29,533 research outputs found

    The Projection Postulate of Quantum Mechanics on the Lightcone

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    We discuss an interpretation of the projection postulate that implies collapse of the wavefunction along the lightcone.Comment: 5 pages, LaTex, SJSU/TP-93-1

    Can Future Events Influence the Present?

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    Widom, Srivastava, and Sassaroli have published [Phys. Lett. A 203, 255 (1995)] a calculation which purports to show that "future events can affect present events". In this note an error in their calculation is identified.Comment: 3 pages, LaTeX, no figure

    Why Darwin was English

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    A ‘late developer’ argument, common to Psychology and Economic History, can be used to explain cultural innovation. It argues that the 19th century theory of natural selection arose in England and not Germany because of – and not in spite of – England’s scientific backwardness. Measured in terms of institutions, communities, and ideas, the relative retardation of English science was precisely what enabled it to adopt German advances in novel ways

    Software engineering (Encylopedia entry)

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    The Curious Case of Lyman Alpha Emitters: Growing Younger from z ~ 3 to z ~ 2?

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    Lyman Alpha Emitting (LAE) galaxies are thought to be progenitors of present-day L* galaxies. Clustering analyses have suggested that LAEs at z ~ 3 might evolve into LAEs at z ~ 2, but it is unclear whether the physical nature of these galaxies is compatible with this hypothesis. Several groups have investigated the properties of LAEs using spectral energy distribution (SED) fitting, but direct comparison of their results is complicated by inconsistencies in the treatment of the data and in the assumptions made in modeling the stellar populations, which are degenerate with the effects of galaxy evolution. By using the same data analysis pipeline and SED fitting software on two stacked samples of LAEs at z = 3.1 and z = 2.1, and by eliminating several systematic uncertainties that might cause a discrepancy, we determine that the physical properties of these two samples of galaxies are dramatically different. LAEs at z = 3.1 are found to be old (age ~ 1 Gyr) and metal-poor (Z < 0.2 Z_Sun), while LAEs at z = 2.1 appear to be young (age ~ 50 Myr) and metal-rich (Z > Z_Sun). The difference in the observed stellar ages makes it very unlikely that z = 3.1 LAEs evolve directly into z = 2.1 LAEs. Larger samples of galaxies, studies of individual objects and spectroscopic measurements of metallicity at these redshifts are needed to confirm this picture, which is difficult to reconcile with the effects of 1 Gyr of cosmological evolution.Comment: Minor revision, accepted for publication in ApJ

    Response to Richards

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    Emil du Bois-Reymond (1818-1896) complicates the historiography of the reception of Darwinism. His presentation of the theory was anti-teleological, a fact that refutes the claim that German Darwinists were Romantic
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