arXiv subjects

D. Blair

Publications and source records attributed to D. Blair.

59 records · Page 4Linked to original sources

arXiv2007

An improved method for estimating source densities using the temporal distribution of Cosmological Transients

It has been shown that the observed temporal distribution of transient events in the cosmos can be used to constrain their rate density. Here we show that the peak flux--observation time relation takes the form of a power law that is invariant to the luminosity distribution of the sources, and that the method can be greatly improved by invoking time reversal invariance and the temporal cosmological principle. We demonstrate how the method can be used to constrain distributions of transient events, by applying it to Swift gamma-ray burst data and show that the peak flux--observation time relation is in good agreement with recent estimates of source parameters. We additionally show that the intrinsic time dependence allows the method to be used as a predictive tool. Within the next year of Swift observation, we find a 50% chance of obtaining a peak flux greater than that of GRB 060017 -- the highest Swift peak flux to date -- and the same probability of detecting a burst with peak flux > 100 photons s^{-1} cm^{-2} within 6 years.

astro-ph↗

arXiv2007

Application of the Probability Event Horizon filter to constrain the local rate density of binary black hole inspirals with Advanced LIGO

The temporal evolution of the gravitational wave background signal resulting from stellar-mass binary black hole (BBH) inspirals has a unique statistical signature. We describe the application of a new filter, based on the `probability event horizon' (PEH) concept, that utilizes both the temporal and spatial source distribution to constrain the local rate density, $r_{0}$, of BBH inspiral events in the nearby Universe. Assuming Advanced LIGO sensitivities and an upper rate of Galactic BBH inspirals of $ 30\hspace{1mm}\mathrm{Myr}^{-1}$, we simulate GW data and apply a fitting procedure to the PEH filtered data. To determine the accuracy of the PEH filter in constraining $r_{0}$, a comparison is made with a fit to the brightness distribution of events. We apply both methods to a data stream containing a background of Gaussian distributed false alarms. We find that the brightness distribution yields lower standard errors, but is biased by the false alarms. In comparison the PEH method is less prone to errors resulting from false alarms but has a lower resolution as fewer events contribute to the data. Used in combination, the PEH and brightness distribution methods provide an improved estimate of the rate density.

astro-ph↗

arXiv1999

High-Acceleration Patterns in Thin Vibrated Granular Layers

Theoretical and experimental study of high-acceleration patterns in vibrated granular layers is presented. The order parameter model based on parametric Ginzburg-Landau equation is used to describe strongly nonlinear excitations including hexagons, interface between flat anti-phase domains and new localized objects, super-oscillons. The experiments confirmed the existence of super-oscillons and bound states of super-oscillons and interfaces. On the basis of order parameter model we predict analytically and confirm experimentally that the additional subharmonic driving results in controlled motion of the interfaces.

cond-mat.soft↗

arXiv1999

Electrostatically-Driven Granular Media: Phase Transitions and Coarsening

We report the experimental and theoretical study of electrostatically driven granular material. We show that the charged granular medium undergoes a hysteretic first order phase transition from the immobile condensed state (granular solid) to a fluidized dilated state (granular gas) with a changing applied electric field. In addition we observe a spontaneous precipitation of dense clusters from the gas phase and subsequent coarsening - coagulation of these clusters. Molecular dynamics simulations shows qualitative agreement with experimental results.

cond-mat.soft↗

arXiv1998

Controlled Dynamics of Interfaces in a Vibrated Granular Layer

We present experimental study of a topological excitation, {\it interface}, in a vertically vibrated layer of granular material. We show that these interfaces, separating regions of granular material oscillation with opposite phases, can be shifted and controlled by a very small amount of an additional subharmonic signal, mixed with the harmonic driving signal. The speed and the direction of interface motion depends sensitively on the phase and the amplitude of the subharmonic driving.

patt-sol↗