Interactions/bonds/couplings are actions between system’s components. Components may also interact with themselves which is called a self-interaction. Self-interactions are important for creating multistability (multiple stable states) of systems.  Interactions/bonds/couplings can be physical, for example two molecules, planets or galaxies attracting each other, (or they can be) informational. A player-opponent dyad is an example of informational (mostly visual) interaction (although it can often be physical through body contact). The action of a player by perceived information constrains the opponent to act in a certain way and his/her action informationally constrains the first player to act accordingly. Discussion is another example of informational interaction. The talk of a person is being constrained by the talk of others and vice versa. Of course, informational interactions are always performed by physical means (sound, light etc.). Hence, interactions are a significant part of the system’s internal and external context. They are of utmost importance in forming the collective behavior of system’s components. Interactions between excitations (particles) of elementary physical fields are called fundamental interactions. These interactions form composite systems with emergent properties such as protons, neutrons, atoms. For example, atoms have different (emergent) properties than the particles they consist of, such as: protons, neutrons and electrons.

Couplings can be also unidirectional. For example, the day-night cycle unidirectionally drives animal’s behavioral states (e.g. wake-sleep cycle…). However, these behavioral states of animals do not influence the day-night cycle. The intensity of interactions may be symmetrical or asymmetrical. For example a player may pass the ball to his/her teammate more frequently (asymmetrically) than the other way around. In a similar vein, one speaker can talk to the group members more frequently than they do to her/him. Symmetry would mean an equal share in both directions of communication (passes or talk). Interactions may be short–range or long–range. Short-range interactions are usually called –local– because they occur between system’s components which are spatially nearest or at least close neighbors (e.g., two neighboring molecular layers forming the cellular membrane). If interactions spread over larger number of components which are not nearest or close neighbors then they are called long-range (e.g., players on opposite sides of the football field). Interactions can create collective states which influence each of the individual components. This is called a global coupling. For example, a person may decide to join a large group and change his/her running direction because the collective behavior of the group changed his/her intention.

Networks

In systems of many components interactions/bonds/couplings between components create networks . For example, characters in any theatre piece, opera, novel, film, or the life itself, form a network of informational/communicational interactions. One can consider characters as being the nodes (vertices) and their informational flows as edges of the network. Depending on the different personalities of characters and their communications unexpected individual and collective effects occur.

In a similar vein, players in sport teams, form networks of passing, visual, auditory and physical interactions. Organizations such as political parties and corporations, as well as roads between and within cities are yet another example of networked interactions.  Inter- atomic and inter-molecular interactions, as well as elementary particle interactions, form networks, as well. The Internet itself and all social networks inside it, form a giant network of information flows.

In our cells there are different interrelated networks of interactions such as: gene, metabolic and signaling. Our organism and organs (e.g. the central nervous system  are networks of interacting components.

By slow change of the context, networks change their  collective activity through a phase transition into different self-organized stable collective  states, such as: synchronization and polarization.

Robert Hristovski  21.01.2016