115,026 research outputs found
Gaussian integrability of distance function under the Lyapunov condition
In this note we give a direct proof of the Gaussian integrability of distance
function as provided
the Lyapunov condition holds for symmetric diffusion Markov operators, which
answers a question proposed in Cattiaux-Guillin-Wu [6, Page 295]. The similar
argument still works for diffusions processes with unbounded diffusion
coefficients and for jump processes such as birth-death chains. An analogous
discussion is also made under the Gozlan's condition arising from [9,
Proposition 3.5].Comment: 11 pages, published, ECP. Some extensions to unbounded diffusions and
jump processes have been added, and two referees' suggestions incorporate
Presentations of Galois groups of maximal extensions with restricted ramification
Motivated by the work of Lubotzky, we use Galois cohomology to study the
difference between the number of generators and the minimal number of relations
in a presentation of the Galois group of the maximal extension of a
global field that is unramified outside a finite set of places, as
varies among a certain family of extensions of a fixed global field . We
prove a generalized version of the global Euler-Poincar\'{e} Characteristic,
and define a group , for each finite simple -module , to
generalize the work of Koch about the pro- completion of to
study the whole group . In the setting of the nonabelian Cohen-Lenstra
heuristics, we prove that the objects studied by the Liu--Wood--Zureick-Brown
conjecture are always achievable by the random group that is constructed in the
definition the probability measure in the conjecture.Comment: Comments are welcom
Finding binary active galactic nuclei by the centroid shift in imaging surveys
The census of binary active galactic nuclei (AGNs) is important in order to
understand the merging history of galaxies and the triggering of AGNs. However,
there is still no efficient method for selecting the candidates of binary AGNs.
The non-synchronous variations of the two AGNs in one binary system will induce
the shift of the image centroid. Since the astrometric error is normally much
smaller than the angular resolution of telescopes, it is possible to detect
such shifts even in the unresolved system via multi-epoch observations. We
perform some simulations and find that hundreds of observations are required to
discover compact binary AGNs. This method is suitable for the future
large-scale surveys, e.g., the Large Synoptic Survey Telescope, and it might
lead to a large sample of binary AGNs with a 1-2 yr survey.Comment: 4 pages, 4 figures, published in Astronomy & Astrophysic
- …