arXiv subjects

Marcel Ausloos

Publications and source records attributed to Marcel Ausloos.

At least 127 records · Page 7Linked to original sources

arXiv2012

Discrete Model of Ideological Struggle Accounting for Migration

A discrete in time model of ideological competition is formulated taking into account population migration. The model is based on interactions between global populations of non-believers and followers of different ideologies. The complex dynamics of the attracting manifolds is investigated. Conversion from one ideology to another by means of (i) mass media influence and (ii) interpersonal relations is considered. Moreover a different birth rate is assumed for different ideologies, the rate being assumed to be positive for the reference population, made of initially non-believers. Ideological competition can happen in one or several regions in space. In the latter case, migration of non-believers and adepts is allowed; this leads to an enrichment of the ideological dynamics. Finally, the current ideological situation in the Arab countries and China is commented upon from the point of view of the presently developed mathematical model. The massive forced conversion by Ottoman Turks in the Balkans is briefly discussed.

physics.soc-ph↗

arXiv2012

Information Society: Modeling A Complex System With Scarce Data

Considering electronic implications in the Information Society (IS) as a complex system, complexity science tools are used to describe the processes that are seen to be taking place. The sometimes troublesome relationship between the information and communication new technologies and e-society gives rise to different problems, some of them being unexpected. Probably, the Digital Divide (DD) and the Internet Governance (IG) are among the most conflictive ones of internationally based e-Affairs. Admitting that solutions should be found for these problems, certain international policies are required. In this context, data gathering and subsequent analysis, as well as the construction of adequate physical models are extremely important in order to imagine different future scenarios and suggest some subsequent control. In the main text, mathematical modelization helps for visualizing how policies could e.g. influence the individual and collective behavior in an empirical social agent system. In order to show how this purpose could be achieved, two approaches, (i) the Ising model and (ii) a generalized Lotka-Volterra model are used for DD and IG considerations respectively. It can be concluded that the social modelization of the e-Information Society as a complex system provides insights about how DD can be reduced and how the a large number of weak members of the IS could influence the outcomes of the IG.

physics.soc-ph↗

arXiv2010

Structural and Magnetic Properties of Nanosized Barium Hexaferrite Powders Obtained by Microemulsion Technique

Thin hexagonal barium hexaferrite particles synthesized using the microemulsion technique were studied. A water-in-oil reverse microemulsion system with cetyltrimethylammonium bromide (CTAB) as a cationic surfactant, n-butanol as a co-surfactant, n-hexanol as a continuous oil phase, and an aqueous phase were used. The microstructural and magnetic properties were investigated. The particles obtained were mono-domain with average particle size 280 nm. The magnetic properties of the powder were investigated at 4.2 K and at room temperature. The saturation magnetization was 48.86 emu/g and the coercivity, 2.4 x 105 A/m at room temperature. The anisotropy field Ha and magneto-crystalline anisotropy K1 were 1.4 x 106 A/m and 2.37 x 105 J/m3, respectively.

cond-mat.mtrl-sci↗

arXiv2009

Has the world economy reached its globalization limit?

The economy globalization measure problem is discussed. Four macroeconomic indices of twenty among the "richest" countries are examined. Four types of "distances" are calculated.Two types of networks are next constructed for each distance measure definition. It is shown that the globalization process can be best characterised by an entropy measure, based on entropy Manhattan distance. It is observed that a globalization maximum was reached in the interval 1970-2000. More recently a deglobalization process is observed.

physics.data-an↗

arXiv2009

A model of ideological struggle

A general model for opinion formation and competition, like in ideological struggles is formulated. The underlying set is a closed one, like a country but in which the population size is variable in time. Several ideologies compete to increase their number of adepts. Such followers can be either converted from one ideology to another or become followers of an ideology though being previously ideologically-free. A reverse process is also allowed. We consider two kinds of conversion: unitary conversion, e.g. by means of mass communication tools, or binary conversion, e.g. by means of interactions between people. It is found that the steady state,when it exists, depends on the number of ideologies. Moreover when the number of ideologies increases some tension arises between them. This tension can change in the course of time. We propose to measure the ideology tensions through an appropriately defined scale index.

