191 research outputs found

    Running Spectral Index and Formation of Primordial Black Hole in Single Field Inflation Models

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    A broad range of single field models of inflation are analyzed in light of all relevant recent cosmological data, checking whether they can lead to the formation of long-lived Primordial Black Holes (PBHs). To that end we calculate the spectral index of the power spectrum of primordial perturbations as well as its first and second derivatives. PBH formation is possible only if the spectral index increases significantly at small scales, i.e. large wave number kk. Since current data indicate that the first derivative αS\alpha_S of the spectral index nS(k0)n_S(k_0) is negative at the pivot scale k0k_0, PBH formation is only possible in the presence of a sizable and positive second derivative ("running of the running") βS\beta_S. Among the three small-field and five large-field models we analyze, only one small-field model, the "running mass" model, allows PBH formation, for a narrow range of parameters. We also note that none of the models we analyze can accord for a large and negative value of αS\alpha_S, which is weakly preferred by current data.Comment: 26 pages, 5 figures, Refs. added, Minor textual change; version to appear in JCA

    The Physics of the B Factories

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    Conjugated Polymer-Based Hybrid Materials for Turn-On Detection of CO2 in Plant Photosynthesis

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    Contains fulltext : 161972.pdf (publisher's version ) (Open Access

    Characterization of defects of mullite fibers prepared by polyvinyl butyral as spinning aid

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    Mullite fibers have been synthesized using polyvinyl butyral as spinning aids. Defects including cracks, core-sheath structure, randomly arranged powders, shots and rough surface were observed. The results showed that circumferential cracks were terminated by the main axial crack. The thermal shrinkage could be considered as the reason for the formation of cracks and core-sheath structure. Improper control of heat treatment resulted in the rough surface around fibers. The wet gel fibers were easily inserted by some alumina powders which were used to obtain the uniform shrinkage during calcinations in the kiln
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