1,985 research outputs found
Three dimensional Lifshitz black hole and the Korteweg-de Vries equation
We consider a solution of three dimensional New Massive Gravity with a
negative cosmological constant and use the AdS/CTF correspondence to inquire
about the equivalent two dimensional model at the boundary. We conclude that
there should be a close relation with the Korteweg-de Vries equation.Comment: 4 page
Holographic Superconductors with various condensates in Einstein-Gauss-Bonnet gravity
We study holographic superconductors in Einstein-Gauss-Bonnet gravity. We
consider two particular backgrounds: a -dimensional Gauss-Bonnet-AdS black
hole and a Gauss-Bonnet-AdS soliton. We discuss in detail the effects that the
mass of the scalar field, the Gauss-Bonnet coupling and the dimensionality of
the AdS space have on the condensation formation and conductivity. We also
study the ratio for various masses of the scalar field and
Gauss-Bonnet couplings.Comment: 21 pages, 10 figures. accepted for publication in PR
Dynamical evolution of non-minimally coupled scalar field in spherically symmetric de Sitter spacetimes
We investigate the dynamical behavior of a scalar field non-minimally coupled
to Einstein's tensor and Ricci scalar in geometries of asymptotically de Sitter
spacetimes. We show that the quasinormal modes remain unaffected if the scalar
field is massless and the black hole is electrically chargeless. In the massive
case, the coupling of both parameters produces a region of instability in the
spacetime determined by the geometry and field parameters. In the Schwarzschild
case, every solution for the equations of motion with has a range of
values of the coupling constant that produces unstable modes. The case
is the most unstable one, with a threshold value for stability in the coupling.
For the charged black hole, the existence of a range of instability in
is strongly related to geometry parameters presenting a region of stability
independent of the chosen parameter.Comment: 31 pages; 11 figures, 8 tables and typos correcte
Analysis of geometries with closed timelike curves
This work deals with the analysis of cylindrically symmetric and stationary
space-times with closed timelike curves. The equation of
motion describing the evolution of a massive scalar field in a
space-time is obtained. A class of space-times with closed
timelike curves describing cosmic strings and cylinders is studied in detail.
In such space-times, both massive particles as well as photons can reach the
non-causal region. Geodesics and closed timelike curves are calculated and
investigated. We have observed that massive particles and photons describe,
essentially, two kinds of trajectories: confined orbits and scattering states.
The analysis of the light cones show us clearly the intersection between future
and past inside the non-causal region. Exact solutions for the equation of
motion of massive scalar field propagating in cosmic strings and cylinder
space-times are presented. Quasinormal modes for the scalar field have been
calculated in static and rotating cosmic cylinders. We found unstable modes in
the rotating cases. Rotating as well as static cosmic strings, i.e., without
regular interior solutions, do not display quasinormal modes for the scalar
field. We conclude presenting a conjecture relating closed timelike curves and
space-time instability.Comment: PhD thesis (in Portuguese), Advisor: Prof. Dr. Elcio Abdalla, 155
pages, 31 figures, May 201
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