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Scientific Report 2007-2009
Condensed matter physics and biophysics
C11. Statistical physics of information and social dynamics
Statistical physics has proven to be a very fruitful
framework to describe phenomena outside the realm of
traditional physics. The last years have witnessed the
attempt by physicists to study collective phenomena
emerging from the interactions of individuals as elementary
units in social structures [1]. Our group is particularly
active on a wide list of topics ranging from opinion,
cultural and language dynamics to the dynamics of
online social communities. In all these activities a crucial
element is the information shared in specific groups
and one is interested in understanding how this information
emerges, spreads and gets shared, is organized
and eventually retrieved. Here we only summarizes a
few examples.
Online social systems and human computing
The rise of Web 2.0 has dramatically changed the
way we view the relation between on-line information
and on- line users and prompts a new research agenda
which complements the Web Science vision with analytical
tools and modeling paradigms from the theory of
complex networks. User-driven information networks in
particular, i.e., networks of on-line resources built in a
bottom-up fashion by Web users, have gained a central
role and are regarded as an increasingly important asset.
Understanding their structure and evolution brings forth
new challenges because user-driven information networks
entangle cognitive, behavioral and social aspects of human
agents with the structure of the underlying technological
system, effectively creating techno-social systems
that display rich emergent features and emergent semantics
[2]. These subjects have been investigated in the
framework of EU STREP Project TAGora (www.tagoraproject.eu).
Information Theory and Complexity One of the
most challenging issues of recent years is presented by the
overwhelming mass of available data. While this abundance
of information and the extreme accessibility to it
represents an important cultural advance, it raises on the
other hand the problem of retrieving relevant information.
Clearly the need for effective tools for information
retrieval and analysis is becoming more urgent as the
databases continue to grow. Recently we introduced a
new automatic method for the extraction of information
codified as sequences of characters. The method exploits
concepts of information theory to address the fundamental
problem of identifying and defining the most suitable
tools to extract, in a automatic and agnostic way, information
from a generic string of characters.
Phylogenetics While well established results are
available for perfect phylogenies (i.e. evolutionary history
that can be associated to a tree topology), when a
deviation from a tree-like structure has to be considered
very little is known, despite the efforts in this direction.
Our activity on phylogeny reconstruction aims at providing
methods to identify and to correctly take into
account deviations from perfect phylogenies and also at
providing the community with suitable benchmarks to
test the validity of inferred phylogenies. One crucial
problem, once a tree or a network is reconstructed, is
to determine how reliable it is, i.e. how well it represents
the true evolutionary history.
Language dynamics Language dynamics is an
emerging field that focuses on all processes related to
the emergence, change, evolution, interactions and extinction
of languages [3]. Our activity in this area has
been focused so far to the introduction of ”simple” language
games to investigate the emergence of names in
a population of individuals. The Naming Game (NG)
possibly represents the simplest example of the complex
processes leading progressively to the establishment
of human-like languages. More recently we introduced
a promising modeling scheme to investigate the emergence
of categories, the Category Game (CG) [4]. In this
framework we addressed the open problem concerning
the emergence of a small number of forms out of a diverging
number of meanings, e.g., the basic color terms
for colors (see Figure 1).
Figure 1: An example of the results of the Category Game.
After 10 4 games, the pattern of categories and associated
color terms are stable throughout the population. Different
agents in one population have slightly different category
boundaries, but the agreement is almost perfect (larger than
90%). As for each category, a focal color point is defined as
the average of the midpoints of the same category across the
population. Different populations may develop different final
patterns.
References
1. C. Castellano et al., Rev. Mod. Phys. 81 591 (2009).
2. C. Cattuto et al., PNAS 106, 10511(2009).
3. V. Loreto et al., Nature Physics, 3, 758 (2007).
4. A. Puglisi et al., PNAS 105, 7936 (2008).
Authors
V. Loreto, A. Baldassarri, A. Capocci, C. Castellano, C.
Cattuto, A. Puglisi, V.D.P. Servedio
http://www.informationdynamics.it/
Sapienza Università di Roma 64 Dipartimento di Fisica