30 research outputs found
Lifshitz quasinormal modes and relaxation from holography
We obtain relaxation times for field theories with Lifshitz scaling and with
holographic duals Einstein-Maxwell-Dilaton gravity theories. This is done by
computing quasinormal modes of a bulk scalar field in the presence of Lifshitz
black branes. We determine the relation between relaxation time and dynamical
exponent z, for various values of boundary dimension d and operator scaling
dimension. It is found that for d>z+1, at zero momenta, the modes are
non-overdamped, whereas for d<=z+1 the system is always overdamped. For d=z+1
and zero momenta, we present analytical results.Comment: 16 pages and 5 figure
Krylov complexity in a natural basis for the Schr\"odinger algebra
We investigate operator growth in quantum systems with two-dimensional
Schr\"odinger group symmetry by studying the Krylov complexity. While feasible
for semisimple Lie algebras, cases such as the Schr\"odinger algebra which is
characterized by a semi-direct sum structure are complicated. We propose to
compute Krylov complexity for this algebra in a natural orthonormal basis,
which produces a pentadiagonal structure of the time evolution operator,
contrasting the usual tridiagonal Lanczos algorithm outcome. The resulting
complexity behaves as expected. We advocate that this approach can provide
insights to other non-semisimple algebras.Comment: 18 pages, 4 figures. v2: Typos corrected and references added. v3:
Restructured some sentence
Action complexity for semi-classical black holes
Publisher's version (útgefin grein)We adapt the complexity as action prescription (CA) to a semi-classical model of two-dimensional dilaton gravity and determine the rate of increase of holographic complexity for an evaporating black hole. The results are consistent with our previous numerical results for semi-classical black hole complexity using a volume prescription (CV) in the same model, but the CA calculation is fully analytic and provides a non-trivial positive test for the holographic representation of the black hole interior.Peer Reviewe
An Outsider's Perspective on Information Recovery in de Sitter Space
Entanglement islands play a crucial role in our understanding of how Hawking
radiation encodes information in a black hole, but their relevance in
cosmological spacetimes is less clear. In this paper, we continue our
investigation of information recovery in de Sitter space and construct a
two-dimensional model of gravity containing a domain wall that interpolates
between de Sitter space and Rindler space. The Rindler wedges introduce
weakly-gravitating asymptotic regions from which de Sitter space can be probed,
yielding an outside perspective of the cosmological horizon. In contrast to
earlier works, backreaction effects are under control by considering a quantum
state that only breaks the thermal equilibrium of the Bunch-Davies state for a
finite time. This allows information to be decoded from the Gibbons-Hawking
radiation in a controlled fashion.Comment: minor corrections, 32 pages, 8 figure
Correlation functions in theories with Lifshitz scaling
The 2+1 dimensional quantum Lifshitz model can be generalised to a class of higher dimensional free field theories that exhibit Lifshitz scaling. When the dynamical critical exponent equals the number of spatial dimensions, equal time correlation functions of scaling operators in the generalised quantum Lifshitz model are given by a d-dimensional higher-derivative conformal field theory. Autocorrelation functions in the generalised quantum Lifshitz model in any number of dimensions can on the other hand be expressed in terms of autocorrelation functions of a two-dimensional conformal field theory. This also holds for autocorrelation functions in a strongly coupled Lifshitz field theory with a holographic dual of Einstein-Maxwell-dilaton type. The map to a two-dimensional conformal field theory extends to autocorrelation functions in thermal states and out-of-equilbrium states preserving symmetry under spatial translations and rotations in both types of Lifshitz models. Furthermore, the spectrum of quasinormal modes of scalar field perturbations in Lifshitz black hole backgrounds can be obtained analytically at low spatial momenta and exhibits a linear dispersion relation at z = d. At high momentum, the mode spectrum can be obtained in a WKB approximation and displays very different behaviour compared to holographic duals of conformal field theories. This has implications for thermalisation in strongly coupled Lifshitz field theories with z > 1.Peer reviewe
Holographic complexity: stretching the horizon of an evaporating black hole
Publisher's version (útgefin grein)We obtain the holographic complexity of an evaporating black hole in the semi-classical RST model of two-dimensional dilaton gravity, using a volume prescription that takes into account the higher-dimensional origin of the model. For classical black holes, we recover the expected late time behaviour of the complexity, but new features arise at the semi-classical level. By considering the volume inside the stretched horizon of the evolving black hole, we obtain sensible results for the rate of growth of the complexity, with an early onset of order the black hole scrambling time followed by an extended period where the rate of growth tracks the shrinking area of the stretched horizon as the black hole evaporates.Peer Reviewe