176 research outputs found
Constituents of the soft X-ray background
The X-ray background is generated by various classes of objects and variety
of emission mechanisms. Relative contribution of individual components depends
on energy. The goal is to assess the integral emission of the major components
of the soft X-ray background (extragalactic discrete sources dominated by AGNs,
galactic plasma, and the Warm/Hot Intergalactic Medium), investigating the
angular structure of the background. Fluctuations of the background are
measured using the auto-correlation function of the XRB determined in 5 energy
bands between 0.3 and 4.5 keV. The investigation is based on the extensive
observational data set selected from the XMM-Newton archives. Amplitudes of the
auto-correlation functions calculated in three energy bands above ~1 keV are
consistent with the conjecture that the background fluctuations result solely
from clustering of sources which produce the background. At energies below 1
keV the relative fluctuation amplitude decreases indicating that a fraction of
the soft XRB is associated with a smooth plasma emission in the Galaxy. It is
shown, however, that the mean spectrum of extragalactic discrete sources
steepens in the soft X-rays and is not well represented by a single power law
in the energy range 0.3-4.5 keV. The WHIM contribution to the total background
fluctuations is small and consistent with the WHIM properties derived from the
cross-correlation of the XRB with galaxies.Comment: 7 pages, 2 figure
Examples of non-compact quantum group actions
We present two examples of actions of non-regular locally compact quantum
groups on their homogeneous spaces. The homogeneous spaces are defined in a way
specific to these examples, but the definitions we use have the advantage of
being expressed in purely -algebraic language. We also discuss
continuity of the obtained actions. Finally we describe in detail a general
construction of quantum homogeneous spaces obtained as quotients by compact
quantum subgroups.Comment: 13 pages, LaTe
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