Difference between revisions of "Evolution operator"
From Encyclopedia of Mathematics
(TeX done) |
(Seems better, see talk page) |
||
| Line 3: | Line 3: | ||
====Comments==== | ====Comments==== | ||
| − | In general, an evolution operator can be defined as a (not necessarily linear) operator-function $U(t,s)$ satisfying 1) and 2). If $t,s$ are not subjected to restrictions, 3) is satisfied automatically. | + | In general, an evolution operator can be defined as a (not necessarily linear) operator-function $U(t,s)$ satisfying 1) and 2). If $t,s$ are not subjected to restrictions, 3) is satisfied automatically. Under some circumstances, the restriction $t \ge s$ is a natural one, and the inverse need not exist at all. |
====References==== | ====References==== | ||
Latest revision as of 18:43, 16 October 2017
A linear operator-function $U(t,s)$ of two variables $t$ and $s$ that satisfies the properties 1) $U(s,s) = I$; 2) $U(t,x)U(x,s) = U(t,s)$; and 3) $U(t,s) = U(s,t)^{-1}$.
Comments
In general, an evolution operator can be defined as a (not necessarily linear) operator-function $U(t,s)$ satisfying 1) and 2). If $t,s$ are not subjected to restrictions, 3) is satisfied automatically. Under some circumstances, the restriction $t \ge s$ is a natural one, and the inverse need not exist at all.
References
| [a1] | A. Pazy, "Semigroups of linear operators and applications to partial differential equations" , Springer (1983) pp. Chapt. 5 |
How to Cite This Entry:
Evolution operator. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Evolution_operator&oldid=42088
Evolution operator. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Evolution_operator&oldid=42088
This article was adapted from an original article by M.I. Voitsekhovskii (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article