15 results on '"Gardini, L."'
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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.
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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. Memory effects on binary choices with impulsive agents: Bistability and a new BCB structure.
- Author
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Gardini, L., Dal Forno, A., and Merlone, U.
- Subjects
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PHASE space , *LINEAR operators , *MEMORY - Abstract
After the seminal works by Schelling, several authors have considered models representing binary choices by different kinds of agents or groups of people. The role of the memory in these models is still an open research argument, on which scholars are investigating. The dynamics of binary choices with impulsive agents has been represented, in the recent literature, by a one-dimensional piecewise smooth map. Following a similar way of modeling, we assume a memory effect which leads the next output to depend on the present and the last state. This results in a two-dimensional piecewise smooth map with a limiting case given by a piecewise linear discontinuous map, whose dynamics and bifurcations are investigated. The map has a particular structure, leading to trajectories belonging only to a pair of straight lines. The system can have, in general, only attracting cycles, but the related periods and periodicity regions are organized in a complex structure of the parameter space. We show that the period adding structure, characteristic for the one-dimensional case, also persists in the two-dimensional one. The considered cycles have a symbolic sequence which is obtained by the concatenation of the symbolic sequences of cycles, which play the role of basic cycles in the bifurcation structure. Moreover, differently from the one-dimensional case, the coexistence of two attracting cycles is now possible. The bistability regions in the parameter space are investigated, evidencing the role of different kinds of codimension-two bifurcation points, as well as in the phase space and the related basins of attraction are described. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
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4. 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
5. 2D discontinuous piecewise linear map: Emergence of fashion cycles.
- Author
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Gardini, L., Sushko, I., and Matsuyama, K.
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DISCRETE-time systems , *FASHION , *PIECEWISE linear approximation , *BIFURCATION theory , *CONTINUOUS time systems - Abstract
We consider a discrete-time version of the continuous-time fashion cycle model introduced in Matsuyama, 1992. Its dynamics are defined by a 2D discontinuous piecewise linear map depending on three parameters. In the parameter space of the map periodicity, regions associated with attracting cycles of different periods are organized in the period adding and period incrementing bifurcation structures. The boundaries of all the periodicity regions related to border collision bifurcations are obtained analytically in explicit form. We show the existence of several partially overlapping period incrementing structures, that is, a novelty for the considered class of maps. Moreover, we show that if the time-delay in the discrete time formulation of the model shrinks to zero, the number of period incrementing structures tends to infinity and the dynamics of the discrete time fashion cycle model converges to those of continuous-time fashion cycle model. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
6. Lozi map embedded into the 2D border collision normal form.
- Author
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Sushko, I., Avrutin, V., and Gardini, L.
- Subjects
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ROTATIONAL motion - Abstract
A 2D piecewise linear continuous two-parameter map known as the Lozi map is a special case of the 2D border collision normal form depending on four parameters. In the present paper, we investigate how the bifurcation structure of the Lozi map is incorporated into the bifurcation structure of the 2D border collision normal form using an analytical representation of the boundaries of the largest periodicity regions related to the cycles with rotation number 1/n, n ⩾ 3. At the centre bifurcation boundary of the stability domain of the fixed point both maps are conservative which leads to a quite intricate bifurcation structure near this boundary. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
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7. Nonsmooth one-dimensional maps: some basic concepts and definitions.
- Author
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Sushko, I., Gardini, L., and Avrutin, V.
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SMOOTHING (Numerical analysis) , *DYNAMICAL systems , *DIFFERENCE equations - Abstract
The main purpose of the present survey is to contribute to the theory of dynamical systems defined by one-dimensionalpiecewise monotone maps. We recall some definitions known from the theory ofsmoothmaps, which are applicable to piecewise smooth ones, and discuss the notions specific for the considered class of maps. To keep the presentation clear for the researchers working in other fields, especially in applications, many examples are provided. We focus mainly on the notions and concepts which are used for the investigation of various kinds of attractors of a map and related bifurcation structures observed in its parameter space. [ABSTRACT FROM PUBLISHER]
- Published
- 2016
- Full Text
- View/download PDF
8. KNOT POINTS IN TWO-DIMENSIONAL MAPS AND RELATED PROPERTIES.
- Author
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Tramontana, F., Gardini, L., Fournier-Prunaret, D., and Charge, P.
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KNOT theory , *BIFURCATION theory , *JACOBIAN matrices , *FOLIATIONS (Mathematics) , *EQUATIONS - Abstract
We consider the class of two-dimensional maps of the plane for which there exists a whole one-dimensional singular set (for example, a straight line) that is mapped into one point, called a "knot point" of the map. The special character of this kind of point has been already observed in maps of this class with at least one of the inverses having a vanishing denominator. In that framework, a knot is the so-called focal point of the inverse map (it is the same point). In this paper, we show that knots may also exist in other families of maps, not related to an inverse having values going to infinity. Some particular properties related to focal points persist, such as the existence of a "point to slope" correspondence between the points of the singular line and the slopes in the knot, lobes issuing from the knot point and loops in infinitely many points of an attracting set or in invariant stable and unstable sets. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
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9. On the Fractal Structure of Basin Boundaries in Two-Dimensional Noninvertible Maps.
- Author
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Agliari, A., Gardini, L., and Mira, C.
