71 research outputs found
Competitive dynamics of lexical innovations in multi-layer networks
We study the introduction of lexical innovations into a community of language
users. Lexical innovations, i.e., new terms added to people's vocabulary, play
an important role in the process of language evolution. Nowadays, information
is spread through a variety of networks, including, among others, online and
offline social networks and the World Wide Web. The entire system, comprising
networks of different nature, can be represented as a multi-layer network. In
this context, lexical innovations diffusion occurs in a peculiar fashion. In
particular, a lexical innovation can undergo three different processes: its
original meaning is accepted; its meaning can be changed or misunderstood
(e.g., when not properly explained), hence more than one meaning can emerge in
the population; lastly, in the case of a loan word, it can be translated into
the population language (i.e., defining a new lexical innovation or using a
synonym) or into a dialect spoken by part of the population. Therefore, lexical
innovations cannot be considered simply as information. We develop a model for
analyzing this scenario using a multi-layer network comprising a social network
and a media network. The latter represents the set of all information systems
of a society, e.g., television, the World Wide Web and radio. Furthermore, we
identify temporal directed edges between the nodes of these two networks. In
particular, at each time step, nodes of the media network can be connected to
randomly chosen nodes of the social network and vice versa. In so doing,
information spreads through the whole system and people can share a lexical
innovation with their neighbors or, in the event they work as reporters, by
using media nodes. Lastly, we use the concept of "linguistic sign" to model
lexical innovations, showing its fundamental role in the study of these
dynamics. Many numerical simulations have been performed.Comment: 23 pages, 19 figures, 1 tabl
Is Poker a Skill Game? New Insights from Statistical Physics
During last years poker has gained a lot of prestige in several countries
and, beyond to be one of the most famous card games, it represents a modern
challenge for scientists belonging to different communities, spanning from
artificial intelligence to physics and from psychology to mathematics. Unlike
games like chess, the task of classifying the nature of poker (i.e., as 'skill
game' or gambling) seems really hard and it also constitutes a current problem,
whose solution has several implications. In general, gambling offers equal
winning probabilities both to rational players (i.e., those that use a
strategy) and to irrational ones (i.e., those without a strategy). Therefore,
in order to uncover the nature of poker, a viable way is comparing performances
of rational versus irrational players during a series of challenges. Recently,
a work on this topic revealed that rationality is a fundamental ingredient to
succeed in poker tournaments. In this study we analyze a simple model of poker
challenges by a statistical physics approach, with the aim to uncover the
nature of this game. As main result we found that, under particular conditions,
few irrational players can turn poker into gambling. Therefore, although
rationality is a key ingredient to succeed in poker, also the format of
challenges has an important role in these dynamics, as it can strongly
influence the underlying nature of the game. The importance of our results lies
on related implications, as for instance in identifying the limits poker can be
considered as a `skill game' and, as a consequence, which kind of format must
be chosen to devise algorithms able to face humans.Comment: 12 pages, 4 figure
Statistical Physics of the Spatial Prisoner's Dilemma with Memory-Aware Agents
We introduce an analytical model to study the evolution towards equilibrium
in spatial games, with `memory-aware' agents, i.e., agents that accumulate
their payoff over time. In particular, we focus our attention on the spatial
Prisoner's Dilemma, as it constitutes an emblematic example of a game whose
Nash equilibrium is defection. Previous investigations showed that, under
opportune conditions, it is possible to reach, in the evolutionary Prisoner's
Dilemma, an equilibrium of cooperation. Notably, it seems that mechanisms like
motion may lead a population to become cooperative. In the proposed model, we
map agents to particles of a gas so that, on varying the system temperature,
they randomly move. In doing so, we are able to identify a relation between the
temperature and the final equilibrium of the population, explaining how it is
possible to break the classical Nash equilibrium in the spatial Prisoner's
Dilemma when considering agents able to increase their payoff over time.
Moreover, we introduce a formalism to study order-disorder phase transitions in
these dynamics. As result, we highlight that the proposed model allows to
explain analytically how a population, whose interactions are based on the
Prisoner's Dilemma, can reach an equilibrium far from the expected one; opening
also the way to define a direct link between evolutionary game theory and
statistical physics.Comment: 7 pages, 5 figures. Accepted for publication in EPJ-
Fermionic Networks: Modeling Adaptive Complex Networks with Fermionic Gases
We study the structure of Fermionic networks, i.e., a model of networks based
on the behavior of fermionic gases, and we analyze dynamical processes over
them. In this model, particle dynamics have been mapped to the domain of
networks, hence a parameter representing the temperature controls the evolution
of the system. In doing so, it is possible to generate adaptive networks, i.e.,
networks whose structure varies over time. As shown in previous works, networks
generated by quantum statistics can undergo critical phenomena as phase
transitions and, moreover, they can be considered as thermodynamic systems. In
this study, we analyze Fermionic networks and opinion dynamics processes over
them, framing this network model as a computational model useful to represent
complex and adaptive systems. Results highlight that a strong relation holds
between the gas temperature and the structure of the achieved networks.
Notably, both the degree distribution and the assortativity vary as the
temperature varies, hence we can state that fermionic networks behave as
adaptive networks. On the other hand, it is worth to highlight that we did not
find relation between outcomes of opinion dynamics processes and the gas
temperature. Therefore, although the latter plays a fundamental role in gas
dynamics, on the network domain its importance is related only to structural
properties of fermionic networks.Comment: 19 pages, 5 figure
Gaussian Networks Generated by Random Walks
We propose a random walks based model to generate complex networks. Many
authors studied and developed different methods and tools to analyze complex
networks by random walk processes. Just to cite a few, random walks have been
adopted to perform community detection, exploration tasks and to study temporal
networks. Moreover, they have been used also to generate scale-free networks.
