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arXiv:2112.14089 · Physical review. D/Physical review. D.

Fast scrambling due to rotating shockwaves in BTZ

Vinay Malvimat, Rohan R. Poojary

Published Jun 21, 2022• 14 citations
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Abstract

We study the perturbation due to rotating shockwaves in Banados-Teitelboim-Zanelli geometries at late times and analyze the change in mutual information between the two subsystems belonging to the dual ${\mathrm{CFT}}_{L}$ and ${\mathrm{CFT}}_{R}$. We find that the scrambling of mutual information is in general governed by the Lyapunov index ${\ensuremath{\lambda}}_{L}$ which is bounded by $\ensuremath{\kappa}=\frac{2\ensuremath{\pi}}{\ensuremath{\beta}(1\ensuremath{-}\ensuremath{\mu}\mathcal{L})}\ensuremath{\ge}\frac{2\ensuremath{\pi}}{\ensuremath{\beta}}$, where $\ensuremath{\mu}={r}_{\ensuremath{-}}/{r}_{+}$ and $\mathcal{L}$ is the angular momentum of the shockwave. For the special case of $\mathcal{L}=1$ we find the mutual information analytically and show that it is characterized by ${\ensuremath{\lambda}}_{L}=\ensuremath{\kappa}/2$ with the scrambling time for large black holes given as ${t}_{*}=\frac{\ensuremath{\beta}(1\ensuremath{-}\ensuremath{\mu})}{\ensuremath{\pi}}\mathrm{log}S$.

