3,957 research outputs found
A Holographic Path to the Turbulent Side of Gravity
We study the dynamics of a 2+1 dimensional relativistic viscous conformal
fluid in Minkowski spacetime. Such fluid solutions arise as duals, under the
"gravity/fluid correspondence", to 3+1 dimensional asymptotically anti-de
Sitter (AAdS) black brane solutions to the Einstein equation. We examine
stability properties of shear flows, which correspond to hydrodynamic
quasinormal modes of the black brane. We find that, for sufficiently high
Reynolds number, the solution undergoes an inverse turbulent cascade to long
wavelength modes. We then map this fluid solution, via the gravity/fluid
duality, into a bulk metric. This suggests a new and interesting feature of the
behavior of perturbed AAdS black holes and black branes, which is not readily
captured by a standard quasinormal mode analysis. Namely, for sufficiently
large perturbed black objects (with long-lived quasinormal modes), nonlinear
effects transfer energy from short to long wavelength modes via a turbulent
cascade within the metric perturbation. As long wavelength modes have slower
decay, this lengthens the overall lifetime of the perturbation. We also discuss
various implications of this behavior, including expectations for higher
dimensions, and the possibility of predicting turbulence in more general
gravitational scenarios.Comment: 24 pages, 10 figures; v2: references added, and several minor change
When function meets emotion, change can happen: societal value propositions and disruptive potential in fintechs
Fintechs, as providers of digital service innovations and as highly relevant and novel channels through which to deliver entrepreneurial finance based on the creative use of state-of-the-art technology in the financial domain, have thus far mainly been addressed in research by examining the functional aspects of their value propositions (VPs). This article thus sets out to gain insights into the interplay and overall role of societal VPs as potential antecedents and change catalysts in the formation of the often promised disruptive potential of fintechs for the financial sector. In an inductive, theory-building approach, the authors first examine how societal VPs transcend individual functional and emotional ones for entrepreneurs, and conclude with a conceptual model of how the former can build up the disruptive potential of fintechs and deliver apt solutions for entrepreneurs seeking finance
On characteristic initial data for a star orbiting a black hole
We take further steps in the development of the characteristic approach to
enable handling the physical problem of a compact self-gravitating object, such
as a neutron star, in close orbit around a black hole. We examine different
options for setting the initial data for this problem and, in order to shed
light on their physical relevance, we carry out short time evolution of this
data. To this end we express the matter part of the characteristic gravity code
so that the hydrodynamics are in conservation form. The resulting gravity plus
matter relativity code provides a starting point for more refined future
efforts at longer term evolution. In the present work we find that,
independently of the details of the initial gravitational data, the system
quickly flushes out spurious gravitational radiation and relaxes to a
quasi-equilibrium state with an approximate helical symmetry corresponding to
the circular orbit of the star.Comment: 20 pages, 10 figure
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