Dark Matter Decay and the Abundance of Ultracompact Minihalos

Ultracompact minihalos would be formed if there are larger density perturbations ($0.0003 < \delta\rho/\rho < 0.3$) in the earlier epoch. The density profile of them is steeper than the standard dark matter halos. If the dark matter can annihilate or decay into the standard particles, e.g., photons, these objects would be the potential astrophysical sources. In order to be consistent with the observations, such as $Fermi$, the abundance of ultracompact minihalos must be constrained. On the other hand, the formation of these objects has very tight relation with the primordial curvature perturbations on smaller scale, so the fraction of ultracompact minihalos is very important for modern cosmology. In previous works, the studies are focused on the dark matter annihilation for these objects. But if the dark matter is not annihilated, the dark matter decay is another important possible case. On the other hand, the abundance of ultracompact minihalos is related to many other parameters, such as the mass of dark matter, the decay channels and the density profile of dark matter halo. One of the important aspects of this work is that we investigate the $\gamma$-ray signals from nearby ultracompact minihalos due to dark matter decay and another important aspect is to study in detail how the different decay channels and density profiles affect the constraints on the abundance of ultracompact minihalos.Comment: 11 pages, 4 figures, 1 table. Comments Welcome!! Some presentations are improved and added, figures are replotted according to the referees' suggestion. The constraints on the primordial curvature perturbations are also given. Accepted for publication in EP

The molecular basis for ethnic variation and histological subtype differences in prostate cancer.

Prostate cancer is a common malignancy among men in Western countries. Recently the morbidity and mortality of prostate cancer increase dramatically in several oriental countries including China. Rapidly evolving technology in molecular biology such as high-throughput sequencing and integrative analysis of genomic and transcriptomic landscapes have enabled the identification of key oncogenic events for prostate cancer initiation, progression and resistance to hormonal therapy. These surging data of prostate cancer genome also provide insights on ethnic variation and the differences in histological subtype of this disease. In this review, differences in the incidence of prostate cancer and the prevalence of main genetic alterations between Asian and Western populations are discussed. We also review the recent findings on the mechanisms underlying neuroendocrine differentiation of prostate cancer and the development of small cell neuroendocrine carcinoma after androgen deprivation therapy