Modelling the social dynamics of contagion and discovery using dynamical processes on complex networks.

PhD Thesis.Complex networks have been successfully used to describe the social structure on top of which many real-world social processes take place. In this thesis, I focus on the development of network models that aim at capturing the fundamental mechanisms behind the dynamics of adoption of ideas, behaviours, or items. I start considering the transmission of a single idea from one individual to another, in an epidemic-like fashion. Recent evidence has shown that mechanisms of complex contagion can effectively capture the fundamental rules of social reinforcement and peer pressure proper of social systems. Along this line, I propose a model of complex recovery in which the social influence mechanism acts on the recovery rule rather than on the infection one, leading to explosive behaviours. Yet, in human communication, interactions can occur in groups. I thus expand the pairwise representation given by graphs using simplicial complexes instead. I develop a model of simplicial contagion, showing how the inclusion of these higher-order interactions can dramatically alter the spreading dynamics. I then consider an individual and model the dynamics of discovery as paths of sequential adoptions, with the first visit of an idea representing a novelty. Starting from the empirically observed dynamics of correlated novelties, according to which one discovery leads to another, I develop a model of biased random walks in which the exploration of the interlinked space of possible discoveries has the byproduct of influencing also the strengths of their connections. Balancing exploration and exploitation, the model reproduces the basic footprints of real-world innovation processes. Nevertheless, people do not live and work in isolation, and social ties can shape their behaviours. Thus, I consider interacting discovery processes to investigate how social interactions contribute to the collective emergence of new ideas and teamwork, and explorers can exploit opportunities coming from their social contacts

Topology Reconstruction of Dynamical Networks via Constrained Lyapunov Equations

The network structure (or topology) of a dynamical network is often unavailable or uncertain. Hence, we consider the problem of network reconstruction. Network reconstruction aims at inferring the topology of a dynamical network using measurements obtained from the network. In this technical note we define the notion of solvability of the network reconstruction problem. Subsequently, we provide necessary and sufficient conditions under which the network reconstruction problem is solvable. Finally, using constrained Lyapunov equations, we establish novel network reconstruction algorithms, applicable to general dynamical networks. We also provide specialized algorithms for specific network dynamics, such as the well-known consensus and adjacency dynamics.Comment: 8 page

Putting Chinese natural knowledge to work in an eighteenth-century Swiss canton: the case of Dr Laurent Garcin

Symposium: S048 - Putting Chinese natural knowledge to work in the long eighteenth centuryThis paper takes as a case study the experience of the eighteenth-century Swiss physician, Laurent Garcin (1683-1752), with Chinese medical and pharmacological knowledge. A Neuchâtel bourgeois of Huguenot origin, who studied in Leiden with Hermann Boerhaave, Garcin spent nine years (1720-1729) in South and Southeast Asia as a surgeon in the service of the Dutch East India Company. Upon his return to Neuchâtel in 1739 he became primus inter pares in the small local community of physician-botanists, introducing them to the artificial sexual system of classification. He practiced medicine, incorporating treatments acquired during his travels. taught botany, collected rare plants for major botanical gardens, and contributed to the Journal Helvetique on a range of topics; he was elected a Fellow of the Royal Society of London, where two of his papers were read in translation and published in the Philosophical Transactions; one of these concerned the mangosteen (Garcinia mangostana), leading Linnaeus to name the genus Garcinia after Garcin. He was likewise consulted as an expert on the East Indies, exotic flora, and medicines, and contributed to important publications on these topics. During his time with the Dutch East India Company Garcin encountered Chinese medical practitioners whose work he evaluated favourably as being on a par with that of the Brahmin physicians, whom he particularly esteemed. Yet Garcin never went to China, basing his entire experience of Chinese medical practice on what he witnessed in the Chinese diaspora in Southeast Asia (the ‘East Indies’). This case demonstrates that there were myriad routes to Europeans developing an understanding of Chinese natural knowledge; the Chinese diaspora also afforded a valuable opportunity for comparisons of its knowledge and practice with other non-European bodies of medical and natural (e.g. pharmacological) knowledge.postprin

College of Arts and Sciences

Cornell University Courses of Study Vol. 101 2009/201