tsunami’ setups. For small temperatures of the two baths, we derive an analytical formula for the time dependence of the entanglement entropy. This replaces the entanglement tsunami-like behaviour seen for high temperatures. Finally, we check that strong subadditivity holds in this time-dependent system, as well as further more general entanglement inequalities for five or more regions recently derived for the static case.
KW  - Physics
KW  - AdS-CFT Correspondence
KW  - Gauge-gravity correspondence
KW  - Holography and condensed matter physics (AdS/CMT)
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-173798
VL  - 2017
IS  - 10
ER  -