7 results on '"Radi, D."'
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2. Causes of fragile stock market stability.
- Author
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Gardini, L., Radi, D., Schmitt, N., Sushko, I., and Westerhoff, F.
- Subjects
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STOCK exchanges , *MARKET makers , *STOCK prices , *RATE of return on stocks , *DYNAMICAL systems - Abstract
We develop a behavioral stock market model in which a market maker adjusts stock prices with respect to the orders of chartists, fundamentalists and sentiment traders. We analytically prove that the mere presence of sentiment traders, i.e. traders who optimistically buy stocks in rising markets and pessimistically sell stocks in falling markets, compromises the stability of stock markets. In particular, this means that instead of converging towards their fundamental value, stock prices either display endogenous oscillatory dynamics or converge towards nonfundamental fixed points – observations that challenge standard stability claims offered in the pertinent literature. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
3. A piecewise smooth model of evolutionary game for residential mobility and segregation.
- Author
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Radi, D. and Gardini, L.
- Subjects
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PIECEWISE linear approximation , *GAME theory in biology , *RESIDENTIAL mobility , *INTERNAL migration - Abstract
The paper proposes an evolutionary version of a Schelling-type dynamic system to model the patterns of residential segregation when two groups of people are involved. The payoff functions of agents are the individual preferences for integration which are empirically grounded. Differently from Schelling's model, where the limited levels of tolerance are the driving force of segregation, in the current setup agents benefit from integration. Despite the differences, the evolutionary model shows a dynamics of segregation that is qualitatively similar to the one of the classical Schelling's model: segregation is always a stable equilibrium, while equilibria of integration exist only for peculiar configurations of the payoff functions and their asymptotic stability is highly sensitive to parameter variations. Moreover, a rich variety of integrated dynamic behaviors can be observed. In particular, the dynamics of the evolutionary game is regulated by a one-dimensional piecewise smooth map with two kink points that is rigorously analyzed using techniques recently developed for piecewise smooth dynamical systems. The investigation reveals that when a stable internal equilibrium exists, the bimodal shape of the map leads to several different kinds of bifurcations, smooth, and border collision, in a complicated interplay. Our global analysis can give intuitions to be used by a social planner to maximize integration through social policies that manipulate people's preferences for integration. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
4. Evolutionary technology adoption in an oligopoly market with forward-looking firms.
- Author
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Lamantia, F. and Radi, D.
- Subjects
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OLIGOPOLIES , *IMPERFECT competition , *BIFURCATION theory , *PIECEWISE linear approximation , *CORPORATE profits - Abstract
In this paper, we propose an evolutionary oligopoly game of technology adoption in a market with isoelastic demand and two possible (linear) production technologies. While one technology is characterized by lower marginal costs, the magnitude of fixed costs entails that a technology does not necessarily dominate the other. Firms are forward-looking as they assess the profitability of employing either technology according to the corresponding expected profits. The dynamics of the system is studied through a piecewise-smooth map, for which we present a local stability analysis of equilibria and show the occurrence of smooth and border collision bifurcations. Global analysis of the model is also presented to show the coexistence of attractors and its economic significance. This investigation reveals that firms can fail to learn to adopt the more efficient technology. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
5. Oral contraceptive pills: Risky or protective in case of Trichinella spiralis infection?
- Author
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Hasby Saad, M. A., Radi, D. A., and Hasby, E. A.
- Subjects
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TRICHINELLA spiralis , *CONTRACEPTIVE drugs , *IN vivo studies , *LABORATORY rats , *PHYSIOLOGICAL effects of estrogen - Abstract
The aim of this study was to investigate how Trichinella spiralis infection can be affected by contraceptive pills in vivo. Methods included six groups of female Wistar rats; healthy, Trichinella infected, receiving combined contraceptive pills (COCPs), receiving progestin only pills (POPs), infected receiving COCPs and infected receiving POPs. Parasite burden was measured; adult worm counts, gravidity, larvae and reproductive capacity index). Histopathological examination, immunohistochemical detection of C-kit+ mast cells and Foxp3+ T-reg. cells in intestinal sections, eosinophils muscle infiltration and CPK level were performed. Rats infected and receiving COCPs showed a significant increase in parasitic burden, and infected receiving POPs showed a significant reduction compared to infected only, with a significant increase in nongravid females (Mean total worms=964.40±55.9, 742±52.63, 686±31.68, larvae/g=5030±198.75, 2490±143.18 and 4126±152,91, respectively). Intestinal sections from infected receiving COCPs showed intact mucosa (though the high inflammatory cells infiltrate), and significant increase in C-kit+ mast cells number and intensity (30.20±4.15 and 60.40±8.29), and Foxp3+ T-reg. cells (10±1.58). Infected receiving POPs showed a significantly less CPK (5886±574.40) and eosinophilic muscle infiltration (58±13.51). Oestrogen-containing pills established a favourable intestinal environment for Trichinella by enhancing Foxp+T-reg. cells and stabilizing C-kit+mast cells, while POPs gave a potential protection with less gravidity, larval burden and eosinophilic infiltrate. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
6. Reaching consensus on rumors.
- Author
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Merlone, U. and Radi, D.
- Subjects
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RUMOR , *CONSENSUS (Social sciences) , *MARKOV processes , *FORMALIZATION (Philosophy) , *STOCHASTIC processes , *SOCIAL facts - Abstract
Abstract: An important contribution in sociophysics is the Galam’s model of rumors spreading. This model provides an explanation of rumors spreading in a population and explains some interesting social phenomena such as the diffusion of hoaxes. In this paper the model has been reformulated as a Markov process highlighting the stochastic nature of the phenomena. This formalization allows us to derive conditions for consensus to be reached and for the existence of some interesting phenomena such as the emergence of impasses. The proposed formulation allows a deeper and more comprehensive analysis of the diffusion of rumors. [Copyright &y& Elsevier]
- Published
- 2014
- Full Text
- View/download PDF
7. Exploitation of renewable resources with differentiated technologies: An evolutionary analysis.
- Author
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Lamantia, F. and Radi, D.
- Subjects
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RESOURCE exploitation , *DYNAMICAL systems , *ENVIRONMENTAL impact analysis , *HYBRID systems , *RENEWABLE energy industry , *DISCRETE-time systems - Abstract
In this paper, we propose a dynamical model of technology adoption for the exploitation of a renewable natural resource. Each technology has a different efficiency and environmental impact. The process of technology adoption over time is modeled through an evolutionary game employed by profit maximizing exploiters. The loss in profits due to lower efficiency levels of environmentally-friendly technologies can be counterbalanced by the higher consumers’ propensity to pay for greener goods. The dynamics of the resource take place in continuous time, whereas the technology choice can be revised either in continuous-time or in discrete-time. In the latter case, the model assumes the form of a hybrid system, whose dynamics is mainly explored numerically. We shows that: (1) overexploitation of the resource arises whenever the reduction in harvesting due to a lower efficiency of clean technology is more than compensated by a higher propensity to pay for greener goods; (2) the difference between the fixed costs of these technologies can be exogenously fixed to provide an incentive for adopting clean technology without affecting the long-run level of the resource; and (3) in some cases, discrete switching of the technology causes overshooting in the dynamics whereas in others it enhances the stability of the system. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
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