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Articles 1 - 4 of 4
Full-Text Articles in Physical Sciences and Mathematics
Extended Green-Liouville Asymptotics And Vacuum Polarization For Lukewarm Black Holes, Cormac Breen, Adrian Ottewill
Extended Green-Liouville Asymptotics And Vacuum Polarization For Lukewarm Black Holes, Cormac Breen, Adrian Ottewill
Articles
We consider a quantum field on a lukewarm black hole spacetime. We introduce a new uniform approximation to the radial equation, constructed using an extension of Green-Liouville asymptotics. We then use this new approximation to construct the renormalized vacuum polarization in the Hartle-Hawking vacuum. Previous calculations of the vacuum polarization rely on the WKB approximation to the solutions of the radial equation, however the nonuniformity of the WKB approximations obscures the results of these calculations near both horizons. The use of our new approximation eliminates these obscurities, enabling us to obtain explicitly finite and easily calculable values of the vacuum …
Relativistic Particle Acceleration In Tangled Magnetic Fields, Stephen O'Sullivan, Brian Reville, Andrew Taylor
Relativistic Particle Acceleration In Tangled Magnetic Fields, Stephen O'Sullivan, Brian Reville, Andrew Taylor
Conference papers
We present simulations of the transport of fast particles through three-dimensional turbulent magnetic field configurations. A time dependency is imposed on the plane wave modes used in constructing these fields such than acceleration via the second-order Fermi process is possible. We consider simulations of models with low and high turbulence levels for non-relativistic waves. The predictions of quasi-linear theory are discussed with respect to the simulation data. We conclude that for pure stochastic acceleration via Alfvén waves to be plausible as the generator of UHECR in Cen A, the baryon number density would need to be several orders of magnitude …
A Model For Predicting Extragalactic Jet Lifetimes, Daniel S. Spicer, Robert Bingham, Stephen O'Sullivan
A Model For Predicting Extragalactic Jet Lifetimes, Daniel S. Spicer, Robert Bingham, Stephen O'Sullivan
Articles
Abstract. In this letter, we propose a model to explain the disintegration of ex- tragalactic jets and to predict the associated timescale. The model assumes that a jet is current and charge neutral as well as collimated at its source; however, the forward electron current gradually decays producing a magnetic field transverse to the direction of jet propagation. This growing transverse magnetic field eventually causes the jet to disintegrate.
Off To A Good Start: Using Clustering To Select The Initial Training Set In Active Learning, Rong Hu, Brian Mac Namee, Sarah Jane Delany
Off To A Good Start: Using Clustering To Select The Initial Training Set In Active Learning, Rong Hu, Brian Mac Namee, Sarah Jane Delany
Conference papers
Active learning (AL) is used in textual classification to alleviate the cost of labelling documents for training. An important issue in AL is the selection of a representative sample of documents to label for the initial training set that seeds the process, and clustering techniques have been successfully used in this regard. However, the clustering techniques used are nondeterministic which causes inconsistent behaviour in the AL process. In this paper we first illustrate the problems associated with using non-deterministic clustering for initial training set selection in AL. We then examine the performance of three deterministic clustering techniques for this task …