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The motivation and the current status of top-down models as sources of ultrahigh energy cosmic rays (UHECR) are reviewed. Stimulated by the AGASA excess, they were proposed as the main source of UHECRs beyond the GZK cutoff. Meanwhile searches for their signatures have limited their contribution to the UHECR flux to be subdominant, while the theoretical motivation for these searches remained strong: Topological defects are a generic consequence of Grand Unified Theories and superheavy particles are a creditable dark matter candidate. While Fermi/GLAST results should help to improve soon bounds on topological defects from the diffuse gamma-ray background, the most promising detection method are UHE neutrino searches. Superheavy dark matter can be restricted or detected by its characteristic galactic anisotropy combined with searches for UHE photons.
Ultra-high energy cosmic rays (UHECRs) are particles, likely protons and/or nuclei, with energies up to $10^{20}$ eV that are observed through the giant air showers they produce in the atmosphere. These particles carry the information on the most ext
HS Hydrae is a short period eclipsing binary (P_orb=1.57 day) that belongs to a rare group of systems observed to have rapidly changing inclinations. This evolution is due to a third star on an intermediate orbit, and results in significant differenc
We carried out deep searches for CO line emission in the outer disk of M33, at R>7 kpc, and examined the dynamical conditions that can explain variations in the mass distribution of the molecular cloud throughout the disk of M33. We used the IRAM-30~
Modeling the distribution of high dimensional data by a latent tree graphical model is a common approach in multiple scientific domains. A common task is to infer the underlying tree structure given only observations of the terminal nodes. Many algor
Landau suggested that the low-temperature properties of metals can be understood in terms of long-lived quasiparticles with all complex interactions included in Fermi-liquid parameters, such as the effective mass $m^{star}$. Despite its wide applicab