About this Research Topic
Collective behavior of organisms is readily observed in nature. Birds travelling in flocks, ants forming supply lines and, on a much smaller scale, bacteria forming biofilms are just a few common examples. It is a long-standing question how such organization emerges from the rules that individual organisms follow and the way they interact. This question is not only of profound theoretical importance, it is also of great practical value. For instance, predictions of the herding behavior of caribou would help conservation efforts and disrupting biofilm formation is important for the design and maintenance of medical equipment.
At this point, there is no overarching theoretical description of emergent behaviour across space and time scales. Most research is either based on experimental observations or on computer simulations. These simulations come in different kinds and produce different types of descriptions of emergent behavior. In this Research Topic, we aim to bring together experts in modelling, experimental and computational techniques to formulate the state of affairs, explore the strengths and weaknesses of current approaches and draw up a road map for future interdisciplinary research efforts, ultimately aiming at a unified theory of emergent behavior, its origin, mechanisms and control.
Models of collective behaviour roughly come in two classes: agent-based and continuous. The former prescribe rules for each individual, thus allowing for a detailed description of the underlying physiology, while the latter describe the evolution of population densities directly. For many research questions, the simulation of sufficiently many agents over a sufficiently long time scale is not feasible and continuum modelling is a more promising approach.
Conceptually, continuum models could be considered in the "thermodynamic limit" of agent-based models. However, an exact link is hard to establish in the presence of complicated interactions, inhomogeneous media and other such complications. The first question we pose in this Research Topic is: How are agent-based and continuum models related? Both a-priori links, i.e. a derivation of one from the other, and a-posteiori links, i.e. a comparison of predictions, are of interest.
Secondly, we aim to relate predictions from either model type to experimental observations of aggregation of organisms at a large and small scale. Such predictions can be based on direct numerical simulations as well as mathematical analysis.
The third question we pose is to what extent pattern formation is universal. Can we compare emergent behaviour of different organisms, using different communication strategies ?
Lastly, we aim to provide an outlook. What are the most important outstanding questions ? What are the most promising techniques and theoretical ideas ?
This Research Topic will be open both to original contributions and to review-type papers. Original contributions can discuss novel models, new analysis of existing models, novel analysis techniques and the critical evaluation of model predictions in one or more of the following fields:
continuum (e.g. kinetic, non-local, PDE ) models of aggregation, agent-based modelling, experimental results or combinations of these. Overview papers can discuss the history of recent advances and outlook of certain sub-fields or research questions and will be coordinated to avoid overlap.
We welcome submissions by multi-disciplinary teams and cross-comparisons of results and ideas.
Keywords: Animal aggregation, active matter, biofilm formation, kinetic models, non-local PDEs
Important Note: All contributions to this Research Topic must be within the scope of the section and journal to which they are submitted, as defined in their mission statements. Frontiers reserves the right to guide an out-of-scope manuscript to a more suitable section or journal at any stage of peer review.