86,675 research outputs found
AdS black holes with higher derivative corrections in presence of string cloud
We consider asymptotically AdS black hole solutions in presence of string
clouds and higher derivative corrections. We find that it admits three black
hole solutions within a region of the parameter space. In order to examine the
stabilities of these solutions we consider a thermodynamic analysis. Using
holography, we have studied the quark-antiquark distance and binding energy in
the dual gauge theory.Comment: 25 pages, 27 figures, LaTe
Holographic Response of Electron Clouds
In order to make progress towards more realistic models of holographic
fermion physics, we use gauge/gravity duality to compute the dispersion
relations for quasinormal modes and collective modes for the electron cloud
background, i.e. the non-zero temperature version of the electron star. The
results are compared to the corresponding results for the Schwarzschild and
Reissner-Nordstr\"om black hole backgrounds, and the qualitative differences
are highlighted and discussed.Comment: 27 page
Using all-sky differential photometry to investigate how nocturnal clouds darken the night sky in rural areas
Artificial light at night has affected most of the natural nocturnal
landscapes worldwide and the subsequent light pollution has diverse effects on
flora, fauna and human well-being. To evaluate the environmental impacts of
light pollution, it is crucial to understand both the natural and artificial
components of light at night under all weather conditions. The night sky
brightness for clear skies is relatively well understood and a reference point
for a lower limit is defined. However, no such reference point exists for
cloudy skies. While some studies have examined the brightening of the night sky
by clouds in urban areas, the published data on the (natural) darkening by
clouds is very sparse. Knowledge of reference points for the illumination of
natural nocturnal environments however, is essential for experimental design
and ecological modeling to assess the impacts of light pollution. Here we use
differential all-sky photometry with a commercial digital camera to investigate
how clouds darken sky brightness at two rural sites. The spatially resolved
data enables us to identify and study the nearly unpolluted parts of the sky
and to set an upper limit on ground illumination for overcast nights at sites
without light pollution.Comment: 17 pages, 6 figure
Holographic metals at finite temperature
A holographic dual description of a 2+1 dimensional system of strongly
interacting fermions at low temperature and finite charge density is given in
terms of an electron cloud suspended over the horizon of a charged black hole
in asymptotically AdS spacetime. The electron star of Hartnoll and Tavanfar is
recovered in the limit of zero temperature, while at higher temperatures the
fraction of charge carried by the electron cloud is reduced and at a critical
temperature there is a second order phase transition to a configuration with
only a charged black hole. The geometric structure implies that finite
temperature transport coefficients, including the AC electrical conductivity,
only receive contributions from bulk fermions within a finite band in the
radial direction.Comment: LaTex 16 pages, 12 figures, v2: Added reference. Error in free energy
corrected. Phase transition to AdS-RN black brane is third order rather than
second order as was claimed previousl
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