9,412 research outputs found

    Correlation and Fluctuation in Multiparticle Production: Some Closing Remarks

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    Some general comments are made on the evolution of this series of workshops and on some features of this particular Workshop without attempting to summarize all the talks presented.Comment: Closing talk at the 11th Workshop on Correlation and Fluctuation in Multiparticle Production, Hangzhou, China, Nov. 21-24, 200

    Photoionization cross sections of rovibrational levels of the B^1ÎŁ^+_u state of H_2

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    We report theoretical cross sections for direct photoionization of specific rovibrational levels of the B ^1Σ^+_u electronic state of H_2. The calculated cross sections differ considerably from values recently determined by resonant enhanced multiphoton ionization (REMPI) studies. In an attempt to understand the disagreement, we analyze in detail the REMPI dynamics and find that the multiphoton ionization probability is extremely sensitive to the spatial and temporal profiles of the laser pulses. Accurate characterization of laser profiles and their jitter is therefore necessary for a comparison between theory and experiment

    A simple encoding of a quantum circuit amplitude as a matrix permanent

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    A simple construction is presented which allows computing the transition amplitude of a quantum circuit to be encoded as computing the permanent of a matrix which is of size proportional to the number of quantum gates in the circuit. This opens up some interesting classical monte-carlo algorithms for approximating quantum circuits.Comment: 6 figure

    (2+1) resonant enhanced multiphoton ionization of H_2 via the E, F^(1)ÎŁ^+_g state

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    In this paper, we report the results of ab initio calculations of photoelectron angular distributions and vibrational branching ratios for the (2+1) REMPI of H_2 via the E, F^(1)Σ^+_g state, and compare these with the experimental data of Anderson et al. [Chem. Phys. Lett. 105, 22 (1984)]. These results show that the observed non‐Franck–Condon behavior is predominantly due to the R dependence of the transition matrix elements, and to a lesser degree to the energy dependence. This work presents the first molecular REMPI study employing a correlated wave function to describe the Rydberg–valence mixing in the resonant intermediate state

    New methods and results for quantification of lightning-aircraft electrodynamics

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    The NASA F-106 collected data on the rates of change of electromagnetic parameters on the aircraft surface during over 700 direct lightning strikes while penetrating thunderstorms at altitudes from 15,000 t0 40,000 ft (4,570 to 12,190 m). These in situ measurements provided the basis for the first statistical quantification of the lightning electromagnetic threat to aircraft appropriate for determining indirect lightning effects on aircraft. These data are used to update previous lightning criteria and standards developed over the years from ground-based measurements. The proposed standards will be the first which reflect actual aircraft responses measured at flight altitudes. Nonparametric maximum likelihood estimates of the distribution of the peak electromagnetic rates of change for consideration in the new standards are obtained based on peak recorder data for multiple-strike flights. The linear and nonlinear modeling techniques developed provide means to interpret and understand the direct-strike electromagnetic data acquired on the F-106. The reasonable results obtained with the models, compared with measured responses, provide increased confidence that the models may be credibly applied to other aircraft

    Discovering Implicational Knowledge in Wikidata

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    Knowledge graphs have recently become the state-of-the-art tool for representing the diverse and complex knowledge of the world. Examples include the proprietary knowledge graphs of companies such as Google, Facebook, IBM, or Microsoft, but also freely available ones such as YAGO, DBpedia, and Wikidata. A distinguishing feature of Wikidata is that the knowledge is collaboratively edited and curated. While this greatly enhances the scope of Wikidata, it also makes it impossible for a single individual to grasp complex connections between properties or understand the global impact of edits in the graph. We apply Formal Concept Analysis to efficiently identify comprehensible implications that are implicitly present in the data. Although the complex structure of data modelling in Wikidata is not amenable to a direct approach, we overcome this limitation by extracting contextual representations of parts of Wikidata in a systematic fashion. We demonstrate the practical feasibility of our approach through several experiments and show that the results may lead to the discovery of interesting implicational knowledge. Besides providing a method for obtaining large real-world data sets for FCA, we sketch potential applications in offering semantic assistance for editing and curating Wikidata

    Particle alignments and shape change in 66^{66}Ge and 68^{68}Ge

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    The structure of the N≈ZN \approx Z nuclei 66^{66}Ge and 68^{68}Ge is studied by the shell model on a spherical basis. The calculations with an extended P+QQP+QQ Hamiltonian in the configuration space (2p3/22p_{3/2}, 1f5/21f_{5/2}, 2p1/22p_{1/2}, 1g9/21g_{9/2}) succeed in reproducing experimental energy levels, moments of inertia and QQ moments in Ge isotopes. Using the reliable wave functions, this paper investigates particle alignments and nuclear shapes in 66^{66}Ge and 68^{68}Ge. It is shown that structural changes in the four sequences of the positive- and negative-parity yrast states with even JJ and odd JJ are caused by various types of particle alignments in the g9/2g_{9/2} orbit. The nuclear shape is investigated by calculating spectroscopic QQ moments of the first and second 2+2^+ states, and moreover the triaxiality is examined by the constrained Hatree-Fock method. The changes of the first band crossing and the nuclear deformation depending on the neutron number are discussed.Comment: 18 pages, 21 figures; submitted to Phys. Rev.

    Further results on the cross norm criterion for separability

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    In the present paper the cross norm criterion for separability of density matrices is studied. In the first part of the paper we determine the value of the greatest cross norm for Werner states, for isotropic states and for Bell diagonal states. In the second part we show that the greatest cross norm criterion induces a novel computable separability criterion for bipartite systems. This new criterion is a necessary but in general not a sufficient criterion for separability. It is shown, however, that for all pure states, for Bell diagonal states, for Werner states in dimension d=2 and for isotropic states in arbitrary dimensions the new criterion is necessary and sufficient. Moreover, it is shown that for Werner states in higher dimensions (d greater than 2), the new criterion is only necessary.Comment: REVTeX, 19 page

    Ecology and Management of Pemphigus betae (Hemiptera: Aphididae) in Sugar Beet

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    Published ArticlePemphigus betae Doane (Hemiptera: Aphididae), is a sporadic pest of sugar beet (Beta vulgaris L. var. vulgaris) in all major sugar beet production regions of North America. These oval-shaped, pale-yellowish insects, with a body length ranging from 1.9–2.4mm, secrete a waxy material, giving their subterranean colonies a moldy appearance. Poplars in the genus Populus L. are the preferred primary hosts, while sugar beet and certain weed species, such as common lambsquarters (Chenopodium album L.) and kochia (Kochia scoparia (L.)), are among the secondary hosts. Pemphigus betae has a complex and varied life cycle and is usually heteroecious and holocyclic, although anholocyclic apterae are known to overwinter in the soil. Heavy infestations of this aphid can induce significant reductions in yield, sugar content, and recoverable sugar. Under conditions of extreme stress and heavy infestations, the alienicolae can induce stunting, chlorosis, wilting, and even death of sugar beet plants. Accurately establishing population densities for sugarbeet root aphids presents a challenge, because the economic important stage of this insect is subterranean. However, use of a fall root rating index aids in estimating relative population densities. Furthermore, root aphids are especially difficult to control by means of conventional insecticides. For this reason, integrated pest management tactics, including the use of host plant resistance, cultural control techniques, and the use of natural enemies, should take precedence
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