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SUMMARY:Network Economics seminar / Diffusion and Cascading Behavior in Ra
 ndom Networks - Marc LeLarge
DTSTART:20101210T110000Z
DTEND:20101210T120000Z
UID:TALK28368@talks.cam.ac.uk
CONTACT:Microsoft Research Cambridge Talks Admins
DESCRIPTION:The spread of new ideas\, behaviors or technologies has been e
 xtensively studied using epidemic models. Here we consider a model of diff
 usion where the individuals' behavior is the result of a strategic choice.
  We study a simple coordination game with binary choice and give a conditi
 on for a new action to become widespread in a random network. We also anal
 yze the possible equilibria of this game and identify conditions for the c
 oexistence of both strategies in large connected sets. Finally we look at 
 how can firms use social networks to promote their goals with limited info
 rmation.\nOur results differ strongly from the one derived with epidemic m
 odels. \nIn particular\, we show that connectivity plays an ambiguous role
 : while it allows the diffusion to spread\, when the network is highly con
 nected\, the diffusion is also limited by high-degree nodes which are very
  stable. In the case of a sparse random network of interacting agents\, we
  compute the contagion threshold for a general diffusion model and show th
 e existence of (continuous and discontinuous) phase transitions. We also c
 ompute the minimal size of a seed of new adopters in order to trigger a gl
 obal cascade if these new adopters can only be sampled without any informa
 tion on the graph. We show that this minimal size has a non-trivial behavi
 or as a function of the average connectivity. Our analysis extends methods
  developed in the random graphs literature based on the properties of empi
 rical distributions of independent random variables\, and leads to simple 
 proofs.\n\n
LOCATION:Small lecture theatre\, Microsoft Research Ltd\, 7 J J Thomson Av
 enue (Off Madingley Road)\, Cambridge
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