Cosmic Topological Defects, Highest Energy Cosmic Rays, and the Baryon Asymmetry of the Universe

The lack of a high energy cutoff in the cosmic ray spectrum together with an apparently isotropic distribution of arrival directions for the highest energy events have strongly constrained most models proposed for the generation of these particles. An overview of the theoretical proposals are presented along with their most general signatures. Future experimental tests of the different proposals are discussed.

Electroweak baryogenesis has become a topic of much recent activity [1]. Here we discuss a new scenario which has the advantage of being insensitive to the order of the electroweak phase transition. We briefly review a mechanism [2] using unstable electroweak strings [3] and discuss in detail a mechanism [4] using topological defects (in particular cosmic strings) left behind after a previous phase transition.

Super-high energy corpuscular and gamma rays as well as cosmic high--power density sources are hard to explain in a galaxy model framework. Attempts to include some of those phenomena in the Standard Cosmological Model also encounter serious difficulties. In the present paper an alternative cosmological concept is discussed. There are several features in it. First of all, the whole Universe (Grand Universe) is a multitude of typical universes, like ours, evenly made of eith...

Cosmic rays with energies exceeding $10^{20}\eV$ have been detected. The origin of these highest energy cosmic rays remains unknown. Established astrophysical acceleration mechanisms encounter severe difficulties in accelerating particles to these energies. Alternative scenarios where these particles are created by the decay of cosmic topological defects have been suggested in literature. In this paper we study the possibility of producing the highest energy cosmic rays throu...

We will discuss the main relevant aspects of the physics of ultra high energy cosmic rays. After a short recap of the experimental evidences, we will review theoretical models aiming at describing the sources of these extremely energetic particles opening a window on the highest energies universe. We will discuss the production of secondary particles and the possible tests of new physics that ultra high energy cosmic rays could provide.

The universe should be dark at energies exceeding $\sim 5\times 10^{19}$ eV. This simple but solid prediction of our best known particle physics is not confirmed by observations, that seem to suggest a quite different picture. Numerous events have in fact been detected in this energy region, with spectra and anisotropy features that defy many conventional and unconventional explanations. Is there a problem with known physics or is this a result of astrophysical uncertainties?...

A tiny hypermagnetic field generated before the electroweak phase transition (EWPT) associated to the generation of elementary particle masses can polarize the early Universe hot plasma at huge redshifts z > 10^15. The anomalous violation of the right-handed electron current characteristic of the EWPT converts the lepton asymmetry into a baryon asymmetry. Under reasonable approximations, the magnetic field strength inferred by requiring such "leptogenic" origin for the observ...

The origin of cosmic rays is one of the major unresolved questions in astrophysics. In particular, the highest energy cosmic rays observed possess macroscopic energies and their origin is likely associated with the most energetic processes in the Universe. They thus provide a probe of physics and astrophysics at energies that are unreached in laboratory experiments. Theoretical explanations range from acceleration of charged particles in astrophysical environments to particle...

In this paper we briefly discuss the problem of the origin of Ultra High Energy Cosmic Rays in the framework of Top-Down models. We show that, for high energy of decays and in a wide range of spectra of injected protons, their extragalactic flux is consistent with the observed fluxes of cosmic rays in the energy range 0.1 E_{GZK}< E < 10E_{GZK}. For suitable energy and spectra of injected protons, the contribution of galactic sources is moderate, in this energy range, but it ...

We consider origins of the baryon asymmetry which we observe today. We review the progress of electroweak-scale baryogenesis, and show a new mechanism, string-scale baryogenesis.