We propose a different view of the dilemma concerning the coldness of the local cosmic flow and its repercussions for the global Universe. We stress the fact that our cosmic neighbourhood embodies a region of rather particular circumstances, whose dynamics and kinematics are substantially influenced by its location in between the Great Attractor region and the Pisces-Perseus chain. On the basis...

Recently we have shown that the observed knee structure is reproduced well by a superposition of the hypothetical extragalactic cosmic rays modulated by the galactic wind and the galactic cosmic rays originating in supernova remnants. We reexamine this model assuming the chemical composition of the hypothetical extragalactic cosmic rays is the same as that of the galactic cosmic rays of superno...

We investigate the problem of transition from galactic cosmic rays to extragalactic ultra high energy cosmic rays. Using the model for extragalactic ultra high energy cosmic rays and observed all-particle cosmic ray spectrum, we calculate the galactic spectrum of iron nuclei in the energy range 108 − 109 GeV. The flux and spectrum predicted at lower energies agree well with the KASCADE data. Th...

The isotropic component of the γ-ray flux between 100MeV and 100EeV (10 eV) contains important information about the origin of highest energy cosmic rays and the extragalactic magnetic field (EGMF). Using numerical simulations of extragalactic cosmic and γ-ray propagation we show that an average fraction of ≃ 10% γ-rays in the total cosmic ray flux around 10EeV would imply both a non-accelerati...

In this paper the collision of two cosmic string loops is studied. After collision junctions are formed and the loops are entangled. We show that after their formation the junctions start to unzip and the loops disentangle. This analysis provides a theoretical understanding of the unzipping effect observed in numerical simulations of a network of cosmic strings with more than one type of cosmic...

The deep imaging of the field of an observed lensing event by a cosmic string reveals many additional lensing events. We study the statistics of such string lensing. We derive explicit expressions for the distributions of image separations of lensing by a cosmic string and point out that they are quite sensitive to parameters which characterize the cosmic string, such as the redshift and tensio...

We address some current theoretical issues around ultra-high energy cosmic rays. We recall that scenarios producing more γ−rays than cosmic rays up to high redshift can in general only provide a sub-dominant contribution to the ultra-high energy cosmic ray flux. This includes extra-galactic top-down and the Z-burst scenarios. Finally we discuss the influence of large scale cosmic magnetic field...