The Essence of Dynamical Systems
- A dynamical system is a system in which a function describes the time dependence of a point in a geometrical space
- Said another way, a dynamical system is a collection of random variables that is indexed by time
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A stochastic dynamical system is a dynamic system subjected to the effects of noise
- In other words, a dynamic system is considered to be stochastic if the system requires mapping its inputs to outputs using probabilities
- A deterministic dynamical system is a dynamic system that isn't subjected to the effect of noise
- We will be interested in stochastic dynamical systems in the majority of our research
Systems and States
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In our case, a system refers to a collection of states indexed by time, which represents some broader notion
- Some examples of this include the stock market, weather, etc.
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A state refers to a distinct observation of some random variable
- Some examples of this include if the stock market goes up, the weather being sunny, etc.
State Space versus Sample Space
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State Spaces are used in Dynamics
- State spaces imply that there is a time progression and that our system will assume different states as time progresses
- For example, the state space of the largest number up to roll is a number from the following state space:
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Sample Spaces are used more often in Statistics
- A sample space represents a set of distinct observations of some random variable
- There is typically a probability distribution associated with each state
- For example, the sample space of a single die roll is the following
- In summary, we expect to be thinking about probabilities when we hear sample spaces, unlike state spaces, which do not carry the same connotation
- State spaces are typically indexed by time, unlike sample spaces, which do not carry the same connotation
References
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