10,875 research outputs found

    The structure of spider's web fast escaping sets

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    Building on recent work by Rippon and Stallard, we explore the intricate structure of the spider's web fast escaping sets associated with certain transcendental entire functions. Our results are expressed in terms of the components of the complement of the set (the 'holes' in the web). We describe the topology of such components and give a characterisation of their possible orbits under iteration. We show that there are uncountably many components having each of a number of orbit types, and we prove that components with bounded orbits are quasiconformally homeomorphic to components of the filled Julia set of a polynomial. We also show that there are singleton periodic components and that these are dense in the Julia set.Comment: 18 page

    Evaporation of a packet of quantized vorticity

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    A recent experiment has confirmed the existence of quantized turbulence in superfluid He3-B and suggested that turbulence is inhomogenous and spreads away from the region around the vibrating wire where it is created. To interpret the experiment we study numerically the diffusion of a packet of quantized vortex lines which is initially confined inside a small region of space. We find that reconnections fragment the packet into a gas of small vortex loops which fly away. We determine the time scale of the process and find that it is in order of magnitude agreement with the experiment.Comment: figure 1a,b,c and d, figure2, figure

    Coronal loop seismology using multiple transverse loop oscillation harmonics

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    Context. TRACE observations (23/11/1998 06:35:57−06:48:43 UT) in the 171 Å bandpass of an active region are studied. Coronal loop oscillations are observed after a violent disruption of the equilibrium. Aims. The oscillation properties are studied to give seismological estimates of physical quantities, such as the density scale height. Methods. A loop segment is traced during the oscillation, and the resulting time series is analysed for periodicities. Results. In the loop segment displacement, two periods are found: 435.6 ± 4.5 s and 242.7 ± 6.4 s, consistent with the periods of the fundamental and 2nd harmonic fast kink oscillation. The small uncertainties allow us to estimate the density scale height in the loop to be 109 Mm, which is about double the estimated hydrostatical value of 50 Mm. Because a loop segment is traced, the amplitude dependence along the loop is found for each of these oscillations. The obtained spatial information is used as a seismological tool to give details about the geometry of the observed loop
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