Statefinder diagnosis in a non-flat universe and the holographic model of dark energy

In this paper, we study the holographic dark energy model in non-flat universe from the statefinder viewpoint. We plot the evolutionary trajectories of the holographic dark energy model for different values of the parameter $c$ as well as for different contributions of spatial curvature, in the statefinder parameter-planes. The statefinder diagrams characterize the properties of the holographic dark energy and show the discrimination between this scenario and other dark energy models. As we show, the contributions of the spatial curvature in the model can be diagnosed out explicitly by the statefinder diagrams. Furthermore, we also investigate the holographic dark energy model in the $w-w'$ plane, which can provide us with a useful dynamical diagnosis complement to the statefinder geometrical diagnosis.Comment: 16 pages, 4 figures; final versio

Modeling and measurement of two-layer-canopy interception losses in a subtropical mixed forest of central-south China

International audienceThe original Gash analytical model and the sparse Gash's model have been applied to simulate rainfall interception losses from the two canopy layers in Shaoshan forest of central-south China during 2003. The total estimated interception loss from the two canopy layers is 478.4 mm with an error of 12.4 mm or 2.7% of total measured interception loss (466.0 mm). Both the original Gash model for top-canopy interception loss and the sparse model for sub-canopy loss overestimate interception losses. The simulated results show that the interception losses in top-canopy is 182.6 mm with an overestimation of 4.9% of measured losses and that in sub-canopy is 295.8 mm with an overestimation of 1.3%. The simulated values of the top-canopy suggest that 47% of the simulated interception losses are evaporated in the stage of "during storms" and 38% in "after storms", which is similar to the published results in temperate and tropical forests. However, the modelled losses from the sub-canopy show that 17% of interception losses are evaporated in "during storms" and 70% in "after storms", which is deviated from the reported results. The simulated results of two canopy interception losses in Shaoshan forest indicate that canopy structures may strongly impact hydrological fluxes in forested ecosystems

Modelling and measurement of two-layer-canopy interception losses in a subtropical evergreen forest of central-south China

International audienceThe original Gash analytical model and the sparse Gash's model were combined to simulate rainfall interception losses from the top- and sub-canopy layers in Shaoshan evergreen forest located in central-south China in 2003. The total estimated interception loss from the two canopy layers was 334.1 mm with an overestimation of 39.8 mm or 13.5% of the total measured interception (294.3 mm). The simulated interception losses of the top- and sub-canopy suggested that the simulated interception losses in the stages of ''during storms'' and ''after storms'' were in good agreement with the published ones. Both the original Gash model and the sparse model overestimated the interception losses, but the sparse model gave more accurate estimates than the original Gash model

The Measure for the Multiverse and the Probability for Inflation

We investigate the measure problem in the framework of inflationary cosmology. The measure of the history space is constructed and applied to inflation models. Using this measure, it is shown that the probability for the generalized single field slow roll inflation to last for $N$ e-folds is suppressed by a factor $\exp(-3N)$, and the probability for the generalized $n$-field slow roll inflation is suppressed by a much larger factor $\exp(-3nN)$. Some non-inflationary models such as the cyclic model do not suffer from this difficulty.Comment: 16 page

Ages and Masses of 0.64 million Red Giant Branch stars from the LAMOST Galactic Spectroscopic Survey

We present a catalog of stellar age and mass estimates for a sample of 640\,986 red giant branch (RGB) stars of the Galactic disk from the LAMOST Galactic Spectroscopic Survey (DR4). The RGB stars are distinguished from the red clump stars utilizing period spacing derived from the spectra with a machine learning method based on kernel principal component analysis (KPCA). Cross-validation suggests our method is capable of distinguishing RC from RGB stars with only 2 per cent contamination rate for stars with signal-to-noise ratio (SNR) higher than 50. The age and mass of these RGB stars are determined from their LAMOST spectra with KPCA method by taking the LAMOST - $Kepler$ giant stars having asteroseismic parameters and the LAMOST-TGAS sub-giant stars based on isochrones as training sets. Examinations suggest that the age and mass estimates of our RGB sample stars with SNR $>$ 30 have a median error of 30 per cent and 10 per cent, respectively. Stellar ages are found to exhibit positive vertical and negative radial gradients across the disk, and the age structure of the disk is strongly flared across the whole disk of $6<R<13$\,kpc. The data set demonstrates good correlations among stellar age, [Fe/H] and [$\alpha$/Fe]. There are two separate sequences in the [Fe/H] -- [$\alpha$/Fe] plane: a high--$\alpha$ sequence with stars older than $\sim$\,8\,Gyr and a low--$\alpha$ sequence composed of stars with ages covering the whole range of possible ages of stars. We also examine relations between age and kinematic parameters derived from the Gaia DR2 parallax and proper motions. Both the median value and dispersion of the orbital eccentricity are found to increase with age. The vertical angular momentum is found to fairly smoothly decrease with age from 2 to 12\,Gyr, with a rate of about $-$50\,kpc\,km\,s$^{-1}$\,Gyr$^{-1}$. A full table of the catalog is public available online.Comment: 16 pages, 22 figures,accepted by MNRA