23,691 research outputs found

    Localization to delocalization transition in a driven nonlinear cavity array

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    We study nonlinear cavity arrays where the particle relaxation rate in each cavity increases with the excitation number. We show that coherent parametric inputs can drive such arrays into states with commensurate filling that form non-equilibrium analogs of Mott insulating states. We explore the boundaries of the Mott insulating phase and the transition to a delocalized phase with spontaneous first order coherence. While sharing many similarities with the Mott insulator to superfluid transition in equilibrium, the phase-diagrams we find also show marked differences. Particularly the off diagonal order does not become long range since the influence of dephasing processes increases with increasing tunneling rates.Comment: 7 pages, 8 figure

    The many assembly histories of massive void galaxies as revealed by integral field spectroscopy

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    We present the first detailed integral field spectroscopy study of nine central void galaxies with M*>10¹⁰Mʘ using the Wide Field Spectrograph to determine how a range of assembly histories manifest themselves in the current day Universe.While the majority of these galaxies are evolving secularly, we find a range of morphologies, merger histories and stellar population distributions, though similarly low Hα-derived star formation rates (10¹⁰Mʘ have similarly low star formation rates

    The Shane Wirtanen counts: Observability of the galaxy correlation function

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    For an explicit test of the ability to recover the galaxy two-point correlation function from the Lick catalog of Shane and Wirtanen, we have applied the reduction and analysis methods of Seidner et al. and Groth and Peebles to model galaxy distributions that have known plate and field "errors" and that are high-fidelity simulations of the Lick sample. The model galaxy space distribution is constructed with the Soneira-Peebles prescription, which generates model distributions which have two-, three-, and four-point correlation functions in good agreement with the observed correlation functions. The space distribution is projected onto the sky with and without plate "errors." The Seidner et al. analysis recovers the plate factors in the former case with an error of 6.3%, as originally estimated. The two-point correlation function estimated from the "corrected" model catalog reproduces the built-in correlation function including the break from the power law. This is also true if the angular scale of the break is increased or decreased by a factor of 1.76 from the observed value. We also compare a map of the corrected counts with a map of the counts projected without plate errors and find that the corrected map is a good visual representation of the galaxy distribution. Finally, we construct a simulation which includes systematic variations in plate sensitivity with observer and time-so called "plate shape gradients." Once again, the correlation function of the model catalog reproduces the built in correlation function

    The density of mid-sized Kuiper belt objects from ALMA thermal observations

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    The densities of mid-sized Kuiper belt objects are a key constraint into understanding the assembly of objects in the outer solar system. These objects are critical for understanding the currently unexplained transition from the smallest Kuiper belt objects with densities lower than that of water to the largest objects with significant rock content. Mapping this transition is made difficult by the uncertainties in the diameters of these objects, which maps into an even larger uncertainty in volume and thus density. The substantial collecting area of the Atacama Large Millimeter Array allows significantly more precise measurements of thermal emission from outer solar system objects and could potentially greatly improve the density measurements. Here we use new thermal observations of four objects with satellites to explore the improvements possible with millimeter data. We find that effects due to effective emissivity at millimeter wavelengths make it difficult to use the millimeter data directly to find diameters and thus volumes for these bodies. In addition, we find that when including the effects of model uncertainty, the true uncertainties on the sizes of outer solar system objects measured with radiometry are likely larger than those previously published. Substantial improvement in object sizes will likely require precise occultation measurements.Comment: AJ, in pres

    Synthesis of α-hydroxy-β,β-difluoro-γ-ketoesters via [3,3]sigmatropic rearrangements

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    Readily available γ,γ-difluorinated allylic alcohols obtained from trifluoroethanol were esterified efficiently. Exposure to strong base (LDA) afforded the ester enolates, in which chelation both controlled configuration and stabilised against fragmentation, which were trapped as their silyl ketene acetals. Rearrangement occurred to afford base-sensitive acid products. Esterification under mild conditions afforded the purifiable methyl esters in which the masked ketone had been released. Educts with either a benzyloxy or an allyloxy group at the α-position could be deprotected releasing the alcohols

    Long-Term Dynamics and the Orbital Inclinations of the Classical Kuiper Belt Objects

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    We numerically integrated the orbits of 1458 particles in the region of the classical Kuiper Belt (41 AU < a < 47 AU) to explore the role of dynamical instabilities in sculpting the inclination distribution of the classical Kuiper Belt Objects (KBOs). We find that the selective removal of low-inclination objects by overlapping secular resonances (nu_17 and nu_18) acts to raise the mean inclination of the surviving population of particles over 4 billion years of interactions with Jupiter, Saturn, Uranus and Neptune, though these long-term dynamical effects do not themselves appear to explain the discovery of KBOs with inclinations near 30 degrees. Our integrations also imply that after 3 billion years of interaction with the massive planets, high inclination KBOs more efficiently supply Neptune-encountering objects, the likely progenitors of short-period comets, Centaurs, and scattered KBOs. The secular resonances at low inclinations may indirectly cause this effect by weeding out objects unprotected by mean motion resonances during the first 3 billion years.Comment: 23 pages, including 10 figures. Accepted for publication in A