- Subjects
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FRACTALS , *MATHEMATICAL mappings , *BIFURCATION theory - Abstract
In this paper we give an example of transition to fractal basin boundary in a two-dimensional map coming from the applicative context, in which the hard-fractal structure can be rigorously proved. That is, not only via numerical examples, although theoretically guided, as often occurs in maps coming from the applications, but also via analytical tools. The proposed example connects the two-dimensional maps of the real plane to the well-known complex map. [ABSTRACT FROM AUTHOR]
- Published
- 2003
- Full Text
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10. Invariant Curves and Focal Points in a Lyness Iterative Process.
- Author
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Gardini, L., Bischi, G.I., and Mira, C.
- Subjects
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ITERATIVE methods (Mathematics) , *INVARIANTS (Mathematics) , *RECURSIVE sequences (Mathematics) - Abstract
We investigate the properties of recurrence of the type [formula], known as Lyness iterations from [Lyness, 1942, 1945, 1961] and recently analyzed by several authors in the case a > 0, see e.g. [Kocic et al., 1993; Csornyei & Laczkovich, 2000]. We reconsider Lyness recurrences at the light of some recent results on iterated maps with denominator, given in [Bischi et al., 1999a], where new kinds of singularities, such as focal points and prefocal curves, have been defined. In this paper, in particular, we give an answer to one of the open problems proposed in [Kocic & Ladas, 1993, pp. 141] concerning the dynamic behavior of Lyness recurrences for a < 0. We also give some new results in the case a > 0, and we improve a previous result on Lyness "periodic recurrences". [ABSTRACT FROM AUTHOR]
- Published
- 2003
- Full Text
- View/download PDF
11. Bifurcations of steady forced flows in spectral models of rotating fluids.
- Author
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Gardini, L., Lupini, R., and Tebaldi, C.
- Subjects
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PHASE equilibrium , *OSCILLATIONS , *BIFURCATION theory , *PHYSICS - Abstract
In systems of ordinary differential equations representing the truncation to any order of the spectral, barotropic vorticity equation for two-dimensional flows in rotating fluids, subject to constant forcing and dissipation, large values of absolute rotation inhibit the occurrence of equilibrium states other than the basic, forced regime, and promote transitions to periodic oscillations, via Hopf bifurcation. [ABSTRACT FROM AUTHOR]
- Published
- 1987
- Full Text
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12. Hicks’ trade cycle revisited: cycles and bifurcations
- Author
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Gallegati, M., Gardini, L., Puu, T., and Sushko, I.
- Subjects
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BIFURCATION theory , *CURVES , *HYPOTHESIS , *MATHEMATICS - Abstract
In the Trade Cycle, Hicks introduced the idea that endogenous fluctuations could be coupled with a growth process via nonlinear processes. To argue for this hypothesis, Hicks used a piecewise-linear model. This paper shows the need for a reinterpretation of Hicks’ contribution in the light of a more careful mathematical investigation. In particular, it will be shown that only one bound is needed to have non explosive outcome if the equilibrium point is an unstable focus. It will also be shown that when the fixed point is unstable the attracting set has a particular structure: It is a one-dimensional closed invariant curve, made up of a finite number of linear pieces, on which the dynamics are either periodic or quasi-periodic. The conditions under which the model produces periodic or quasi-periodic trajectories and the related bifurcations as a function of the main economic parameters are determined. [Copyright &y& Elsevier]
- Published
- 2003
- Full Text
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13. Bifurcation structure in the skew tent map and its application as a border collision normal form.
- Author
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Sushko, I., Avrutin, V., and Gardini, L.
- Subjects
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BIFURCATION theory , *DYNAMICAL systems , *LINEAR operators - Abstract
The goal of the present paper is to collect the results related to dynamics of a one-dimensional piecewise linear map widely known as the skew tent map. These results may be useful for the researchers working on theoretical and applied problems in the field of nonsmooth dynamical systems. In particular, we propose the complete description of the bifurcation structure of the parameter space of the skew tent map, providing the related proofs. It is also shown how these results can be used to classify border collision bifurcations in one-dimensional piecewise smooth maps. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
14. Bifurcation structure in the skew tent map and its application as a border collision normal form.
- Author
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Sushko, I., Avrutin, V., and Gardini, L.
- Subjects
- *
BIFURCATION theory , *NUMERICAL solutions to differential equations , *NUMERICAL solutions to nonlinear differential equations , *BIFURCATION diagrams , *CATASTROPHE theory (Mathematics) - Abstract
The goal of the present paper is to collect the results related to dynamics of a one-dimensional piecewise linear map widely known as the skew tent map. These results may be useful for the researchers working on theoretical and applied problems in the field of nonsmooth dynamical systems. In particular, we propose the complete description of the bifurcation structure of the parameter space of the skew tent map, providing the related proofs. It is also shown how these results can be used to classify border collision bifurcations in one-dimensional piecewise smooth maps. [ABSTRACT FROM PUBLISHER]
- Published
- 2016
- Full Text
- View/download PDF
15. Border collision bifurcation of a resonant closed invariant curve.
- Author
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Zhusubaliyev, Zh. T., Avrutin, V., Sushko, I., and Gardini, L.
- Subjects
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NEIGHBORHOODS , *BIFURCATION diagrams - Abstract
This paper contributes to studying the bifurcations of closed invariant curves in piecewise-smooth maps. Specifically, we discuss a border collision bifurcation of a repelling resonant closed invariant curve (a repelling saddle-node connection) colliding with the border by a point of the repelling cycle. As a result, this cycle becomes attracting and the curve is destroyed, while a new repelling closed invariant curve appears (not in a neighborhood of the previously existing invariant curve), being associated with quasiperiodic dynamics. This leads to a global restructuring of the phase portrait since both curves mentioned above belong to basin boundaries of coexisting attractors. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
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