Sensitivity of nonequilibrium systems

Simple mechanisms through which nonequilibrium structures can be influenced by external fields are discussed. It is shown that a very weak gravitational or electric field can have a large influence on selection or creation of structures. In the absence of cooperativity, the influence of a weak field, to the leading order, is characterized by the ratio (E_int/kT), where E_int is the energy of interaction; however, when there is far-from-equilibrium cooperativity, it is shown that the influence of the field is characterized by $\text{(E}{}_{\mathrm{int}}\text{kT)}{}^{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}$.