CompositeSystemen

CompositeSystemen, or composite systems, refer to physical, logical, or engineered systems that are composed of two or more subsystems that interact with each other. The behavior of a composite system cannot be fully understood by examining any single component in isolation, because the interactions give rise to collective dynamics, exchange of energy and information, and sometimes emergent properties.

In classical physics and engineering, the state of a composite system is described by the states of its subsystems. If coupling is negligible, the total state is approximately the Cartesian product of subsystem states, and the total energy is the sum of the subsystems plus a (often small) interaction term. When coupling is significant, equations of motion or state equations must include interaction terms.

In quantum mechanics, the state space is the tensor product of the subsystems' Hilbert spaces. Composite systems can be entangled, meaning the state of the whole cannot be written as a product of subsystem states. Observables decompose into subsystem observables but outcomes can be correlated beyond classical limits; partial tracing yields reduced states.

Examples include molecules composed of atoms, electrical networks, mechanical assemblies, computer systems, and ecological or socio-technical systems. In control and systems engineering, modular design and hierarchical modeling rely on the concept of subsystems and their interfaces.

Modeling approaches emphasize interfaces, coupling mechanisms, and conservation laws. The behavior of a composite system often exhibits emergent properties, robustness, and complexity that are not obvious from the parts alone.