Coexistence of pure and mixed states in nonlinear maps

Coherence and interaction are important concepts in physics. While interaction describes a relation between individual objects such as forces acting between distinguishable particles, coherent objects exist with the sole purpose of describing a single object. For example, each component of a vector provides us with only partial information. The whole picture is revealed only when the components are coherently related to their generating vector. Another example is a singlet of two spin ½- particles. The true nature of these two coherent particles is described by a spin-less single particle. Apparently it seems that objects can be either coherent or lion-coherent but they cannot be both simultaneously. This is almost true. We show that a system can be described simultaneously as coherent and lion-coherent but an observer can distinguish only one concept at a time. (paper)