9 research outputs found
Bifurcations in a convection problem with temperature-dependent viscosity
A convection problem with temperature-dependent viscosity in an infinite
layer is presented. As described, this problem has important applications in
mantle convection. The existence of a stationary bifurcation is proved together
with a condition to obtain the critical parameters at which the bifurcation
takes place. For a general dependence of viscosity with temperature a numerical
strategy for the calculation of the critical bifurcation curves and the most
unstable modes has been developed. For a exponential dependence of viscosity on
temperature the numerical calculations have been done. Comparisons with the
classical Rayleigh-B\'enard problem with constant viscosity indicate that the
critical threshold decreases as the exponential rate parameter increases.Comment: 16 pages, 5 figure
Numerical model of the supercontinental cycle stages: Integral transfer of the oceanic crust material and mantle viscous shear stresses
Exoplanet Biosignatures: Future Directions
Abstract We introduce a Bayesian method for guiding future directions for detection of life on exoplanets. We describe empirical and theoretical work necessary to place constraints on the relevant likelihoods, including those emerging from better understanding stellar environment, planetary climate and geophysics, geochemical cycling, the universalities of physics and chemistry, the contingencies of evolutionary history, the properties of life as an emergent complex system, and the mechanisms driving the emergence of life. We provide examples for how the Bayesian formalism could guide future search strategies, including determining observations to prioritize or deciding between targeted searches or larger lower resolution surveys to generate ensemble statistics and address how a Bayesian methodology could constrain the prior probability of life with or without a positive detection. Key Words: Exoplanets—Biosignatures—Life detection—Bayesian analysis. Astrobiology 18, 779–824