9 research outputs found
Microscopic model for the logarithmic size effect on the Curie point in Barab\'asi-Albert networks
We found that numbers of fully connected clusters in Barab\'asi-Albert (BA)
networks follow the exponential distribution with the characteristic exponent
. The critical temperature for the Ising model on the BA network is
determined by the critical temperature of the largest fully connected cluster
within the network. The result explains the logarithmic dependence of the
critical temperature on the size of the network .Comment: 5 pages, 2 figure
Self-organized criticality in a model of collective bank bankruptcies
The question we address here is of whether phenomena of collective
bankruptcies are related to self-organized criticality. In order to answer it
we propose a simple model of banking networks based on the random directed
percolation. We study effects of one bank failure on the nucleation of
contagion phase in a financial market. We recognize the power law distribution
of contagion sizes in 3d- and 4d-networks as an indicator of SOC behavior. The
SOC dynamics was not detected in 2d-lattices. The difference between 2d- and
3d- or 4d-systems is explained due to the percolation theory.Comment: For Int. J. Mod. Phys. C 13, No. 3, six pages including four figure
A simple model of bank bankruptcies
Interbank deposits (loans and credits) are quite common in banking system all
over the world. Such interbank co-operation is profitable for banks but it can
also lead to collective financial failures. In this paper we introduce a new
model of directed percolation as a simple representation for contagion process
and mass bankruptcies in banking systems. Directed connections that are
randomly distributed between junctions of bank lattice simulate flows of money
in our model. Critical values of a mean density of interbank connections as
well as static and dynamic scaling laws for the statistic of avalange
bankruptcies are found. Results of computer simulations for the universal
profile of bankruptcies spreading are in a qualitative agreement with the third
wave of bank suspensions during The Great Depression in the USA.Comment: 8 pages, 6 Encapsulated Postscript figures, to be published in
Physica A (2001
Ferromagnetic Phase Transition in Barabasi-Albert Networks
Ising spins put onto a Barabasi-Albert scale-free network show an effective
phase transition from ferromagnetism to paramagnetism upon heating, with an
effective critical temperature increasing as the logarithm of the system size.
Starting with all spins up and upon equilibration pinning the few
most-connected spins down nucleates the phase with most of the spins down.Comment: 8 pages including figure
Higher order clustering coefficients in Barabasi-Albert networks
Higher order clustering coefficients are introduced for random
networks. The coefficients express probabilities that the shortest distance
between any two nearest neighbours of a certain vertex equals , when one
neglects all paths crossing the node . Using we found that in the
Barab\'{a}si-Albert (BA) model the average shortest path length in a node's
neighbourhood is smaller than the equivalent quantity of the whole network and
the remainder depends only on the network parameter . Our results show that
small values of the standard clustering coefficient in large BA networks are
due to random character of the nearest neighbourhood of vertices in such
networks.Comment: 10 pages, 4 figure
The Comet Interceptor Mission
Here we describe the novel, multi-point Comet Interceptor mission. It is dedicated to the exploration of a little-processed long-period comet, possibly entering the inner Solar System for the first time, or to encounter an interstellar object originating at another star. The objectives of the mission are to address the following questions: What are the surface composition, shape, morphology, and structure of the target object? What is the composition of the gas and dust in the coma, its connection to the nucleus, and the nature of its interaction with the solar wind? The mission was proposed to the European Space Agency in 2018, and formally adopted by the agency in June 2022, for launch in 2029 together with the Ariel mission. Comet Interceptor will take advantage of the opportunity presented by ESA’s F-Class call for fast, flexible, low-cost missions to which it was proposed. The call required a launch to a halo orbit around the Sun-Earth L2 point. The mission can take advantage of this placement to wait for the discovery of a suitable comet reachable with its minimum ΔV capability of 600 ms−1. Comet Interceptor will be unique in encountering and studying, at a nominal closest approach distance of 1000 km, a comet that represents a near-pristine sample of material from the formation of the Solar System. It will also add a capability that no previous cometary mission has had, which is to deploy two sub-probes – B1, provided by the Japanese space agency, JAXA, and B2 – that will follow different trajectories through the coma. While the main probe passes at a nominal 1000 km distance, probes B1 and B2 will follow different chords through the coma at distances of 850 km and 400 km, respectively. The result will be unique, simultaneous, spatially resolved information of the 3-dimensional properties of the target comet and its interaction with the space environment. We present the mission’s science background leading to these objectives, as well as an overview of the scientific instruments, mission design, and schedule
Self-organized criticality in a model of collective bank bankruptcies
The question we address here is of whether phenomena of collective bankruptcies are related to self-organized criticality. In order to answer it we propose a simple model of banking networks based on the random directed percolation. We study effects of one bank failure on the nucleation of contagion phase in a financial market. We recognize the power law distribution of contagion sizes in 3d- and 4d-networks as an indicator of SOC behavior. The SOC dynamics was not detected in 2d-lattices. The difference between 2d- and 3d- or 4d-systems is explained due to the percolation theory.