Quasi-stationary states of game-driven systems: a dynamical approach

Evolutionary game theory is a framework to formalize the evolution of collectives ("populations") of competing agents that are playing a game and, after every round, update their strategies to maximize individual payoffs. There are two complementary approaches to modeling evolution of player populations. The first addresses essentially finite populations by implementing the apparatus of Markov chains. The second assumes that the populations are infinite and operates with a system of mean-field deterministic differential equations. By using a model of two antagonistic populations, which are playing a game with stationary or periodically varying payoffs, we demonstrate that it exhibits metastable dynamics that is reducible neither to an immediate transition to a fixation (extinction of all but one strategy in a finite-size population) nor to the mean-field picture. In the case of stationary payoffs, this dynamics can be captured with a system of stochastic differential equations and interpreted as a stochastic Hopf bifurcation. In the case of varying payoffs, the metastable dynamics is much more complex than the dynamics of the means

Mutual synchronization of oscillations in a system of coupled evolutionary games

The purpose of this study is to investigate collective dynamics of coupled communities that evolve according to the population game «Battle of the Sexes». A separate community includes two interacting populations of players of opposite sex, where each player has one of two possible competing behavior strategies. It is necessary to determine the possibility of mutual synchronization of oscillations in the number of players adhering to a particular strategy, build a synchronization region, and also evaluate the dependence of the properties of oscillations on the coupling strength. Methods. In this paper, we study the system of evolutionary games «Battle of the Sexes» interacting through migration. To simulate the evolutionary game dynamics we make use of the stochastic Moran process, as well as the Monte Carlo method to sample game trajectories. Mutual synchronization is defined by the appropriately generalized criteria of frequency and phase locking. Results. It is shown that the system of coupled evolutionary games «Battle of the Sexes» demonstrates mutual synchronization of oscillations under sufficiently strong coupling. In particular, oscillation frequencies of two communities get adjusted to each other and begin to coincide at some interaction parameter, while the oscillations themselves become almost identical. A similar result was also observed for an ensemble of more than two communities. Conclusion. The dependence of the average frequencies of community oscillations on the coupling strength was determined, the adjustment of oscillations with an increase in the coupling strength was demonstrated, thereby showing the possibility of mutual synchronization in the model of coupled evolutionary games «Battle of the Sexes». The region of frequency synchronization was numerically found

Comparative statistical study of two local clustering coefficient formulations as tropical cyclone markers for climate networks

We introduce a new formulation of local clustering coefficient for weighted correlation networks. This new formulation is based upon a definition introduced previously in the neuroscience context and aimed at compensating for spurious correlations caused by indirect interactions. We modify this definition further by replacing Pearson's pairwise correlation coefficients and three-way partial correlation coefficients by the respective Kendall's rank correlations. This reduces statistical sample size requirements to compute the correlations, which translates into the possibility of using shorter time windows and hence into a shorter response time of the real-time climate network analysis. We construct evolving climate networks of mean sea level pressure fluctuations and analyze anomalies of local clustering coefficient in these networks. We develop a broadly applicable statistical methodology to study association between spatially inhomogeneous georeferenced multivariate time series and binary-valued spatiotemporal data (or other data reducible to this representation) and use it to compare the newly proposed formulation of local clustering coefficient (for weighted correlation networks) to the conventional one (for unweighted graphs) in terms of the association of these measures in climate networks to tropical cyclones. Thus we substantiate the previously made observation that tropical cyclones are associated with anomalously high values of local clustering coefficient, and confirm that the new formulation shows a stronger association

Solving the problem of credit defaults in retail sector

The article analyzes dynamics of the volume and annual rate of loan delinquency of the country’s population for intermediate quarter dates, compares default retail credit portfolios with similar portfolio of organizations, and determines the main reasons for appearance of population’s debts before banks. It is concluded that it is necessary for banks to focus on development of their own tools and technologies of payment recovery, related to determination of early problematic debt for the purpose of taking preventive measures for preventing the appearance of past-due debts, which is possible under the condition of investing money assets into own analytical and technological tools. An approach to segmentation of debts and factors that could be used as indicators in the process of accompanying and servicing of credits are offered.peer-reviewe

