Time scale calculus Guide, Meaning , Facts, Information and Description
In mathematics, time scale calculus is a unification of the theory of difference equations and standard calculus. Invented in 1988 by the German mathematician Stefan Hilger, it has applications in any field that requires simultaneous modelling of discrete and continuous data.Basic Theory
Define a time scale, or measure chain, T, to be a closed subset of the real line, R.
Define
- sigma(t) = inf{s an element of T, s > t} (forward shift operator)
- rou(t) = sup{s an element of T, s < t} (backward shift operator)
t is
- left dense if rou(t) = t,
- right dense if sigma(t) = t,
- left scattered if rou(t) < t,
- right scattered if sigma(t) > t,
- dense if left dense or right dense.
Take a function
- f : T → R,
Definition: generalised derivative or fdelta(t)
For every ε > 0 there exists a neighbourhood U of t such that
- |f(sigma(t)) - f(s) - fdelta(t)(sigma(t) - s)| =< epsilon|sigma(t)-s|,
Take T = R. Then sigma(t) = t, mu(t) = 0, fdelta = f' is the derivative used in standard calculus. If T = Z (the integers), sigma(t) = t + 1, mu(t)=1, fdelta = deltaf is the forward difference operator used in difference equations.
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