9,011 research outputs found
The relation between black hole masses and Lorentz factors of the jet components in blazars
We explore the relation between black hole mass () and the motion
of the jet components for a sample of blazars. The Very Long Baseline Array
(VLBA) 2cm Survey and its continuation: Monitoring of Jets in active galactic
nuclei (AGNs) with VLBA Experiments (MOJAVE) have observed 278 radio-loud AGNs,
of which 146 blazars have reliable measurements on their apparent velocities of
jet components. We calculate the minimal Lorentz factors for these sources from
their measured apparent velocities, and their black hole masses are estimated
with their broad-line widths. A significant intrinsic correlation is found
between black hole masses and the minimal Lorentz factors of the jet
components, which the Eddington ratio is only weakly correlated with the
minimal Lorentz factor, which may imply that the Blandford-Znajek (BZ)
mechanism may dominate over the Blandford-Payne (BP) mechanism for the jet
acceleration (at least) in blazars.Comment: 18 pages, 5 figures, 3 tables, submitted to ChJA
Differential Inequalities in Multi-Agent Coordination and Opinion Dynamics Modeling
Distributed algorithms of multi-agent coordination have attracted substantial
attention from the research community; the simplest and most thoroughly studied
of them are consensus protocols in the form of differential or difference
equations over general time-varying weighted graphs. These graphs are usually
characterized algebraically by their associated Laplacian matrices. Network
algorithms with similar algebraic graph theoretic structures, called being of
Laplacian-type in this paper, also arise in other related multi-agent control
problems, such as aggregation and containment control, target surrounding,
distributed optimization and modeling of opinion evolution in social groups. In
spite of their similarities, each of such algorithms has often been studied
using separate mathematical techniques. In this paper, a novel approach is
offered, allowing a unified and elegant way to examine many Laplacian-type
algorithms for multi-agent coordination. This approach is based on the analysis
of some differential or difference inequalities that have to be satisfied by
the some "outputs" of the agents (e.g. the distances to the desired set in
aggregation problems). Although such inequalities may have many unbounded
solutions, under natural graphic connectivity conditions all their bounded
solutions converge (and even reach consensus), entailing the convergence of the
corresponding distributed algorithms. In the theory of differential equations
the absence of bounded non-convergent solutions is referred to as the
equation's dichotomy. In this paper, we establish the dichotomy criteria of
Laplacian-type differential and difference inequalities and show that these
criteria enable one to extend a number of recent results, concerned with
Laplacian-type algorithms for multi-agent coordination and modeling opinion
formation in social groups.Comment: accepted to Automatic
Generation of pure, ionic entangled states via linear optics
In this paper, we propose a novel scheme to generate two-ion maximally
entangled states from either pure product states or mixed states using linear
optics. Our new scheme is mainly based on the ionic interference. Because the
proposed scheme can generate pure maximally entangled states from mixed states,
we denote it as purification-like generation scheme. The scheme does not need a
Bell state analyzer as the existing entanglement generation schemes do, it also
avoids the difficulty of synchronizing the arrival time of the two scattered
photons faced by the existing schemes, thus the proposed new entanglement
generation scheme can be implemented more easily in practice.Comment: 6 pages, 4 figure
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