Hypergraph topological quantities for tagged social networks (2009)
Zlatić, Vinko, Ghoshal, Gourab, Caldarelli, Guido
Recent years have witnessed the emergence of a new class of social networks, that require us to move beyond previously employed representations of complex graph structures. A notable example is that...
Random hypergraphs and their applications (2009)
Ghoshal, Gourab, Zlatic, Vinko, Caldarelli, Guido, Newman, M. E. J.
In the last few years we have witnessed the emergence, primarily in on-line communities, of new types of social networks that require for their representation more complex graph structures than have...
Schroedinger-like PageRank equation and localization in the WWW (2008)
Perra, Nicola, Zlatic, Vinko, Chessa, Alessandro, Conti, Claudio, Donato, Debora, Caldarelli, Guido
The WorldWide Web is one of the most important communication systems we use in our everyday life. Despite its central role, the growth and the development of the WWW is not controlled by any central...
Barabasi Queueing Model and Invasion Percolation on a tree (2008)
Gabrielli, Andrea, Caldarelli, Guido
In this paper we study the properties of the Barab\'asi model of queueing under the hypothesis that the number of tasks is steadily growing in time. We map this model exactly onto an Invasion...
On the rich-club effect in dense and weighted networks (2008)
Zlatic, Vinko, Bianconi, Ginestra, Diaz-Guilera, Albert, Garlaschelli, Diego, Rao, Francesco, Caldarelli, Guido
For many complex networks present in nature only a single instance, usually of large size, is available. Any measurement made on this single instance cannot be repeated on different realizations. In...
Self-Organization and Complex Networks (2008)
Caldarelli, Guido, Garlaschelli, Diego
In this chapter we discuss how the results developed within the theory of fractals and Self-Organized Criticality (SOC) can be fruitfully exploited as ingredients of adaptive network models. In order...
A Self-organized model for network evolution (2008)
Caldarelli, Guido, Capocci, Andrea, Garlaschelli, Diego
Here we provide a detailed analysis, along with some extensions and additonal investigations, of a recently proposed self-organised model for the evolution of complex networks. Vertices of the...
Algorithms for representing network centrality, groups and density and clustered graph representation
Projects founded by the European Commission under the Information Society Technologies Programme (1998-2002) Geographical information plays an important role in the physical representation of the Net...
Projects founded by the European Commission under the Information Society Technologies Programme (1998-2002) The ability of drawing very large networks as e.g. large computer networks is of great...
Memory and Self Organization (2007)
Matteo Marsili Guido, Guido Caldarelli
The main result of this letter is that SOC naturally arises as a result of memory effects. We show that memory effects provide the mechanism for self organization. A general procedure to investigate...
Guido Caldarelli, Amos Maritan, Michele Vendruscolo
A temperature-like parameter is introduced in ordinary sandpiles models. A temperature dependent probability distribution is assigned for the sand toppling on sites of any height. In mean field...
Folksonomies and clustering in the collaborative system CiteULike (2007)
Capocci, Andrea, Caldarelli, Guido
We analyze CiteULike, an online collaborative tagging system where users bookmark and annotate scientific papers. Such a system can be naturally represented as a tripartite graph whose nodes...
Uncovering the topology of configuration space networks (2007)
Gfeller, David, Rios, Paolo De Los, De Lachapelle, David Morton, Caldarelli, Guido, Rao, Francesco
The configuration space network (CSN) of a dynamical system is an effective approach to represent the ensemble of configurations sampled during a simulation and their dynamic connectivity. To...
Critical transient in the Barab\'asi model of human dynamics (2007)
Gabrielli, Andrea, Caldarelli, Guido
We introduce an exact probabilistic description for L=2 of the Barab\'asi model for the dynamics of a list of L tasks. This permits to study the problem out of stationarity, and to solve explicitly...
Damaging and Cracks in Thin Mud Layers (2006)
Cafiero, Raffaele, Caldarelli, Guido, Gabrielli, Andrea
We present a detailed study of a two-dimensional minimal lattice model for the description of mud cracking in the limit of extremely thin layers. In this model each bond of the lattice is assigned to...
Fractal Growth from Local Instabilities (2006)
Cafiero, Raffaele, Caldarelli, Guido
We study, both with numerical simulations and theoretical methods, a cellular automata model for continuum equations describing growth processes in the presence of an external flux of particles. As a...
Self-organized network evolution coupled to extremal dynamics (2006)
Garlaschelli, Diego, Capocci, Andrea, Caldarelli, Guido
The interplay between topology and dynamics in complex networks is a fundamental but widely unexplored problem. Here, we study this phenomenon on a prototype model in which the network is shaped by a...
Trading strategies in the Italian interbank market (2006)
Iori, Giulia, Reno', Roberto, De Masi, Giulia, Caldarelli, Guido
Using a data set which includes all transactions among banks in the Italian money market, we study their trading strategies and the dependence among them. We use the Fourier method to compute the...
