Statistical Analysis of the Correlation between Active Galactic Nuclei and Ultra-High Energy Cosmic Rays

We develop the statistical methods for comparing two sets of arrival directions of cosmic rays in which the two-dimensional distribution of arrival directions is reduced to the one-dimensional distributions so that the standard one-dimensional Kolmogorov-Smirnov test can be applied. Then we apply them to the analysis of correlation between the ultra-high energy cosmic rays (UHECR) with energies above $5.7\times10^{19}$ eV, observed by Pierre Auger Observatory (PAO) and Akeno Giant Air Shower Array (AGASA), and the active galactic nuclei (AGN) within the distance 100 Mpc. For statistical test, we set up the simple AGN model for UHECR sources in which a certain fraction of observed UHECR are originated from AGN within a chosen distance, assuming that all AGN have equal luminosity and smearing angle of UHECR, and the remaining fraction are from the isotropic background contribution. For the PAO data, our methods exclude not only a hypotheses that the observed UHECR are simply isotropically distributed but also a hypothesis that they are completely originated from the selected AGN. But, the addition of appropriate amount of isotropic component either through the background contribution or through the large smearing effect improves the correlation greatly and makes the AGN hypothesis for UHECR sources a viable one. We also point out that restricting AGN within the distance bin of 40-60 Mpc happens to yield a good correlation without appreciable isotropic component and large smearing effect. For the AGASA data, we don't find any significant correlation with AGN.Comment: 18 pages, 9 figures, a version published in JCA

Revisit of Correlation Analysis between Active Galactic Nuclei and Ultra-High Energy Cosmic Rays

We update the previous analysis of correlation between ultra-high energy cosmic rays (UHECR) and active galactic nuclei (AGN), using 69 UHECR events with energy $E\ge55\,{\rm EeV}$ released in 2010 by Pierre Auger observatory and 862 AGN within the distance $d\le100\,{\rm Mpc}$ listed in the 13th edition of V\'eron-Cetty and V\'eron AGN catalog. To make the test hypothesis definite, we use the simple AGN source model in which UHECR are originated both from AGN, with the fraction $f_A$, and from the isotropic background. We treat all AGN as equal sources of UHECR, and introduce the smearing angle $\theta_s$ to incorporate the effects of intervening magnetic fields. We compare the arrival direction distributions observed by PAO and expected from the model by the correlational angular distance distribution (CADD) method. CADD method rules out the AGN dominance model with a small smearing angle ($f_A\gtrsim0.7$ and $\theta_s\lesssim6^\circ$). Concerning the isotropy, CADD shows that the distribution of PAO data is marginally consistent with isotropy. The best fit model lies around the AGN fraction $f_A=0.4$ and the moderate smearing angle $\theta_s=10^\circ$. For the fiducial value $f_A=0.7$, the best probability of CADD was obtained at a rather large smearing angle $\theta_{\rm s}=46^\circ$. Our results imply that for the whole AGN to be viable sources of UHECR, either an appreciable amount of additional isotropic background or the large smearing effect is required. Thus, we try to bin the distance range of AGN to narrow down the UHECR sources and found that the AGN residing in the distance range $60-80\,{\rm Mpc}$ have good correlation with the updated PAO data. It is an indication that further study on the subclass of AGN as the UHECR source may be quite interesting.Comment: 24 pages, 10 figures, 2 table

Correlation between Ultra-high Energy Cosmic Rays and Active Galactic Nuclei from Fermi Large Area Telescope

We study the possibility that the $\gamma$-ray loud active galactic nuclei (AGN) are the sources of ultra-high energy cosmic rays (UHECR), through the correlation analysis of their locations and the arrival directions of UHECR. We use the $\gamma$-ray loud AGN with $d\le 100 {\rm Mpc}$ from the second Fermi Large Area Telescope AGN catalog and the UHECR data with $E\ge 55 {\rm EeV}$ observed by Pierre Auger Observatory. The distribution of arrival directions expected from the $\gamma$-ray loud AGN is compared with that of the observed UHECR using the correlational angular distance distribution and the Kolmogorov-Smirnov test. We conclude that the hypothesis that the $\gamma$-ray loud AGN are the dominant sources of UHECR is disfavored unless there is a large smearing effect due to the intergalactic magnetic fields.Comment: 14 pages, 3 figures, 1 tabl

A dark matter solution from the supersymmetric axion model

We study the effect of the late decaying saxino (the scalar superpartner of the axion) and find out that there is a possible dark matter solution from a class of supersymmetric extensions of the invisible axion model. In this class of models, the saxino which decays into two axions acts as the late decaying particle which reconciles the cold dark matter model with high values of the Hubble constant. Recent observations of the Hubble constant are converging to $H_0=70\!-\!80\,{\rm km}\,{\rm sec}^{-1}\,{\rm Mpc}^{-1}$, which would be inconsistent with the standard mixed dark matter model. This class of models provides a plausible framework for the alternative cold dark matter plus late decaying particle model, with the interesting possibility that both cold dark matter and the extra radiation consist of axion.Comment: 11 pages, no figure, REVTEX 3.

Orbifolds with continuous Wilson lines and soft terms

Orbifold compactifications with continuous Wilson lines have very interesting characteristics and as a consequence they are candidates to obtain realistic models. We perform an analysis of the soft supersymmetry-breaking terms arising in this type of compactifications. We also compare these results with those of orbifolds without including continuous Wilson lines. Their phenomenological properties turn out to be similar.Comment: 7 pages, LaTe

Cosmology of Antisymmetric Tensor Field in D-brane Universe

We analyze homogeneous, anisotropic cosmology driven by a self-interacting ``massive'' antisymmetric tensor field $B_{\mu\nu}$ which is present in string theories with D-branes. Time-dependent magnetic $B$ field existing in the early universe can lead to the Bianchi type I universe. Evolutions of such a tensor field are solved exactly or numerically in the universe dominated by vacuum energy, radiation, and $B$ field itself. The matter-like behavior of the $B$ field (dubbed as ``$B$-matter'') ensures that the anisotropy disappears at late time and thus becomes unobservable in a reasonable cosmological scenario. Such a feature should be contrasted to the cosmology of the conventional massless antisymmetric tensor field.Comment: 13 page