Dependence of progeny abundance for summer chum salmon (<i>Oncorhynchys keta</i>) in the Amur River on the parents abundance

For almost the century the landings of summer chum salmon in the Amur were approximately in 5 times lower that the landings of fall chum salmon, in spite on almost the same fishing efforts. However, its catches were very high in the 1990-2000s, even higher that for the fall chum salmon, that contradicts to conceptions on its lower absolute fecundity, smaller spawning grounds, and higher vulnerability of its reproduction on unfavorable external factors. Relationship of mature progeny abundance for summer chum salmon with number of their parents is analyzed. The data on the parents and progeny abundance were calculated from fishery statistics, including cited data, considering annual catch as 50 % of the stock. The highest recruitment of summer chum salmon is estimated as 19.08 · 106 ind. that is comparable with the strength of the fall chum salmon year-classes. The spawning stock of 1.94 · 106 ind. is enough to produce this progeny, but the population growth is much lower with the lower spawning stock, that is a real reason for slow recovery of the summer chum salmon stock, though potentially both races could be equally abundant. To maintain the stock of summer chum salmon at the highest level, an optimal number of parents should be passed to the spawning grounds, within rather narrow range, that is difficult to control in conditions of the big river

The Formation of Indicator Framework for Effective Assessment of Investment Attractiveness of the Region

Despite the in-depth study of many theoretical aspects of investment activities and assessment of investment attractiveness, today the impact of the investment policy on the development of an effective strategy and the formation of favorable investment climate is not properly reflected in the contemporary research. At the same time unstable situation in socio-economic development of Russia requires new approaches to the problem of investment activity. In this regard, the article provides indicator framework to assess properly the investment attractiveness of the region's economy relating to foreign direct investment in the current context. At that, the proposed indicator framework is based on a number of principles, which allow achieving the objective assessment of investment attractiveness of regions and feasibility of the concerned indicators. Keywords: foreign direct investment, investment activity, investment climate, assessment of investment attractiveness, region's economy. JEL Classifications: F21; F51; H77; O2

Efficacy and safety of levosalbutamol in patients with mild to moderate asthma compared with racemic salbutamol: results of a crossover placebo-controlled study

Aim. Effectiveness and safety of levosalbutamol metered dose inhaler (MDI) in comparison with placebo and salbutamol. Materials and methods. In this multicenter, randomized, placebo-controlled, 3-period crossover study, all asthma patients (n=91) received levosalbutamol (90 mcg), salbutamol (180 mcg), and placebo using standard MDI. Pulmonary function testing – forced expiratory volume in the first second (FEV1) and forced vital capacity (FVC) – was performed 45 and 15 minutes before and 5, 10, 15, 30, 60, 90, 120, 180, 240, 300 and 360 minutes after dosing. The primary efficacy endpoint was the baseline-corrected area under FEV1 curve from 0 to 6 hours (AUC(0–6h)). Secondary endpoints were the baseline adjusted FEV1 and FVC peak values, as well as the onset of drug action. Results. The FEV1 AUC0–6 hours analysis confirmed similar bronchodilatory levosalbutamol and salbutamol effect (p=0.595), significantly improved compared with placebo (p0.001). The peak values of FEV1 and FVC after levosalbutamol or salbutamol dosing were similar (p=0.643) and significantly higher compared with placebo group (p0.001). The active therapy effect was observed 5 minutes after dosing and throughout the entire observation period up to 6 hours, however, there was some tendency towards a longer duration of action of levosalbutamol compared to salbutamol. Levosalbutamol was well tolerated by patients; after levosalbutamol dosing twiсе fewer adverse reactions were observed compared to salbutamol. Conclusion. Levosalbutamol at a 90-mcg dose showed efficacy similar to that of salbutamol at a dose of 180 mcg, assosiated with a good safety profile