3,720 research outputs found

    Hydrodynamic scaling from the dynamics of relativistic quantum field theory

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    Hydrodynamic behavior is a general feature of interacting systems with many degrees of freedom constrained by conservation laws. To date hydrodynamic scaling in relativistic quantum systems has been observed in many high energy settings, from cosmic ray detections to accelerators, with large particle multiplicity final states. Here we show first evidence for the emergence of hydrodynamic scaling in the dynamics of a relativistic quantum field theory. We consider a simple scalar λϕ4\lambda \phi^4 model in 1+1 dimensions in the Hartree approximation and study the dynamics of two colliding kinks at relativistic speeds as well as the decay of a localized high energy density region. The evolution of the energy-momentum tensor determines the dynamical local equation of state and allows the measurement of the speed of sound. Hydrodynamic scaling emerges at high local energy densities.Comment: 4 pages, 4 color eps figures, uses RevTex, v2 some typos corrected and references adde

    High temperature turbine engine structure

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    A high temperature ceramic/metallic turbine engine includes a metallic housing which journals a rotor member of the turbine engine. A ceramic disk-like shroud portion of the engine is supported on the metallic housing portion and maintains a close running clearance with the rotor member. A ceramic spacer assembly maintains the close running clearance of the shroud portion and rotor member despite differential thermal movements between the shroud portion and metallic housing portion

    Vegetarianism

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    Ethical vegetarians maintain that vegetarianism is morally required. The principal reasons offered in support of ethical vegetarianism are: (i) concern for the welfare and well-being of the animals being eaten, (ii) concern for the environment, (iii) concern over global food scarcity and the just distribution of resources, and (iv) concern for future generations. Each of these reasons is explored in turn, starting with a historical look at ethical vegetarianism and the moral status of animals

    An extreme ultraviolet spectrometer experiment for the Shuttle Get Away Special Program

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    An extreme ultraviolet (EUV) spectrometer experiment operated successfully during the STS-7 mission in an experiment to measure the global and diurnal variation of the EUV airglow. The spectrometer is an F 3.5 Wadsworth mount with mechanical collimator, a 75 x 75 mm grating, and a bare microchannel plate detector providing a spectral resolution of 7 X FWHM. Read-out of the signal is through discrete channels or resistive anode techniques. The experiment includes a microcomputer, 20 Mbit tape recorder, and a 28V, 40 Ahr silver-zinc battery. It is the first GAS payload to use an opening door. The spectrometer's 0.1 x 4.2 deg field of view is pointed vertically out of the shuttle bay. During the STS-7 flight data were acquired continuously for a period of 5 hours and 37 minutes, providing spectra of the 570 A to 850 A wavelength region of the airglow. Five diurnal cycles of the 584 A emission of neutral helium and the 834 A emission of ionized atomic oxygen were recorded. The experiment also recorded ion events and pressure pulses associated with thruster firings. The experiment is to fly again on Mission 41-F

    Integral correlation measures for multiparticle physics

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    We report on a considerable improvement in the technique of measuring multiparticle correlations via integrals over correlation functions. A modification of measures used in the characterization of chaotic dynamical sytems permits fast and flexible calculation of factorial moments and cumulants as well as their differential versions. Higher order correlation integral measurements even of large multiplicity events such as encountered in heavy ion collisons are now feasible. The change from ``ordinary'' to ``factorial'' powers may have important consequences in other fields such as the study of galaxy correlations and Bose-Einstein interferometry.Comment: 23 pages, 6 tar-compressed uuencoded PostScript figures appended, preprint TPR-92-4

    A Sensitivity Study Relating to Neighbourhood-scale Fast Local Urban Climate Modelling within the Built Environment

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    The rapid increase in urban populations during the last century, together with the threat of climate change has motivated research focusing on the impact of land-use on urban climates. High-resolution neighbourhood-scale modelling tools developed to account for the complex three-dimensional surfaces and volumes within an urban area are able to predict temperature perturbations over an urban domain with reference to varying land-use. However, land-use classes chosen to model the urban landscape often reflect the function, rather than the material, and hence overlook different building materials that compose the built environment. The purpose of this study is to demonstrate that in order to robustly assess local climate variations, it is important to use representative land-use parameters that account for materials that form the urban landscape, instead of functions. The response of a high-resolution local climate model to an improved parameterization of the built environment is investigated using the local-scale urban climate modelling tool, ADMS-Urban. In this study, a more elaborate set of land-use classes is collated which distinguishes between different building materials that have varying thermal parameters. A novel approach to calculating the thermal admittance is proposed, reflecting different building materials used for the building facades and the roofs. This study demonstrates that refining model input parameters to correctly represent various construction materials used within the urban tissue, as well as the proposed, advanced method for calculating thermal admittance leads to significant temperature differences compared to when broad assumptions are used, especially under low wind conditions common in equatorial cities. Validation studies are planned that will demonstrate the accuracy of model predictions in comparison to observed temperature data in order to identify threshold criteria required to produce realistic urban climate predictions. Following this example of best practice, the existing modelling tools can reliably be used for the simulation of complex future scenarios and for a robust assessment of the relevant health implications

    Multiplicity Distributions and Rapidity Gaps

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    I examine the phenomenology of particle multiplicity distributions, with special emphasis on the low multiplicities that are a background in the study of rapidity gaps. In particular, I analyze the multiplicity distribution in a rapidity interval between two jets, using the HERWIG QCD simulation with some necessary modifications. The distribution is not of the negative binomial form, and displays an anomalous enhancement at zero multiplicity. Some useful mathematical tools for working with multiplicity distributions are presented. It is demonstrated that ignoring particles with pt<0.2 has theoretical advantages, in addition to being convenient experimentally.Comment: 24 pages, LaTeX, MSUHEP/94071

    Random and Correlated Phases of Primordial Gravitaional Waves

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    The phases of primordial gravity waves is analysed in detail within a quantum mechanical context following the formalism developed by Grishchuk and Sidorov. It is found that for physically relevant wavelengths both the phase of each individual mode and the phase {\it difference} between modes are randomly distributed. The phase {\it sum} between modes with oppositely directed wave-vectors, however, is not random and takes on a definite value with no rms fluctuation. The conventional point of view that primordial gravity waves appear after inflation as a classical, random stochastic background is also addressed.Comment: 14 pages, written in REVTE
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