1,189 research outputs found

    Massive gravitons dark matter scenario revisited

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    We reexamine the massive graviton dark matter scenario (MGCDM) which was recently considered as an alternative to dark energy models. When introducing the native and effective equations of state (EoS), it is shown that there is no phantom phase in the evolution toward the far past. Also we show that the past accelerating phase arises from the interaction between massive graviton and cold dark matter.Comment: 13 pages, 6 figure

    A Feasibility Study on the Application of TVDI on Accessing Wildfire Danger in the Korean Peninsula

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    Wildfire is a major natural disaster affecting socioeconomics and ecology. Remote sensing data have been widely used to estimate the wildfire danger with an advantage of higher spatial resolution. Among the several wildfire related indices using remote sensing data, Temperature Vegetation Dryness Index (TVDI) assesses wildfire danger based on both Normalized Difference Vegetation Index (NDVI) and Land Surface Temperature (LST). Although TVDI has physical advantages by considering both weather and vegetation condition, previous studies have shown TVDI does not performed well compare to other wildfire related indices over the Korean Peninsula. In this study we have attempted multiple modification to improve TVDI performance over the study region. In-situ measured air temperature was employed to increase accuracy, regression line was generated using monthly data to include seasonal effect, and TVDI was calculated at each province level to consider vegetation type and local climate. The modified TVDI calculation method was evaluated in wildfire cases and showed significant improvement in wildfire danger estimation

    Holographic interacting dark energy in the braneworld cosmology

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    We investigate a model of brane cosmology to find a unified description of the radiation-matter-dark energy universe. It is of the interacting holographic dark energy with a bulk-holographic matter χ\chi. This is a five-dimensional cold dark matter, which plays a role of radiation on the brane. Using the effective equations of state ωΛeff\omega^{\rm eff}_{\rm \Lambda} instead of the native equations of state ωΛ\omega_{\rm \Lambda}, we show that this model cannot accommodate any transition from the dark energy with ωΛeff≥−1\omega^{\rm eff}_{\rm \Lambda}\ge-1 to the phantom regime ωΛeff<−1\omega^{\rm eff}_{\rm \Lambda}<-1. Furthermore, the case of interaction between cold dark matter and five dimensional cold dark matter is considered for completeness. Here we find that the redshift of matter-radiation equality zeqz_{\rm eq} is the same order as zeqob=2.4×104Ωmh2z^{\rm ob}_{\rm eq}=2.4\times10^{4} \Omega_{\rm m}h^2. Finally, we obtain a general decay rate Γ\Gamma which is suitable for describing all interactions including the interaction between holographic dark energy and cold dark matter.Comment: 17 pages, 4 figure
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