We have collected polarimetric ice sounding radar data on Brunt, George VI and Ronne ice shelves using a vector network analyser as a continuous wave step-frequency radar. Being a wideband phase sensitive instrument, the radar allowed the vectorial nature of the interaction between radio waves and the ice and reflecting surface to be explored. Single crystals of ice are birefringent not only at...

In several merging clusters of galaxies so-called cluster radio relics have been observed. These are extended radio sources which do not seem to be associated with any radio galaxy. Two competing physical mechanisms to accelerate the radio emitting electrons have been proposed: (i) diffusive shock acceleration and (ii) adiabatic compression of fossil radio plasma by merger shock waves. Here the...

A new method is explored to detect extensive air showers: the measurement of radio waves emitted during the propagation of the electromagnetic shower component in the magnetic field of the Earth. Recent results of the pioneering experiment LOPES are discussed. It registers radio signals in the frequency range between 40 and 80 MHz. The intensity of the measured radio emission is investigated as...

In the early days of telecommunication,' technically advanced nations quickly recognized the usefulness of the telegraph in international commerce. There was, however, a considerable obstacle to the development of the new technology's commercial potential. As one observer of this era of telecommunication history points out, "humanity could not fully benefit from all the miraculous possibilities...

We evaluate the Liénard-Wiechert field of a rotating superluminal point source numerically and show that this radiation field has the following intrinsic characteristics. (i) It is sharply focused along a narrow, rigidly rotating spiral-shaped beam that embodies the cusp of the envelope of the emitted wave fronts. (ii) It consists of either one or three concurrent polarization modes (depending ...

We present results from a controlled numerical experiment investigating the effect of stellar density gas on the coalescence of binary black holes (BBHs) and the resulting gravitational waves (GWs). This investigation is motivated by the proposed stellar core fragmentation scenario for BBH formation and the associated possibility of an electromagnetic counterpart to a BBH GW event. We employ fu...

Adapting and extending the techniques developed in recent work with Vasy for the study of the Cauchy horizon of cosmological spacetimes, we obtain boundedness, regularity and decay of linear scalar waves on subextremal Reissner–Nordström and (slowly rotating) Kerr spacetimes, without any symmetry assumptions; in particular, we provide simple microlocal and scattering theoretic proofs of analogo...

In many ways, roboticians and the human brain are faced with the same problem: How does one control movement from a distance? In both cases, delays in the transmission of information play an important role, either because the distances to be covered are long (imagine controlling a robot arm on the moon from a command center on Earth), or because the underlying hardware is slow (nerves transmit ...

The multiplicity of stable convection patterns in a rotating spherical fluid shell heated from the inner boundary and driven by a central gravity field is presented. These solution branches that arise as rotating waves (RWs) are traced for varying Rayleigh number while their symmetry, stability, and bifurcations are studied. At increased Rayleigh numbers all the RWs undergo transitions to modul...

We describe the steps involved in performing searches for sources of transient radio emission such as Rotating Radio Transients (RRATs), and present 10 new transient radio sources discovered in a re-analysis of the Parkes Multi-beam Pulsar Survey. Followup observations of each new source as well as one previously known source are also presented. The new sources suggest that the population of tr...