Network science has been successfully applied in recent years in many worldwide systems and processes. These include financial systems [1,2] and social systems [3,4]. I will present and discuss some examples including (i) how network science can be useful to distinguish between fake news and real news [3], (ii) how to identify bottlenecks in urban traffic [5], (iii) how scientists switch...
Individuals form groups, which subsequently develop larger domains via competition and coalescence. How much have these social processes in common with established mechanisms of phase transitions in physics? Are nucleation in metastable systems or spinodal decomposition of thermodynamic phases or percolation in porous media suitable paradigms for modeling the emergence of large social groups?...
Starting with classical work of Barabási and Albert, the issue with preferential attachment rules is a fundamental problem for modeling evolving networks. Linear preferential attachment rule (also called rich get richer rule or Matthew effect) is the most popular mechanism that leads to power-law vertex degree distribution. However, original preferential attachment rule that appears in...
Bibliometric research often focuses on the extreme levels of granularity. On the one hand, it focuses on the analysis of individual papers, from the other discussing the features of the entire citation network, losing an intermediate stage of the achievements of one scientist. During the talk, I will try to present the known models of such track records. We will consider how to construct the...
The dynamics of price changes involves very complex processes and constitutes one of the central issues in Econophysics. The functional forms of return distributions considered and reported in the literature include the Levy distribution and its truncated variant, power-laws and, in particular, its inverse-cubic case, the q-Gaussians and the stretched exponentials. These may vary among the...
The multiscaling behaviour of financial time-series is one of the acknowledged stylized facts in the literature [1]. The source of the measured multifractality in financial markets has been long debated [2,3]. In this talk I will discuss the origin of multiscaling in financial time-series, investigate how to best quantify it [4,5] and I will introduce a new methodology that provides a robust...
Interaction is the basic feature of economic systems. Although it is possible to imagine a primitive self-sustained tribe, in the case of a developed economy the interaction (in positive and negative sense i.e. cooperation and competition) are a crucial factor of development. Those interactions are influenced by some events or the state of the systems. The special cases are global events such...
It is common nowadays to have to deal with information spreading on multilayer networks and often identification of the origin of said propagation can be a crucial task. We examine the issue of locating the source of Susceptible-Infected spreading process in a multilayer network using the Bayesian inference and the maximum likelihood method established for general networks and adapted here to...
Applying the Galam model of opinion dynamics to predict the outcome of the November 2020 US presidential election, I concluded on Trump victory at the edge. My prediction has failed. On the one hand, a massive Biden victory would have meant my failure was significant implying to revisit the basic elements of the model to find out which relevant ingredient has been missed. On the other hand,...
A common issue when analyzing real-world complex systems is that the interactions that characterize them often change over time: this makes it difficult to find optimal models that describe this evolution and can be estimated from data, particularly when the driving rules are not known. Here we offer a new perspective on the development of models for time-varying interactions introducing a...
We examine parliamentary attendance data of the 2008–2012, the 2012–2016 and the 2016–2020 legislatures of Lithuanian parliament. In our exploration of the data set we consider cumulative attendance series of the representatives in the parliament as individual traces of the particles. In this scenario we observe that empirical series exhibit superdiffusive behavior. Similar observation was...
The vulnerability of democratic processes is under scrutiny after scandals related to Cambrige Analytica (2016 U.S. elections, the Brexit referendum, and elections in Kenya). The deceptive use of social media in the US, the European Union and several Asian countries, increased social and political polarization across world regions. Finally, there are straightforward frauds like Crimea...
The "endo-exo" problem in complex systems (ecology, earthquakes, financial volatility, epileptic seizures…) and how to disentangle the long-term memory (Hurst, etc.) from time-varying trends?
The "endo-exo" problem -- i.e., decomposing system activity into exogenous and endogenous parts -- lies at the heart of statistical identification in many fields of science. E.g., consider the problem...
This work is about the social dynamics observed at the onset and during the evolution of a financial bubble. Our characterization detects demographic trends in the flux of new investors buying the Nokia asset, i.e. the most representative dotcom stock of the Nordic Stock Exchange during the dotcom bubble. We track the flux of new investors entering the market daily, and we yearly compare their...
Understanding how people interact, form friendships, and formulate opinions is vital for predicting evolution of social systems. Heider Balance Theory (HBT) takes into account dynamics of social triads by considering the well-known rules: a friend of my friend as well as an enemy of my enemy are my friends, and a friend of my enemy as well as an enemy of my friend are my enemies. To capture...
The talk reports our search for a flexible formulation of the process of removal of cognitive dissonance when identifying enemies and friends. The list of methods includes sets of nonlinear differential equations and cellular automata with different neighborhoods. Results are described on the balanced-imbalanced phase transition on networks of different topology, jammed and dynamic states...
Lots of people get information from social media, where users can exchange messages. In most cases, content transmits without any changes. Sometimes, users modify form or content of the message before passing it on. Understanding the mechanism of message mutation could allow us to become more resistant to misinformation and better identify fake news.
