Non-binary classification trees

The main objective of this paper is to implement non-binary splits into Gelfand et al.'s modification of the CART algorithm. Multi-way splits can sometimes better reflect the structure of data than binary splits. Methods for the construction and comparison of such splits are described.     

Stationary distributions in Kolmogorov-Petrovski- Piskunov-type models with an infinite number of particles

A model of population dynamics in continuous time on the lattice contains the Kolmogorov-Petrovski-Piskunov equation as a special case. A limit distribution exists. The first three moments and the correlation function are expressed.     

Exploring Subcultural Trajectories: Racist Skinhead Disengagement,Desistance, and Countercultural Value Persistence

ABSTRACT

This study analyzes the life histories and subcultural trajectories of people who have at one time but no longer identify as racist skinheads. We find that, on the one hand, people are far more malleable with their subcultural identities than is commonly understood by law enforcement and researchers concerned with criminal desistance, and on the other hand, this does not necessitate a total abdication of stable subcultural identities and values as some recent post-subculture scholars have asserted. Accordingly, we conceptualize the phenomena of subcultural trajectories and discuss the implications of these findings for future scholarship on subcultural participation and desistance as well as for potential public policies to successfully fight racism.     

Career mobility and job flocking

Flocking is oftentimes used to metaphorically describe social behavior. Do people actually flock in a way that avian species do? This paper develops a purely ecological mechanism for explaining similarity in human behavior by distinguishing between social networks of person-to-person ties and ecological networks of ties of observability. I test the “information center hypothesis” [Ibis 115 (1973) 517] from bioecology on the career mobility of professional managers who all graduated from the same university. In this case, spatial proximity in birds is replaced with sociodemographic homophily on an acquired status characteristic among persons. The results indicate that homophilous individuals exchange information about a favorable destination state by ecological ties of observability, that is, they follow the career mobility of fellow alumni and “flock” along with them.     

A Heuristic for the Maximum Independent Set Problem Based on Optimization of a Quadratic Over a Sphere

For a given graph the maximum independent set problem is to find a maximum subset of vertices no two of which are adjacent. We propose a heuristic for the maximum independent set problem which utilizes classical results for the problem of optimization of a quadratic function over a sphere. The efficiency of the approach is confirmed by results of numerical experiments on DIMACS benchmarks.