D N Schramm

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We examine the possibility that a nearby supernova explosion could have caused one or more of the mass extinctions identified by paleontologists. We discuss the possible rate of such events in the light of the recent suggested identification of Geminga as a supernova remnant less than 100 parsec (pc) away and the discovery of a millisecond pulsar about 150(More)
For almost 30 years, the predictions of big-bang nucleosynthesis have been used to test the big-bang model to within a fraction of a second of the bang. The agreement between the predicted and observed abundances of deuterium, helium-3, helium-4, and lithium-7 confirms the standard cosmology model and allows accurate determination of the baryon density,(More)
We consider the production of 3 He and 2 H by 4 He photodisintegration initiated by non-thermal energy releases during early cosmic epochs. We find that this process cannot be the predominant source of primordial 2 H since it would result in anomalously high 3 He/D ratios in conflict with standard chemical evolution assumptions. We apply this fact to(More)
Recently, a possible clustering of a subset of observed ultra-high energy cosmic rays above approximately 40 EeV (4 x 10(19) eV) in pairs near the supergalactic plane was reported. We show that a confirmation of this effect would provide information on the origin and nature of these events and, in case of charged primaries, imply interesting constraints on(More)
We explore the difficulties with a primordial origin of variations of D/H in quasar absorption systems. In particular we examine options such as a very large-scale inhomogeneity in the baryon content of the universe. We show that very large-scale (much larger than 1 Mpc) isocurvature perturbations are excluded by current cosmic microwave background(More)
  • i I Shapiro, C C Counselman, B Iii, King, P J E Peebles, H.-J Treder +15 others
  • 2011
discussion of the appropriateness of Robertson-Walker coordinates in symmetric cosmological models. We describe an extension of the gauge theory of weak and electromagnetic interactions to SU(8) U(1). The extended theory naturally insures universality, absence of right-handed currents in P and muon decay, flavor conservation in neutral currents, etc. ;(More)