We propose a simple model in which...
A realistic description of the social processes leading to the increasing reluctance to various vaccination forms is a very challenging task. This is due to the complexity of the psychological and social mechanisms determining the individual and group positioning versus vaccination and the associated activities. Understanding the role played by social media and the Internet in the current...
The COVID-19 outbreak has so far caused millions of cases and deaths globally. Human behaviour has been identified as the key factor in the spread of the SARS-CoV-2 virus and there is considerable interest in understanding the relationship between the way people act in response to the infection risk and the disease progress. Mathematical modelling has been at the centre of policy-making aimed...
Increasingly, vast data sets collected about complex network activities via monitoring and sensing devices define dynamics of these networks. This creates a challenge for controlling them, since it requires formal definition of network dynamics. In this talk, we introduce a framework for deriving the formal definition of complex network’s dynamics from data. It provides an important...
To prevent the spread of COVID-19, many cities, states, and countries have `locked down', restricting economic activities in non-essential sectors. Such lockdowns have substantially shrunk production in most countries. This study examines how the economic effects of lockdowns in different regions interact through supply chains, which are a network of firms for production, by simulating an...
Echo chambers and polarisation dynamics are as of late a very prominent topic in scientific communities around the world. As these phenomena directly affect our lives, and seemingly more and more as our societies and communication channels evolve, it becomes ever so important to understand the intricacies of novel opinion dynamics in the modern era. We build upon an existing echo chambers and...
We study the q-voter model with bounded confidence on the complete graph. Agents can be in one of three states. Two types of agents behaviour are investigated: conformity and independence. We analyze whether this system is qualitatively different from a corresponding model without bounded confidence. Our main results are the following. Firstly, the system has two phase transitions: one between...
We study an agent-based model of innovation diffusion on the Watts-Strogatz random graphs. The model is based on the $q$-voter model with a noise (with nonconformity, in the terminology of social psychology), which has been previously used to describe the diffusion of green products and practices. It originates from the $q$-voter model with independence, known also as the noisy nonlinear voter...
The current world keeps evolving, and in our era the challenge of "too much data" keeps popping up, in particular in the world of portfolio optimization, therein lies the opportunity of providing more accurate results through the use of the relatively new tools developed in the random matrix theory literature to reduce the bias in the sample covariance matrix of some financial data (real or...
The main goal of our work is to show how ideas change in social networks. Our analysis is based on three concepts: (i) temporal networks [1], (ii) the Axelrod model of culture dissemination [2], (iii) the garbage can model of organizational choice [3]. The use of the concept of temporal networks allows us to show the dynamics of ideas spreading processes in networks, thanks to the analysis of...
Empirical time series of inter-event or waiting times are investigated using a modified Multifractal Detrended Fluctuation Analysis operating on fluctuations of mean detrended dynamics. The core of the extended multifractal analysis is the non-monotonic behavior of the generalized Hurst exponent $h(q)$ -- the fundamental exponent in the study of multifractals. The consequence of this behavior...
We investigate the binary $q$-voter model with generalized anticonformity on random Erdős–Rényi graphs. The generalization refers to the freedom of choosing the size of the influence group independently for the case of conformity $q_c$ and anticonformity $q_a$. This model was studied before on the complete graph, which corresponds to the mean-field approach, and on such a graph discontinuous...
Elucidating what factors are salient in emerging interactions in social networks is still an open question. Thus, we develop an agent-based model for generating interactions in signed networks. The ABMs, based on the Activity Driven Network model, use signed relations between agents to reproduce their interaction frequencies and crucial network distributions. The calibration and validation...
We applied the moving average cluster entropy to study long-range correlation, dynamics and heterogeneity of financial time series, and to propose an alternative method to portfolio estimation.
The cluster entropy relies on the Shannon entropy $S(P_i) = - \sum_i P_i \ln P_i$. The probability distribution function of each asset $i$ is obtained intersecting the asset time series $y(t)$ with...
In the age of social media there is more and more need to understand how do people create relations using those. The objective here was not only to look if relations are being created as a consequence of social interactions, but also to separate emergence of positive and negative relations. The knowledge we can gain here could benefit a wide spectrum of applications - from purely scietific to...
Macroeconomic analyses are, to a large extent, based on firm segmentation and creating homogeneous groups of entities. Thanks to this procedure one can estimate indicators (e.g., various Key Performance Indicators) with high accuracy and examine trends of the market. Unfortunately, the drawback is that segmentation algorithms based on distance measures model average values and are not suitable...
Social stratification, the division of society into groups, can result from historical and social factors and reflect economic inequality. Ethnicity, gender, and race are examples of subgroups where people belonging to one can be privileged in terms of status, power, and wealth. In fact, in many societies, dominant classes are composed of many people associated with one group, and economic...
