1,572 research outputs found
Black Branes as Piezoelectrics
We find a realization of linear electroelasticity theory in gravitational
physics by uncovering a new response coefficient of charged black branes,
exhibiting their piezoelectric behavior. Taking charged dilatonic black strings
as an example and using the blackfold approach we measure their elastic and
piezolectric moduli. We also use our results to draw predictions about the
equilibrium condition of charged dilatonic black rings in dimensions higher
than six.Comment: v2: 9 pages; important sign corrections in section 3 and other minor
corrections; published in PR
Hydrodynamics for charge density waves and their holographic duals
We formulate a theory of dissipative hydrodynamics with spontaneously broken
translations, describing charge density waves in a clean isotropic electronic
crystal. We identify a novel linear transport coefficient, lattice pressure,
capturing the effects of background strain and thermal expansion in a crystal.
We argue that lattice pressure is a generic feature of systems with
spontaneously broken translations and must be accounted for while building and
interpreting holographic models. We also provide the first calculation of the
coefficients of thermal and chemical expansion in a holographic electronic
crystal.Comment: v2: 7pp, added references and comment
An X-ray view of the very faint black hole X-ray transient Swift J1357.2-0933 during its 2011 outburst
We report on the X-ray spectral (using XMM-Newton data) and timing behavior
(using XMM-Newton and Rossi X-ray Timing Explorer [RXTE] data) of the very
faint X-ray transient and black hole system Swift J1357.2-0933 during its 2011
outburst. The XMM-Newton X-ray spectrum of this source can be adequately fitted
with a soft thermal component with a temperature of ~0.22 keV (using a disc
model) and a hard, non-thermal component with a photon index of ~1.6 when using
a simple power-law model. In addition, an edge at ~ 0.73 keV is needed likely
due to interstellar absorption. During the first RXTE observation we find a 6
mHz quasi-periodic oscillation (QPO) which is not present during any of the
later RXTE observations or during the XMM-Newton observation which was taken 3
days after the first RXTE observation. The nature of this QPO is not clear but
it could be related to a similar QPO seen in the black hole system H 1743-322
and to the so-called 1 Hz QPO seen in the dipping neutron-star X-ray binaries
(although this later identification is quite speculative). The observed QPO has
similar frequencies as the optical dips seen previously in this source during
its 2011 outburst but we cannot conclusively determine that they are due to the
same underlying physical mechanism. Besides the QPO, we detect strong
band-limited noise in the power-density spectra of the source (as calculated
from both the RXTE and the XMM-Newton data) with characteristic frequencies and
strengths very similar to other black hole X-ray transients when they are at
low X-ray luminosities. We discuss the spectral and timing properties of the
source in the context of the proposed very high inclination of this source. We
conclude that all the phenomena seen from the source cannot, as yet, be
straightforwardly explained neither by an edge-on configuration nor by any
other inclination configuration of the orbit.Comment: 9 pages, 4 figures, 1 table. Accepted for publication in MNRA
- …