The Î-ray burst of 1997 February 28 is analyzed within the Electromagnetic Black Hole model. We first estimate the value of the total energy deposited in the dyadosphere, Mdyaa nd the amount of baryonic matter left over by the EMBH progenitor star, B = MBC 2/Edya- We then consider the role of the interstellar medium number density njsMand of the ratio R between the effective emitting area and the total surface area of the 7-ray burst source, in reproducing the prompt emission and the X-ray afterglow of this burst. Some considerations are also done concerning the possibility of explaining, within the theory, the observed evidence for a supernova in the optical afterglow.
N2 - The Î-ray burst of 1997 February 28 is analyzed within the Electromagnetic Black Hole model. We first estimate the value of the total energy deposited in the dyadosphere, Mdyaa nd the amount of baryonic matter left over by the EMBH progenitor star, B = MBC 2/Edya- We then consider the role of the interstellar medium number density njsMand of the ratio R between the effective emitting area and the total surface area of the 7-ray burst source, in reproducing the prompt emission and the X-ray afterglow of this burst. Some considerations are also done concerning the possibility of explaining, within the theory, the observed evidence for a supernova in the optical afterglow.
AB - The Î-ray burst of 1997 February 28 is analyzed within the Electromagnetic Black Hole model. We first estimate the value of the total energy deposited in the dyadosphere, Mdyaa nd the amount of baryonic matter left over by the EMBH progenitor star, B = MBC 2/Edya- We then consider the role of the interstellar medium number density njsMand of the ratio R between the effective emitting area and the total surface area of the 7-ray burst source, in reproducing the prompt emission and the X-ray afterglow of this burst. Some considerations are also done concerning the possibility of explaining, within the theory, the observed evidence for a supernova in the optical afterglow.
We discuss the physics of diffusive compression acceleration of charged particles. This mechanism is similar to diffusive shock acceleration, which is well known, except that it applies to a gradual compression of the plasma, rather than a shock. It also applies to fluctuations in velocity, such as turbulence. We present the results from theoretical and numerical calculations for a variety of applications of this mechanism. These include: acceleration of particles by corotating solarwind compressions, acceleration in a sinusoidally varying fluid flow, the formation of high-energy tails in pickup-ion distributions, and the acceleration of Galactic cosmic rays by turbulent flows in the interstellar medium. We also show that this mechanism naturally favors acceleration of particles with larger gyroradii. This may help explain recent observations of some solar-energetic particle observations showing abundance enhancements that increase with particle gyroradius.
N2 - We discuss the physics of diffusive compression acceleration of charged particles. This mechanism is similar to diffusive shock acceleration, which is well known, except that it applies to a gradual compression of the plasma, rather than a shock. It also applies to fluctuations in velocity, such as turbulence. We present the results from theoretical and numerical calculations for a variety of applications of this mechanism. These include: acceleration of particles by corotating solarwind compressions, acceleration in a sinusoidally varying fluid flow, the formation of high-energy tails in pickup-ion distributions, and the acceleration of Galactic cosmic rays by turbulent flows in the interstellar medium. We also show that this mechanism naturally favors acceleration of particles with larger gyroradii. This may help explain recent observations of some solar-energetic particle observations showing abundance enhancements that increase with particle gyroradius.
AB - We discuss the physics of diffusive compression acceleration of charged particles. This mechanism is similar to diffusive shock acceleration, which is well known, except that it applies to a gradual compression of the plasma, rather than a shock. It also applies to fluctuations in velocity, such as turbulence. We present the results from theoretical and numerical calculations for a variety of applications of this mechanism. These include: acceleration of particles by corotating solarwind compressions, acceleration in a sinusoidally varying fluid flow, the formation of high-energy tails in pickup-ion distributions, and the acceleration of Galactic cosmic rays by turbulent flows in the interstellar medium. We also show that this mechanism naturally favors acceleration of particles with larger gyroradii. This may help explain recent observations of some solar-energetic particle observations showing abundance enhancements that increase with particle gyroradius.
All of this caused Ballard to informally subtitle the paper, "How Nearby Stars Bumped a Planet out of the Habitable Zone." More information:iopscience.iop.org/0004-637XJournal information:Astrophysical Journal
The nature of my refusal to believe in the centrality of the kind of proof recommended by the Central Dogma will eventually reveal itself to be the theme of this week's installment, but for the moment I'm referring to the notion that proving theorems is what the members of the guild of mathematicians have in common. This is hardly a notion peculiar to me; after all, the subtitle of Bettina Heintz's sociological study Die Innenwelt der Mathematik is Zur Kultur und Praxis einer beweisenden Disziplin \u2014 \u201Con the culture and practice of a proving discipline.\u201D But this is obviously nonsense. One look at the stands in the Career Fair, or for that matter at the stands in the exhibition area, is enough to disabuse anyone of this notion. Very few of the jobs on offer at the Career Fair have any use for proofs as the end product of an employee's activity. Some sort of proof may be of value to show that a particular calculation does in fact show what the employee claims, or that the algorithm works as advertised, or that the encryption is secure or that the decryption is reliable. But the end product is the calculation, or the algorithm, or the encryption, or the decryption. Most mathematicians are applied mathematicians,1 most applied mathematicians are not working in an academic setting, and the employers at the Career Fair are looking for candidates who can solve problems; proofs are usually optional.
The formal verification of \u201Cnearly a thousand non-linear inequalities,\u201D on the other hand, could serve as the model of Hacking's leibnizian proof, pure reasoning without any more understanding than what was already present at the top level, perfectly adapted to travel in interstellar space, or in no physical universe whatsoever.
The second example is the film Quest for Fire, a film aboutcavemen who have and then lose fire. This loss is the crux of the film, butfor my purposes in responding to Dan, the plot matters less than how the filmhandles language: the movie takes place entirely in subtitles. Actors inQuest for Fire speak a prehistoric language created by science fictionlanguage experimentalist Anthony Burgess. In doing so, the film bravelyinsists on a point that so much science fiction would deny--the flexibilityof language. The question raised with this intervention is why should weassume that twentieth-century English would be the dominant language of thefuture? Doing so forecloses radical rethinkings of many kinds of translation,not only linguistic but cultural and historical translations as well.
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