On Source Density Evolution of Gamma-ray Bursts

Recent optical afterglow observations of gamma-ray bursts indicate a setting and distance scale that many relate to star-formation regions. In this paper, we use $$ and a set of artificial trigger thresholds to probe several potential GRB source density evolutionary scenarios. In particular, we compare a uniform subset of BATSE 4B data to cosmological scenarios where GRBs evolve as the comoving density, the star formation rate, the QSO rate, and the SN Type Ic rate. Standard candle bursts with power-law spectra and a universe without vacuum energy were assumed. Our results significantly favor a comoving density model, implying that GRB source density evolution is weaker than expected in these evolutionary scenarios. GRB density might still follow star-formation rates given proper concurrent GRB luminosity evolution, significant beaming, significant error in standard candle assumptions, or were a significant modification of star formation rate estimates to occur.Comment: 12 pages, 4 figures, accepted by Ap

Willingness to Pay for Brand Reputation: Lessons from the Volkswagen Diesel Emissions Scandal

In this study, we use the announcement of the Volkswagen emissions scandalon September 18, 2015, as an exogenous shock to measure consumers’ willing-ness to pay (WTP) for brand reputation. Only Volkswagen diesel cars producedin2009-2015were announced as emissions violators. Using eBay car auction data,we estimate the impacts of the scandal on the prices of Volkswagen emissionsnon-violatingcars. Our difference-in-differences estimates show that final bid prices decreased by 14% and 9% in diesel and gasoline car markets, respectively, whichpurely reflected a decline in consumers’ WTP for Volkswagen’s brand reputation.Additionally, the difference in price-drops between the violating and non-violating diesel cars is statistically insignificant. This may be due to the fact that consumers rationally adjust their WTP by expecting compensation which will almost surely be provided by Volkswagen for violating models

Bi-Directional Energy Cascades and the Origin of Kinetic Alfv\'enic and Whistler Turbulence in the Solar Wind

The observed sub-proton scale turbulence spectrum in the solar wind raises the question of how that turbulence originates. Observations of keV energetic electrons during solar quite-time suggest them as possible source of free energy to drive the turbulence. Using particle-in-cell simulations, we explore how free energy in energetic electrons, released by an electron two-stream instability drives Weibel-like electromagnetic waves that excite wave-wave interactions. Consequently, both kinetic Alfv\'enic and whistler waves are excited that evolve through inverse and forward magnetic energy cascades.Comment: 12 pages, 5 figures, Submitted to Physical Review Letter

Electron Holes and Heating in the Reconnection Dissipation Region

Using particle-in-cell simulations and kinetic theory, we explore the current-driven turbulence and associated electron heating in the dissipation region during 3D magnetic reconnection with a guide field. At late time the turbulence is dominated by the Buneman and lower hybrid instabilities. Both produce electron holes that co-exist but have very different propagation speeds. The associated scattering of electrons by the holes enhances electron heating in the dissipation region.Comment: 14 pages, 5 figures, submitted to GR