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43
On the Nature of the Stock Market: Simulation and Experiments
, 2000
"... Over the last few years there has been a surge of activity within the physics community in the emerging field of Econophysics—the study of economic systems from a physicist’s perspective. Physicists tend to take a different view than economists and other social scientists, being interested in such t ..."
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Over the last few years there has been a surge of activity within the physics community in the emerging field of Econophysics—the study of economic systems from a physicist’s perspective. Physicists tend to take a different view than economists and other social scientists, being interested in such topics as phase transitions and fluctuations. In this dissertation two simple models of stock exchange are developed and simulated numerically. The first is characterized by centralized trading with a market maker. Fluctuations are driven by a stochastic component in the agents ’ forecasts. As the scale of the fluctuations is varied a critical phase transition is discovered. Unfortunately, this model is unable to generate realistic market dynamics. The second model discards the requirement of centralized trading. In this case the stochastic driving force is Gaussiandistributed “news events ” which are public knowledge. Under variation of the control parameter the model exhibits two phase transitions: both a first and a secondorder (critical). The decentralized model is able to capture many of the interesting properties
Perturbing the topology of the Game of Life increases its robustness to asynchrony
, 2004
"... Abstract. An experimental analysis of the asynchronous version of the “Game of Life ” is performed to estimate how topology perturbations modify its evolution. We focus on the study of a phase transition from an “inactivesparse phase ” to a “labyrinth phase ” and produce experimental data to quanti ..."
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Abstract. An experimental analysis of the asynchronous version of the “Game of Life ” is performed to estimate how topology perturbations modify its evolution. We focus on the study of a phase transition from an “inactivesparse phase ” to a “labyrinth phase ” and produce experimental data to quantify these changes as a function of the density of the initial configuration, the value of the synchrony rate, and the topology missinglink rate. An interpretation of the experimental results is given using the hypothesis that initial “germs ” colonize the whole lattice and the validity of this hypothesis is tested. 1
Critical Values in Asynchronous Random Boolean Networks
 Advances in Artificial Life, ECAL2003
, 2003
"... Wherever we see life, we see dierent kinds of complex networks, reason why they are studied across various elds of science. Random Boolean Networks (RBNs) form a special class in which the links between the nodes and the boolean functions are speci ed at random. ..."
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Cited by 9 (1 self)
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Wherever we see life, we see dierent kinds of complex networks, reason why they are studied across various elds of science. Random Boolean Networks (RBNs) form a special class in which the links between the nodes and the boolean functions are speci ed at random.
Distributed simulation with cellular automata: Architecture and applications
 In J. Pavelka, G. Tel, & M. Bartosek (Eds
, 1999
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Directed Percolation arising in Stochastic Cellular Automata Analysis
, 2008
"... Cellular automata are both seen as a model of computation and as tools to model real life systems. Historically they were studied under synchronous dynamics where all the cells of the system are updated at each time step. Meanwhile the question of probabilistic dynamics emerges: on the one hand, to ..."
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Cited by 8 (2 self)
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Cellular automata are both seen as a model of computation and as tools to model real life systems. Historically they were studied under synchronous dynamics where all the cells of the system are updated at each time step. Meanwhile the question of probabilistic dynamics emerges: on the one hand, to develop cellular automata which are capable of reliable computation even when some random errors occur [24,14,13]; on the other hand, because synchronous dynamics is not a reasonable assumption to simulate real life systems. Among cellular automata a specific class was largely studied in synchronous dynamics: the elementary cellular automata (ECA). These are the "simplest" cellular automata. Nevertheless they exhibit complex behaviors and even Turing universality. Several studies [20,7,8,5] have focused on this class under αasynchronous dynamics where each cell has a probability α to be updated independently. It has been shown that some of these cellular automata exhibit interesting behavior such as phase transition when the asynchronicity rate α varies. Due to their richness of behavior, probabilistic cellular automata are also very hard to study. Almost nothing is known of their behavior [20]. Understanding these "simple " rules is a key step to analyze more complex systems. We present here a coupling between oriented percolation and ECA 178 and confirms observations made in [5] that percolation may arise in cellular automata. As a consequence this coupling shows that there is a positive probability that the ECA 178 does not reach a stable configuration with positive probability as soon as the initial configuration is not a stable configuration and α> 0.996. Experimentally, this result seems to stay true as soon as α> αc ≈ 0.5.
The Effects of Randomness in Asynchronous 1D Cellular Automata
, 1994
"... Cellular automata are used as models of emergent computation and artificial life. They are usually simulated under synchronous and deterministic conditions. Thus, they are evolved without the existence of randomness, or noise. However, noise is unavoidable in the real world. The objective of the pre ..."