In this work, we define a random walker that plays the role of
"edges-generator". In particular, the random walker generates new connections
and uses these ones to visit each node of a network. As result, the proposed
model allows to achieve networks provided with a Gaussian degree distribution,
and moreover, some features as the clustering coefficient and the assortativity
show a critical behavior. Finally, we performed numerical simulations to study
the behavior and the properties of the cited model.Comment: 12 pages, 6 figure
Poker Cash Game: a Thermodynamic Description
Poker is one of the most popular card games, whose rational investigation
represents also one of the major challenges in several scientific areas,
spanning from information theory and artificial intelligence to game theory and
statistical physics. In principle, several variants of Poker can be identified,
although all of them make use of money to make the challenge meaningful and,
moreover, can be played in two different formats: tournament and cash game. An
important issue when dealing with Poker is its classification, i.e., as a
`skill game' or as gambling. Nowadays, its classification still represents an
open question, having a long list of implications (e.g., legal and healthcare)
that vary from country to country. In this study, we analyze Poker challenges,
considering the cash game format, in terms of thermodynamics systems. Notably,
we propose a framework to represent a cash game Poker challenge that, although
based on a simplified scenario, allows both to obtain useful information for
rounders (i.e., Poker players), and to evaluate the role of Poker room in this
context. Finally, starting from a model based on thermodynamics, we show the
evolution of a Poker challenge, making a direct connection with the probability
theory underlying its dynamics and finding that, even if we consider these
games as `skill games', to take a real profit from Poker is really hard.Comment: 9 pages, 1 figure. Contribute to the proceedings "Mathematical
Physics: from Theory to Applications" (European Physics Press
Poker as a Skill Game: Rational vs Irrational Behaviors
In many countries poker is one of the most popular card games. Although each
variant of poker has its own rules, all involve the use of money to make the
challenge meaningful. Nowadays, in the collective consciousness, some variants
of poker are referred to as games of skill, others as gambling. A poker table
can be viewed as a psychology lab, where human behavior can be observed and
quantified. This work provides a preliminary analysis of the role of
rationality in poker games, using a stylized version of Texas Hold'em. In
particular, we compare the performance of two different kinds of players, i.e.,
rational vs irrational players, during a poker tournament. Results show that
these behaviors (i.e., rationality and irrationality) affect both the outcomes
of challenges and the way poker should be classified.Comment: 15 pages, 5 figure
An Evolutionary Strategy based on Partial Imitation for Solving Optimization Problems
In this work we introduce an evolutionary strategy to solve combinatorial
optimization tasks, i.e. problems characterized by a discrete search space. In
particular, we focus on the Traveling Salesman Problem (TSP), i.e. a famous
problem whose search space grows exponentially, increasing the number of
cities, up to becoming NP-hard. The solutions of the TSP can be codified by
arrays of cities, and can be evaluated by fitness, computed according to a cost
function (e.g. the length of a path). Our method is based on the evolution of
an agent population by means of an imitative mechanism, we define `partial
imitation'. In particular, agents receive a random solution and then,
interacting among themselves, may imitate the solutions of agents with a higher
fitness. Since the imitation mechanism is only partial, agents copy only one
entry (randomly chosen) of another array (i.e. solution). In doing so, the
population converges towards a shared solution, behaving like a spin system
undergoing a cooling process, i.e. driven towards an ordered phase. We
highlight that the adopted `partial imitation' mechanism allows the population
to generate solutions over time, before reaching the final equilibrium. Results
of numerical simulations show that our method is able to find, in a finite
time, both optimal and suboptimal solutions, depending on the size of the
considered search space.Comment: 18 pages, 6 figure
Social Influences in Opinion Dynamics: the Role of Conformity
We study the effects of social influences in opinion dynamics. In particular,
we define a simple model, based on the majority rule voting, in order to
consider the role of conformity. Conformity is a central issue in social
psychology as it represents one of people's behaviors that emerges as a result
of their interactions. The proposed model represents agents, arranged in a
network and provided with an individual behavior, that change opinion in
function of those of their neighbors. In particular, agents can behave as
conformists or as nonconformists. In the former case, agents change opinion in
accordance with the majority of their social circle (i.e., their neighbors); in
the latter case, they do the opposite, i.e., they take the minority opinion.
Moreover, we investigate the nonconformity both on a global and on a local
perspective, i.e., in relation to the whole population and to the social circle
of each nonconformist agent, respectively. We perform a computational study of
the proposed model, with the aim to observe if and how the conformity affects
the related outcomes. Moreover, we want to investigate whether it is possible
to achieve some kind of equilibrium, or of order, during the evolution of the
system. Results highlight that the amount of nonconformist agents in the
population plays a central role in these dynamics. In particular, conformist
agents play the role of stabilizers in fully-connected networks, whereas the
opposite happens in complex networks. Furthermore, by analyzing complex
topologies of the agent network, we found that in the presence of radical
nonconformist agents the topology of the system has a prominent role; otherwise
it does not matter since we observed that a conformist behavior is almost
always more convenient. Finally, we analyze the results of the model by
considering that agents can change also their behavior over time.Comment: 22 pages, 12 figures, appears in Physica A: Statistical Mechanics and
its Applications (volume 414) 201
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