5,971 research outputs found

    Contour spectrograms for POGO analysis

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    Contour spectrograms for POGO analysis in Saturn S-2 and S-4b stage

    Revision of Scheumann’s classification of melilitic lamprophyres and related melilitic rocks in light of new analytical data

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    Dykes of the Late Cretaceous to Early Tertiary (79.5 ± 3.5 to 60.7 ± 2.4 Ma) melilitic rock series of the Osečná Com- plex and the Devil’s Walls dyke swarm, including ultramafic lamprophyres – polzenites – of Scheumann (1913) occur dispersed in the entire Upper Ploučnice River basin in northern Bohemia. Polzenites and associated melilitic rocks are characterized by the mineral association of olivine + melilite ± nephe- line, haüyne, monticellite, phlogopite, calcite, perovskite, spinels and apatite. New data on their mineral and chemical compositions from original Scheumann’s localities (the Vesec, Modlibohov, Luhov types) argue against the abolition of the group of ultramafic lamprophyres and the terms ‘polzenite’ and ‘alnöite’ by the Le Maitre (2002) classification. Marginal facies and numerous flat apophyses of the lopolith-like body known as the Osečná Complex show an olivine micro-melilitolite composition (lamprophyric facies). The porphyritic texture, chemical composition and the presence of characteristic minerals such as monticellite and phlogopite point to their affinity with ultramafic lamprophyres – polze- nites of the Vesec type. Melilite-bearing olivine nephelinites to olivine melilitites (olivine + clinopyroxene + nepheline + melilite ± haüyne and spinels with apatite) form a swarm of subparallel dykes known as the Devil’s Walls. The Scheumann’s non-melilite dyke rock “wesselite”, spatially associated with polzenites and often erroneously attributed to the polzenite group, is an alkaline lamprophyre of monchiquite to camptonite composition (kaersutite + phlogopite + diopside + olivine phenocrysts in groundmass containing clinopyroxene, phlogopite, haüyne, analcime, titanian mag- netite, apatite ± glass/plagioclase). First K–Ar data show Oligocene ages (30.9 ± 1.2 to 27.8 ± 1.1 Ma) and an affinity to the common tephrite–basanite rock series

    Dark Matter and Dark Radiation

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    We explore the feasibility and astrophysical consequences of a new long-range U(1) gauge field ("dark electromagnetism") that couples only to dark matter, not to the Standard Model. The dark matter consists of an equal number of positive and negative charges under the new force, but annihilations are suppressed if the dark matter mass is sufficiently high and the dark fine-structure constant α^\hat\alpha is sufficiently small. The correct relic abundance can be obtained if the dark matter also couples to the conventional weak interactions, and we verify that this is consistent with particle-physics constraints. The primary limit on α^\hat\alpha comes from the demand that the dark matter be effectively collisionless in galactic dynamics, which implies α^104\hat\alpha \lesssim 10^{-4} for TeV-scale dark matter. These values are easily compatible with constraints from structure formation and primordial nucleosynthesis. We raise the prospect of interesting new plasma effects in dark matter dynamics, which remain to be explored.Comment: 14 pages, 6 figures Updated equations and figure
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