Inhomogeneous models of interacting dark matter and dark energy

We derive and analyze a class of spherically symmetric cosmological models whose source is an interactive mixture of inhomogeneous cold dark matter (DM) and a generic homogeneous dark energy (DE) fluid. If the DE fluid corresponds to a quintessense scalar field, the interaction term can be associated with a well motivated non--minimal coupling to the DM component. By constructing a suitable volume average of the DM component we obtain a Friedman evolution equation relating this average density with an average Hubble scalar, with the DE component playing the role of a repulsive and time-dependent $\Lambda$ term. Once we select an ``equation of state'' linking the energy density ($\mu$) and pressure ($p$) of the DE fluid, as well as a free function governing the radial dependence, the models become fully determinate and can be applied to known specific DE sources, such as quintessense scalar fields or tachyonic fluids. Considering the simple equation of state $p= (\gamma-1) \mu$ with $0\leq\gamma <2/3$, we show that the free parameters and boundary conditions can be selected for an adequate description of a local DM overdensity evolving in a suitable cosmic background that accurately fits current observational data. While a DE dominated scenario emerges in the asymptotic future, with total $\Omega$ and $q$ tending respectively to 1 and -1/2 for all cosmic observers, the effects of inhomogeneity and anisotropy yield different local behavior and evolution rates for these parameters in the local overdense region. We suggest that the models presented can be directly applied to explore the effects of various DE formalisms on local DM cosmological inhomogeneities.Comment: 15 pages, revtex4, 10 eps figure

Functional and genetic analysis of regulatory regions of coliphage H-19B: location of shiga-like toxin and lysis genes suggest a role for phage functions in toxin release

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74784/1/j.1365-2958.1998.00890.x.pd

Study on Driving Forces of UGC Adoption Behavior in Service Industry: A Platform Feature Based Model

Part 1: Digital ServicesInternational audienceNowadays, User Generated Content (UGC) influences consumers profoundly in their decision-making. UGC is more credible than advertising as common users generate it. The influencing power traditionally held by enterprises has shift to consumers dramatically. Current research mostly focus on the changes in consumer behavior after adoption of UGC, ignoring the source—factors that influence customers to choose and adopt certain UGC information, especially those related to social media platform features, emotion and attitude. Based on Information Adoption Model (IAM), this study introduces two types of trust and platform feature related factors to construct a new theoretical model, to comprehensively interpret information adoption behavior in service industry, aiming to provide theoretical contributions by extending IAM and according theory in new research settings