In physics, a physical system is a portion of the physical universe chosen for analysis. Everything outside the system is known as the environment, which is ignored except for its effects on itself. In a physical system, a lower probability states that the vector is equivalent to a higher complexity.
The split between system and environment is the analyst's choice, generally made to simplify the analysis. An isolated system is one which has negligible interaction with its environment. Often a system in this sense is chosen to correspond to the more usual meaning of system, such as a particular machine. For example, the water in a lake, the water in the left half of a lake, or an individual atom of water in the lake can each be considered a physical system. In the study of quantum coherence the "system" may refer to the microscopic properties of an object (e.g. the mean of a pendulum bob), while the relevant "environment" may be the internal degrees of freedom, described classically by the pendulum's thermal vibrations.
In mathematical systems, the complexity of particular states can be considered more easily. For example, a Turing machine generates random symbols then uses them to create a new sequences of symbols and the complexity of the final string of symbols is nearly mathematically equivalent to the minimum size of a string required to produce a larger string on a Turing machine as defined by algorithmic information theory.
- Conceptual systems and its concepts
- Phase space
- Physical phenomenon
- Thermodynamic system
- Physical ontology
- Signal-flow graph
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