22,089 research outputs found
Scale-free trees: the skeletons of complex networks
We investigate the properties of the spanning trees of various real-world and
model networks. The spanning tree representing the communication kernel of the
original network is determined by maximizing total weight of edges, whose
weights are given by the edge betweenness centralities. We find that a
scale-free tree and shortcuts organize a complex network. The spanning tree
shows robust betweenness centrality distribution that was observed in
scale-free tree models. It turns out that the shortcut distribution
characterizes the properties of original network, such as the clustering
coefficient and the classification of networks by the betweenness centrality
distribution
Inhomogeneous substructures hidden in random networks
We study the structure of the load-based spanning tree (LST) that carries the
maximum weight of the Erdos-Renyi (ER) random network. The weight of an edge is
given by the edge-betweenness centrality, the effective number of shortest
paths through the edge. We find that the LSTs present very inhomogeneous
structures in contrast to the homogeneous structures of the original networks.
Moreover, it turns out that the structure of the LST changes dramatically as
the edge density of an ER network increases, from scale free with a cutoff,
scale free, to a starlike topology. These would not be possible if the weights
are randomly distributed, which implies that topology of the shortest path is
correlated in spite of the homogeneous topology of the random network.Comment: 4 pages, 4 figure
Quantum super-cavity with atomic mirrors
We study single-photon transport in an array of coupled microcavities where
two two-level atomic systems are embedded in two separate cavities of the
array. We find that a single-photon can be totally reflected by a single
two-level system. However, two separate two-level systems can also create,
between them, single-photon quasi-bound states. Therefore, a single two-level
system in the cavity array can act as a mirror while a different type of cavity
can be formed by using two two-level systems, acting as tunable "mirrors",
inside two separate cavities in the array. In analogy with superlattices in
solid state, we call this new "cavity inside a coupled-cavity array" a
super-cavity. This supercavity is the quantum analog of Fabry-Perot
interferometers. Moreover, we show that the physical properties of this quantum
super-cavity can be adjusted by changing the frequencies of these two-level
systems.Comment: 13 pages, 9 figure
Research needs for planning and policy
노트 : Korean Agriculture Sector Study (KASS) Researcher Workshop (1973 : Seoul, KR
Systematic analysis of group identification in stock markets
We propose improved methods to identify stock groups using the correlation
matrix of stock price changes. By filtering out the marketwide effect and the
random noise, we construct the correlation matrix of stock groups in which
nontrivial high correlations between stocks are found. Using the filtered
correlation matrix, we successfully identify the multiple stock groups without
any extra knowledge of the stocks by the optimization of the matrix
representation and the percolation approach to the correlation-based network of
stocks. These methods drastically reduce the ambiguities while finding stock
groups using the eigenvectors of the correlation matrix.Comment: 9 pages, 7 figure
Kass development issues
노트 : Korean Agriculture Sector Study (KASS) Decision Maker Workshop (1973 : Seoul, KR
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