physics.soc-ph↗

arXiv2009

Entropy correlation distance method applied to study correlations between the Gross Domestic Product of rich countries

The Theil index is much used in economy and finance; it looks like the Shannon entropy, but pertains to event values rather than to their probabilities. Any time series can be remapped through the Theil index. Correlation coefficients can be evaluated between the new time series, thereby allowing to study their mutual statistical distance, - to be contrasted to the usual correlation distance measure for the primary time series. As an example this entropy-like correlation distance method (ECDM) is applied to the Gross Domestic Product of 20 rich countries in order to test some economy globalization process. Hierarchical distances allow to construct (i) a linear network, (ii) a Locally Minimal Spanning Tree. The role of time averaging in finite size windows is illustrated and discussed. It is also shown that the mean distance between the most developed countries, was decreasing since 1960 till 2000, - which we consider to be a proof of globalization of the economy for these countries.

physics.data-an↗

arXiv2008

Statistical dynamics of religion evolutions

A religion affiliation can be considered as a "degree of freedom" of an agent on the human genre network. A brief review is given on the state of the art in data analysis and modelization of religious "questions" in order to suggest and if possible initiate further research, ... after using a "statistical physics filter". We present a discussion of the evolution of 18 so called religions, as measured through their number of adherents between 1900 and 2000. Some emphasis is made on a few cases presenting a minimum or a maximum in the investigated time range, - thereby suggesting a competitive ingredient to be considered, beside the well accepted "at birth" attachement effect. The importance of the "external field" is still stressed through an Avrami late stage crystal growth-like parameter. The observed features and some intuitive interpretations point to opinion based models with vector, rather than scalar, like agents.

physics.soc-ph↗

arXiv2008

Introducing the q-Theil index

Starting from the idea of Tsallis on non-extensive statistical mechanics and the {\it q-entropy} notion, we recall the Theil index $Th$ and transform it into the $Th_q$ index. Both indices can be used to map onto themselves any time series in a non linear way. We develop an application of the $Th_q$ to the GDP evolution of 20 rich countries in the time interval [1950 - 2003] and search for a proof of globalization of their economies. First we calculate the distances between the "new" time series and to their mean, from which such data simple networks are constructed. We emphasize that it is useful to, and we do, take into account different time "parameters": (i) the moving average time window for the raw time series to calculate the $Th_q$ index; (ii) the moving average time window for calculating the time series distances; (iii) a correlation time lag. This allows us to deduce optimal conditions to measure the features of the network, i.e. the appearance in 1970 of a globalization process in the economy of such countries and the present beginning of deviations. The $q$ value hereby used is that which measures the overall data distribution and is equal to 1.8125.

physics.data-an↗

arXiv2008

Numerical simulation of the magnetization of high-temperature superconductors: 3D finite element method using a single time-step iteration

We make progress towards a 3D finite-element model for the magnetization of a high temperature superconductor (HTS): We suggest a method that takes into account demagnetisation effects and flux creep, while it neglects the effects associated with currents that are not perpendicular to the local magnetic induction. We consider samples that are subjected to a uniform magnetic field varying linearly with time. Their magnetization is calculated by means of a weak formulation in the magnetostatic approximation of the Maxwell equations (A-phi formulation). An implicit method is used for the temporal resolution (Backward Euler scheme) and is solved in the open source solver GetDP. Picard iterations are used to deal with the power law conductivity of HTS. The finite element formulation is validated for an HTS tube with large pinning strength through the comparison with results obtained with other well-established methods. We show that carrying the calculations with a single time-step (as opposed to many small time-steps) produce results with excellent accuracy in a drastically reduced simulation time. The numerical method is extended to the study of the trapped magnetization of cylinders that are drilled with different arrays of columnar holes arranged parallel to the cylinder axis.

cond-mat.supr-con↗

arXiv2008

Measurement of the magnetic field inside the holes of a drilled bulk high-Tc superconductor