Temperature in complex networks (2006)
Garlaschelli, Diego, Ahnert, Sebastian E., Fink, Thomas M. A., Caldarelli, Guido
Various statistical-mechanics approaches to complex networks have been proposed to describe expected topological properties in terms of ensemble averages. Here we extend this formalism by introducing...
Spectral methods cluster words of the same class in a syntactic dependency network (2005)
Cancho, Ramon Ferrer I, Capocci, Andrea, Caldarelli, Guido
We analyze here a particular kind of linguistic network where vertices representwords and edges stand for syntactic relationships between words. The statisticalproperties of these networks have been...
Loops structure of the Internet at the Autonomous System Level (2004)
Bianconi, Ginestra, Caldarelli, Guido, Capocci, Andrea
We present here a study of the clustering and cycles in the graph of Internet at the Autonomous Systems level. We show that,even if the whole structure is changing with time, the statistical...
Detecting communities in large networks (2004)
Capocci, Andrea, Servedio, Vito D. P., Caldarelli, Guido, Colaiori, Francesca
We develop an algorithm to detect community structure in complex networks. The algorithm is based on spectral methods and takes into account weights and links orientations. Since the method detects...
Preferential Exchange: Strengthening Connections in Complex Networks (2003)
Caldarelli, Guido, Coccetti, Fabrizio, Rios, Paolo De Los
Many social, technological and biological interactions involve network relationships whose outcome intimately depends on the structure of the network and on the strengths of the connections. Yet,...
Caldarelli, Guido, Cartozo, Cecile Caretta, Rios, Paolo De Los, Servedio, Vito D. P.
The widespread occurrence of an inverse square relation in the hierarchical distribution of sub-communities within communities (or sub-species within species) has been recently invoked as a signature...
The scale-free topology of market investments (2003)
Garlaschelli, Diego, Battiston, Stefano, Castri, Maurizio, Servedio, Vito D. P., Caldarelli, Guido
We propose a network description of large market investments, where both stocks and shareholders are represented as vertices connected by weighted links corresponding to shareholdings. In this...
Number of h-cycles in the Internet at the Autonomous Systems level (2003)
Bianconi, Ginestra, Caldarelli, Guido, Capocci, Andrea
We present here a study of the clustering and cycles present in the graph of Internet at the Autonomous Systems level. Even if the whole structure is changing with time, we present some evidence that...
Vertex Intrinsic Fitness: How to Produce Arbitrary Scale-Free Networks (2003)
Servedio, Vito D. P., Caldarelli, Guido, Butta`, Paolo
We study a recent model of random networks based on the presence of an intrinsic character of the vertices called fitness. The vertices fitnesses are drawn from a given probability distribution...
Assortative model for social networks (2003)
Catanzaro, Michele, Caldarelli, Guido, Pietronero, Luciano
In this paper we present a new version of a network growth model, generalized in order to describe the behavior of social networks. The case of study considered is the preprint archive at...
Generalized Network Growth: from Microscopic Strategies to the Real Internet Properties (2003)
Caldarelli, Guido, Rios, Paolo De Los, Pietronero, Luciano
In this paper we present a generalized model for network growth that links the microscopical agent strategies with the large scale behavior. This model is intended to reproduce the largest number of...
Cycles structure and local ordering in complex networks (2002)
Caldarelli, Guido, Pastor-Satorras, Romualdo, Vespignani, Alessandro
We study the properties of metrics aimed at the characterization of grid-like ordering in complex networks. These metrics are based on the global and local behavior of cycles of order four, which are...
Topology of correlation based minimal spanning trees in real and model markets (2002)
Bonanno, Giovanni, Caldarelli, Guido, Lillo, Fabrizio
We present here a topological characterization of the minimal spanning tree that can be obtained by considering the price return correlations of stocks traded in a financial market. We compare the...
Dynamic Fracture Model for Acoustic Emission (2002)
Minozzi, Manuela, Caldarelli, Guido, Pietronero, Luciano, Zapperi, Stefano
We study the acoustic emission produced by micro-cracks using a two-dimensional disordered lattice model of dynamic fracture, which allows to relate the acoustic response to the internal damage of...
Cold and Warm Denaturation of Proteins (2002)
Caldarelli, Guido, Rios, Paolo De Los
We introduce a simplified protein model where the water degrees of freedom appear explicitly (although in an extremely simplified fashion). Using this model we are able to recover both the warm and...
Percolation in real Wildfires (2001)
Caldarelli, Guido, Frondoni, Raffaella, Gabrielli, Andrea, Montuori, Marco, Retzlaff, Rebecca, Ricotta, Carlo
This paper focuses on the statistical properties of wild-land fires and, in particular, investigates if spread dynamics relates to simple invasion model. The fractal dimension and lacunarity of three...
Statistical Features of Drainage Basins in Mars Channel Networks (2001)
Caldarelli, Guido, Rios, Paolo De Los, Montuori, Marco
Erosion by flowing water is one of the major forces shaping the surface of Earth. Studies in the last decade have shown, in particular, that the drainage region of rivers, where water is collected,...
