Université de Fribourg

Statistical mechanics of competitive resource allocation using agent-based models

Chakraborti, Anirban ; Challet, Damien ; Chatterjee, Arnab ; Marsili, Matteo ; Zhang, Yi-Cheng ; Chakrabarti, Bikas K.

In: Physics Reports, 2015, vol. 552, p. 1–25

Demand outstrips available resources in most situations, which gives rise to competition, interaction and learning. In this article, we review a broad spectrum of multi-agent models of competition (El Farol Bar problem, Minority Game, Kolkata Paise Restaurant problem, Stable marriage problem, Parking space problem and others) and the methods used to understand them analytically. We emphasize the...

Université de Fribourg

Emergence of heterogeneity in a noncompetitive resource allocation problem

Matzke, Christina ; Challet, Damien

In: Physical Review E statistical, nonlinear, and soft matter physics, 2011, vol. 84, no. 1, p. 016107

Tuning one’s shower in some hotels may turn into a challenging coordination game with imperfect information. The temperature sensitivity increases with the number of agents, making the problem possibly unlearnable. Because there is in practice a finite number of possible tap positions, identical agents are unlikely to reach even approximately their favorite water temperature. We show that a...

Université de Fribourg

Structure-preserving desynchronization of minority games

Mosetti, Giancarlo ; Challet, Damien ; Solomon, S.

In: The European Physical Journal B, 2009, vol. 71, no. 4, p. 573-577

Perfect synchronicity in N-player games is a useful theoretical dream, but communication delays are inevitable and may result in asynchronous interactions. Some systems such as financial markets are asynchronous by design, and yet most theoretical models assume perfectly synchronized actions. We propose a general method to transform standard models of adaptive agents into asynchronous systems...

Université de Fribourg

Emergence of product differentiation from consumer heterogeneity and asymmetric information

Lü, L. ; Medo, Matúš ; Zhang, Yi-Cheng ; Challet, Damien

In: The European Physical Journal B, 2008, vol. 64, no. 2, p. 293-300

We introduce a fully probabilistic framework of consumer product choice based on quality assessment. It allows us to capture many aspects of marketing such as partial information asymmetry, quality differentiation, and product placement in a supermarket.

Université de Fribourg

Feedback and efficiency in limit order markets

Challet, Damien

In: Physica A: Statistical Mechanics and its Applications, 2008, vol. 387, no. 15, p. 3831-3836

A consistency criterion for price impact functions in limit order markets is proposed that prohibits chain arbitrage exploitation. Both the bid-ask spread and the feedback of sequential market orders of the same kind onto both sides of the order book are essential to ensure consistency at the smallest time scale. All the stocks investigated in Paris Stock Exchange have consistent price impact...

Université de Fribourg

Taking a shower in Youth Hostels: risks and delights of heterogeneity

Matzke, Christina ; Challet, Damien

Tuning one's shower in some hotels may turn into a challenging coordination game with imperfect information. The temperature sensitivity increases with the number of agents, making the problem possibly unlearnable. Because there is in practice a finite number of possible tap positions, identical agents are unlikely to reach even approximately their favorite water temperature. Heterogeneity allows...

Université de Fribourg

The therapy to shock therapy: optimal dynamical policies for transition economies

Challet, Damien ; Solomon, Sorin ; Yaari, Gur

We show that a simple model reproduces very closely the evolution of the GDP in constant dollars of many countries during the times of recession and recovery. A theoretical analysis illustrates how an optimal dynamical policy reduces both recession duration and severity, and increases the value of GDP at all times. We propose a criterion to distinguish a posteriori a dynamical policy from a...

Université de Fribourg

Fat tails, long memory, maturity and ageing in open-source software projects

Challet, Damien ; Valverde, Sergi

We report activity data analysis on several open source software projects, focusing on time between modifications and on the number of files modified at once. Both have fat-tailed distributions, long-term memory, and display systematic non-trivial cross-correlations, suggesting that quiet periods are followed by cascading modifications. In addition the maturity of a software project can be...

Université de Fribourg

Dynamical instabilities in a simple minority game with discounting

Challet, Damien ; De Martino, Andrea ; Marsili, Matteo

In: Journal of Statistical Mecanics, Theory and Experiment (2008) L04004

We explore the effect of discounting and experimentation in a simple model of interacting adaptive agents. Agents belong to either of two types and each has to decide whether to participate a game or not, the game being profitable when there is an excess of players of the other type. We find the emergence of large fluctuations as a result of the onset of a dynamical instability which may arise...

Université de Fribourg

Minority games with heterogeneous timescales

Mosetti, Giancarlo ; Challet, Damien ; Zhang, Yi-Cheng

In: Physica A: Statistical Mechanics and its Applications, 2006, vol. 365, no. 2, p. 529-542

Minority games where groups of agents remember, react or incorporate information with different timescales are investigated. We support our findings by analytical arguments whenever possible.