Abstract. The interstellar medium (ISM) reveals strongly inhomogeneous structures at every scale. These structures do not seem completely random since they obey certain power laws. Larson’s law (1981) σ ∝ R and the plausible assumption of virial equilibrium justify to consider fractals as a possible description of the ISM. In the following we investigate how self-gravitation, differential rotat...

The Arecibo H i Strip Survey probed the halos of ∼300 cataloged galaxies and the environments of ∼14 groups with sensitivity to neutral hydrogen masses ≥ 10 M⊙. The survey detected no objects with properties resembling the High Velocity Clouds (HVCs) associated with the Milky Way or Local Group. If the HVCs were typically MHI = 10 7.5 M⊙ objects distributed throughout groups and galaxy halos at...

Based on the HVZ theorem and dilation analyticity of the pseudorelativistic no-pair Jansen-Hess operator, it is shown that for subcritical potential strength (Z ≤ 90) the singular continuous spectrum is absent. The bound is slightly higher (Z ≤ 102) for the Brown-Ravenhall operator whose eigenvalues λ are, by the virial theorem, confined to λ < 2m if Z ≤ 50.

We reconsider the original argument, based on the virial theorem, by which Zwicky was first led to conjecture the existence of a missing mass, and point out that, without any justification, he neglects the contribution of the forces due to the matter lying outside the considered system, Now, it is true that the contribution of the outer mass to the virial vanishes if the gravitational field is ...