y T[é]{}cnicas, Argentina'
- 'Centro At[ó]{}mico Bariloche, 8400 S. C. de Bariloche, Argentina'
author:
- 'M. N. Kuperman'
- 'S. Risau-Gusman'
title: The topological issues of cooperation
---

Introduction
============

The emergence of cooperation in different real systems has been puzzling researchers in several areas devoted to the study of systems involving social, economic or biological organization. Even though each of these systems is conformed by single units with natural competitive tendencies, the emergence of collective behaviours is undeniable. While natural selection operates through competition, cooperation is essential to the evolution and emergence of higher degrees of complexity. The struggle between competition and cooperation is then one of the keys in understanding the self organization of complex systems conformed by interacting units. Still, many questions arise regarding how such opposites forces can coexist.

The survival of the cooperative behavior is a classical problem of game theoretical approaches [@mayn]. In this context, the paradigmatic Prisoner’s Dilemma game [@axel] has been widely studied in different versions. It is usually formulated as a standard model for the confrontation between cooperative and selfish behaviors. For many years it was implemented in zero dimensional systems, where every player can interact with any other, until the 