Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Contribution of microlensing to X-ray variability of distant QSOs   We consider a contribution of microlensing to the X-ray variability of
high-redshifted QSOs. Cosmologically distributed gravitational microlenses
could be localized in galaxies (or even in bulge or halo of gravitational
macrolenses) or could be distributed in a uniform way. We have analyzed both
cases of such distributions. We found that the optical depth for gravitational
microlensing caused by cosmologically distributed deflectors could be
significant and could reach $10^{-2} - 0.1$ at $z\sim 2$. This means that
cosmologically distributed deflectors may contribute significantlly to the
X-ray variability of high-redshifted QSOs ($z>2$). Considering that the upper
limit of the optical depth ($\tau\sim 0.1$) corresponds to the case where dark
matter forms cosmologically distributed deflectors, observations of the X-ray
variations of unlensed QSOs can be used for the estimation of the dark matter
fraction of microlenses.

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The categories of this paper are: plasm-ph
24
The categories of this paper are: dg-ga
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The categories of this paper are: chem-ph
35
The categories of this paper are: mtrl-th
20
The categories of this paper are: acc-phys
0
The categories of this paper are: hep-ph
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The categories of this paper are: funct-an
8
The categories of this paper are: hep-ex
18
The categories of this paper are: econ
11
The categories of this paper are: hep-lat
15
The categories of this paper are: nucl-ex
21
The categories of this paper are: adap-org
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The categories of this paper are: cmp-lg
12
The categories of this paper are: nucl-th
16
The categories of this paper are: stat
3
The categories of this paper are: physics