Reconstruction of Source and Cosmic Magnetic Field Characteristics from Clusters of Ultra-High Energy Cosmic Rays

We present a detailed Monte Carlo study coupled to a likelihood analysis of the potential of next generation ultra-high energy cosmic ray experiments to reconstruct properties of the sources and the extra-galactic magnetic field. Such characteristics are encoded in the distributions of arrival time, direction, and energy of clusters of charged cosmic rays above a few 10**(19) eV. The parameters we consider for reconstruction are the emission timescale, total fluence (or power), injection spectrum, and distance of the source, as well as the r.m.s. field strength, power spectrum, and coherence length of the magnetic field. We discuss five generic situations which can be identified relatively easily and allow a reasonable reconstruction of at least part of these parameters. Our numerical code is set up such that it can easily be applied to the data from future experiments.Comment: 23 latex pages, 11 postscript figures included, uses (and includes) elsart.sty and epsf.sty. Submitted to Astroparticle Physic

Ultra-High Energy Cosmic Ray Propagation in the Local Supercluster

We present detailed numerical simulations and analytical approximations of the propagation of nucleons above 10**(19) eV in the Local Supercluster, assuming that the ambient magnetic field is turbulent, and its strength 0.01 < B_rms < 1 micro-Gauss. In such strong magnetic fields, protons in the low energy part of the spectrum, 10**(19) eV < E < E_C diffuse, while the higher energy particles, with E > E_C propagate along nearly straight lines. The magnitude of the transition energy E_C depends mainly on the strength of the magnetic field, the coherence length, and the distance to the source; for B_rms=0.1 micro-Gauss, a largest eddy of length 10 Mpc, and a distance to the source of 10 Mpc, E_C=100 EeV. Our numerical treatment substantially improves on previous analytical approximations, as it allows to treat carefully the transition between the two propagation regimes, as well as the effects due to inhomogeneities expected on scales of a few Mpc. We show that a turbulent magnetic field B_rms=0.1 micro-Gauss, close to equipartition, would allow to reproduce exactly the observed spectrum of ultra high energy cosmic rays, up to the highest energy observed, for a distance to the source below 10 Mpc, for the geometry of the Local Supercluster, i.e. a sheet of thickness 10 Mpc. Diffusion, in this case, allows to reproduce the high flux beyond the Greisen Zatsepin Kuzmin cut-off, with a soft injection spectrum proportional to E**(-2.4). Moreover, the large deflection angles at the highest energies observed, typically 10 degrees for the above values, would explain why no close-by astrophysical counterpart could be associated with these events.Comment: 17 latex pages (tightened format), 9 updated postscript figures, uses revtex.sty and epsf.sty, extended discussion of numerical results, to appear in Astroparticle Physic

Probing Grand Unified Theories with Cosmic Ray, Gamma-Ray and Neutrino Astrophysics

We explore scenarios where the highest energy cosmic rays are produced by new particle physics near the grand unification scale. Using detailed numerical simulations of extragalactic nucleon, gamma-ray, and neutrino propagation, we show the existence of an interesting parameter range for which such scenarios may explain part of the data and are consistent with all observational constraints. A combination of proposed observatories for ultra-high energy cosmic rays, neutrino telescopes of a few kilometer scale, and gamma-ray astrophysics instruments should be able to test these scenarios. In particular, for neutrino masses in the eV range, exclusive neutrino decay modes of superheavy particles can give rise to neutrino fluxes comparable to those predicted in models of active galactic nuclei.Comment: 15 latex pages, 5 postscript figures included, uses revtex.sty and psfig.sty. Submitted to Physical Review

Gamma-Ray Bursts: The Underlying Model

A pedagogical derivation is presented of the ``fireball'' model of gamma-ray bursts, according to which the observable effects are due to the dissipation of the kinetic energy of a relativistically expanding wind, a ``fireball.'' The main open questions are emphasized, and key afterglow observations, that provide support for this model, are briefly discussed. The relativistic outflow is, most likely, driven by the accretion of a fraction of a solar mass onto a newly born (few) solar mass black hole. The observed radiation is produced once the plasma has expanded to a scale much larger than that of the underlying ``engine,'' and is therefore largely independent of the details of the progenitor, whose gravitational collapse leads to fireball formation. Several progenitor scenarios, and the prospects for discrimination among them using future observations, are discussed. The production in gamma- ray burst fireballs of high energy protons and neutrinos, and the implications of burst neutrino detection by kilometer-scale telescopes under construction, are briefly discussed.Comment: In "Supernovae and Gamma Ray Bursters", ed. K. W. Weiler, Lecture Notes in Physics, Springer-Verlag (in press); 26 pages, 2 figure

Results from the fly’s eye experiment

We report recently analyzed results on the energy spectrum, and composition of cosmic rays above 0.3 EeV. We observe a break in the spectrum at 3 EeV and a changing composition. The results can be explained by a simple two component model: galactic cosmic rays dominated by heavy primaries and an extragalactic component dominated by light primaries. The observed isotropic arrival direction distribution is consistent with the predictions of this model. A 320 EeV event was also recorded. © 1995 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87516/2/839_1.pd

Oral history interview with Fernando J. Corbato

Transcript, 97 pp. Audio file available at http://purl.umn.edu/95580Corbató discusses computer science research, especially time-sharing, at the Massachusetts Institute of Technology (MIT). Topics in the first session include: Phil Morse and the establishment of the Computation Center, Corbató's management of the Computation Center, the development of the WHIRLWIND computer, John McCarthy and research on time-sharing, cooperation between International Business Machines (IBM) and MIT, and J. C. R. Licklider and the development of Project MAC. Topics in the second session include: time-sharing, the development of MULTICS by the General Electric (GE) Computer Division, IBM's reaction to MIT working with GE, the development of CTSS, the development of UNIX in cooperation with Bell Labs, interaction with the Information Processing Techniques Office of the Defense Advanced Research Projects Agency, interaction with Honeywell after they purchased GE's Computer Division, and the transformation of Project MAC into the Laboratory for Computer Science

A calculation of the energy bands of the graphite crystal by means of the tight-binding method

Thesis: Ph. D., Massachusetts Institute of Technology. Dept. of Physics, 1956Vita. Appendix contains numerous pamphlets.Includes bibliographical references (leaves 109-110).by Fernando José Corbató.Ph. D.Ph. D. Massachusetts Institute of Technology. Dept. of Physic