Muon Acceleration in Cosmic-ray Sources

Many models of ultra-high energy cosmic-ray production involve acceleration in linear accelerators located in Gamma-Ray Bursts magnetars, or other sources. These source models require very high accelerating gradients, $10^{13}$ keV/cm, with the minimum gradient set by the length of the source. At gradients above 1.6 keV/cm, muons produced by hadronic interactions undergo significant acceleration before they decay. This acceleration hardens the neutrino energy spectrum and greatly increases the high-energy neutrino flux. We rule out many models of linear acceleration, setting strong constraints on plasma wakefield accelerators and on models for sources like Gamma Ray Bursts and magnetars.Comment: 5 pgs. submitted for publicatio

Profit Sharing Between Governments and Multinationals in Natural Resource Extraction: Evidence From a Firm-Level Panel

The "fairness" of negotiations between countries and resource extracting firms is subject to many accusations and counter-accusations and may be argued, in many instances, to impact the subsequent economic benefit to a host country from extraction. This paper examines the role of host country governance on the share of government take from extraction revenue. We attempt to disentangle a number of competing hypotheses regarding the relationship between governance and government take using panel data for US resource extracting multinational corporations (MNCs) operating abroad from the Bureau of Economic Analysis of the US Department of Commerce over 1982-1999. Using fixed effects regression, we find a statistically significant positive impact of institutional quality on government take. The nature of this relationship -- whether this represents the result of a "corruption premium" paid by US MNCs or the exploitation of poor governance in negotiating government take -- is not completely clear. The evidence presented does, however, indicate that potential forms of bargaining power other than institutional quality (e.g., outside options to the deal) do increase government take, indicating that bargaining power may nonetheless be an important factor.

TeV Neutrinos from Successful and Choked Gamma-Ray Bursts

Core collapse of massive stars resulting in a relativistic fireball jet which breaks through the stellar envelope is a widely discussed scenario for gamma-ray burst production. For very extended or slow rotating stars, the fireball may be unable to break through the envelope. Both penetrating and choked jets will produce, by photo-meson interactions of accelerated protons, a burst of neutrinos with energies in excess of 5 TeV while propagating in the envelope. The predicted flux, from both penetrating and chocked fireballs, should be easily detectable by planned cubic kilometer neutrino telescopes.Comment: Phys.Rev.Letters, in press, final version accepted 8/31/01 (orig. 3/17/01

Towards a Model for the Progenitors of Gamma-Ray Bursts

We consider models for gamma-ray bursts in which a collimated jet expands either into a homogeneous medium or into a stellar wind environment, and calculate the expected afterglow temporal behavior. We show that (i) following a break and a faster decay, afterglows should exhibit a flattening, which may be detectable in both the radio and optical bands; (ii) Only observations at times much shorter than a day can clearly distinguish between a fireball interacting with a homogeneous medium and one interacting with a stellar wind. Using our results we demonstrate that constraints can be placed on progenitor models. In particular, existing data imply that while some long duration bursts may be produced by collapses of massive stars, it is almost certain that not all long duration bursts are produced by such progenitors.Comment: 13 pages; Submitted to Ap

On the Absence of Spurious Eigenstates in an Iterative Algorithm Proposed By Waxman

We discuss a remarkable property of an iterative algorithm for eigenvalue problems recently advanced by Waxman that constitutes a clear advantage over other iterative procedures. In quantum mechanics, as well as in other fields, it is often necessary to deal with operators exhibiting both a continuum and a discrete spectrum. For this kind of operators, the problem of identifying spurious eigenpairs which appear in iterative algorithms like the Lanczos algorithm does not occur in the algorithm proposed by Waxman

Improving the Convergence of an Iterative Algorithm Proposed By Waxman

In the iterative algorithm recently proposed by Waxman for solving eigenvalue problems, we point out that the convergence rate may be improved. For many non-singular symmetric potentials which vanish asymptotically, a simple analytical relationship between the coupling constant of the potential and the ground state eigenvalue is obtained which can be used to make the algorithm more efficient

GeV Photons from Ultra High Energy Cosmic Rays accelerated in Gamma Ray Bursts

Gamma-ray bursts are produced by the dissipation of the kinetic energy of a highly relativistic fireball, via the formation of a collisionless shock. When this happens, Ultra High Energy Cosmic Rays up to 10^20 eV are produced. I show in this paper that these particles produce, via synchrotron emission as they cross the acceleration region, photons up to 300 GeV which carry away a small, ~0.01, but non-negligible fraction of the total burst energy. I show that, when the shock occurs with the interstellar medium, the optical depth to photon-photon scattering, which might cause energy degradation of the photons, is small. The burst thusly produced would be detected at Earth simultaneoulsy with the parent gamma-ray burst, although its duration may differ significantly from that of the lower energy photons. The expected fluences, ~10^{-5}-10^{-6} erg/cm^2 are well within the range of planned detectors. A new explanation for the exceptional burst GRB 940217 is discussed.Comment: Accepted for publication in The Physical Review Letters. 4 pages, RevTeX needed, no figure

Rex E. Lee Conference on the Office of the Solicitor General of the United States: Clinton II Panel

I will say a few words about Dickerson, both because Michael has made it impossible not to and also because in some ways it represents the very best about how all of the wonderful, tried-and-true processes of the SG\u27s Office ought to work. Dickerson was very much like the other case that Michael talked about (which is one of, I think, two significant privilege controversies which the Independent Counsel laid on our doorstep). These cases may have appeared to the outside world as paradigmatically cases in which we would be hearing from the White House, or talking to the White House, or thinking about things other than the long-term institutional interests of the United States. But absolutely nothing of the sort ever happened, nor was any effort made by any political person to intrude in our decision-making policy

Gamma-Ray Burst Afterglow: Polarization and Analytic Light Curves

GRB afterglow polarization is discussed. We find an observable, up to 10%, polarization, if the magnetic field coherence length grows at about the speed of light after the field is generated at the shock front. Detection of a polarized afterglow would show that collisionless ultrarelativistic shocks can generate strong large scale magnetic fields and confirm the synchrotron afterglow model. Non-detection, at a 1% level, would imply that either the synchrotron emission model is incorrect, or that strong magnetic fields, after they are generated in the shock, somehow manage to stay un-dissipated at ``microscopic'', skin depth, scales. Analytic lightcurves of synchrotron emission from an ultrarelativistic self-similar blast wave are obtained for an arbitrary electron distribution function, taking into account the effects of synchrotron cooling. The peak synchrotron flux and the flux at frequencies much smaller than the peak frequency are insensitive to the details of the electron distribution function; hence their observational determination would provide strong constraints on blast wave parameters.Comment: 19 pages, submitted to Ap

No Radio Afterglow from the Gamma-Ray Burst of February 28, 1997

We present radio observations of the gamma-ray burster GRB 970228 made with the Very Large Array (VLA) and the Owens Valley Radio Observatory (OVRO) spanning a range of postburst timescales from one to 300 days. A search for a time-variable radio source was conducted covering an area which included a fading X-ray source and an optical transient, both of which are thought to be the long wavelength counterparts to the gamma-ray burst. At the position of the optical transient sensitive limits between 10 uJy and 1 mJy can be placed on the absence of a radio counterpart to GRB 970228 between 1.4 and 240 GHz. We apply a simple formulation of a fireball model which has been used with some success to reproduce the behavior of the optical and X-ray light curves. Using this model we conclude that the radio non-detections are consistent with the peak flux density of the afterglow lying between 20-40 uJy and it requires that the optical flux peaked between 4 and 16 hours after the burst.Comment: ApJ Let (submitted