arXiv subjects

D. Eichler

Publications and source records attributed to D. Eichler.

24 records · Page 2Linked to original sources

arXiv1999

A Compact Fireball Model of Gamma Ray Bursts

It is proposed that the gamma ray burst photons near the peak of the spectrum at several hundred KeV are produced on very compact scales, where photon production is limited by blackbody effects and/or the requirement of energetic quanta ($E>2m_e c^2$) for efficient further production. The fast variation of order milliseconds in the time profile is then a natural expectation, given the other observed GRB parameters. Analytic calculations are presented to show that the escape of non-thermal, energetic gamma rays can emerge within a second of the thermal photons from a gammasphere of below $10^{12}$ cm. The minimum asymptotic bulk Lorentz factor in this model is found to be of order several hundred if the photosphere is of order $3 \times 10^{11}$ cm and greater for larger or smaller photospheric radii. It is suggested that prompt UHE gamma rays might provide a new constraint on the asymptotic Lorentz factor of the outflow.

astro-ph↗

arXiv1999

Searching for Granularity of the Vacuum

The hypothesis is considered that the vacuum is a Lorentz non-invariant foam in which translational symmetry is spontaneously broken at the Planck or grand unification scale. This could possibly be observed via Rayleigh scattering of ultrahigh energy quanta, and it appears to be ruled out for spin 1/2 leptons and independently testable for photons. A weaker version of the hypothesis predicts (for otherwise massless neutrinos) irreversible neutrino mixing over a length scale of $l_{Planck}(E_ν/E_{Planck})^{-2}$ in comoving cosmic coordinates for a purely four dimensional universe, and, for neutrinos that have spin 3/2 in a higher dimensional manifold above the energy scale $ηE_{Planck}$, the mixing is predicted to take place over a scale of $η^{-4}$ times this length. Such neutrino mixing might also be observable with atmospheric and solar neutrino experiments.

astro-ph↗

arXiv1998

Shading and Smothering of Gamma Ray Bursts

The gamma ray burst (GRB) 980425 is distinctive in that it seems to be associated with supernova (SN) 1998bw, has no X-ray afterglow, and has a single peak light curve and a soft spectrum. The supernova is itself unusual in that its expansion velocity exceeds c/6. We suggest that many of these features can be accounted for with the hypothesis that we observe the GRB along a penumbral line of sight that contains mainly photons that have scattered off ejected baryons. The hypothesis suggests a baryon poor jet (BPJ) existing within a baryon rich outflow. The sharp distinction can be attributed to whether or not the magnetic field lines thread an event horizon. Such a configuration suggests that there will be some non-thermal acceleration of pick-up ex-neutrons within the BPJ. This scenario might produce observable spallation products and neutrinos.

astro-ph↗

arXiv1998

Spectroscopy Of Low Metallicity Giant H II Regions: A grid of low Metallicity Stellar atmospheres

We calculate a grid of spherically symmetric OB stellar atmospheres at low metallicities, including both non-local thermodynamic equilibrium (NLTE) and metal line blanketing effects. This is done to assess the uncertainties in helium abundance determination by nebular codes due to input stellar atmosphere models. The more sophisticated stellar atmosphere models we use can differ from LTE models by as much as 40 percent in the ratio of He to H-ionizing photons.

astro-ph↗

arXiv1998

Self Inhibiting Heat-Flux

Heat-transfer through weakly magnetized diffuse astrophysical plasmas excites whistlers. This leads to electron whistler resonant scattering, a reduction of the electron mean-free path, and heat-flux inhibition. However, only whistlers propagating at a finite angle to the magnetic field (off-axis) can scatter the heat-flux carrying electrons. Thus, the level of heat flux-inhibition along the magnetic field lines depends on the presence of off-axis whistlers.

astro-ph↗

arXiv1998

Nearly Closed Loops in Biological Systems as Electromagnetic Receptors

It is noted here that when a nearly closed loop in a biological system, such as a self-synapsing (autapsing) neuron or mutually synapsing pair, is exposed to an AC magnetic field, the induced electric fields in the insulating gaps can be many orders of magnitude larger than the average values typically discussed in the literature.$^{1,2}$ It is suggested that animal nervous systems might possibly be affected in selected spots by man-made alternating magnetic fields at weaker levels than previously supposed. Radio and microwave radiation should be considered particularly suspect.

physics.bio-ph↗