Hans Joachim Blome

Leptonic jets from young stellar objects

Various explanations of the bipolar-flow phenomenon in star-forming regions are compared and confronted with the observed facts. It is concluded that stellar-wind interpretations are inconsistent with the constraints. The ‘exotic’ property of young stellar objects may be their extreme spin which implies strong magnetic fields and vacuum discharges above thee± pair-formation threshold (of 1012 eV). Pair-plasma jets are thought to be centrifugally driven by young stars during their first 104±1 years of rapid rotation.

The observational discrimination of Friedmann-Lemaître models

AbstractIt is the purpose of this paper to illustrate the interrelation between the problems of the ‘missing mass’, the galactic age and the cosmological constant A (or its equivalent quantum vacuum densityρv).The inflationary picture of the early universe predicts that our present universe should have a very nearlyEuclidean metric. If we accept this concept, one would have to discriminate between two rather extreme Euclidean cosmological models:(1)The standard model with ∧=0 and a densityρc = 3H028πG. There are difficulties ifH0≥5- km s−1 Mpc−1 and the galactic aget0≥14×109 years.(2)The Euclidean Friedmann-Lemaître models with ∧>0, i.e., Δgt;0, i.e.,ρv=ρc −ρo, whereρo is the present matter density, including the nonrelativistic dark matter. Hereρv ‘competes’ with the missing mass. Measurements of apparent diameters of galaxies up to redshifts of 2 will permit one to discriminate between the models provided that size evolution of galaxies can be determined or neglected (see Figure 3).