49,017 research outputs found
On the Six-dimensional Kerr Theorem and Twistor Equation
The Kerr theorem is revisited as part of the twistor program in six
dimensions. The relationship between pure spinors and integrable 3-planes is
investigated. The real condition for Lorentzian spacetimes is seen to induce a
projective property in the space of solutions, reminiscent of the quaternionic
structure of the 6-dimensional Lorentz group. The twistor equation (or Killing
spinor equations generically) also has an interpretation as integrable null
planes and a family of Einstein spacetimes with this property are presented in
the Kerr-Schild fashion.Comment: JHEP style, 19 pages, minor corrections. Matches printed versio
Signature of a Cosmic String Wake at
In this paper, we describe the results of N-body simulation runs, which
include a cosmic string wake of tension on top of the
usual fluctuations. To obtain a higher resolution of the wake in
the simulations compared to previous work, we insert the effects of the string
wake at a lower redshift and perform the simulations in a smaller volume. A
curvelet analysis of the wake and no-wake maps is applied, indicating that the
presence of a wake can be extracted at a three-sigma confidence level from maps
of the two-dimensional dark matter projection down to a redshift of .Comment: 8 pages, 6 figures; We have improved the analysis and results. The
text now agrees with the published versio
Isomonodromy, Painlev\'e Transcendents and Scattering off of Black Holes
We apply the method of isomonodromy to study the scattering of a generic
Kerr-NUT-(A)dS black hole. For generic values of the charges, the problem is
related to the connection problem of the Painlev\'e VI transcendent. We review
a few facts about Painlev\'e VI, Garnier systems and the Hamiltonian structure
of flat connections in the Riemann sphere. We then outline a method for
computing the scattering amplitudes based on Hamilton-Jacobi structure of
Painlev\'e, and discuss the implications of the generic result to black hole
complementarity.Comment: 40 pages, 4 figures, JHEP styl
The web of federal crimes in Brazil: topology, weaknesses, and control
Law enforcement and intelligence agencies worldwide struggle to find
effective ways to fight and control organized crime. However, illegal networks
operate outside the law and much of the data collected is classified.
Therefore, little is known about criminal networks structure, topological
weaknesses, and control. In this contribution we present a unique criminal
network of federal crimes in Brazil. We study its structure, its response to
different attack strategies, and its controllability. Surprisingly, the network
composed of multiple crimes of federal jurisdiction has a giant component,
enclosing more than a half of all its edges. This component shows some typical
social network characteristics, such as small-worldness and high clustering
coefficient, however it is much "darker" than common social networks, having
low levels of edge density and network efficiency. On the other side, it has a
very high modularity value, . Comparing multiple attack strategies, we
show that it is possible to disrupt the giant component of the network by
removing only of its edges or nodes, according to a module-based
prescription, precisely due to its high modularity. Finally, we show that the
component is controllable, in the sense of the exact network control theory, by
getting access to of the driver nodes.Comment: 9 pages, 5 figure
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