Information Spread across Social Network Services with Usersxe2x80x99 Information Indifference Behavior This paper investigates the dynamics of information spread across social network services (SNSs) such as Twitter using the susceptibleinfectedrecovered (SIR) model. In most practical applications, an exact analytic solution is not available for the SIR model, so previous studies have largely been based on the assumption that the probability of a node having the target information is independent of whether or not its neighbors have that information. In contrast, we herein propose a different approach based on an assumption called the xe2x80x9cstrong correlation assumptionxe2x80x9d, in which the probability of a node having the target information is strongly correlated with whether its neighboring nodes have that information. We then analyze information spread for the SIR model and show that the use of the strong correlation assumption makes it possible to analyze the spread of information with far greater accuracy than the node independence assumption.

Latencybounded Target Set Selection in Signed Networks It is welldocumented that social networks play a considerable role in information spreading. The dynamic processes governing the diffusion of information have been studied in many fields, including epidemiology, sociology, economics, and computer science. A widely studied problem in the area of viral marketing is the target set selection: in order to market a new product, hoping it will be adopted by a large fraction of individuals in the network, which set of individuals should we xe2x80x9ctargetxe2x80x9d (for instance, by offering them free samples of the product)? In this paper, we introduce a diffusion model in which some of the neighbors of a node have a negative influence on that node, namely, they induce the node to reject the feature that is supposed to be spread. We study the target set selection problem within this model, first proving a strong inapproximability result holding also when the diffusion process is required to reach all the nodes in a couple of rounds. Then, we consider a set of restrictions under which the problem is approximable to some extent.