12 research outputs found
Analytic approximation to 5 dimensional Black Holes with one compact dimension
We study black hole solutions in space, using an expansion to
fourth order in the ratio of the radius of the horizon, , and the
circumference of the compact dimension, . A study of geometric and
thermodynamic properties indicates that the black hole fills the space in the
compact dimension at . At the same value of
the entropies of the uniform black string and of the black hole are
approximately equal.Comment: 21 pages, 4 figures. Replaces previous version, with added references
and slightly altered discussio
Small Black Holes on Branes: Is the horizon regular or singular ?
We investigate the following question: Consider a small mass, with
(the ratio of the Schwarzschild radius and the bulk curvature length) much
smaller than 1, that is confined to the TeV brane in the Randall-Sundrum I
scenario. Does it form a black hole with a regular horizon, or a naked
singularity? The metric is expanded in and the asymptotic form of
the metric is given by the weak field approximation (linear in the mass). In
first order of we show that the iteration of the weak field
solution, which includes only integer powers of the mass, leads to a solution
that has a singular horizon. We find a solution with a regular horizon but its
asymptotic expansion in the mass also contains half integer powers.Comment: Accepted for publication in PR
A 6 dimensional symmetric model with warped physical space
The Randall-Sundrum model is studied in 6 dimension with AdS or dS
metric in the physical 4 dimensional space. Two solutions are found, one with
induced 5-dimensional gravity terms added to the induced cosmological constant
terms. We study the graviton modes in both solutions by transforming the mass
eigenvalue equation to a Schrodinger equation with a volcano potential. The
spectrum of gravitational excitations depends on the input parameters of the
theory, the six dimensional and the effective four-dimensional cosmological
constants. The model gives a physically acceptable spectrum if the 4
dimensional cosmological constant is sufficiently small.Comment: 14 pages, 3 tables, 2 references adde
Einstein-Gauss-Bonnet black strings
We construct uniform black-string solutions in Einstein-Gauss-Bonnet gravity
for all dimensions between five and ten and discuss their basic properties.
Closed form solutions are found by taking the Gauss-Bonnet term as a
perturbation from pure Einstein gravity. Nonperturbative solutions are
constructed by solving numerically the equations of the model. The
Gregory-Laflamme instability of the black strings is explored via linearized
perturbation theory. Our results indicate that new qualitative features occur
for , in which case stable configurations exist for large enough values of
the Gauss-Bonnet coupling constant. For other dimensions, the black strings are
dynamically unstable and have also a negative specific heat. We argue that this
provides an explicit realization of the Gubser-Mitra conjecture, which links
local dynamical and thermodynamic stability. Nonuniform black strings in
Einstein-Gauss-Bonnet theory are also constructed in six spacetime dimensions.Comment: 33 pages, 11 figure
Sleep apnoea in Australian men: disease burden, co-morbidities, and correlates from the Australian longitudinal study on male health
BACKGROUND: Obstructive sleep apnoea is a common disorder with under-rated clinical impact, which is increasingly being recognised as having a major bearing on global disease burden. Men are especially vulnerable and become a priority group for preventative interventions. However, there is limited information on prevalence of the condition in Australia, its co-morbidities, and potential risk factors. METHODS: We used data from 13,423 adult men included in the baseline wave of Ten to Men, an Australian national study of the health of males, assembled using stratified cluster sampling with oversampling from rural and regional areas. Those aged 18-55 years self-completed a paper-based questionnaire that included a question regarding health professional-diagnosed sleep apnoea, physical and mental health status, and health-related behaviours. Sampling weights were used to account for the sampling design when reporting the prevalence estimates. Odds ratios were used to describe the association between health professional-diagnosed sleep apnoea and potential correlates while adjusting for age, country of birth, and body-mass index (BMI). RESULTS: Prevalence of self-reported health professional-diagnosed sleep apnoea increased from 2.2 % in age 18-25 years to 7.8 % in the age 45-55 years. Compared with those without sleep apnoea, those with sleep apnoea had significantly poorer physical, mental, and self-rated health as well as lower subjective wellbeing and poorer concentration/remembering (p < 0.001 for all). Sleep apnoea was significantly associated with older age (p < 0.001), unemployment (p < 0.001), asthma (p = 0.011), chronic obstructive pulmonary disease/chronic bronchitis (p = 0.002), diabetes (p < 0.001), hypercholesterolemia (p < 0.001), hypertension (p < 0.001), heart attack (p < 0.001), heart failure (p < 0.001), angina (p < 0.001), depression (p < 0.001), post-traumatic stress disorder (p < 0.001), other anxiety disorders (p < 0.001), schizophrenia (p = 0.002), overweight/obesity (p < 0.001), insufficient physical activity (p = 0.006), smoking (p = 0.005), and high alcohol consumption (p < 0.001). CONCLUSION: Health professional-diagnosed sleep apnoea is relatively common, particularly in older males. Associations between sleep apnoea and cardiovascular, metabolic, respiratory, and psychiatric disorders have important clinical and public health implications. As men are especially vulnerable to sleep apnoea as well as some of its chronic co-morbidities, they are potentially a priority group for health interventions. Modifiable lifestyle related factors such as smoking, alcohol consumption, level of physical activity and BMI are possible key foci for interventions