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Cellular automata are used as models of emergent computation and artificial life. They are usually simulated under synchronous and deterministic conditions. Thus, they are evolved without the existence of randomness, or noise. However, noise is unavoidable in the real world. The objective of the present paper is to show three major effects caused by the existence or nonexistence of randomness in the computation order, which is a type of environmental noise, experimentally in twoneighbor onedimensional asynchronous cellular automata (1DACA). The first major effect is that certain 1DACA, which generate nonchaotic patterns when not randomized, generate &quot;edgeofchaos &quot; patterns when randomized. Some of these patterns are similar to those generated using Wolfram's class IV automata or coupled map lattices. The second is that certain properties of 1DACA, such as mortality of domains of 1's or splitting domains of 0's into two, are fully expressed in their spatiotemporal patterns if the computation order is randomized, though they are only partially expressed if not randomized. The third is that phantom phenomena, which almost never occur if there is no noise, sometimes occur when randomized. The characteristics of patterns generated by several 1DACA are drastically changed from uniform patterns to patterns with multiple or chaotic phases when the randomness is weaken. Several other phenomena are also observed.
Searching for Rhythms in Asynchronous Random Boolean Networks
 Alife VII: Proceedings of the Seventh International Conference
"... Many interesting properties of Boolean networks, cellular automata, and other models of complex systems rely heavily on the use of synchronous updating of the individual elements. This has motivated some researchers to claim that, if the natural systems being modelled lack any clear evidence of ..."
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Many interesting properties of Boolean networks, cellular automata, and other models of complex systems rely heavily on the use of synchronous updating of the individual elements. This has motivated some researchers to claim that, if the natural systems being modelled lack any clear evidence of synchronously driven elements, then asynchronous rules should be used by default. Given that standard asynchronous updating precludes the possibility of strictly cyclic attractors, does this mean that asynchronous Boolean networks, cellular automata, etc., are inherently bad choices at the time of modelling rhythmic phenomena ? In this paper we focus on this subsidiary issue for the case of Asynchronous Random Boolean Networks (ARBNs). We nd that it is rather simple to dene measures of pseudoperiodicity by using correlations between states and suciently relaxed statistical constraints. These measures can be used to guide an evolutionary search process to nd appropriate exam...
On Fireflies, Cellular Systems, and Evolware
"... Many observers have marveled at the beauty of the synchronous flashing of fireflies that has an almost hypnotic effect. In this paper we consider the issue of evolving twodimensional cellular automata as well as random boolean networks to solve the firefly synchronization task. The task was success ..."
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Cited by 4 (1 self)
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Many observers have marveled at the beauty of the synchronous flashing of fireflies that has an almost hypnotic effect. In this paper we consider the issue of evolving twodimensional cellular automata as well as random boolean networks to solve the firefly synchronization task. The task was successfully solved by means of cellular programming based coevolution performing computations in a completely local manner, each cell having access only to its immediate neighbor's states. An FPGAbased...
Asynchronous 1D Cellular Automata and the Effects of Fluctuation and Randomness  Extended version 
, 1997
"... Cellular automata are used as models of emergent computation and artificial life. They are usually simulated under synchronous and deterministic conditions. Thus, they are evolved without existence of noise, i.e., fluctuation or randomness. However, noise is unavoidable in real world. The target of ..."
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Cited by 4 (0 self)
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Cellular automata are used as models of emergent computation and artificial life. They are usually simulated under synchronous and deterministic conditions. Thus, they are evolved without existence of noise, i.e., fluctuation or randomness. However, noise is unavoidable in real world. The target of the present paper is to show the following two effects and several other phenomena caused by existence or nonexistence of noise in the computation order in onedimensional asynchronous cellular automata (1DACA) experimentally. One major effect is that certain properties of 2neighbor 1DACA are fully expressed in their patterns if certain level of noise exists, though they are only partially expressed if no noise exists. The patterns generated by 1DACA may have characteristics, such as mortality of domains of 1's or splitting domains of 0's into two. These characteristics, which are coded in the "chromosome" of the automata, i.e., the lookup table, are fully expressed only when the computa...
Extensions to Time Warp Parallel Simulation for Spatial Decomposed Applications
 In Proceedings of the Fourth United Kingdom Simulation Society Conference (UKSim 99
, 1999
"... In recent years, the use of discrete event simulation to solve problems from natural sciences has become more common as the dynamic time evolution of the realworld system is naturally incorporated in the discrete event system model. The parallel simulation of these discrete event systems puts some ..."
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In recent years, the use of discrete event simulation to solve problems from natural sciences has become more common as the dynamic time evolution of the realworld system is naturally incorporated in the discrete event system model. The parallel simulation of these discrete event systems puts some extra requirements on the parallel synchronization schemes such as Time Warp. The large scientific problems require efficient memory management both time and space efficientand parallelism control to achieve satisfactory performance.