We use macroscopic holes drilled in a bulk YBCO superconductor to probe its magnetic properties in the volume of the sample. The sample is subjected to an AC magnetic flux with a density ranging from 30mT to 130mT and the flux in the superconductor is probed by miniature coils inserted in the holes. In a given hole, three different penetration regimes can be observed: (i) the shielded regime, where no magnetic flux threads the hole; (ii) the gradual penetration regime, where the waveform of the magnetic field has a clipped sine shape whose fundamental component scales with the applied field; and (iii) the flux concentration regime, where the waveform of the magnetic field is nearly a sine wave, with an amplitude exceeding that of the applied field by up to a factor of two. The distribution of the penetration regimes in the holes is compared with that of the magnetic flux density at the top and bottom surfaces of the sample, and is interpreted with the help of optical polarized light micrographs of these surfaces. We show that the measurement of the magnetic field inside the holes can be used as a local characterization of the bulk magnetic properties of the sample.

cond-mat.supr-con↗

arXiv2008

Statistical-mechanics approach to a reinforcement learning model with memory

We introduce a two-player model of reinforcement learning with memory. Past actions of an iterated game are stored in a memory and used to determine player's next action. To examine the behaviour of the model some approximate methods are used and confronted against numerical simulations and exact master equation. When the length of memory of players increases to infinity the model undergoes an absorbing-state phase transition. Performance of examined strategies is checked in the prisoner' dilemma game. It turns out that it is advantageous to have a large memory in symmetric games, but it is better to have a short memory in asymmetric ones.

cond-mat.stat-mech↗

arXiv2008

High frequency intrinsic modes in El Niño Southern Oscillation Index

Recent $daily$ data of the Southern Oscillation Index have been analyzed. The power spectrum indicates major intrinsic geophysical short periods. We find interesting ``high frequency'' oscillations at 24, 27, 37, 76, 100 and 365 days. In particular the 24 days peaks may correspond to the Branstator-Kushnir wave, the 27 days may be due to the moon effect rotation, the 37 days peaks is most probably related to the Madden and Julian Oscillation. It is not yet clear the explanations for the 76 days which may be associated with interseasonal oscillation in the tropical atmosphere; the 100 days could be resulting from a mere beat between the 37 and 27 periods, or the 76 and 365 days. Next these periods are used to reconstruct the signal and to produce a forecast for the next 9 months, at the time of writing. After cleansing the signal of those periodicities a detrended fluctuation analysis is performed to reveal the nature of the stochastic structures in the signal and whether specific correlation can be found. We study the evolution of the distribution of first return times, in particular between $extreme$ $events$. A markedly significant difference from the expected distribution for uncorrelated events is found.

physics.data-an↗

arXiv2008

Convergence and cluster structures in EU area according to fluctuations in macroeconomic indices

The cluster analysis methods are used in order to perform a comparative study of 15 EU countries in relation with the fluctuations of some basic macroeconomic indicators. The statistical distances between countries are calculated for various moving time windows, and the time variation of the mean statistical distance is investigated. The decreasing of the mean statistical distance between EU countries is reflected in the correlated fluctuations of the basic ME indicators: GDP, GDP/capita, Consumption and Investments. This empirical evidence can be seen as an economic aspect of globalization. The Moving Average Minimal Length Path (MAMLP) algorithm allows to search for a cluster-like structures derived both from the hierarchical organization of countries and from their relative movement inside the hierarchy. It is found that the strongly correlated countries with respect to GDP fluctuations can be partitioned into stable clusters. Some of the highly correlated countries, with respect to GDP fluctuations, display strong correlations also in the Final Consumption Expenditure, while others are strongly correlated in Gross Capital Formation. On the other hand, one notices the similitude of the classifications regarding GDP and Net Exports fluctuations as concerns the squared sum of the correlation coefficients (so called country sensitivity). The final structure proves to be robust against the constant size time window moving over the scanned time interval. The policy implications of the above empirical results concern the economic clusters arising in the presence of Marshallian externalities and the relationships between trade barriers, R&D incentives and growth that must be accounted in elaborating a cluster-promotion policy.

