3,191 research outputs found

    Using mutual information to measure order in model glass-formers

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    Whether or not there is growing static order accompanying the dynamical heterogeneity and increasing relaxation times seen in glassy systems is a matter of dispute. An obstacle to resolving this issue is that the order is expected to be amorphous and so not amenable to simple order parameters. We use mutual information to provide a general measurement of order that is sensitive to multi-particle correlations. We apply this to two glass-forming systems (2D binary mixtures of hard disks with different size ratios to give varying amounts of hexatic order) and show that there is little growth of amorphous order in the system without crystalline order. In both cases we measure the dynamical length with a four-point correlation function and find that it increases significantly faster than the static lengths in the system as density is increased. We further show that we can recover the known scaling of the dynamic correlation length in a kinetically constrained model, the 2-TLG.Comment: 10 pages, 12 Figure

    Consistency Checks for Two-Body Finite-Volume Matrix Elements. II. Perturbative Systems

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    Using the general formalism presented in [Phys. Rev. D 94, 013008 (2016); Phys. Rev. D 100, 034511 (2019)], we study the finite-volume effects for the 2 þ J → 2 matrix element of an external current coupled to a two-particle state of identical scalars with perturbative interactions. Working in a finite cubic volume with periodicity L, we derive a 1=L expansion of the matrix element through O(1=L5) and find that it is governed by two universal current-dependent parameters, the scalar charge and the threshold two particle form factor. We confirm the result through a numerical study of the general formalism and additionally through an independent perturbative calculation. We further demonstrate a consistency with the Feynman-Hellmann theorem, which can be used to relate the 1=L expansions of the ground-state energy and matrix element. The latter gives a simple insight into why the leading volume corrections to the matrix element have the same scaling as those in the energy, 1=L3, in contradiction to Phys. Rev. D 91, 074509 (2015), which found a 1=L2 contribution to the matrix element. We show here that such a term arises at intermediate stages in the perturbative calculation, but cancels in the final result

    Consistency Checks for Two-Body Finite-Volume Matrix Elements: Conserved Currents and Bound States

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    Recently, a framework has been developed to study form factors of two-hadron states probed by an external current. The method is based on relating finite-volume matrix elements, computed using numerical lattice QCD, to the corresponding infinite-volume observables. As the formalism is complicated, it is important to provide nontrivial checks on the final results and also to explore limiting cases in which more straightforward predictions may be extracted. In this work we provide examples on both fronts. First, we show that, in the case of a conserved vector current, the formalism ensures that the finite-volume matrix element of the conserved charge is volume independent and equal to the total charge of the two-particle state. Second, we study the implications for a two-particle bound state. We demonstrate that the infmite-volume limit reproduces the expected matrix element and derive the leading finite-volume corrections to this result for a scalar current. finally, we provide numerical estimates for the expected size of volume effects in future lattice QCD calculations of the deuteron\u27s scalar charge. We find that these effects completely dominate the infinite-volume result for realistic lattice volumes and that applying the present formalism, to analytically remove an infinite series of leading volume corrections, is crucial to reliably extract the infinite-volume charge of the state

    The R-Process Alliance: Chemical Abundances for a Trio of R-Process-Enhanced Stars -- One Strong, One Moderate, One Mild

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    We present detailed chemical abundances of three new bright (V ~ 11), extremely metal-poor ([Fe/H] ~ -3.0), r-process-enhanced halo red giants based on high-resolution, high-S/N Magellan/MIKE spectra. We measured abundances for 20-25 neutron-capture elements in each of our stars. J1432-4125 is among the most r-process rich r-II stars, with [Eu/Fe]= +1.44+-0.11. J2005-3057 is an r-I star with [Eu/Fe] = +0.94+-0.07. J0858-0809 has [Eu/Fe] = +0.23+-0.05 and exhibits a carbon abundance corrected for evolutionary status of [C/Fe]_corr = +0.76, thus adding to the small number of known carbon-enhanced r-process stars. All three stars show remarkable agreement with the scaled solar r-process pattern for elements above Ba, consistent with enrichment of the birth gas cloud by a neutron star merger. The abundances for Sr, Y, and Zr, however, deviate from the scaled solar pattern. This indicates that more than one distinct r-process site might be responsible for the observed neutron-capture element abundance pattern. Thorium was detected in J1432-4125 and J2005-3057. Age estimates for J1432-4125 and J2005-3057 were adopted from one of two sets of initial production ratios each by assuming the stars are old. This yielded individual ages of 12+-6 Gyr and 10+-6 Gyr, respectively.Comment: 30 pages, includes a long table, 5 figure

    First-year compliance with the Nevada Clean Indoor Air Act

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    Objectives: We quantitatively evaluated compliance with the Nevada Clean Indoor Air Act (NCIAA) by different types of businesses in Nevada and determined whether compliance affected indoor concentrations of benzene and 3-ethenyl pyridine (3-EP), markers of tobacco smoke. Methods: Managers of 181 businesses in Washoe County, Nevada, were interviewed about business characteristics and practices and policies related to smoking. During unannounced visits, compliance data and air samples (n=66) were collected from interviewed businesses and from an additional sample (n = 56) of businesses without knowledge of the study. Results: Overall compliance, as defined by the NCIAA, was low (28.2%). Benzene concentrations were higher in casino restaurants than in other businesses, although most complied with the requirements of the ban. Neither benzene nor 3-EP concentrations differed significantly between compliant and non-compliant businesses. Conclusions: The finding that casino restaurants had poorer air quality despite their compliance with the NCIAA suggests that compliance alone may not be sufficient to reduce exposure to secondhand smoke, particularly in buildings with both nonsmoking and smoking areas
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