16,051 research outputs found
Localised Black Holes
We numerically construct asymptotically global black holes that are localised on the . These are
solutions to type IIB supergravity with horizon topology that
dominate the theory in the microcanonical ensemble at small energies. At higher
energies, there is a first-order phase transition to
-Schwarzschild. By the AdS/CFT
correspondence, this transition is dual to spontaneously breaking the
R-symmetry of super Yang-Mills down to . We extrapolate
the location of this phase transition and compute the expectation value of the
resulting scalar operators in the low energy phase.Comment: 11 pages, 6 figure
Lumpy AdS S Black Holes and Black Belts
Sufficiently small Schwarzschild black holes in global AdSS are
Gregory-Laflamme unstable. We construct new families of black hole solutions
that bifurcate from the onset of this instability and break the full SO
symmetry group of the S down to SO. These new "lumpy" solutions are
labelled by the harmonics . We find evidence that the branch
never dominates the microcanonical/canonical ensembles and connects through a
topology-changing merger to a localised black hole solution with S
topology. We argue that these S black holes should become the dominant
phase in the microcanonical ensemble for small enough energies, and that the
transition to Schwarzschild black holes is first order. Furthermore, we find
two branches of solutions with . We expect one of these branches to
connect to a solution containing two localised black holes, while the other
branch connects to a black hole solution with horizon topology which we call a "black belt".Comment: 20 pages (plus 17 pages for Appendix on Kaluza-Klein Holography), 14
figure
SUPPLY AND PRICE IMPACT OF THE ARP AND PIK PROGRAMS
Agricultural and Food Policy,
Terrestrial planets across space and time
The study of cosmology, galaxy formation and exoplanets has now advanced to a
stage where a cosmic inventory of terrestrial planets may be attempted. By
coupling semi-analytic models of galaxy formation to a recipe that relates the
occurrence of planets to the mass and metallicity of their host stars, we trace
the population of terrestrial planets around both solar-mass (FGK type) and
lower-mass (M dwarf) stars throughout all of cosmic history. We find that the
mean age of terrestrial planets in the local Universe is Gyr for FGK
hosts and Gyr for M dwarfs. We estimate that hot Jupiters have
depleted the population of terrestrial planets around FGK stars by no more than
, and that only of the terrestrial planets at the
current epoch are orbiting stars in a metallicity range for which such planets
have yet to be confirmed. The typical terrestrial planet in the local Universe
is located in a spheroid-dominated galaxy with a total stellar mass comparable
to that of the Milky Way. When looking at the inventory of planets throughout
the whole observable Universe, we argue for a total of and terrestrial planets around FGK and M
stars, respectively. Due to light travel time effects, the terrestrial planets
on our past light cone exhibit a mean age of just Gyr. These
results are discussed in the context of cosmic habitability, the Copernican
principle and searches for extraterrestrial intelligence at cosmological
distances.Comment: 11 pages, 8 figures. v.2: Accepted for publication in ApJ. Some
changes in quantitative results compared to v.1, mainly due to differences in
IMF assumption
Holographic Description of Finite Size Effects in Strongly Coupled Superconductors
Despite its fundamental and practical interest, the understanding of
mesoscopic effects in strongly coupled superconductors is still limited. Here
we address this problem by studying holographic superconductivity in a disk and
a strip of typical size . For , where depends on
the chemical potential and temperature, we have found that the order parameter
vanishes. The superconductor-metal transition at is controlled
by mean-field critical exponents which suggests that quantum and thermal
fluctuations induced by finite size effects are suppressed in holographic
superconductors. Intriguingly, the effective interactions that bind the order
parameter increases as decreases. Most of these results are consistent
with experimental observations in Pb nanograins at low temperature and
qualitatively different from the ones expected in a weakly coupled
superconductor.Comment: 4 pages, 3 figure
Mechanisms of fragmentation of Al-W granular composites under dynamic loading
Numerical simulations of Aluminum (Al) and Tungsten (W) granular composite
rings under various dynamic loading conditions caused by explosive loading were
examined. Three competing mechanisms of fragmentation were observed: a
continuum level mechanism generating large macrocracks described by the
Grady-Kipp fragmentation mechanism, a mesoscale mechanism generating voids and
microcracks near the initially unbonded Al/W interfaces due to tensile strains,
and a mesoscale jetting due to the development of large velocity gradients
between the W particles and adjacent Al. These mesoscale mechanisms can be used
to tailor the size of the fragments by selecting an appropriate initial
mesostructure for a given loading condition.Comment: 10 pages, 3 figures, submitted to AP
Assessment of maternal referral systems used for a rural Zambian hospital: the development of setting specific protocols for the identification of complications
Background: In resource-limited countries, it is estimated that up to 75% of maternal deaths are preventable. Maternal referral systems are an effective measure to help prevent these deaths. Objective: The objective of this study was to delineate criteria that health care workers use to identify obstetrical emergencies and make referrals, in order to evaluate the effectiveness of the established referral system and to implement improvements to this system.Methods: Using a qualitative study design, the individuals with the highest level of formal obstetrics training at 10 health posts that refer to a rural Zambian hospital were surveyed using semi-structured interviews regarding their referral protocols. Data were analyzed through open-coding. At the conclusion of the interview, standardized referral protocols for obstetric emergen- cies derived from published guidelines and local practices were distributed.Results: Identified complications resulting in referral most commonly included post-partum hemorrhage (70%), prolonged labor (70%), malpresentation (50%), antepartum hemorrhage (40%), and retained placenta (40%). While numerous reasons for referral were identified, there was little consensus on the referral protocol used for each complication. Obstacles to successful referral most commonly included cellular network disruptions (70%), distance (50%), and lack of transportation (30%). The referral protocols distributed to health posts covered only 11 of the 23 complications cited as the most common reason for referral.Conclusion: The referral criteria and protocols were updated to include all of the reported complications. We propose this document for others working in resource-limited settings attempting to establish or evaluate a maternal referral systems.Keywords: Maternal referral systems, Zambian hospital, protocols, complications
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