DOI
10.1103/physrevd.105.126019

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•Mar 26, 2018•0 citations
We study the perturbation due to rotating shockwaves in Banados-Teitelboim-Zanelli geometries at late times and analyze the change in mutual information between the two subsystems belonging to the dual CFTL{\mathrm{CFT}}_{L}CFTL​ and CFTR{\mathrm{CFT}}_{R}CFTR​. We find that the scrambling of mutual information is in general governed by the Lyapunov index \ensuremathλL{\ensuremath{\lambda}}_{L}\ensuremathλL​ which is bounded by \ensuremathκ=2\ensuremathπ\ensuremathβ(1\ensuremath−\ensuremathμL)\ensuremath≥2\ensuremathπ\ensuremathβ\ensuremath{\kappa}=\frac{2\ensuremath{\pi}}{\ensuremath{\beta}(1\ensuremath{-}\ensuremath{\mu}\mathcal{L})}\ensuremath{\ge}\frac{2\ensuremath{\pi}}{\ensuremath{\beta}}\ensuremathκ=\ensuremathβ(1\ensuremath−\ensuremathμL)2\ensuremathπ​\ensuremath≥\ensuremathβ2\ensuremathπ​, where \ensuremathμ=r\ensuremath−/r+\ensuremath{\mu}={r}_{\ensuremath{-}}/{r}_{+}\ensuremathμ=r\ensuremath−​/r+​ and L\mathcal{L}L is the angular momentum of the shockwave. For the special case of L=1\mathcal{L}=1L=1 we find the mutual information analytically and show that it is characterized by \ensuremathλL=\ensuremathκ/2{\ensuremath{\lambda}}_{L}=\ensuremath{\kappa}/2\ensuremathλL​=\ensuremathκ/2 with the scrambling time for large black holes given as t∗=\ensuremathβ(1\ensuremath−\ensuremathμ)\ensuremathπlogS{t}_{*}=\frac{\ensuremath{\beta}(1\ensuremath{-}\ensuremath{\mu})}{\ensuremath{\pi}}\mathrm{log}St∗​=\ensuremathπ\ensuremathβ(1\ensuremath−\ensuremathμ)​logS.
We compute the disruption of mutual information between the hemispherical subsystems on the left and right conformal field theories of a thermofield double state described by a Kerr geometry in AdS4{\mathrm{AdS}}_{4}AdS4​ due to shock waves along the equatorial plane. The shock waves and the subsystems considered respect the axisymmetry of the geometry. At late times, the disruption of the mutual information is given by the lengthening of the Hubeny-Rangamani-Takayanagi surface connecting the two subsystems; we compute the minimum value of the Lyapunov index-${\ensuremath{\lambda}}_{L}^{(\mathrm{min})}$ at late times and find that it is bounded by $\ensuremath{\kappa}=\frac{2\ensuremath{\pi}{T}_{H}}{(1\ensuremath{-}\ensuremath{\mu}\mathcal{L})}$, where $\ensuremath{\mu}$ is the horizon velocity, and L\mathcal{L}L is the angular momentum per unit energy of the shock wave. At very late times, we find the scrambling time for such a system is governed by $\ensuremath{\kappa}$ with $\ensuremath{\kappa}{t}_{*}=\mathrm{log}\mathcal{S}$ for large black holes with a large entropy S\mathcal{S}S. We also find a term that increases the scrambling time by $\mathrm{log}(1\ensuremath{-}\ensuremath{\mu}\mathcal{L}{)}^{\ensuremath{-}1}$ but which does not scale with the entropy of the Kerr geometry.
Abstract In this paper, we investigate the entanglement entropy of the rotating BTZ black hole perturbed by a massive back-reacting free falling particle. Then, mutual information between two finite intervals in two asymptotic regions of rotating BTZ is derived. It allows us to find the scrambling time, the time scale in which mutual information vanishes. We give a dual large c CFT description in terms of a thermofield double state with different temperatures for left and right moving modes that is perturbed by a local operator. Exact matching between gravity and CFT results is obtained.
Abstract Out-of-time-order correlators (OTOCs) that capture maximally chaotic properties of a black hole are determined by scattering processes near the horizon. This prompts the question to what extent OTOCs display chaotic behaviour in horizonless microstate geometries. This question is complicated by the fact that Lyapunov growth of OTOCs requires nonzero temperature, whereas constructions of microstate geometries have been mostly restricted to extremal black holes. In this paper, we compute OTOCs for a class of extremal black holes, namely maximally rotating BTZ black holes, and show that on average they display “slow scrambling”, characterized by cubic (rather than exponential) growth. Superposed on this average power-law growth is a sawtooth pattern, whose steep parts correspond to brief periods of Lyapunov growth associated to the nonzero temperature of the right-moving degrees of freedom in a dual conformal field theory. Next we study the extent to which these OTOCs are modified in certain “superstrata”, horizonless microstate geometries corresponding to these black holes. Rather than an infinite throat ending on a horizon, these geometries have a very deep but finite throat ending in a cap. We find that the superstrata display the same slow scrambling as maximally rotating BTZ black holes, except that for large enough time intervals the growth of the OTOC is cut off by effects related to the cap region, some of which we evaluate explicitly.
Abstract We introduce a local operational protocol for measuring quantum information scrambling in a curved spacetime background. In this framework, two Unruh-DeWitt (UDW) detectors, coupled to a massless conformally coupled scalar field in the Hartle–Hawking vacuum of the non-rotating ( 2 + 1 ) -dimensional Banados–Teitelboim–Zanelli (BTZ) black hole, serve as local probes. Evaluating the detector out-of-time-ordered correlator requires a fourth-order Dyson series expansion. Within the scrambling regime, this correlator exhibits exponential growth with Lyapunov exponent, exactly saturating the Maldacena–Shenker–Stanford bound at the global Hawking temperature. Governed by the black hole surface gravity, the Lyapunov exponent is universal and independent of detector positions, energy gaps, and coupling strengths. Furthermore, the scrambling amplitude shows a monotonic dependence on the radial positions of the detectors, vanishing at the event horizon and increasing outward. Local two-level probes thus witness the maximal chaos of the BTZ geometry without reconstructing the global quantum field state.
We compute the mutual information between finite intervals in two non-compact 2d CFTs in the thermofield double formulation after one of them has been locally perturbed by a primary operator at some time tω in the large c limit. We determine the time scale, called the scrambling time, at which the mutual information vanishes and the original entanglement between the thermofield double gets destroyed by the perturbation. We provide a holographic description in terms of a free falling particle in the eternal BTZ black hole that exactly matches our CFT calculations. Our results hold for any time tω . In particular, when the latter is large, they reproduce the bulk shock-wave propagation along the BTZ horizon description.
The AdS/CFT correspondence and quantum entanglement (or quantum information). This is one of topics exciting many physicists in this decade. And black holes always play a role of inspiring lab in many cases. In this thesis, we will discuss about scrambling of quantum entanglement and complexity of states in AdS/CFT. In both topics, black holes are expected to be the fastest processors of quantum information. This thesis contains brief reviews of each topics and our own works. One work is an explicit calculation of fast scrambling time in two dimensional holographic CFTs and three dimensional BTZ black holes using the two-sided mutual information. This calculation is a first CFT counterpart of Shenker-Stanford’s work in the gravity dual and an extension of their shock-wave approximation to finite time region in the gravity side. Another work is about socalled optimization procedure of Euclidean path- integrals in CFTs. The optimization procedure gives us a new way to extract dual geometries only from CFT data. And it also gives a new proposal for the definition of complexity of states in CFTs.