Discretized Diffusion Processes (2000)
Ciliberti, Stefano, Caldarelli, Guido, Rios, Paolo De Los, Pietronero, Luciano, Zhang, Yi-Cheng
We study the properties of the ``Rigid Laplacian'' operator, that is we consider solutions of the Laplacian equation in the presence of fixed truncation errors. The dynamics of convergence to the...
Putting Proteins back into Water (2000)
Rios, Paolo De Los, Caldarelli, Guido
We introduce a simplified protein model where the solvent (water) degrees of freedom appear explicitly (although in an extremely simplified fashion). Using this model we are able to recover the...
Fractal Growth from Local Instabilities (2000)
Cafiero, Raffaele, Caldarelli, Guido
We study, both with numerical simulations and theoretical methods, a cellular automata model for continuum equations describing growth processes in the presence of an external flux of particles. As a...
Roughness of fracture surfaces (2000)
Parisi, Andrea, Caldarelli, Guido, Pietronero, Luciano
We study the fracture surface of three dimensional samples through a model for quasi-static fractures known as Born Model. We find for the roughness exponent a value of 0.5 expected for ``small...
Damaging and Cracks in Thin Mud Layers (2000)
Cafiero, Raffaele, Caldarelli, Guido, Gabrielli, Andrea
We present a detailed study of a two-dimensional minimal lattice model for the description of mud cracking in the limit of extremely thin layers. In this model each bond of the lattice is assigned to...
Invasion Percolation with Temperature and the Nature of SOC in Real Systems (1999)
Gabrielli, Andrea, Caldarelli, Guido, Pietronero, Luciano
We show that the introduction of thermal noise in Invasion Percolation (IP) brings the system outside the critical point. This result suggests a possible definition of SOC systems as ordinary...
Cold and Warm Denaturation of Hydrophobic Polymers (1999)
Rios, Paolo De Los, Caldarelli, Guido
We introduce a polymer model where the transition from swollen to compact configurations is due to interactions between the monomers and the solvent. These interactions are the origin of the...
Stationary Self-Organized Fractal Structures in an Open,Dissipative Electrical System (1998)
Marani, Marco, Banavar, Jayanth R., Caldarelli, Guido, Maritan, Amos, Rinaldo, Andrea
We study the stationary state of a Poisson problem for a system of N perfectly conducting metal balls driven by electric forces to move within a medium of very low electrical conductivity onto which...
Modelling coevolution in multispecies communities (1998)
Caldarelli, Guido, Higgs, Paul G., McKane, Alan J.
We introduce the Webworld model, which links together the ecological modelling of food web structure with the evolutionary modelling of speciation and extinction events. The model describes dynamics...
Fixed scale transformation approach for born model of fractures (1995)
Caldarelli, Guido, Vespignani, Alessandro
We use the Fixed Scale Transformation theoretical approach to study the problem of fractal growth in fractures generated by using the Born Model. In this case the application of the method is more...
Optimal path and directed percolation (1995)
De Los Rios, Paolo, Caldarelli, Guido, Maritan, Amos, Seno, Flavio
An efficient transfer matrix technique is introduced to study directed optimal paths in two and three dimensions.
Memory and Self Organization (1994)
Marsili, Matteo, Caldarelli, Guido
The main result of this letter is that SOC naturally arises as a result of memory effects. We show that memory effects provide the mechanism for self organization. A general procedure to investigate...
A NUMERICAL STUDY ON THE EVOLUTION OF PORTFOLIO RULES
Guido Caldarelli, M. Piccioni, E. Sciubba
In this paper we test computationally the performance of CAPM in an evolutionary setting. In particular we study the stability of wealth distribution in a financial market where some traders invest...
A network analysis of the Italian overnight money market
Iori, Giulia, De Masi, Giulia, Precup, Ovidiu Vasile, Gabbi, Giampaolo, Caldarelli, Guido
A Network Analysis of the Italian Overnight Money Market
Giulia Iori, Giulia De Masi, Ovidiu Precup, Giampaolo Gabbi, Guido Caldarelli
The objective of this paper is to analyze, by employing methods of statistical mechanics of complex networks, the network topology of the Italian segment of the European overnight money market. We...
Trading strategies in the Italian Interbank Market
Giulia Iori, Roberto Renò, Giulia De Masi, Guido Caldarelli
Using a data set which includes all transactions among banks in the Italian money market, we study their trading strategies and the dependence among them. We use the Fourier method to compute the...
A fitness model for the Italian Interbank Money Market
Giulia De Masi, Giulia Iori, Guido Caldarelli
We use the theory of complex networks in order to quantitatively characterise the formation of communities in a particular financial market. The system is composed by different banks exchanging on a...
The scale-free topology of market investments
Diego Garlaschelli, Stefano Battiston, Maurizio Castri, Guido Caldarelli
We propose a network description of large market investments, where both stocks and shareholders are represented as vertices connected by weighted links corresponding to shareholdings. In this...
Trading strategies in the Italian interbank market
Giulia Iori, Roberto Reno', Giulia De Masi, Guido Caldarelli
Using a data set which includes all transactions among banks in the Italian money market, we study their trading strategies and the dependence among them. We use the Fourier method to compute the...