The term "hierarchy" when applied to networks can mean one of the few structures: simple order hierarchy meaning ordering of elements, nested hierarchy that is multi-level community structure or flow hierarchy defined by directed links that show causal or control structure in the network.
We introduce two measures of node depth for flow hierarchy in directed networks, measuring the level of...
Spreading processes play an increasingly important role in modeling for diffusion networks, information propagation, marketing and opinion setting. We address the problem of learning of a spreading model such that the predictions generated from this model are accurate and could be subsequently used for the optimization, and control of diffusion dynamics. Unfortunately, full observations of the...
We introduce a generalized version of the noisy q-voter model, one of the most popular opinion dynamics models, in which voters can be in one of s≥2 states. As in the original binary q-voter model, which corresponds to s=2, at each update randomly selected voter can conform to its q randomly chosen neighbors (copy their state) only if all q neighbors are in the same state. Additionally, a...
One of the challenges faced by today's societies is to deal with the growing polarization. Here, we propose an agent-based model incorporating theories of structural balance and homophily. Most of the literature identify a structurally balanced state as a polarized one. However, we show that these two states are not always equivalent. We study a multilayer system with one layer related to the...
I present the issue of quantifying the impact of modern maritime piracy practises on world trade. For this purpose the case of Somali piracy is investigated. Data is carefully analysed with the statistical methodology of modern empirical economics to identify the causal effect of pirate attacks on trade volumes and transportation costs. This is a good example for the detection of small causal...
A new type of in-depth microscopic analysis is presented for the Yard-Sale model, one of the most well known multi-agent market exchange models. This approach led to the classification and study of the individual strategies carried out by the agents undergoing transactions, as given by their risk propensity. These findings allowed to determine a region of parameters for which the strategies...
The Covid-19 pandemic has affected not only economies of particular countries but the entire world economic system. It is not surprising that also currency exchange rates are not left untouched by the current crisis. The main objective of our study here is to assess the similarity between the time series of currency exchange rates and the Covid-19 time series (e.g., we investigate the...
The Axelrod model is a well known model of culture development and dissemination describing a possible mechanism for emergence of cultural domains. It is based on two sociological phenomena: homophily and the theory of social influence. Technically, it assumes that every culture is represented by a vector of F cultural traits (features), each taking any of q allowed opinions (values). The...
We review a number of basic stylized facts of the interbank market that have
emerged from the empirical literature over the last years. Our objective is to explain these
findings as emergent properties of dynamic agent-based model of the interaction within the
banking sector. To this end, we develop a simple dynamic model of interbank credit
relationships. Starting from a given balance...
The title of this talks is inspired by the Timur Kuran’s book entitled “Private Truths, Public Lies. The Social Consequences of Preference Falsification”. During my presentation I will talk about the idea and real-life examples of Preference Falsification (PF). Furthermore, I will propose a simple binary agent-based model, which allows to describe PF by introducing two levels of the opinion:...
As a result of the COVID19 pandemic, more higher-level education courses have moved to online channels, raising challenges in monitoring students’ learning progress. Thanks to the development of learning technologies, learning behaviours can be recorded at a more fine-grain level of detail, which can then be further analysed. Inspired by approaching education as a complex system, this research...
We study the voter model dynamics in the presence of confidence and bias. We assume two types of voters. Unbiased voters (UV) whose confidence is indifferent to the state of the voter and biased voters (BV) whose confidence is biased towards a common fixed preferred state. We study the problem analytically on the complete graph using mean field theory and on a random network topology using the...
The problem of estimating covariance matrix plays a fundamental role in portfolio selection. Recently a new estimator of large-dimensional covariance matrices has been proposed to reduce out-of-sample risk of large portfolios. The estimator is called non-linear shrinkage estimators. We derive an analytic formula for the non-linear shrinkage estimator of large dimensional covariance for...
There are two primary goals of this talk. First, we propose a flexible algorithm that can simulate various scenarios of state/government intervention. Secondly, we analyze in detail the scenario with the widest possible spectrum of stationary states. It exhibits the critical behavior of the market of competing firms, depending on the degree of government intervention and the activity level of...
Recently a simple master equation with growth and reset terms was considered for modeling in a unified manner distributions observed in complex systems [1]. Income and wealth are two basic socio-economic quantities that are frequently used to characterize social inequalities. Beginning with the pioneering work of Vilfredo Pareto, the distribution of these quantities were intensively studied...
Financial markets are characterized by an enormous network of connections and factors that can influence the structure and dynamics of the system. One of the youngest part of the modern financial markets are cryptocurrencies. Since the Bitcoin invention in 2009, the cryptocurrency market has experienced striking development over the last few years - from being entirely peripheral to the...
We are studying the transfer entropy, under different estimations and variants, between a set of Twitter accounts belonging to politicians and millionaires to measure the effect that their comments have on the behavior of bitcoin. Additionally, we have included among the possible drivers of bitcoin to Google Trends and a heterogeneous portfolio of metals and composite indices. The...
