Group theory for unified model building

We update the constraints on the fraction of the Universe going into primordial black holes in the mass range ${10}^{9}--{10}^{17}\text{ }\text{ }\mathrm{g}$ associated with the effects of their evaporations on big bang nucleosynthesis and the extragalactic photon background. We include for the first time all the effects of quark and gluon emission by black holes on these constraints and account for the latest observational developments. We then discuss the other constraints in this mass range and show that these are weaker than the nucleosynthesis and photon background limits, apart from a small range ${10}^{13}--{10}^{14}\text{ }\text{ }\mathrm{g}$, where the damping of cosmic microwave background anisotropies dominates. Finally we review the gravitational and astrophysical effects of nonevaporating primordial black holes, updating constraints over the broader mass range $1--{10}^{50}\text{ }\text{ }\mathrm{g}$.

New cosmological constraints on primordial black holes

Low-energy phenomenology of superstring-inspired E6 models

Model of 'Calculable' Majorana Neutrino Masses

Sigma term update

>The Mossbauer effect provides a tool to investigate the angular dependence and the polarization of individual com ponents emitted in the nuclear Zeeman effect. A discussion of the physical picture of the photon polarization in Fe/sup 57/ is followed by the general theory of elliptical polarization in the Mossbauer effect. The experimental arrangement to measure this polarization is described, and relevant results are given. (auth)

Elliptical Polarization of Fe 57 Gamma Rays

Production of charged pions by 730-MeV protons from hydrogen and selected nuclei

A search for bursts of air-shower events from Hercules X-1 at energies above 50 TeV during the calendar period 2 April 1986 to 5 July 1987 yielded two significant bursts, both occurring on UT 24 July 1986. The events during these bursts were pulsed with a period of 1.235 68 s, significantly different from estimates of the contemporaneous x-ray period. The probability that this represents random statistical fluctuations of the background is estimated to be 2 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}5}$. The muon content of the burst events is anomalous when compared with expectations from $\ensuremath{\gamma}$-ray showers.

Ultrahigh-energy pulsed emission from Hercules X-1 with anomalous air-shower muon production.

We report a result of (1\ifmmode\pm\else\textpm\fi{}4)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}7}$ for the parity-nonconserving component in the $p\ensuremath{-}p$ nuclear cross section at 15 MeV Our experiment uses rapid spin reversal of a longitudinally polarized proton beam and an unpolarized ${\mathrm{H}}_{2}$ target Sources of systematic error are discussed and found to be ${10}^{\ensuremath{-}7}$

Test of Parity Conservation in p-p Scattering

Hyperfine splitting of Fe/sup 57/ nuclei as a function of an external field H and of temperature was studied. The internal fleld is proportional to the (time) average of the z component of the Fe/sup 57/; measurements of the splitting permit determination of the electronic polarization of Fe. ln certain metals, the splitting vanishes in zero external field at 1.5 to 4 deg K and increases as the external field is increased to saturation, corresponding to complete polarization, at large fields and low temperatures. The splitting is a function of H/T, and may be represented by Brillouin functions. The local magnetic moment, the associated angular momentum, and the saturated internal field are parameters of the Brillouin function. (L.N.N.)

D. E. Nagle

Papers

Elliptical Polarization of Fe 57 Gamma Rays

Production of charged pions by 730-MeV protons from hydrogen and selected nuclei

Ultrahigh-energy pulsed emission from Hercules X-1 with anomalous air-shower muon production.

Test of Parity Conservation in p-p Scattering

Paramagnetism of Fe Impurities in Transition Metals