q-fin.GN↗

arXiv2008

Dislocation induced ac Josephson effect in high-T_c superconductors

A possible scenario for an ac Josephson effect initiated by the flow of dislocations through a mechanically loaded but electrically unbiased superconductor is proposed. The characteristic voltages due to the motion of dislocations in loaded (under the applied stress of 10^7N/m^2) YBCO crystals are estimated to be of the order of a few picovolts (which corresponds to the Josephson frequency of 10 kHz).

cond-mat.supr-con↗

arXiv2008

Cluster Expansion Method for Evolving Weighted Networks Having Vector-like Nodes

The Cluster Variation Method known in statistical mechanics and condensed matter is revived for weighted bipartite networks. The decomposition of a Hamiltonian through a finite number of components, whence serving to define variable clusters, is recalled. As an illustration the network built from data representing correlations between (4) macro-economic features, i.e. the so called $vector$ $components$, of 15 EU countries, as (function) nodes, is discussed. We show that statistical physics principles, like the maximum entropy criterion points to clusters, here in a (4) variable phase space: Gross Domestic Product (GDP), Final Consumption Expenditure (FCE), Gross Capital Formation (GCF) and Net Exports (NEX). It is observed that the $maximum$ entropy corresponds to a cluster which does $not$ explicitly include the GDP but only the other (3) ''axes'', i.e. consumption, investment and trade components. On the other hand, the $minimal$ entropy clustering scheme is obtained from a coupling necessarily including GDP and FCE. The results confirm intuitive economic theory and practice expectations at least as regards geographical connexions. The technique can of course be applied to many other cases in the physics of socio-economy networks.

physics.soc-ph↗

arXiv2008

Risk of Population Extinction from Periodic and Abrupt Changes of Environment

A simulation model of a population having internal (genetic) structure is presented. The population is subject to selection pressure coming from the environment which is the same in the whole system but changes in time. Reproduction has a sexual character with recombination and mutation. Two cases are considered - oscillatory changes of the environment and abrupt ones (catastrophes). We show how the survival chance of a population depends on maximum allowed size of the population, the length of the genotypes characterising individuals, selection pressure and the characteristics of the climate changes, either their period of oscillations or the scale of the abrupt shift.

nlin.AO↗

arXiv2007

Clusters in weighted macroeconomic networks : the EU case. Introducing the overlapping index of GDP/capita fluctuation correlations

GDP/capita correlations are investigated in various time windows (TW), for the time interval 1990-2005. The target group of countries is the set of 25 EU members, 15 till 2004 plus the 10 countries which joined EU later on. The TW-means of the statistical correlation coefficients are taken as the weights (links) of a fully connected network having the countries as nodes. Thereafter we define and introduce the overlapping index of weighted network nodes. A cluster structure of EU countries is derived from the statistically relevant eigenvalues and eigenvectors of the adjacency matrix. This may be considered to yield some information about the structure, stability and evolution of the EU country clusters in a macroeconomic sense.

physics.soc-ph↗

arXiv2007

Magnetic shielding properties of high-temperature superconducting tubes subjected to axial fields

We have experimentally studied the magnetic shielding properties of a cylindrical shell of BiPbSrCaCuO subjected to low frequency AC axial magnetic fields. The magnetic response has been investigated as a function of the dimensions of the tube, the magnitude of the applied field and the frequency. These results are explained quantitatively by employing the method of Brandt (1998 Phys. Rev. B 58 6506) with a Jc(B) law appropriate for a polycrystalline material. Specifically, we observe that the applied field can sweep into the central region either through the thickness of the shield or through the opening ends, the latter mechanism being suppressed for long tubes. For the first time, we systematically detail the spatial variation of the shielding factor (the ratio of the applied field over the internal magnetic field) along the axis of a high-temperature superconducting tube. The shielding factor is shown to be constant in a region around the centre of the tube, and to decrease as an exponential in the vicinity of the ends. This spatial dependence comes from the competition between two mechanisms of field penetration. The frequency dependence of the shielding factor is also discussed and shown to follow a power law arising from the finite creep exponent n.

cond-mat.supr-con↗