7,780 research outputs found

    Space telescope observatory management system preliminary test and verification plan

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    The preliminary plan for the Space Telescope Observatory Management System Test and Verification (TAV) is provided. Methodology, test scenarios, test plans and procedure formats, schedules, and the TAV organization are included. Supporting information is provided

    Protons as the prime contributors to the storm time ring current

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    Following a large magnetic storm (17 June 1972), Explorer 45 measured the equatorial particle populations and magnetic field. Using data obtained during the symmetic recovery phase, it is shown that through a series of self-consistent calculations, the measured protons with energies from 1 to 872 keV, can account for the observed ring current magnetic effects within experimental uncertainities. This enables an upper limit to be set for the heavy ion contribution to the storm time ring current

    Transport Properties of a Chain of Anharmonic Oscillators with random flip of velocities

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    We consider the stationary states of a chain of nn anharmonic coupled oscillators, whose deterministic hamiltonian dynamics is perturbed by random independent sign change of the velocities (a random mechanism that conserve energy). The extremities are coupled to thermostats at different temperature TℓT_\ell and TrT_r and subject to constant forces τℓ\tau_\ell and τr\tau_r. If the forces differ τℓ≠τr\tau_\ell \neq \tau_r the center of mass of the system will move of a speed VsV_s inducing a tension gradient inside the system. Our aim is to see the influence of the tension gradient on the thermal conductivity. We investigate the entropy production properties of the stationary states, and we prove the existence of the Onsager matrix defined by Green-kubo formulas (linear response). We also prove some explicit bounds on the thermal conductivity, depending on the temperature.Comment: Published version: J Stat Phys (2011) 145:1224-1255 DOI 10.1007/s10955-011-0385-

    Fluctuations and Ergodicity of the Form Factor of Quantum Propagators and Random Unitary Matrices

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    We consider the spectral form factor of random unitary matrices as well as of Floquet matrices of kicked tops. For a typical matrix the time dependence of the form factor looks erratic; only after a local time average over a suitably large time window does a systematic time dependence become manifest. For matrices drawn from the circular unitary ensemble we prove ergodicity: In the limits of large matrix dimension and large time window the local time average has vanishingly small ensemble fluctuations and may be identified with the ensemble average. By numerically diagonalizing Floquet matrices of kicked tops with a globally chaotic classical limit we find the same ergodicity. As a byproduct we find that the traces of random matrices from the circular ensembles behave very much like independent Gaussian random numbers. Again, Floquet matrices of chaotic tops share that universal behavior. It becomes clear that the form factor of chaotic dynamical systems can be fully faithful to random-matrix theory, not only in its locally time-averaged systematic time dependence but also in its fluctuations.Comment: 12 pages, RevTEX, 4 figures in eps forma

    Periodic-Orbit Theory of Level Correlations

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    We present a semiclassical explanation of the so-called Bohigas-Giannoni-Schmit conjecture which asserts universality of spectral fluctuations in chaotic dynamics. We work with a generating function whose semiclassical limit is determined by quadruplets of sets of periodic orbits. The asymptotic expansions of both the non-oscillatory and the oscillatory part of the universal spectral correlator are obtained. Borel summation of the series reproduces the exact correlator of random-matrix theory.Comment: 4 pages, 1 figure (+ web-only appendix with 2 pages, 1 figure

    HERschel Observations of Edge-on Spirals (HEROES). II: Tilted-ring modelling of the atomic gas disks

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    Context. Edge-on galaxies can offer important insights in galaxy evolution as they are the only systems where the distribution of the different components can be studied both radially and vertically. The HEROES project was designed to investigate the interplay between the gas, dust, stars and dark matter (DM) in a sample of 7 massive edge-on spiral galaxies. Aims. In this second HEROES paper we present an analysis of the atomic gas content of 6 out of 7 galaxies in our sample. The remaining galaxy was recently analysed according to the same strategy. The primary aim of this work is to constrain the surface density distribution, the rotation curve and the geometry of the gas disks in a homogeneous way. In addition we identify peculiar features and signs of recent interactions. Methods. We construct detailed tilted-ring models of the atomic gas disks based on new GMRT 21-cm observations of NGC 973 and UGC 4277 and re-reduced archival HI data of NGC 5907, NGC 5529, IC 2531 and NGC 4217. Potential degeneracies between different models are resolved by requiring a good agreement with the data in various representations of the data cubes. Results. From our modelling we find that all but one galaxy are warped along the major axis. In addition, we identify warps along the line of sight in three galaxies. A flaring gas layer is required to reproduce the data only for one galaxy, but (moderate) flares cannot be ruled for the other galaxies either. A coplanar ring-like structure is detected outside the main disk of NGC 4217, which we suggest could be the remnant of a recent minor merger event. We also find evidence for a radial inflow of 15 +- 5 km/s in the disk of NGC 5529, which might be related to the ongoing interaction with two nearby companions. (Abridged)Comment: 39 pages, 38 figures, Accepted for publication in Astronomy & Astrophysic

    Classical versus Quantum Time Evolution of Densities at Limited Phase-Space Resolution

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    We study the interrelations between the classical (Frobenius-Perron) and the quantum (Husimi) propagator for phase-space (quasi-)probability densities in a Hamiltonian system displaying a mix of regular and chaotic behavior. We focus on common resonances of these operators which we determine by blurring phase-space resolution. We demonstrate that classical and quantum time evolution look alike if observed with a resolution much coarser than a Planck cell and explain how this similarity arises for the propagators as well as their spectra. The indistinguishability of blurred quantum and classical evolution implies that classical resonances can conveniently be determined from quantum mechanics and in turn become effective for decay rates of quantum correlations.Comment: 10 pages, 3 figure

    Anomalous diffusion for a class of systems with two conserved quantities

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    We introduce a class of one dimensional deterministic models of energy-volume conserving interfaces. Numerical simulations show that these dynamics are genuinely super-diffusive. We then modify the dynamics by adding a conservative stochastic noise so that it becomes ergodic. System of conservation laws are derived as hydrodynamic limits of the modified dynamics. Numerical evidence shows these models are still super-diffusive. This is proven rigorously for harmonic potentials
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