مجید اسحاقی گرجی

In this paper, using Evolutionary Game Theory, we study the evolution of currency as an important and influential problem in the world economy by presenting three new models. In examining the evolution of two different currencies, we prove that if the parties chose either of the two currencies with a fixed probability, it will not have an impact on the evolutionary process of these currencies. Considering a new action based on either the possibility of using any two currencies or a preference between the two currencies, we illustrate their impact on the evolution-ary process of currencies. In fact, we examine the impact of different actions and strategies on the evolutionary process between the two types of currencies.

Implementation credit rating for Corporates is influenced by Different circum-stances, systems, processes, and cultures in each country. In this study, we pro-posed a Factor analysis modified approach for determine important factors on real data set of 123 accepted corporate in Tehran Securities Exchange for the years 2009-2017 of diverse range of 52 variable. We estimated the priority score for 49 factors. The three factors, Debt to Equity Ratio, Current debt-to-equity ratio and proprietary ratio exclude due to high correlation with others. The results indicated that three macroeconomic factors: Price Index of Consumer Goods and Services, exchange rate and Interest rate determinants were more effective on the credit ratings. In addition, Financial Ratios and non-Financial Ratios such as Return on equity (ROE), Long-term debt-to-equity ratio, Benefit of the loan, ratio of com-modity to working capital, Current capital turnover, Return on Working Capital, Quick Ratio, Current Ratio, Net Profit margin, Gross profit margin, had effect on credit rating accepted corporate in Tehran Securities Exchange. The Nonparametric statistical test to validate the consistency between AHP ranking and Factor analysis revealed, the new approach has a moderated consistency with AHP. In conclusion, the Factor analysis modified approach could be applied significantly to evaluate efficiency and ranking factors with minimum loss of information.

In this paper, with help of the concept of hyper-rationality, we model the interaction between two investment companies by an important game as trickery game that has special equilibrium which called hyper-equilibrium. In trickery game, one company can choose cooperation with another company until the last moment and finally changes his action to non-cooperation which incur more loss to an opponent. Indeed, the hyper-equilibrium is the point in which only one player can displace equilibrium to another point by changing his action which causes profit or loss to other players so they cannot change their action. Our findings indicate that the kind of behaviour interactive, environmental conditions, and valuation system are based on hostility causes an equilibrium point to incur the maximum loss to an opponent.