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

Bound entangled states with nonzero distillable key rate

In this paper, we present sufficient conditions for states to have positive distillable key rate. Exploiting the conditions, we show that the bound entangled states given by Horodecki et al. [Phys. Rev. Lett. 94, 160502 (2005), quant-ph/0506203] have nonzero distillable key rate, and finally exhibit a new class of bound entangled states with positive distillable key rate, but with negative Devetak-Winter lower bound of distillable key rate for the ccq states of their privacy squeezed versions.Comment: 7 pages, 1 figure, typos corrected, accepted for publication in PR

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

Mirage cosmology with an unstable probe D3-brane

We consider the mirage cosmology by an unstable probe brane whose action is represented by BDI action with tachyon. We study how the presence of tachyon affects the evolution of the brane inflation. At the early stage of the brane inflation, the tachyon kinetic term can play an important role in curing the superluminal expansion in mirage cosmology.Comment: 11 pages, improved presentation with some clarifications, typos corrected, references adde

Analysis of Pay Inequality and its Impacts on Growth and Performance in the Korean Manufacturing Industry

This paper examines the relationship between pay inequality, economic growth, and performance in Korea. Pay inequality is estimated by using Theil's index to identify the factors determining the level of pay inequality, and establish its relationship with economic growth and performance. For the empirical results we use panel data on the Korean manufacturing sector for the period 1993 to 2003. It appears that a large portion of rising pay inequality can be attributed to rising relative pay among the small-sized firms, outside the capital city area and in the ICT sectors which were affected by the economic structural reform since 1997. The findings support the hypothesis of an "augmented" Kuznets Curve, according to which certain developed countries are found on an upward-sloping addendum to the original formulation of Kuznets.pay inequality, financial crisis, Kuznets Curve, economic growth, performance