498 research outputs found
Generalized superconductors from the coupling of a scalar field to the Einstein tensor and their refractive index in massive gravity
We construct the generalized superconductors from the coupling of a scalar
field to the Einstein tensor in the massive gravity and investigate their
negative refraction in the probe limit. We observe that the larger graviton
mass and Einstein tensor coupling parameters both hinder the formation of the
condensation, but the larger graviton mass or smaller coupling parameter makes
it easier for the emergence of the Cave of Winds. Furthermore, we see that the
larger graviton mass but smaller coupling parameter make the range of
frequencies or the range of temperatures larger for which a negative
Depine-Lakhtakia index occurs, which indicates that the graviton mass and
Einstein tensor have completely different effects on the negative refraction.
In addition, we find that the larger graviton mass and coupling parameters both
can reduce the dissipation and improve the propagation in the holographic
setup.Comment: 20 pages, 12 figure
On analytical study of holographic superconductors with Born-Infeld electrodynamics
Based on the Sturm-Liouville eigenvalue problem, Banerjee \emph{et al.}
proposed a perturbative approach to analytically investigate the properties of
the ()-dimensional superconductor with Born-Infeld electrodynamics [Phys.
Rev. D {\bf 87}, 104001 (2013)]. By introducing an iterative procedure, we will
further improve the analytical results and the consistency with the numerical
findings, and can easily extend the analytical study to the higher-dimensional
superconductor with Born-Infeld electrodynamics. We observe that the higher
Born-Infeld corrections make it harder for the condensation to form but do not
affect the critical phenomena of the system. Our analytical results can be used
to back up the numerical computations for the holographic superconductors with
various condensates in Born-Infeld electrodynamics.Comment: 13 pages, 4 tables, accepted for publication in Phys. Lett.
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
Maxwell quasinormal modes on a global monopole Schwarzschild-anti-de Sitter black hole with Robin boundary conditions
We generalize our previous studies on the Maxwell quasinormal modes around
Schwarzschild-anti-de-Sitter black holes with Robin type vanishing energy flux
boundary conditions, by adding a global monopole on the background. We first
formulate the Maxwell equations both in the Regge-Wheeler-Zerilli and in the
Teukolsky formalisms and derive, based on the vanishing energy flux principle,
two boundary conditions in each formalism. The Maxwell equations are then
solved analytically in pure anti-de Sitter spacetimes with a global monopole,
and two different normal modes are obtained due to the existence of the
monopole parameter. In the small black hole and low frequency approximations,
the Maxwell quasinormal modes are solved perturbatively on top of normal modes
by using an asymptotic matching method, while beyond the aforementioned
approximation, the Maxwell quasinormal modes are obtained numerically. We
analyze the Maxwell quasinormal spectrum by varying the angular momentum
quantum number , the overtone number , and in particular, the monopole
parameter . We show explicitly, through calculating quasinormal
frequencies with both boundary conditions, that the global monopole produces
the repulsive force.Comment: 10 pages, 5 figures, to appear in EPJ
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