91 research outputs found
Reaction-Diffusion Processes on Interconnected Scale-Free Networks
We study the two particle annihilation reaction on
interconnected scale free networks, using different interconnecting strategies.
We explore how the mixing of particles and the process evolution are influenced
by the number of interconnecting links, by their functional properties, and by
the interconnectivity strategies in use. We show that the reaction rates on
this system are faster than what was observed in other topologies, due to the
better particle mixing which suppresses the segregation effect, inline with
previous studies performed on single scale free networks.Comment: 11 pages, 5 figure
The Network of Counterparty Risk: Analysing Correlations in OTC Derivatives
Counterparty risk denotes the risk that a party defaults in a bilateral
contract. This risk not only depends on the two parties involved, but also on
the risk from various other contracts each of these parties holds. In rather
informal markets, such as the OTC (over-the-counter) derivative market,
institutions only report their aggregated quarterly risk exposure, but no
details about their counterparties. Hence, little is known about the
diversification of counterparty risk. In this paper, we reconstruct the
weighted and time-dependent network of counterparty risk in the OTC derivatives
market of the United States between 1998 and 2012. To proxy unknown bilateral
exposures, we first study the co-occurrence patterns of institutions based on
their quarterly activity and ranking in the official report. The network
obtained this way is further analysed by a weighted k-core decomposition, to
reveal a core-periphery structure. This allows us to compare the activity-based
ranking with a topology-based ranking, to identify the most important
institutions and their mutual dependencies. We also analyse correlations in
these activities, to show strong similarities in the behavior of the core
institutions. Our analysis clearly demonstrates the clustering of counterparty
risk in a small set of about a dozen US banks. This not only increases the
default risk of the central institutions, but also the default risk of
peripheral institutions which have contracts with the central ones. Hence, all
institutions indirectly have to bear (part of) the counterparty risk of all
others, which needs to be better reflected in the price of OTC derivatives.Comment: 36 pages, 18 figures, 2 table
The network structure of city-firm relations
How are economic activities linked to geographic locations? To answer this
question, we use a data-driven approach that builds on the information about
location, ownership and economic activities of the world's 3,000 largest firms
and their almost one million subsidiaries. From this information we generate a
bipartite network of cities linked to economic activities. Analysing the
structure of this network, we find striking similarities with nested networks
observed in ecology, where links represent mutualistic interactions between
species. This motivates us to apply ecological indicators to identify the
unbalanced deployment of economic activities. Such deployment can lead to an
over-representation of specific economic sectors in a given city, and poses a
significant thread for the city's future especially in times when the
over-represented activities face economic uncertainties. If we compare our
analysis with external rankings about the quality of life in a city, we find
that the nested structure of the city-firm network also reflects such
information about the quality of life, which can usually be assessed only via
dedicated survey-based indicators.Comment: 12 pages, 4 figure
A network approach for the scientific collaboration in the European Framework Programs
We construct the networks of collaboration between partners for projects
carried out with the support of European Commission Framework Programs FP5 and
FP6. We analyze in detail these networks, not only in terms of total number of
projects, but also for the different tools employed, the different geographical
partitions, and the different thematic areas. For all cases we find a scale
free behavior, as expected for such social networks, and also reported in the
literature. In comparing FP5 to FP6, we show that despite a decrease in the
number of signed contracts, and the total number of unique partners, there is
an increase in the average number of collaborative partners per institution.
Furthermore, we establish a measure for the central role (hub) for each
country, by using the Minimum Spanning Tree (MST), which we construct in detail
for each thematic area (e.g. Informatics, Nanoscience, Life Sciences, etc.).
The importance of these network hubs is highlighted, as this information can be
used by policy planners in designing future research plans regarding the
distribution of available funds.Comment: 6 pages, 4 figure
The role of consumer networks in firms' multi-characteristics competition and market-share inequality
We develop a location analysis spatial model of firms' competition in
multi-characteristics space, where consumers' opinions about the firms'
products are distributed on multilayered networks. Firms do not compete on
price but only on location upon the products' multi-characteristics space, and
they aim to attract the maximum number of consumers. Boundedly rational
consumers have distinct ideal points/tastes over the possible available firm
locations but, crucially, they are affected by the opinions of their neighbors.
Proposing a dynamic agent-based analysis on firms' location choice we
characterize multi-dimensional product differentiation competition as adaptive
learning by firms' managers and we argue that such a complex systems approach
advances the analysis in alternative ways, beyond game-theoretic calculations.Comment: 33 pages, 5 figure
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